Rover V8 cooling changes--EWP?

[GreenV8S]

neillr said:

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.

Rapid heat changes can damage engines, but I'm not aware of any problems with the RV8 tolerating sustained temperatures within the normal operating range (say 190F - 230F). Do you have any more details of this "feature"? We don't see much high altitude towing in the TVR community so you may be seeing problems that we don't encounter, but these engines don't have a reputation for heat related problems.

10W40 is nor particularly thick oil and if you have problems that point to low oil pressure when hot then using a thicker oil would seem like a sensible thing to try. These problems usually show up as low oil pressure at low revs and I wouldn't normally expect to hear mechanical noises change at higher revs (unless you're up in the region where lifters start to pump up, which surely won't be the case here) so if it was me I'd want to have a better idea of what's happening to the oil Ps and Ts. Adding a couple of extra temporary sensors seems relatively simple compared to the other mods you're talking about.

It still seems to me that the temperatures you're regarding as dangerously high are not particularly high and the difficulty you're having keeping the engine in your preferred temperature range may be due to the fact you're trying to keep it below the stat fully open temperature under heavy load under conditions where there is limited cooling.

By the way, I wouldn't trust the temp gauge readings unless you've calibrated it, and it's entirely possible that the engine is running hotter than you think and you do genuinely have an overheating problem - but taking those tempts at face value I'm not convinced you do.

[GreenV8S]

Also, do you have a polly-V ancillary drive belt on the front of the engine, and does the engine have a distributor?

[neillr]

If you check out a U.S.-centric Land Rover forum (we were't allowed to import the TD5 diesels), you will read an awful lot about blown head gaskets, cracked blocks, slipped liners, and clattering lifters on the 4.0L and 4.6L engines. I can't say for sure what is happening inside the coolant passages, but I've used a few different measurement techniques (including a borrowed infrared camera) to get the temperatures I've mentioned here.

There is a serpentine belt on the front of the engine, which drives the coolant pump/fan, A/C compressor, and steering pump. The ignition is through two sets of coils driven by the ECM. The coils have less than 5000 miles on them, and the computer is not detecting any misfiring, lean condition, etc. I tend to trust that, since the computer is a hypochondriac.

My reasoning for these modifications is that there's no reason NOT to run the engine as close to 180 as I can get, and plenty of reason to do so. I have personally had a liner slip on one engine after sustained running with coolant temperatures at about 100C. Coolant pressure was good, no leaks, no coolant loss--if there was boiling, it was not because of a pressure leak (at least until after the liner slipped). Also, my impression is that the idle gets rough when oil temperatures are above 200 or so. I didn't bring this up because I don't have data, but it has occurred to me to wonder whether the hydraulic lifters are working properly at those temperatures.

You probably have a good point about getting direct measurement of the oil temperature and pressure before installing more stuff. I'll have to look into one of those sandwich fittings that goes under the oil filter.

I agree, my preferred range of 180F to 190F is difficult to achieve with the available choices of thermostat. I have found that the 180F Stant Superstat opens rapidly enough to do a pretty good job. I would like to try a Robertshaw balanced 180F thermostat which opens even faster, but I haven't found a housing that will work yet.

[anonymous-user]

neillr said:

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.

No idea, we just stuck the engine in when it arrived from JE, and drove it like we stole it for 3 seasons in the AWD club, including winning our class in two of them ;-) Never had any significant engine issues, although we did loose all the coolant once, however that was due to me driving into a large tree at about 30mph (pretty much the only tree on Salisbury plain as it happens........... ;-)

[neillr]

Sorry, who or what is JE? Which type of block was this?

I'm also sadly familiar with vindictive flora.

[stevieturbo]

neillr said:

Sorry, who or what is JE? Which type of block was this?

I'm also sadly familiar with vindictive flora.

At a guess ?

http://johnealesroverv8.co.uk/

[neillr]

Wow, very nice. Perhaps I should have had them do the short block for my rebuild.

[GreenV8S]

neillr said:

There is a serpentine belt on the front of the engine, which drives the coolant pump/fan, A/C compressor, and steering pump. The ignition is through two sets of coils driven by the ECM.

That indicates that you have a full serpentine front end on it which means you have a very good water pump and oil pump as standard. (I can't imagine there are many pre-serpentine 4.6s in production Land Rovers, but it was worth checking.)

[100SRV]

I've experienced cooling problems with Rover V8 and the cure seems to be:
1. Better radiator
2. Moving the hot air away from the radiator

In my application I have an Allisport radiator which was designed specifically for Tomcat Motorsport and has been used with 5.0 litre RV8 in competition trucks.

The air movement is taken care of by two cowled electric cooling fans wired in series-parallel and controlled by an X-Eng bottom hose adaptor which takes an Intermotor thermal switch.

These thermal switches are available in a range of settings, two I've used are:

• Stock part supplied with the adaptor is 50091 which has

first contact closed at 88 and open at 83
second contact closed at 92 and open at 87

• mine is now part number 50101*

First close 84 open 79
Second close 88 open 83

The series-parallel wiring gives fans at half-speed (series) when the first contact closes and full speed when the second contact closes. I've never reached a condition where the second contact has closed.

There is a manual control switch which allows Off (fording) Auto and Full speed
Also I have a red warning light showing that there is need for the fan and a blue one (wired across the fans) showing whether the fans are running or not.
Red only = check for faults
Red and blue = OK
Blue = fans freewheeling in airflow

• Edit to correct the switch part numbers.

Edited by 100SRV on Wednesday 26th October 18:57

[neillr]

Thanks for that info 100SRV. Especially the details on your bottom hose adapter and thermostat wiring. I have a similar three-fan setup on my Jeep, I think I'll use your wiring ideas.

I'm going to get some more data on oil temperatures, and think about everyone's input here. I may very well end up buying an Allisport radiator.

Edited by neillr on Wednesday 26th October 19:22

[100SRV]

neillr said:

Thanks for that info 100SRV. Especially the details on your bottom hose adapter and thermostat wiring. I have a similar three-fan setup on my Jeep, I think I'll use your wiring ideas.

I'm going to get some more data on oil temperatures, and think about everyone's input here. I may very well end up buying an Allisport radiator.

Edited by neillr on Wednesday 26th October 19:22

You are welcome.
Would you like a wiring diagram?

[neillr]

100SRV said:

Would you like a wiring diagram?

Sure, if it's no bother.

[chammyman]

Unfortunately I deal with a lot of these things.

I even have a 2004 D2 v8.

Business partner has a P38 4.0.

The electric fan is rarely on. Its only active if the external temp is over 28 degrees c and the road speed is under 50mph. If it comes on if the ecu detects engine overheat it will stay on until its reset by software. Most in the uk are totally seized and do not work. Its not a big issue here really. Is yours working and free to rotate?

The remote bulb thermostat setup is pretty good they went to this as its a more stable balance throughout the engine. In pipe ones I'm not a fan of.

Main causes of them overheating in my experience is caused by the following;

Big fog lights/light bars on the bumper. I have seen 6 giant cibies fitted 4 above the bumper and 2 under. These killed the airflow through into the radiator.

Crudded up cooling system. Not helped by sometimes the blocks being filled with sand from casting still.

If its ever been used offroad especially wading the gap between the condenser and the radiator will be filled with mud and debris.

The radiator shroud either damaged or missing. This is a common issue if any works been done at the front.

Viscous fan being worn out, not locking up and thus not flowing enough air.

Water pump gouging the front cover and killing coolant flow. Also the water pump needs the metal blades on the closed back impeller not the cheap folded blades.

The oil pump, you say its new is that a new gearset or a new complete housing? If just a gearset the housing may be well gouged. Also if just gears the outer ring may have cracked. I have never pulled one off thats not been cracked.

The oil pump housing has 2 relief valves these stick.

You say you got top hat liners installed, was that all or did you get new cam bearings and core plugs installed? Cam bearings can reduce oil feed and theres a plug that can be knocked to far in again reducing flow.

[neillr]

chammyman:

I disagree about the remote bypass thermostat. In theory it's an improvement, and it probably would have been an improvement if they'd put it in the top radiator hose so that the pellet always gets the full flow of hot coolant (like some Cadillacs used to do). In practice, I suspect that at low RPMs, the flow of hot coolant through the bypass and past the pellet is insufficient to keep the thermostat fully open. My engine temperatures are much more consistent with the inline thermostat.

My electric fan turns on with the A/C, at low speeds. I have verified that it does this and is functional.

The timing cover (and integrated oil pump cover) is new, as well as the gears. The top-hat liners came in a completely rebuilt short block, including new camshafts and bearings. All the other items you mention are either new or recently rebuilt.

I do not have any obstructions to the airflow through the radiator, and the shrouding is all in perfect condition.

[GreenV8S]

neillr said:

I suspect that at low RPMs, the flow of hot coolant through the bypass and past the pellet is insufficient to keep the thermostat fully open.

The Land Rover entry stats are designed to control the pump inlet temperature so they are normally rated slightly cooler than an old-style engine outlet stat. It's a very clever design and very effective in my experience. Personally, I much prefer that over an old-style top stat.

[neillr]

GreenV8S said:

The Land Rover entry stats are designed to control the pump inlet temperature so they are normally rated slightly cooler than an old-style engine outlet stat. It's a very clever design and very effective in my experience. Personally, I much prefer that over an old-style top stat.

My experience is that it is very effective at warming the engine up to operating temperature and holding it there under light load and benign ambient conditions. But once you've worked it hard for a while, it is not very effective at cooling the engine back down. Of course, I changed out the thermostat before I added the oil cooler, which might make a difference.

[GreenV8S]

neillr said:

once you've worked it hard for a while, it is not very effective at cooling the engine back down

Well that's odd. Plumbed in correctly, the entry stat should give an unrestricted bypass and closed rad when the engine is cold, and a closed bypass and unrestricted flow to the rad when the engine is hot. It's hard to see what more a stat could do to give you maximum possible cooling.

[neillr]

GreenV8S said:

Plumbed in correctly, the entry stat should give an unrestricted bypass and closed rad when the engine is cold, and a closed bypass and unrestricted flow to the rad when the engine is hot. It's hard to see what more a stat could do to give you maximum possible cooling.

It should do that. I don't believe that it does. My understanding is that it depends on having some flow through the bypass to heat the thermostat pellet and keep the thermostat open. If the differential pressure across the bypass valve is small (for example, at low revs, when the pump is not working at capacity), perhaps there is not enough flow to keep the thermostat open.

Anyway, why would you want to have ANY bypass flow when you're trying to reduce the engine temperature?

[anonymous-user]

er, the thermostat is a TEMPERATURE dependent valve, and not a FLOW or PRESSURE dependent one!

In basic cars, like your LR, they are simply a little rubber sack full of wax, which expands a lot when it gets hot, this presses on a pin, that sticks further out an pushes the stat valve open. The hotter the wax, the more open the stat. OEMs moved to inlet stats because they prevent excessive thermal cycling during warm up, which is a bad thing, and leads to things like early head gasket failure etc




Bypass flow is important for ensuring that no localised hot spots occur within the engine structure, and hence you can have bypass flow even with a "hot" engine (many cars use the cabin heater loop as the bypass btw)

[100SRV]

neillr said:

Sure, if it's no bother.

I can email you a PDF if you wish?