Rover V8 cooling changes--EWP?
Discussion
Hi all,
I have a 2004 Land Rover Discovery with the 4.6L V8, and I've been doing some experimenting with the cooling system. I'd like some opinions on what to do next. Please note: "Buy a Toyota" or "put in an LS2" are not on the menu.
I live in the Western United States and tow a utility trailer fairly often on trips. Our weather can range from damp and cold to hot and dry, and altitudes can range from sea level to nosebleed. That places a strain on any cooling system, and is a real challenge in the Rover. My goal is to keep the engine between 180*F and 190*F (88C), as it seems to starve the lifters and cams of oil at higher temperatures.
The current engine is a rebuild with flanged liners and improved camshaft bearings. I've ditched the remote bypass thermostat, and I'm using an 82C (180F) inline thermostat. New viscous clutch and mechanical fan, new OEM radiator, new OEM water pump. I've added an oversized engine oil cooler (which was not provided from the factory in the 2004 model year).
Everything works as well as it CAN work. It maintains a pretty constant coolant and oil temperature as long as the temperature is 70F (22C) or less, and works even better if there is some humidity. I'm actually considering adding an oil thermostat to speed up the warm-up on cold days. But on a hot, dry day going up the mountain with a trailer, or idling in heavy traffic with the air conditioning on full blast, the cooling system doesn't keep up. The biggest problem seems to be the flow rate of the pump under 2000RPM--when I back off on the throttle, it doesn't cool down much because the flow rate goes down too. I need a long downhill at speed to get the temperature back under 93C, much less 88C, although with the added oil cooler it will eventually cool off on a level road with the A/C off.
However, I have a dream in which I'm blasting down the freeway at 80mph, up a hill, carrying 7 passengers with the A/C going full bore, while towing a trailer--serenely ignoring the engine temperature which never goes above 190F.
I'm considering three possible modifications to keep things under control in all conditions:
1) Aluminum 3-row radiator. This will cost me about $1000, but I'm not sure it would do anything for me at idle, since the OEM pump is so bad.
2) Custom high-flow water pump, to replace the OEM pump. This would be a custom Flowkooler impeller fitted to the OEM pump housing and shaft, which would create higher flow at low RPM but still not cavitate at higher RPM. This would cost upward of $1000.
3) A Davies-Craig EWP115 as a booster pump, in addition to the mechanical pump. I'm pretty sure this would solve overheating at idle, and I would be able to have it run-on after shutdown which should solve heat soak issues. But does it do anything for me in the 1500RPM to 2000RPM range? This would cost me about $300 all told, so it would be the most cost-effective option if it will solve my problems.
Any opinions?
I have a 2004 Land Rover Discovery with the 4.6L V8, and I've been doing some experimenting with the cooling system. I'd like some opinions on what to do next. Please note: "Buy a Toyota" or "put in an LS2" are not on the menu.
I live in the Western United States and tow a utility trailer fairly often on trips. Our weather can range from damp and cold to hot and dry, and altitudes can range from sea level to nosebleed. That places a strain on any cooling system, and is a real challenge in the Rover. My goal is to keep the engine between 180*F and 190*F (88C), as it seems to starve the lifters and cams of oil at higher temperatures.
The current engine is a rebuild with flanged liners and improved camshaft bearings. I've ditched the remote bypass thermostat, and I'm using an 82C (180F) inline thermostat. New viscous clutch and mechanical fan, new OEM radiator, new OEM water pump. I've added an oversized engine oil cooler (which was not provided from the factory in the 2004 model year).
Everything works as well as it CAN work. It maintains a pretty constant coolant and oil temperature as long as the temperature is 70F (22C) or less, and works even better if there is some humidity. I'm actually considering adding an oil thermostat to speed up the warm-up on cold days. But on a hot, dry day going up the mountain with a trailer, or idling in heavy traffic with the air conditioning on full blast, the cooling system doesn't keep up. The biggest problem seems to be the flow rate of the pump under 2000RPM--when I back off on the throttle, it doesn't cool down much because the flow rate goes down too. I need a long downhill at speed to get the temperature back under 93C, much less 88C, although with the added oil cooler it will eventually cool off on a level road with the A/C off.
However, I have a dream in which I'm blasting down the freeway at 80mph, up a hill, carrying 7 passengers with the A/C going full bore, while towing a trailer--serenely ignoring the engine temperature which never goes above 190F.
I'm considering three possible modifications to keep things under control in all conditions:
1) Aluminum 3-row radiator. This will cost me about $1000, but I'm not sure it would do anything for me at idle, since the OEM pump is so bad.
2) Custom high-flow water pump, to replace the OEM pump. This would be a custom Flowkooler impeller fitted to the OEM pump housing and shaft, which would create higher flow at low RPM but still not cavitate at higher RPM. This would cost upward of $1000.
3) A Davies-Craig EWP115 as a booster pump, in addition to the mechanical pump. I'm pretty sure this would solve overheating at idle, and I would be able to have it run-on after shutdown which should solve heat soak issues. But does it do anything for me in the 1500RPM to 2000RPM range? This would cost me about $300 all told, so it would be the most cost-effective option if it will solve my problems.
Any opinions?
"failing to cool at idle" is nothing to do with the water pump and everything to do with poor cooling system performance BEFORE you started idling....
This is because heat realse at idle is tiny. Typically, idling burns something in the order of 1kg of fuel per HOUR! Compare that to fully load operation at peak power, where your engine is burning something like 150 to 200 times more fuel. (And hence releasing 150 to 200 times more heat!)
What happens is if that if the cooling system is poor, it must heat up to the a temperature that is sufficient to drive the heat to the outside environment. Heat flow depends on a difference in temperature and not an absolute temperature. Although we typically measure the temperature of the coolant in the system (because it's easy to do) this isn't actually what matters to your engine. What matters to your engine is its metal temperatures.
On a poorly cooled system, working hard, metal temperatures in the engine increase, until they are hot enough to push the heat out of the engine components into the coolant. And then, in the radiator, that coolant, which is hotter than the ambient air, pushes the heat it has carried away from the engine, out into the ambient air, which again needs a certain temperature difference. So, the hotter the day, the higher the metal temps in your engine.
Engines that "boil at idle" do so because the metal temps are too hot before idling, so when coolant flow falls, there is insufficient flow rate and you get local, nucleate boiling. This is actually a good thing, as the phase change between water and steam increases heat transfer massively. However, if the radiator can't reject this extra heat, and the BULK of the coolant boils, then the system pressure climbs beyond the header tank cap rating, and the system boils over.
In all cases you need more heat rejection to ambient, ie a bigger/better radiator and NOT more coolant flow!!
This is because heat realse at idle is tiny. Typically, idling burns something in the order of 1kg of fuel per HOUR! Compare that to fully load operation at peak power, where your engine is burning something like 150 to 200 times more fuel. (And hence releasing 150 to 200 times more heat!)
What happens is if that if the cooling system is poor, it must heat up to the a temperature that is sufficient to drive the heat to the outside environment. Heat flow depends on a difference in temperature and not an absolute temperature. Although we typically measure the temperature of the coolant in the system (because it's easy to do) this isn't actually what matters to your engine. What matters to your engine is its metal temperatures.
On a poorly cooled system, working hard, metal temperatures in the engine increase, until they are hot enough to push the heat out of the engine components into the coolant. And then, in the radiator, that coolant, which is hotter than the ambient air, pushes the heat it has carried away from the engine, out into the ambient air, which again needs a certain temperature difference. So, the hotter the day, the higher the metal temps in your engine.
Engines that "boil at idle" do so because the metal temps are too hot before idling, so when coolant flow falls, there is insufficient flow rate and you get local, nucleate boiling. This is actually a good thing, as the phase change between water and steam increases heat transfer massively. However, if the radiator can't reject this extra heat, and the BULK of the coolant boils, then the system pressure climbs beyond the header tank cap rating, and the system boils over.
In all cases you need more heat rejection to ambient, ie a bigger/better radiator and NOT more coolant flow!!
Logic would dictate one certain thing. If the engine is stock and in good condition and the cooling system components you replaced are stock and in good condition and you are using the vehicle in conditions that the OE manufacturer would have extensively tested it in then it shouldn't overheat. The only things you say you modified are the thermostat type and the oil cooler and I can't comment on whether this has caused a problem having no knowledge of the specifics.
However one thing that will guarantee boiling over at idle in particular is if the cooling system is not pressurising to the normal value. I'd start with a pressure test and make absolutely sure there are no leaks and the rad cap or expansion tank cap (whatever your vehicle has) is sealing properly.
I had a friend once with a largish V6 engined car that behaved quite normally under light open road driving conditions but overheated like a pig in heavy traffic in town or when it was being caned. He chased the problem round the houses for ages but all it was was a 50p O ring in the expansion tank cap not sealing properly.
However one thing that will guarantee boiling over at idle in particular is if the cooling system is not pressurising to the normal value. I'd start with a pressure test and make absolutely sure there are no leaks and the rad cap or expansion tank cap (whatever your vehicle has) is sealing properly.
I had a friend once with a largish V6 engined car that behaved quite normally under light open road driving conditions but overheated like a pig in heavy traffic in town or when it was being caned. He chased the problem round the houses for ages but all it was was a 50p O ring in the expansion tank cap not sealing properly.
BTW, to confirm what you've been told above by Max-Torque, the flow rates of your water pump are absolutely nothing to do with your problem. Mechanically driven pumps have to be sized to cope with the worst possible case scenario they face which is at about peak torque when the power output and therefore heat to be rejected is the maximum possible per pump rpm.
If you're towing up a hill at full throttle and peak torque, I think around 2600 rpm on your engine and maybe 150 bhp, you're doing about 3 times the rpm at idle and therefore similarly producing about three times the coolant flow. But at idle the power output is a fraction of what it is at WOT. Even driving the AC and a viscous fan you'll only be producing about 6 bhp from the engine to overcome parasitic and pumping friction and maybe the same again for the fan and A/C. Perhaps 12 bhp total and just over 4 litres of fuel per hour. So the coolant flow is 1/3rd of that at WOT at peak torque to cope with 1/12th of the heat production. It's a no-brainer. There's way more coolant flow than you need and the same applies when you're cruising at anything less than WOT.
If you're overheating at idle then the radiator is not rejecting heat or the coolant is boiling locally inside the engine because the system pressure is too low.
If you're towing up a hill at full throttle and peak torque, I think around 2600 rpm on your engine and maybe 150 bhp, you're doing about 3 times the rpm at idle and therefore similarly producing about three times the coolant flow. But at idle the power output is a fraction of what it is at WOT. Even driving the AC and a viscous fan you'll only be producing about 6 bhp from the engine to overcome parasitic and pumping friction and maybe the same again for the fan and A/C. Perhaps 12 bhp total and just over 4 litres of fuel per hour. So the coolant flow is 1/3rd of that at WOT at peak torque to cope with 1/12th of the heat production. It's a no-brainer. There's way more coolant flow than you need and the same applies when you're cruising at anything less than WOT.
If you're overheating at idle then the radiator is not rejecting heat or the coolant is boiling locally inside the engine because the system pressure is too low.
It's pretty unlikely that your problem is insufficient water flow and much more likely that it is insufficient air flow or water/air heat transfer.
All the EWPs I've see are suitable only for use in addition to the main mechanical pump and if you look at the pressure/flow characteristics you will find that putting them in series with the main pump will strangle the cooling system, greatly increasing the risk of hotspots, especially in a V engine. Those little Davies Craig things are extremely restrictive and very bad news on an engine that is already suffering from overheating. If you want to add an EWP as a booster you would need to add a high flow bypass around it, and that's not easy to do. I have used the bigger DC pump for run-on cooling and it is very effective at washing out heat soak, but in terms of engines under load you should think of it as part of the problem not part of the solution.
A far better approach to look at is increasing the size / heat transfer capability of the radiator and fitting a better fan. If the radiator is more than a few years old it's quite possible that dirt, scale and/or corrosion have reduced it's heat transfer and a new equivalent might work better - but it makes sense to fit an uprated rad if you're considering replacing it. Also make sure that the air coming out of the 'hot' side of the radiator can't recirculate back to the front. Reducing the air flow by 10% makes hardly any difference to your cooling system, but replacing 10% of the cold air with recirculated hot air costs you around 10% of your cooling at a stroke.
All the EWPs I've see are suitable only for use in addition to the main mechanical pump and if you look at the pressure/flow characteristics you will find that putting them in series with the main pump will strangle the cooling system, greatly increasing the risk of hotspots, especially in a V engine. Those little Davies Craig things are extremely restrictive and very bad news on an engine that is already suffering from overheating. If you want to add an EWP as a booster you would need to add a high flow bypass around it, and that's not easy to do. I have used the bigger DC pump for run-on cooling and it is very effective at washing out heat soak, but in terms of engines under load you should think of it as part of the problem not part of the solution.
A far better approach to look at is increasing the size / heat transfer capability of the radiator and fitting a better fan. If the radiator is more than a few years old it's quite possible that dirt, scale and/or corrosion have reduced it's heat transfer and a new equivalent might work better - but it makes sense to fit an uprated rad if you're considering replacing it. Also make sure that the air coming out of the 'hot' side of the radiator can't recirculate back to the front. Reducing the air flow by 10% makes hardly any difference to your cooling system, but replacing 10% of the cold air with recirculated hot air costs you around 10% of your cooling at a stroke.
Thanks for the good replies, everyone. All in all, it sounds like a bigger radiator may be the way to go. There's a couple of details I'm wondering about, though. Kia_diesel, the cooling system performance has remained constant through 3 Rover engines and two Discoveries, with various OEM components replaced. Currently all components are less than 18 months old and have less than 10K miles on them. I suspect Max_Torque will agree that this is a design flaw with the Discovery 2--my suspicion is that it was mostly for the purpose of pleasing the EPA and getting an import license. Only changing the thermostat type and adding the oil cooler has made things manageable.
GreenV8s: I've looked at the pump curve on the D-C units, and they seem to have plenty of flow at low pressure differential. If it is set up to run constantly once the engine is warmed up, would the D-C unit really be a negative to the system flow at higher RPM? All it has to do in that regime is not put suction on the mechanical pump intake.
Max_Torque's point about the waste heat at idle being small is a good one. If the heat rejection is sufficient to keep the block and head temperature under control at throttle, then there should be no problem at idle even if flow is reduced. My experience with adding the oil cooler confirms that--when there is some humidity in the air and there's low load on the A/C, the idle temperatures are stable now that the oil cooler is getting more heat out of the engine.
Still, higher flow should reject more heat, yes? I don't think I'm having trouble with pressure drop across the engine--the coolant temperature runs about 2C to 5C warmer than the head material when everything is warmed up, which makes me think that the heads are getting plenty of coolant. The worst temperature rise comes at about 2000 to 2600 RPM, at load, as Kia_diesel surmised. If I could get higher flow at the same system pressure drop or higher in that RPM range, that would increase heat rejection as I understand things.
I can confirm this somewhat--the engine cools off very nicely going downhill at about 2600RPM. There's very little throttle in that condition, and plenty of flow. Also, as a matter of duty cycle, it's a truck not a race car. The engine works hard in short bursts, and if it can cool off in between no matter what the ambient conditions, then that might be sufficient.
Still, on a hot day it's possible to watch the engine temperature go up about 2C at idle just from turning on the A/C, which increases the effective ambient temperature at the engine radiator. So a bigger radiator is likely the best bang for the buck.
Oh, one other thing. GreenV8s, the Discovery is an interesting beast. Some things are truly excellent on it--the radiator ducting is one of them. I don't think there is any significant leakage of air back to the front of the radiator. The viscous clutch fan is quite good, too, and it's nearly new, about 2000 miles on it. I've thought about putting in an electric fan from a Mustang or Lincoln, but I think I would need a bigger alternator for it, and I'm not convinced that there will be much benefit.
Bigger radiator, ensure only cold air can pass through that radiator. Ensure the fans are powerful and also draw air through as much of the core as possible...and work correctly.
Are all those parts standard ?
You mention an oil cooler...what design ? does it have adequate airflow ? What are oil temps like ?
What are you using for coolant ?
Are all those parts standard ?
You mention an oil cooler...what design ? does it have adequate airflow ? What are oil temps like ?
What are you using for coolant ?
Radiator, mechanical fan, electric fan, and ducting are all factory spec.
The engine oil cooler is the same as the transmission oil cooler that is fitted to the Discovery from the factory. On the older Discovery 2, they were equipped with a 7-tube engine oil cooler, I believe. This was deleted in 2003 when they changed from 4.0L to 4.6L engines, but there are still mounting points for it in front of the radiator and the block still has plugs for the piping. I mounted an 11-tube transmission cooler in the factory location and piped it in to the existing ports. It helped a great deal.
Coolant is the basic green stuff, which is what Land Rover recommends (after having corrosion issues with orange coolant).
I don't know how well that viscous fan is specced, but since it's driven off the crank it'll inherently lose flow capability as the revs drop. An electric fan might move significantly more air in the region that you're interested in, even if it doesn't match the peak flow of the viscous fan.
Do you have access to any specialist forums where you can find out whether this is a common problem with that vehicle and whether there are any known solutions? I suspect a better rad would be the best solution, and an uprated or additional fan would be your second option, but I don''t know how easy these would be to achieve in that engine bay.
An oil cooler in front of the main rad might improve the overall cooling (by taking heat out via the oil) but it'll be compromising the engine coolant cooling to achieve it. If you can re-site the oil cooler downstream of the main rad, that would generally work better.
Do you have access to any specialist forums where you can find out whether this is a common problem with that vehicle and whether there are any known solutions? I suspect a better rad would be the best solution, and an uprated or additional fan would be your second option, but I don''t know how easy these would be to achieve in that engine bay.
An oil cooler in front of the main rad might improve the overall cooling (by taking heat out via the oil) but it'll be compromising the engine coolant cooling to achieve it. If you can re-site the oil cooler downstream of the main rad, that would generally work better.
Edited by GreenV8S on Monday 24th October 00:42
Ha! Yes, this is a known problem. The "solution" is to get a rebuilt engine with flanged cylinder liners to make the engine more tolerant to overheating. Which I have done. But they are still likely to have wear issues with cams, camshaft, and lifters.
The best improvements that I've found are the ones I've done--inline 180*F thermostat and the oil cooler. Yes, the oil cooler is not in the best location, but there's not really a great place for it, because of the extensive ducting behind the grill to ensure that the radiator receives maximum air flow. An additional fan would be difficult--there is already a pretty good-sized electric pusher fan, which comes on with the A/C (under 40 miles per hour) or when engine temperature hits 212. The only real improvement I could make to the fan would be to replace the belt fan with the Mustang GT electric fan I mentioned. That would not solve the issue by itself, but might do the trick in combination with other improvements.
Did you have any further comments on the D-C electric pump being restrictive? I had figured that adding one couldn't hurt, but your input was quite alarming. Did you find it restrictive even when it's running at full voltage?
There's easily enough room to add a third or even fourth row to the radiator. This one would probably work quite well, but would come to about $750 shipped:
http://www.allisport.com/product/discovery-2-v8-al...
Ok, so it would seem there's a design issue with that vehicle in your operating conditions then from what you say. Presumably others over there have looked into this though.
So do I understand correctly there's a viscous clutch fan on the engine side of the radiator and also an electric one on the other side of it?
The last time I had a car with a viscous clutch fan I took it off altogether along with its shroud and never missed the thing. It was doing more to block airflow through the rad than anything else. Might be worth a try.
So do I understand correctly there's a viscous clutch fan on the engine side of the radiator and also an electric one on the other side of it?
The last time I had a car with a viscous clutch fan I took it off altogether along with its shroud and never missed the thing. It was doing more to block airflow through the rad than anything else. Might be worth a try.
Maybe the electric fan is only to supplement the AirCon ?
Get the biggest and best radiator you can and a proper electric fan that shifts a lot of air, Spal offer some "Extreme" models that flow more than their regular fans, although only in a few sizes I think
Readily available in the US, perhaps less so in other parts of the world.
Again ensuring only colder outside air can pass through the rad at all times and that hot air can escape the underbonnet area ok.
Get the biggest and best radiator you can and a proper electric fan that shifts a lot of air, Spal offer some "Extreme" models that flow more than their regular fans, although only in a few sizes I think
Readily available in the US, perhaps less so in other parts of the world.
Again ensuring only colder outside air can pass through the rad at all times and that hot air can escape the underbonnet area ok.
There's a lot of confusion about what cooling an engine properly really means. Engines can live quite happily with high metal temperatures and coolant above 90c but what you must avoid is localised, and especially general, boiling. Higher system pressures increase the boiling point of the coolant which increases the temperature differential to the outside world and the heat rejection and reduces localised boiling. Putting a higher pressure rated tank cap on is a cheap way of finding out if this will help the situation before spending a fortune on bigger rads.
neillr said:
My goal is to keep the engine between 180*F and 190*F (88C), as it seems to starve the lifters and cams of oil at higher temperatures.
(snip)
I've ditched the remote bypass thermostat, and I'm using an 82C (180F) inline thermostat.
That's a pretty low temperature goal and I wonder whether the symptoms you're trying to address could be tackled by some other way than trying to force the engine to run that cold. Bearing in mind that the stat might not be fully open until 15-20F above the nominal temperature, this may be a case of trying to setting unrealistic temperature targets rather than an actual cooling system problem.(snip)
I've ditched the remote bypass thermostat, and I'm using an 82C (180F) inline thermostat.
I'm not familiar with the Disco coolant system layout and I don't know which stat layout it had as standard or what you replaced it with. Do you have the bypass closed and unrestricted flow from the heads to the rad when the stat is fully open? If you have an open bypass (or significant flow through it) plus a partially closed stat this could be limiting your cooling capability.
What are the symptoms when the engine runs 'too hot' as you see it? Do you know what the oil temperature is when these symptoms occur? Extreme oil temperatures might lead to lubrication problems but if you're using the correct spec oil and keeping it within it's rated operating temperature range you shouldn't expect to see any problems. If you are seeing them, I wonder whether you might be better off trying a thicker oil or investigating oil pump / pressure relief valve related problems. Do you monitor the oil pressure?
I do not currently have gauges for oil temperature or pressure. I am able to monitor changes oil temperature, at least, by using an infrared thermometer to measure the outside temperature of the piping to the oil cooler. I have a pretty good idea of the delta-T across the pipe, so I can get pretty close that way.
But I never have to make that measurement when the oil is too hot except as confirmation--I can just listen to the lifters clattering at the rear cylinders! The Rover V8 has a known issue with starving the rear heads of oil when the oil gets thinned out, or at least that's my understanding. Hard experience and listening have taught me that if the oil temperature gets above 210F and stays there, it will soon go above 220F, and bad things start to happen if you do not give it a chance to cool off. The engine runs quietly and smoothly when the oil temperature is less than about 200F. I use 10W40 as per mfg spec. I have known people who use 10W50, but I don't think it really helps much when things get hot.
It is also a "feature" of the Rover V8 that you are likely to crack the block if coolant temperatures get into the 220F range. All in all, it's really best to keep the darn thing cool.
I have the remote bypass thermostat properly deleted. With a good 180F thermostat and the oil cooler, the coolant temperature runs between 187 and 194, as long as there's some humidity in the air and the temperature is 70*F or less. As I said, hot and dry conditions increase the coolant temperature required to reject the same amount of heat. I only know two ways to change that--increase surface area or increase coolant flow.
But I never have to make that measurement when the oil is too hot except as confirmation--I can just listen to the lifters clattering at the rear cylinders! The Rover V8 has a known issue with starving the rear heads of oil when the oil gets thinned out, or at least that's my understanding. Hard experience and listening have taught me that if the oil temperature gets above 210F and stays there, it will soon go above 220F, and bad things start to happen if you do not give it a chance to cool off. The engine runs quietly and smoothly when the oil temperature is less than about 200F. I use 10W40 as per mfg spec. I have known people who use 10W50, but I don't think it really helps much when things get hot.
It is also a "feature" of the Rover V8 that you are likely to crack the block if coolant temperatures get into the 220F range. All in all, it's really best to keep the darn thing cool.
I have the remote bypass thermostat properly deleted. With a good 180F thermostat and the oil cooler, the coolant temperature runs between 187 and 194, as long as there's some humidity in the air and the temperature is 70*F or less. As I said, hot and dry conditions increase the coolant temperature required to reject the same amount of heat. I only know two ways to change that--increase surface area or increase coolant flow.
KiaDiseasel said:
Engines can live quite happily with high metal temperatures and coolant above 90c but what you must avoid is localised, and especially general, boiling.
I think you mean *modern* engines can live quite happily with high metal temperatures. Which the aluminum Rover V8 is not. It was not designed with high temperatures in mind.Was your oil pump fully rebuilt when the engine was done? RV8 never have brilliant oil pressure at idle, because the pump, and the relief valve are pretty poor, and when worn, even worse! If oil temps of just 100C (212F) are causing clattery lifters, something if wrong! My old 5.6 comp safari buggy with a JE motor (sorry, can't remember what cam spec we ran it was 20 years ago....) used to often hit 125degC in the SUMP, let alone in the galleries, especially on slow low gear (ie high rev/load) stages. And that never clattered its hydraulic lifters!
Yes, oil pump was redone. It's only got 5000 miles on it. I've gotten this same behavior across three different engines, though. 100C won't do it, it's just that once the oil gets to that temperature something changes, and it continues to get hotter. The oil cooler has helped quite a bit, in that the oil will eventually cool off if I reduce the load--which it simply would not do with the factory remote bypass thermostat and no oil cooler.
How did you get your V8 to 125C without cracking the block? It's pretty well-understood in the Discovery crowd that coolant temperatures of 105C will crack the block.
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