Engine overheating when idling.

[ramjet]

On 01/05/2023 at 05:42, GreenGoddess said:

I haven't bothered investigating the lack of cool air from the AC yet. When I turn on the AC I can hear a definite audible click which I assume is the clutch engaging. The radiator etc is completely clear of debris (the aluminium radiator looks brand new). 
When you say "feel the various coolant hoses for differences in temperature when in the idling state", are you talking about engine coolant or AC coolant? 

Had a similar issue on a car I had in the past. It is possible for an A/C system to have enough gas in it to run the system, but not enough to create a substantial cooling effect on the air.

I'm with @Chillidoggy as well. Installing a new otter switch is is an easy test and not a wallet breaker.

[snowrx]

Apologies on the thermostat suggestion, My '85 TE has the thermostat in the top of the water pump (easy & cheaper) not the one in the hose system...

Is there a spot in the engine bay where you can loosen a uppermost hose clamp to rule out any possible trapped air in the system?

[TAR]

19 hours ago, GreenGoddess said:

Lotusbits have started selling new replacements. Apparently they’re very good. Not sure about pipe sizes but they’re supposed to be a direct replacement. See here: https://lotusbits.com/product/product-175/

That looks like the one with the incorrect size outlet. I believe that the MY87 used that one. It'll fit but may need a reducer. Unless of course, it's an optical illusion or generic image  

[GreenGoddess]

Thanks Guys

I ordered the thermostat and otter switch today. I’m 99% sure the thermostat is the problem so if I’m going to drain the coolant system I may as well replace the otter switch at the same time. I don’t want to have to fill it up just to drain it again. Besides, the pipe housing the otter switch on my car has the switch on top of the pipe. I may as well turn it 180 degrees so that the switch is on the bottom like on the later cars. This will help avoid any air bubbles “confusing” the switch. 
 

Hopefully I will get this done at the weekend. Fingers crossed I don’t need a reducer for the pipe to the thermostat. 

[Escape]

Have you actually verified your Otter switch is working or not? Just changing parts is not the best way to solve problems. Now more than ever, because a lot of new parts are not of the same quality as the old ones they're replacing...

[Chillidoggy]

What makes you think the thermostat is at fault? You still haven’t proved whether the otter switch is working or not.

[jonwat]

1 hour ago, Chillidoggy said:

You still haven’t proved whether the otter switch is working or not.

Or if the belt is tight enough 

[GreenGoddess]

4 hours ago, Escape said:

Have you actually verified your Otter switch is working or not? Just changing parts is not the best way to solve problems. Now more than ever, because a lot of new parts are not of the same quality as the old ones they're replacing...

No. But when the fans are on it makes zero difference to the coolant temperature.

2 hours ago, Chillidoggy said:

What makes you think the thermostat is at fault? You still haven’t proved whether the otter switch is working or not.

Because when the fans are on it doesn't make any difference to the coolant temperature.

1 hour ago, jonwat said:

Or if the belt is tight enough 

Belt is OK, I checked last night 🙂 

My money is on low coolant circulation. All the pipes look OK, the radiator is new and when I increase the revs the coolant temp goes down. So it's either the water pump or the thermostat restricting the flow in my opinion. When I get it all to pieces I will check the thermostat and otter switch in a pan of boiling water before replacing them.

The engine was rebuilt in Feb 2022 so I'm hoping whoever did it had the sense to either replace the water pump or at least make sure it was in decent condition.

[NG5]

Possibly an internally collapsed hose? that would restrict flow.

Difficult to properly check without removing them, but if any of the hoses feel soft then they may have delaminated and collapsed internally, that would restrict flow. Not uncommon on old hoses.

It's also possible there is an actual part blockage in one of the pipes or hoses from rust, debris or even vermin if a pipe was left open for a while during maintenance. The fact that the rad looks new could indicate that this was an existing problem that the P/O tried to fix by changing the rad.

I have also seen water pumps from other cars (not esprits) where parts of the water pump impeller have broken off, I think due to corrosion when antifreeze/inhibitor has not been used or changed often enough. That both reduces the pump efficiency and puts a lump of metal in the coolant pipes.

Personally I'd take off all the hoses and check them and then poke a flex drain cleaner up the chassis pipes just to check all is clear, then give it all a good flush.

Doubt it's the thermostat, they tend to either work or not, so would be a problem at all revs.

Hope you find the actual problem soon.

[GreenGoddess]

Thanks NG5. I'm hoping it's not debris in the coolant system. The coolant is as clear as it could possibly be with no sediment. If the old thermostat and otter switch pass the boiling water test then I'll have no other option than to start taking all the hoses off. I'm hoping that the thermostat has not been opening fully. That would be preferable to dismantling half the car. 

[Rambo]

From reading some of your earlier posts it sounds like you've always had an overheating problem since purchase of the car??

I wonder if the engine has always overheated before your ownership, hence the rebuild? You would hope at the rebuild stage that belts, water pump, tensioner, idler etc were all replaced. Same goes for the thermostat etc...

[GreenGoddess]

Yes. This problem has persisted. I thought it was due to an airlock at first but it’s taken me a while to notice a pattern of when it would overheat. Only recently I noticed it was only doing it after sitting idling for a couple of minutes. 
 

The turbo wastegate was absolutely seized solid when I got the car. I didn’t notice for a few weeks as I had never had an Esprit before. It was over boosting like crazy which leads me to believe that’s what caused engine failure for the previous owner. It wasn’t a Lotus specialist that rebuilt the engine so they probably weren’t aware of the wastegate issues with these cars and therefore never checked it. 

[NG5]

Long shot...

I know there are various different water pump pullies for the different 4 cyl esprit engines, I don't know what the differences are or if the diameters differ.

Is it possible the wrong and too large pully has been fitted at the rebuild? That could give the symptoms you outline.

On the original mini, for racing it was standard practice to fit a larger water pump pulley to prevent cavitation at high revs, but it did make cooling marginal at idle. The difference in diameter wasn't huge, but it was enough.

Anybody know the differences on the esprit pullies?

[GreenGoddess]

Well that’s certainly a good idea and is worth checking. Thanks 🙏 

[mike.griese]

I think you are still airlocked someplace.  These cars do take some effort to bleed properly.  Normally there is a bleed plug on the radiator by the left hand headlamp lift motor under a small cover.  Since you have a replacement radiator, that bleed may not be present, which could lead to a big bubble in the radiator.  I would suggest getting a coolant system pressure tester and using that to help perform the bleed.  Attach it to the header tank and pump it up.

[GreenGoddess]

The radiator has a bleed plug in the usual place and has been bled properly countless times now. I really cannot see how an airlock is causing this now. I hope it is, because that would be an easy fix but I believe I’m past that stage now. 
Tomorrow I will be spending all day on the car trying to get to the bottom of this. 

[suddsy]

Hi

When your fans run are they sucking not blowing?

If your rad is not blocked cooling on the TE should be more than enough.

 

suddsy

[GreenGoddess]

Good question! I don’t know. I will check that tomorrow. 

[Chillidoggy]

Does the car actually boil over and dump coolant? Or are you going by the gauge showing what looks to be a higher temperature than "normal", i.e. 'running hot'?

Have you verified that the gauge is reading correctly by comparing it with a laser thermometer?

[GreenGoddess]

3 hours ago, Chillidoggy said:

Does the car actually boil over and dump coolant? Or are you going by the gauge showing what looks to be a higher temperature than "normal", i.e. 'running hot'?

Have you verified that the gauge is reading correctly by comparing it with a laser thermometer?

It’s never boiled over or dumped coolant. I’ve never let it get to that stage although the needle on the gauge has hit 140 a couple of times. I tried a laser thermometer a few months ago but it was about as much use as a chocolate teapot. I then tried dipping the temperature sensor in boiling water to see how the gauge reacted. I can’t remember what the reading was but it was lower than 90 degrees. I have since changed the sensor so I might do that test again today. 

[GreenGoddess]

UPDATE SO FAR:

SURPRISE: I found another invoice from Feb last year when the car had the engine work done. On the invoice was a new thermostat, a new otter switch and numerous cooling hoses! 

Today I have had the car up on the jack and I have looked at every single coolant pipe and hose on the car. The rubber hoses all look to be in excellent condition and many of them look new with manufacturer labels still on them and new jubilee clips etc. The thermostat doesn't look original (it has the squared off shoulders of the more modern replacements) but it does have quite a bit of surface dirt and oxidisation so I have no idea how old it actually is. It could well have been new in Feb last year as the invoice would suggest).

I doubled checked the belt tension for the water pump and it is definitely tight enough.

I checked the fans again and, surprisingly, the connector on the centre fan had popped off so only two fans were working. This must have only happened recently. I reconnected it and tested the fans by bridging the wires at the otter switch. All are working OK. 

I ran the engine for ages and kept feeling all the pipes and hoses as they warmed up. Everything seemed to heat up as expected. After about 15 minutes (when the temp gauge was showing approx 90 degrees) the pipe with the otter switch started getting warm which suggests that the thermostat was now open. All as expected. 

Eventually (after about half an hour of idling) the temperature started rising past 90 degrees. It eventually settled at an indicated 120 degrees approx (see attached photo). The fans had still not come on. I therefore manually bridged the wires at the otter switch and the fans activated. I left them running for 10 minutes but the temperature gauge did not move at all. I then re-attached the wires to the otter switch and the fans actually stayed on. This proves that the otter switch had finally been activated which is the first time ever since I got the car. Nevertheless, the temperature did not come down from the 120 degrees. 

Finally I held the engine revs at 2500rpm for a minute and the temperature slowly returned to 90 degrees. 

So, I still think this problem has something to do with inadequate coolant circulation at idle speed. If circulation was good, the temperature would surely start to drop when the fans start running. This leads me back to the thermostat.  

I'm waiting for the car to cool down and then I am going to test the temperature sender in boiling water to see what the temperature gauge says. 

By the way, the fans are pulling warm air AWAY from the radiator instead of forcing cool air onto the radiator. I assume this is the normal rotation direction for the fans?

[drdoom]

Yes, it is normal and preferable to have fans draw air through a rad rather than push. A better picture of your situation is shaping up as you are proceeding. What might be impairing flow through the system such that low revs make it below requirements? Something about the water pump perhaps? Belt tension is very unlikely as this would have greater effect when rev'd than at idle. Perhaps the pump is corroded internally to the point that the impeller has lost some efficiency?

[Rambo]

So, nothing about a replacement water pump in the rebuild invoices?

What if someone had accidentally mixed EG with OAT antifreeze? There'd be a helluva sludge build up which would impair circulation and thermal efficiency

Just a thought.

[GreenGoddess]

Thanks guys. A water pump was not on the rebuild invoice but I would have hoped they’d had the sense to check its condition. 
Someone on Ye Book of Faces suggested that my idle speed might be too low. He said it should be around 950rpm. Mine idles at approx 750rpm. I suppose he has a point and I may as well look at adjusting it. But would 200rpm make such a difference to the coolant circulation at idle? I’m not so sure. 
The only other thing I can think of before removing the thermostat is to check the front of the radiator to see if it is blocked. It’s brand new so I think it’s highly unlikely but I may as well check it. What’s the easiest way to check it? If I remove the front undertray will I be able to see between the radiator and AC condenser?

If all the above fails then the water pump is probably the only thing left that could be causing this. That’s a job I won’t be doing myself. 

[drdoom]

That's a fair point made concerning idle speed. It is quite normal for an engine of higher output to idle as advised in Ye Book, not imperative to idle at a slow rev. Further, it is typical for impeller pumps to fall off efficiency outside of optimal range and you'd find no easier way to either resolve the issue or confirm questionable pump condition than to turn up the idle a touch.