1984 Turbo Esprit overheating after 48 hours of ownership! Seriously worried!

[Andyww]

Removing the thermostat should be a last resort, its a big task, but if you do, in order to test it you have to put the whole housing in a big pan of water and boil it up and wait a few mins. Even if its working properly it wont open if you simply pour hot water into it.

Presumably you have bled the rad, it sounds like an air lock. The gauge can read high in this case as the sender can be out of the water flow so it is measuring the temperature of steam in the pipe instead. With the filler cap off try violently squeezing the left hand rad hose which can be reached through the LH wheelarch as this can sometimes dislodge air pockets and make a big glugging noise then you can top up.

Jacking up the front or rear of the car can help also, and open rad bleed tap. If the air lock is really persistent it could be air getting into the system. These cars are unfortunately very prone to pinhole leaks in the cooling system if the aluminium pipes have not been checked/replaced.

There are two versions of the Otter switch with different temperatures, manual covers these. but in normal driving the fans dont come on usually. Only when stuck in traffic, stationary.

Infra red gauges dont indicate water temperature so I am not sure they are worth bothering with. Not sure why the gauge was reading 60 when sender in boiling water. Doesnt sound right but its wrong in the opposite way to expected. The gauges do go out of whack, even mounting the mechanical voltage regulator the wrong orientation can cause them to be 15 degrees out.

[GreenGoddess]

Thanks Andy. I won’t be removing the thermostat unless I absolutely have to. As you mentioned, it seems to be a big job. 
 

I will try bleeding the system next week when I get chance. I may as well replace the coolant temp sensor as they are cheap and easy to replace. 

[TAR]

15 hours ago, Andyww said:

Even if its working properly it wont open if you simply pour hot water into it.

I was able to successfully test mine using this method. With the water is at boiling point the stat crept open and let the water through. Addition of cold water then closed it.  

[GreenGoddess]

Today I installed a new coolant temp sensor, topped up the coolant and took it for a good 30 minute drive. The temperature gauge sat perfectly steady at just under 90 degrees for the entire trip and warmed up a little bit more when it was parked back in the garage with the engine running. 
I still have no idea why the gauge shot up to nearly 140 degrees when I first drove it. I doubt it was the coolant temp sensor, but at least the car seems to be running fine now which is a huge relief for me. 
Thank you to everyone who contributed to this thread. I have learnt a huge amount about the car from this. 😊

[ekwan]

On 06/09/2022 at 19:52, GreenGoddess said:

Today I installed a new coolant temp sensor, topped up the coolant and took it for a good 30 minute drive. The temperature gauge sat perfectly steady at just under 90 degrees for the entire trip and warmed up a little bit more when it was parked back in the garage with the engine running. 
I still have no idea why the gauge shot up to nearly 140 degrees when I first drove it. I doubt it was the coolant temp sensor, but at least the car seems to be running fine now which is a huge relief for me. 
Thank you to everyone who contributed to this thread. I have learnt a huge amount about the car from this. 😊

Coolant sensors fail in weird ways. The one on my Elise would never exceed 65 degrees 🤣

[drdoom]

We call that "Kwality - With A Capital K !! "

[GreenGoddess]

So it happened again this afternoon. Temp gauge sat perfectly at 90 degrees during a 35 minute drive. Stopped for a coffee and a sit down for 15 minutes then as soon as we set off the temp gauge was rocketing up towards 140 degrees. The fans did not come on. 
 

I turned off the engine and let the car cool down for 10 minutes. Then I drove back home. At one point I noticed the temp gauge AND fuel gauge drop towards minimum which would indicate that the voltage regulator is faulty. The temp stayed at 90 degrees for the remainder of the journey home. 
 

I am therefore going to have to change the voltage regulator in the hope that it’s the root of the problem. Where is it? Is it a simple job?

[Andyww]

Definitely get a solid state one. You can either make one using a suitable semiconductor voltage regulator or there are ready-made ones on Ebay. Its mounted to one of the instrument fixing nuts in the binnacle so you have to loosen the side panels, and move the main panel forwards to access it, going in through the right side. The earth to it must be good.

[Andyww]

On 31/08/2022 at 20:05, TAR said:

I was able to successfully test mine using this method. With the water is at boiling point the stat crept open and let the water through. Addition of cold water then closed it.  

Never got mine to open off the car using that method. It was Pete at PNM who said the whole thing needs to be in boiling water to open and mine did open using that method. I think there are different temp spec versions.

[GreenGoddess]

Thanks Andy, I’ll have a look around for a solid state voltage regulator. 
Regarding the thermostat, am I correct in assuming that the pipe near the radiator that houses the otter switch will remain cold until the thermostat opens? If so, would that be an easy way to test that the thermostat is working? ie feel the pipe to see if it suddenly gets warm?

[Andyww]

Yes thats right, when closed the water is diverted through a bypass route under the engine.

[GreenGoddess]

20 minutes ago, Andyww said:

Yes thats right, when closed the water is diverted through a bypass route under the engine.

Excellent! Thank you. 

[GreenGoddess]

17 hours ago, Andyww said:

Definitely get a solid state one. You can either make one using a suitable semiconductor voltage regulator or there are ready-made ones on Ebay. Its mounted to one of the instrument fixing nuts in the binnacle so you have to loosen the side panels, and move the main panel forwards to access it, going in through the right side. The earth to it must be good.

Is this the thing I need Andy? https://www.ebay.co.uk/itm/282642726457

[Andyww]

Yes thats it.

[GreenGoddess]

2 hours ago, Andyww said:

Yes thats it.

Thank you 🙏 

[Lotusfab]

I spent months messing around on my Turbo when the gauge was reading about 110degrees. I changed everything and the fault was the gauge calibration. Its very easy to check in minutes. Have a look at my restoration blog where I give you the method to check it. When a Turbo is working perfectly the gauge never goes beyond 95 degrees in any external temperature. If it does something is wrong with the system. Mine sits at 75 degrees when moving, even in 35 degrees ambient. When stopped it rises slowly to 85 degrees the fans turn on and it drops to about 80 degrees. Fans turn off and the temperature cycles quite happily, reaches about 90 degrees maximum. It operated all day in plus 35 degrees for the Bond vivant movie, no issues. The gauge calibration is easy to check so do it before spending any money. After that is the gauge is correct expand the fixes. Solid state regulator, thermostat, radiator etc. If the thermostat is original its almost certainly not working properly. Buy one that I sourced which are very good quality and now sold buy lotusbits. If you read my blog I go through everything on the car in detail.

[GreenGoddess]

2 hours ago, Lotusfab said:

I spent months messing around on my Turbo when the gauge was reading about 110degrees. I changed everything and the fault was the gauge calibration. Its very easy to check in minutes. Have a look at my restoration blog where I give you the method to check it. When a Turbo is working perfectly the gauge never goes beyond 95 degrees in any external temperature. If it does something is wrong with the system. Mine sits at 75 degrees when moving, even in 35 degrees ambient. When stopped it rises slowly to 85 degrees the fans turn on and it drops to about 80 degrees. Fans turn off and the temperature cycles quite happily, reaches about 90 degrees maximum. It operated all day in plus 35 degrees for the Bond vivant movie, no issues. The gauge calibration is easy to check so do it before spending any money. After that is the gauge is correct expand the fixes. Solid state regulator, thermostat, radiator etc. If the thermostat is original its almost certainly not working properly. Buy one that I sourced which are very good quality and now sold buy lotusbits. If you read my blog I go through everything on the car in detail.

Thank you. I am beginning to think that it might be the thermostat sticking closed. Both times this "overheating" has happened after starting the car with an already hot engine. I'm wondering if the thermostat closes after turning the engine off for 10 minutes and then takes ages to reopen after starting the car again. But, yes, I suppose it could also be the gauge giving misleading readings, especially as I noticed the fuel gauge and temp gauge dropping simultaneously yesterday briefly. 

When my car is working properly, the temperature gauge stays bang on 90 degrees all the time. The fans on my car have never come on, even when the temp is reading close to 140 degrees. I know the fans definitely work but I haven't confirmed that the otter switch is working properly yet. I am guessing your car may have a thermostat for warmer climates installed, that may explain why your fans come on at 85 degrees?

Do you have a link to your blog so that I can find out how to calibrate the gauge?
 

[Andyww]

The gauge can be tested by removing the sender , connect earth to it and put in boiling water in a kettle and check the gauge reads 100.

It is possible to recalibrate the gauge, I have done it, on the bench but its not worth doing lightly.

If its still erratic after replacing the VR, its likely to be an air lock. They can be persistent. Or could be the thermostat as suggested, wax stats rarely last almost 40 years. 

Another thing to check is the small vent hose which comes off the large pipe next to the sender. Make sure its not blocked and has a run which doesnt dip right down before it reaches the header tank.

[GreenGoddess]

Thanks again. I did test the sender unit in boiling water but I could only get it to read 60 degrees on the gauge which was surprising. They are so cheap and easy to replace that I fitted a new one anyway. But the problem still came back. 
The first time the car “overheated”, the level in the header tank dropped afterwards which would also suggest an air lock. 
If I get time today I will jack the car up at the rear and try giving all the pipes a good squeeze to see if I can free any trapped air. 
The car had an engine rebuild 550 miles ago (before I bought it) so there is a good chance that it could be an air lock as the coolant would obviously have been refilled at the time of the rebuild. 

[Andyww]

If the gauge is off though the sender is the least likely cause, more likely is gauge or voltage reg.

But yes, if the engine has been out, air lock is prime suspect of the issue.

[GreenGoddess]

I don’t suppose there is a way to tell if the car has ever had a new thermostat fitted?

[Barrykearley]

Have you warmed the car up and cracked off the bleed on the top of the radiator??

[GreenGoddess]

3 hours ago, Barrykearley said:

Have you warmed the car up and cracked off the bleed on the top of the radiator??

Not yet. I will do that before I give the pipes a good squeeze. Haven’t had the time today. 👍

[Lotusfab]

9 hours ago, GreenGoddess said:

Thanks again. I did test the sender unit in boiling water but I could only get it to read 60 degrees on the gauge which was surprising. They are so cheap and easy to replace that I fitted a new one anyway. But the problem still came back. 
The first time the car “overheated”, the level in the header tank dropped afterwards which would also suggest an air lock. 
If I get time today I will jack the car up at the rear and try giving all the pipes a good squeeze to see if I can free any trapped air. 
The car had an engine rebuild 550 miles ago (before I bought it) so there is a good chance that it could be an air lock as the coolant would obviously have been refilled at the time of the rebuild. 

Heres my blog

 

Everything you need is on there including the method to recalibrate the temperature gauge. You really should start with an accurate gauge and work from there its easy to recalibrate. It should track correctly within 10 degrees c over the entire range.Watch the gauge as it cools with the thermometer in the boiling water. A large school lab thermometer is best. So to adjust the temp calibration remove the cork atbthe back of the instrument and file off a bit of metal to use as a tool to rotate the calibration mechanism, its all on my blog with pics. Everything you need to save time and methodically fix the issue. If you fans don’t come on at 90 degrees C something is wrong. Maybe the gauge reads 90 degrees but the real temp is lower. It should operate within 5 degrees. This is why you must confirm the gauge is correct before anything else.

Of course fans not coming on with cause an instant overheat and boiling. I have learned you do not have to tip the car on its nose to clear air. The bleed pipe from the top of the expansion tank to the curved cooling pipe must not be kinked this is where the air escapes. If its kinked the air can’t escape and all the coolant will boil out.

[GreenGoddess]

That’s fantastic info. Thank you 🙏 

I will try and get all those tasks done later this week (probably next weekend if I’m honest). 
 

I will report back 👍😊