Pinto overheating issues, temp sensor
Discussion
Yes, I know, there are lots of threads on this already 
I'm working my way through them...
But I have at least one question which I can't seem to find covered anywhere.
Background: NG Henley kitcar, based on (I think) a Mark IV Cortina. I didn't build it, and it has been through several hands before me, so I have no access to the original build material. 2.0l Pinto with no tuning mods.
Car is running hot, and gets progressively hotter. No apparent coolant leaks, but on a long (100 mile+) run I can lose 50-100ml, especially if I have to sit in town traffic for too long. I'm going through the standard checks one by one, but I also seem to have a problem with the temp sensor & gauge (Smiths), probably made worse by some heavy handed fumbling behind the dash a couple of weeks ago (which I'll be investigating / rectifying later).
So, my questions/issues.
The temp sensor is not fully threaded into the block. There is maybe 5mm of thread still showing, and I can't get it any further. Being brass I'm reluctant to push it too hard. The original was badly corroded and has been replaced but neither would go all the way in. Should it be fully threaded in?
If so, it's an awkward spot to get a tap in the hole without moving the distributor, so I've acquired a matching new HT bolt which I was planning to nick across the first few threads and insert to clean the hole threads. Sensible or dangerous?
My Smiths temp gauge needs a voltage regulator (which I have) to run at 10v. But the illumination bulb runs at 12v. Is there a problem with them sharing a common earth? Should the gauge be earthed back to the regulator?
Any advice, thoughts etc gratefully received.
I'm working my way through them...But I have at least one question which I can't seem to find covered anywhere.
Background: NG Henley kitcar, based on (I think) a Mark IV Cortina. I didn't build it, and it has been through several hands before me, so I have no access to the original build material. 2.0l Pinto with no tuning mods.
Car is running hot, and gets progressively hotter. No apparent coolant leaks, but on a long (100 mile+) run I can lose 50-100ml, especially if I have to sit in town traffic for too long. I'm going through the standard checks one by one, but I also seem to have a problem with the temp sensor & gauge (Smiths), probably made worse by some heavy handed fumbling behind the dash a couple of weeks ago (which I'll be investigating / rectifying later).
So, my questions/issues.
The temp sensor is not fully threaded into the block. There is maybe 5mm of thread still showing, and I can't get it any further. Being brass I'm reluctant to push it too hard. The original was badly corroded and has been replaced but neither would go all the way in. Should it be fully threaded in?
If so, it's an awkward spot to get a tap in the hole without moving the distributor, so I've acquired a matching new HT bolt which I was planning to nick across the first few threads and insert to clean the hole threads. Sensible or dangerous?
My Smiths temp gauge needs a voltage regulator (which I have) to run at 10v. But the illumination bulb runs at 12v. Is there a problem with them sharing a common earth? Should the gauge be earthed back to the regulator?
Any advice, thoughts etc gratefully received.
If it threads into the hole well enough to seal it, that should be sufficient. I assume the far end of the hole is open to the water jacket, and it should not make any significant difference how far in the sensor goes as long as it is wetted by moving coolant. I would not go retapping unless you know what the thread is - I don't know that engine, but if this sensor used a tapered thread then retapping it could make matters worse.
Given that the gauge uses a regulated supply on the positive side, I'd expect the negative side to be grounded. Neither side should be taking any significant current or carrying any HF signals so I wouldn't expect any problem with them sharing a ground connection.
If you have suspected overheating problems and are not sure the gauge is accurate, I suggest checking the gauge against the actual coolant temperature should be your first step. As a rough check you can simply choose a metal pipe/housing not solidly connected to anything, such as the outlet spigot from a stat housing, put a thermometer in contact with it and wrap it in insulation to minimise external heat loss. That will give you a temperature reading pretty close to the coolant temperature at that point in the circuit. Preferably measure it somewhere close to the gauge sender - if the gauge is reading the temperature at the top of the engine, anywhere between the engine outlet and the rad inlet would probably be OK.
Given that the gauge uses a regulated supply on the positive side, I'd expect the negative side to be grounded. Neither side should be taking any significant current or carrying any HF signals so I wouldn't expect any problem with them sharing a ground connection.
If you have suspected overheating problems and are not sure the gauge is accurate, I suggest checking the gauge against the actual coolant temperature should be your first step. As a rough check you can simply choose a metal pipe/housing not solidly connected to anything, such as the outlet spigot from a stat housing, put a thermometer in contact with it and wrap it in insulation to minimise external heat loss. That will give you a temperature reading pretty close to the coolant temperature at that point in the circuit. Preferably measure it somewhere close to the gauge sender - if the gauge is reading the temperature at the top of the engine, anywhere between the engine outlet and the rad inlet would probably be OK.
Edited by GreenV8S on Monday 11th June 16:54
Ahhhhh. That would explain things. I spec'd the bolt based on the spec of the sensor (which was marked as M10 1mm). So that would suggest I need the older(?) spec sensor which is npt. Glad I didn't tap that hole.... thanks
Edit: So I've been out to have a closer look at the engine, the sensors etc.
Engine number begins UR, which the Burton Power chart tells me is a Oct 1978 Build. The casting number is 2.0 70HM6015B-A.
Now it gets interesting. The temp sensor that was on the car when I got it, and the replacement one that I fitted (neither of which fully screw down) have YELLOW rings, which the BurtonPower site suggests are the 1/8NPT version. The original part number for this is 1701341. Fishing around I can find versions with this same part number that are M10 1mm and 1/8NPT, but with no consistency on colour, See https://www.buycarparts.co.uk/oen/1701341?gadw=1&a... for example
So is it possible that I'm trying to put a 1/8NPT sensor into a M10 hole, rather than the other way around as previously suggested? Would both yield the same result?
One bit I don't understand is that I must have read that the thread on the part I bought was M10/1, because I definitely didn't measure it, and I was very specific looking for the HT bolts. The ebay item listing no longer exists, and the supplier now doesn't list anything equivalent.
Edit: So I've been out to have a closer look at the engine, the sensors etc.
Engine number begins UR, which the Burton Power chart tells me is a Oct 1978 Build. The casting number is 2.0 70HM6015B-A.
Now it gets interesting. The temp sensor that was on the car when I got it, and the replacement one that I fitted (neither of which fully screw down) have YELLOW rings, which the BurtonPower site suggests are the 1/8NPT version. The original part number for this is 1701341. Fishing around I can find versions with this same part number that are M10 1mm and 1/8NPT, but with no consistency on colour, See https://www.buycarparts.co.uk/oen/1701341?gadw=1&a... for example
So is it possible that I'm trying to put a 1/8NPT sensor into a M10 hole, rather than the other way around as previously suggested? Would both yield the same result?
One bit I don't understand is that I must have read that the thread on the part I bought was M10/1, because I definitely didn't measure it, and I was very specific looking for the HT bolts. The ebay item listing no longer exists, and the supplier now doesn't list anything equivalent.
Edited by StrickoNG on Monday 11th June 22:08
If you're losing water then you have a leak. This in turn will lower the pressure in the system.
Worth pressure testing to see if anything is obvious. Tiny leaks can be difficult to detect as when hot the water evaporates instantly & there may be no tell-tale staining.
Something often overlooked is the radiator/expansion tank cap. Had a similar issue on my RRC some years ago - gauge slightly higher than normal & small coolant loss. No pressure drop when rad cap type pressure tester connected. I have one of the pressure/vacuum pumps & connecting this to a small hose showed that a 15psi cap was releasing at less than 10psi. A new one restored normality.
Worth pressure testing to see if anything is obvious. Tiny leaks can be difficult to detect as when hot the water evaporates instantly & there may be no tell-tale staining.
Something often overlooked is the radiator/expansion tank cap. Had a similar issue on my RRC some years ago - gauge slightly higher than normal & small coolant loss. No pressure drop when rad cap type pressure tester connected. I have one of the pressure/vacuum pumps & connecting this to a small hose showed that a 15psi cap was releasing at less than 10psi. A new one restored normality.
First off, do you actually know what sort of temps you're really getting? IR thermometers are <£10. They're essential for mucking about with cooling systems.
Then sort the basics - is the 'stat behaving properly? Is the rad flowing properly? No airlocks?
If it's getting hotter over time, then what's the score with the fan? Electric or mechanical? If electric, how's it switched? If mechanical, is it permanent or viscous, and is the viscous hub behaving? What about shrouding to the rad?
How's excess heat getting out of the engine bay?
You say you're losing coolant. Where from? The header's overflowing and spitting it out the overflow? Is the pressure cap good?
The gauge/sender and their potential mismatch is just affecting the information you're getting. That's not causing any actual problem you've got, unless the sender's actually leaking.
Then sort the basics - is the 'stat behaving properly? Is the rad flowing properly? No airlocks?
If it's getting hotter over time, then what's the score with the fan? Electric or mechanical? If electric, how's it switched? If mechanical, is it permanent or viscous, and is the viscous hub behaving? What about shrouding to the rad?
How's excess heat getting out of the engine bay?
You say you're losing coolant. Where from? The header's overflowing and spitting it out the overflow? Is the pressure cap good?
The gauge/sender and their potential mismatch is just affecting the information you're getting. That's not causing any actual problem you've got, unless the sender's actually leaking.
Thanks for the responses so far. Hands up, I'm a real beginner with all this, so the basic stuff is all invaluable to me, and I'll admit to a tendency to jump to conclusions too early. Little knowledge, dangerous thing etc.
I didn't realise that IR Thermometers were so cheap, I've just ordered one!
It's a mechanical fan, non viscous, with a shroud. Engine bay is very open at the bottom, and the bonnet side panel (1930's roadster style) are heavily vented. Tank cap is less than a year old, and there is no apparent damage. There is no expansion or overflow tank. Coolant looks cleer, with no sludge, but I will be flushing it when I get a chance. As for leakage., I've just done an 2 week, 1800 mile road trip in the car. Most days, there was no apparent leakage. I only needed to top it up (50-100ml at most) on days where I had been stuck in traffic. But I'll see if I can borrow a pressure test kit.
I'm working my way through various stuff. Air lock could be an issue, but the heater matrix is getting hot water. But it may be the high point of the coolant system.
I'll be back later in the week once I've had chance to put the thermometer on it. Thanks again
I didn't realise that IR Thermometers were so cheap, I've just ordered one!
It's a mechanical fan, non viscous, with a shroud. Engine bay is very open at the bottom, and the bonnet side panel (1930's roadster style) are heavily vented. Tank cap is less than a year old, and there is no apparent damage. There is no expansion or overflow tank. Coolant looks cleer, with no sludge, but I will be flushing it when I get a chance. As for leakage., I've just done an 2 week, 1800 mile road trip in the car. Most days, there was no apparent leakage. I only needed to top it up (50-100ml at most) on days where I had been stuck in traffic. But I'll see if I can borrow a pressure test kit.
I'm working my way through various stuff. Air lock could be an issue, but the heater matrix is getting hot water. But it may be the high point of the coolant system.
I'll be back later in the week once I've had chance to put the thermometer on it. Thanks again
StrickoNG said:
Tank cap is less than a year old
That makes it more, not less suspicious. Cheap and nasty s
te.Can you get your hand to the rad core as the engine warms up? It should be cold until the 'stat opens, then evenly getting warm (then hot) all over. The IR will give a better indication, but that'll give you a good guess as to whether there's any claggy bits in there or the 'stat isn't playing.
But if you covered a good mileage in warm weather without too much problem, I think the iffy gauge is just making you paranoid.
As for the earths - a shared earth between the regulated and unregulated voltages is fine. Have you got a multimeter on there to see what's what?
The gauge is no way calibrated. The sender turns a certain temp to a certain resistance. The gauge turns a certain current to a certain movement. Crappy wiring, poor earths, wrong voltage - they can all cause shenanigans. Really, all it's telling you is "Where is the needle now, compared to normal for this precise combo of bits".
StrickoNG said:
Thanks for the responses so far. Hands up, I'm a real beginner with all this, so the basic stuff is all invaluable to me, and I'll admit to a tendency to jump to conclusions too early. Little knowledge, dangerous thing etc.
I didn't realise that IR Thermometers were so cheap, I've just ordered one!
It's a mechanical fan, non viscous, with a shroud. Engine bay is very open at the bottom, and the bonnet side panel (1930's roadster style) are heavily vented. Tank cap is less than a year old, and there is no apparent damage. There is no expansion or overflow tank. Coolant looks cleer, with no sludge, but I will be flushing it when I get a chance. As for leakage., I've just done an 2 week, 1800 mile road trip in the car. Most days, there was no apparent leakage. I only needed to top it up (50-100ml at most) on days where I had been stuck in traffic. But I'll see if I can borrow a pressure test kit.
I'm working my way through various stuff. Air lock could be an issue, but the heater matrix is getting hot water. But it may be the high point of the coolant system.
I'll be back later in the week once I've had chance to put the thermometer on it. Thanks again
Are you topping it up too much, some expansion space needed. Try just keeping an eye on it without topping up it may have just found it's natural level. I didn't realise that IR Thermometers were so cheap, I've just ordered one!
It's a mechanical fan, non viscous, with a shroud. Engine bay is very open at the bottom, and the bonnet side panel (1930's roadster style) are heavily vented. Tank cap is less than a year old, and there is no apparent damage. There is no expansion or overflow tank. Coolant looks cleer, with no sludge, but I will be flushing it when I get a chance. As for leakage., I've just done an 2 week, 1800 mile road trip in the car. Most days, there was no apparent leakage. I only needed to top it up (50-100ml at most) on days where I had been stuck in traffic. But I'll see if I can borrow a pressure test kit.
I'm working my way through various stuff. Air lock could be an issue, but the heater matrix is getting hot water. But it may be the high point of the coolant system.
I'll be back later in the week once I've had chance to put the thermometer on it. Thanks again
Spoke to the nice folks at BurtonPower about the sensor. They made the same point about it not needing to thread all the way in, so I'm parking that one for the mo. But I may have the wrong colour top......
I've had a good look at the gauges today, and there were a couple of minor things, which I've queried with whoever it is owns the rights to Smiths these days. I've 2 bi-metal gauges, which both are connected to the correct voltage regulator. One had an earth wire to the casing, which is not required, as bi-metals should earth through their respective senders. At least one (not sure about the other) had a metal bulb holder with a single wire, which therefore is earthing through the casing. Smiths now ship with plastic bulb holders, with 2 wires, isolating the illumination from the casing and the workings. Might be nothing , but it might explain some odd behavior on the temp gauge when I put the lights on.... Earth leads and old bulb holders removed, new plastic ones ordered. Hopefully that will let me see how well the gauge is calibrated, once the IR arrives.
The rad is old school, with a pressure cap, and just a plastic overflow pipe. The cap does not look like an expensive model, and I may well have been overfilling..... Something else learnt today. Anyone got an idea what sort of pressure rating I should be looking for when I buy a new cap?
Why do I think it's overheating? I think I had a vapour lock which stopped the engine from idling after a lengthy traffic hold up, with the gauge over 140 AND the heater running flat out, belching very very hot air. When gauge showing just under 140, it continued to turn over for a second or 2 after the power was cut. One of the other drivers on the run had a lot of experience of 1970's engines and immediately pointed to overheating.
But if the IR comes back and tells me it's all fine, I'll be happy as Larry.
Once again, thanks for all the input.
Working tomorrow
I've had a good look at the gauges today, and there were a couple of minor things, which I've queried with whoever it is owns the rights to Smiths these days. I've 2 bi-metal gauges, which both are connected to the correct voltage regulator. One had an earth wire to the casing, which is not required, as bi-metals should earth through their respective senders. At least one (not sure about the other) had a metal bulb holder with a single wire, which therefore is earthing through the casing. Smiths now ship with plastic bulb holders, with 2 wires, isolating the illumination from the casing and the workings. Might be nothing , but it might explain some odd behavior on the temp gauge when I put the lights on.... Earth leads and old bulb holders removed, new plastic ones ordered. Hopefully that will let me see how well the gauge is calibrated, once the IR arrives.
The rad is old school, with a pressure cap, and just a plastic overflow pipe. The cap does not look like an expensive model, and I may well have been overfilling..... Something else learnt today. Anyone got an idea what sort of pressure rating I should be looking for when I buy a new cap?
Why do I think it's overheating? I think I had a vapour lock which stopped the engine from idling after a lengthy traffic hold up, with the gauge over 140 AND the heater running flat out, belching very very hot air. When gauge showing just under 140, it continued to turn over for a second or 2 after the power was cut. One of the other drivers on the run had a lot of experience of 1970's engines and immediately pointed to overheating.
But if the IR comes back and tells me it's all fine, I'll be happy as Larry.
Once again, thanks for all the input.
Working tomorrow
Edited by StrickoNG on Tuesday 12th June 23:22
StrickoNG said:
I've 2 bi-metal gauges, which both are connected to the correct voltage regulator. One had an earth wire to the casing, which is not required, as bi-metals should earth through their respective senders. At least one (not sure about the other) had a metal bulb holder with a single wire, which therefore is earthing through the casing. Smiths now ship with plastic bulb holders, with 2 wires, isolating the illumination from the casing and the workings. Might be nothing , but it might explain some odd behavior on the temp gauge when I put the lights on.... Earth leads and old bulb holders removed, new plastic ones ordered. Hopefully that will let me see how well the gauge is calibrated, once the IR arrives.
I suspect you'll find the gauge isn't very well earthed, so is earthing back through the illumination.StrickoNG said:
The rad is old school, with a pressure cap, and just a plastic overflow pipe. The cap does not look like an expensive model, and I may well have been overfilling..... Something else learnt today. Anyone got an idea what sort of pressure rating I should be looking for when I buy a new cap?
Whatever the engine wants, would be my starting point.StrickoNG said:
Why do I think it's overheating? I think I had a vapour lock which stopped the engine from idling after a lengthy traffic hold up, with the gauge over 140 AND the heater running flat out, belching very very hot air. When gauge showing just under 140, it continued to turn over for a second or 2 after the power was cut. One of the other drivers on the run had a lot of experience of 1970's engines and immediately pointed to overheating.
140degC or 140degF?140degF is only 60degC, way below where the stat should be opening. 140degC is clearly ludicrously WAAAAAAAY past boiling point... So we know the gauge is lying, whatever the calibration.
The vapour lock is most likely fuel, not cooling.
The gauge is definitely lying, and lying a lot.......
First play with the IR thermometer yesterday, after a 35 minute drive back from work, mixed country and urban. Left standing for 10 mins while I retrieved the parcel and but the battery in....
Gauge was just below the line half way between 90 and 140..... (degrees C)
Thermometer read (by the sender)... (Drum roll).... 78 degrees C. Also read the same on top of rad.
Thought this was a bit odd, so checked the thermometer calibration (with a boiling kettle) and it was spot on.
So the gauge is definitely not telling the truth. I've ordered a new sensor which is described as being for Smiths gauges....
Conclusion: maybe the car is not overheating in normal running, but it gets very hot very quickly in traffic. Next steps are to flush the system, check the thermostat and fit an electric fan.....
Thanks for all the help
First play with the IR thermometer yesterday, after a 35 minute drive back from work, mixed country and urban. Left standing for 10 mins while I retrieved the parcel and but the battery in....
Gauge was just below the line half way between 90 and 140..... (degrees C)
Thermometer read (by the sender)... (Drum roll).... 78 degrees C. Also read the same on top of rad.
Thought this was a bit odd, so checked the thermometer calibration (with a boiling kettle) and it was spot on.
So the gauge is definitely not telling the truth. I've ordered a new sensor which is described as being for Smiths gauges....
Conclusion: maybe the car is not overheating in normal running, but it gets very hot very quickly in traffic. Next steps are to flush the system, check the thermostat and fit an electric fan.....
Thanks for all the help
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