Engine overheating when idling.

[LotuStuart]

3 hours ago, Escape said:

but it does sound like a problem with coolant flow, which means the thermostat is a likely suspect.

or water pump.

[LotuStuart]

On 08/05/2023 at 22:29, GreenGoddess said:

I checked the gauge today. When the temperature sensor is in boiling water the gauge reads exactly 100 degrees. I was actually quite impressed! The voltage regulator is fine. I’m aware of its foibles. 👍

How did you power up the gauge when you did this? Was the gauge in the car, or attached to a battery?

What, exactly, differed between how the system is in the car, and how it was in your test set up with the kettle of boiling water?
 

[GreenGoddess]

34 minutes ago, LotuStuart said:

How did you power up the gauge when you did this? Was the gauge in the car, or attached to a battery?

What, exactly, differed between how the system is in the car, and how it was in your test set up with the kettle of boiling water?
 

The gauge remained in the car and was powered normally. Apart from the sender being extended by two pieces of long wire so that it would reach the kettle, nothing was different. 

[LotuStuart]

42 minutes ago, GreenGoddess said:

nothing was different. 

Does the sender have two contacts, or is it earthed in the car and have only one?

IF earthed in the car, that earthing may be the issue.

was the engine running with the kettle test? If not, then the voltage regulator was only regulating the battery voltage, not the alternator voltage. It may have been regulating 12.6v to 12.6v, as opposed to 13.8 volts to 12.6volts.

IF not running, then the regulator could be the issue.

 

The trick is to have everything the same, otherwise you are creating variables. When there is only one different thing, and that makes a difference, the different thing is to blame.

 

(DISCLAIMER-I do not know the set up of this car)

Edited May 15 by LotuStuart

[GreenGoddess]

1 hour ago, LotuStuart said:

Does the sender have two contacts, or is it earthed in the car and have only one?

IF earthed in the car, that earthing may be the issue.

was the engine running with the kettle test? If not, then the voltage regulator was only regulating the battery voltage, not the alternator voltage. It may have been regulating 12.6v to 12.6v, as opposed to 13.8 volts to 12.6volts.

IF not running, then the regulator could be the issue.

 

The trick is to have everything the same, otherwise you are creating variables. When there is only one different thing, and that makes a difference, the different thing is to blame.

 

(DISCLAIMER-I do not know the set up of this car)

The sender is earthed in the car but the part that earths is super clean and contacts well. 
The engine wasn’t running when I did the test. Thanks for the tip about the voltage regulator acting differently when the engine is off, I didn’t know that. 

[LotuStuart]

1 minute ago, GreenGoddess said:

earths is super clean and contacts well. 

Double check this with a multimeter. Attach a separate earth to the outside of the sensor, or where is is connected. Rule out a bad earth!

Then all you are left with on the (3pins?) of the gauge, is the voltage feed. 

Earth, positive, sender. You will have ruled out 2/3...

 

[Sparky]

31 minutes ago, GreenGoddess said:

The engine wasn’t running when I did the test. Thanks for the tip about the voltage regulator acting differently when the engine is off, I didn’t know that. 

Then you didn't read my post.

[GreenGoddess]

1 hour ago, Sparky said:

Then you didn't read my post.

 I did the test before you posted. I would need to repeat the test. But yeah, I missed the bit about not having the engine running. I got a fancy thermocouple thermometer delivered just this afternoon so I can now measure the temps of the pipes properly. 

Edited May 15 by GreenGoddess

[drdoom]

Is it not 10v that the instruments' voltage regulator provides?

[LotuStuart]

9 minutes ago, drdoom said:

Is it not 10v that the instruments' voltage regulator provides?

Possibly-hence

(DISCLAIMER-I do not know the set up of this car)

:)

[Sparky]

Yes, 10v.

[LotuStuart]

5 hours ago, LotuStuart said:

(DISCLAIMER-I do not know the set up of this car)

Hence

(Voltages shown were just examples but I could have made that clear)

[GreenGoddess]

Well I’ve just spent a couple of hours trying to change the voltage regulator and I’m a bit stuck. I’m not sure which wires go where. Can anyone help?

I’ve attached a couple of photos. One shows the regulator in place. The other shows the regulator after I removed it sitting next to the new fangled regulator. I just need to know which wires attach where. 

[GreenGoddess]

Forget that. I think I finally figured it out. I can’t edit or delete the previous post as I left it too long. 

[Escape]

The red wire is the feed, all the others are regulated voltage to the different instruments.

[GreenGoddess]

4 minutes ago, Escape said:

The red wire is the feed, all the others are regulated voltage to the different instruments.

Thanks, my little brain eventually managed to figure that out. Took me a while. 😂

[Escape]

9 hours ago, GreenGoddess said:

Forget that. I think I finally figured it out. I can’t edit or delete the previous post as I left it too long. 

No worries, might be useful for another owner someday. 😉

[NG5]

If anyone fancies making their own solid state voltage regulator all you need is a 7810 chip such as this one https://www.ebay.co.uk/itm/290956646047

The letters at the start can vary depending on manufacturer the ebay one is L7810, others are TS7810 etc

Only about £1 each

Three terminals, in out and ground. they can get a bit hot so attaching to metal or a heat sink is advisable. Small enough to fit inside an original voltage regulator case it you need it to keep looking original. I've made a few over the years.

[LotuStuart]

3 hours ago, NG5 said:

If anyone fancies making their own solid state voltage regulator all you need is a 7810 chip such as this one https://www.ebay.co.uk/itm/290956646047

The letters at the start can vary depending on manufacturer the ebay one is L7810, others are TS7810 etc

Only about £1 each

Three terminals, in out and ground. they can get a bit hot so attaching to metal or a heat sink is advisable. Small enough to fit inside an original voltage regulator case it you need it to keep looking original. I've made a few over the years.

On the one GG is fitting, there appears to be only two wires (old red goes to new red, old green goes to new green).

EDIT-on my PC I can see the word CHASSIS pointing to a mounting hole-GG-ensure this is earthed well there. Out of interest, was the original one earthed?

Edited May 16 by LotuStuart

[GreenGoddess]

1 hour ago, LotuStuart said:

On the one GG is fitting, there appears to be only two wires (old red goes to new red, old green goes to new green).

EDIT-on my PC I can see the word CHASSIS pointing to a mounting hole-GG-ensure this is earthed well there. Out of interest, was the original one earthed?

Ok, I have just finished fitting the new voltage regulator. Not a lot of wiggle room in there is there? 😂

It looks to me as though the new and old regulators are earthed through the mounting hole against the metal frame of the instrument panel. Both old and new regulators are earthed correctly as far as I can tell.

Anyway, it seems to be working ok because the fuel gauge is showing the correct level. I haven’t started the engine yet, I’ll do that another day this week and take it for a drive to see what happens to the temperature gauge. 

Thanks everyone for all your help so far. 😊👍

[GreenGoddess]

Today’s update. 
 

I took the look the car out for a decent drive and the fuel gauge and temp gauges seem to be fine after installing the new voltage regulator. They are giving the same readings as before. 
 

When I got home, I left the car idling for a few minutes and, as per usual, it started to overheat. I attached probes from my new thermocouple thermometer to the car. I cable tied one probe to the metal pipe next to the otter switch, and I cable tied the other to the metal pipe across the rear of the engine bay next to the coolant temperature sender. 
 

The temperature gauge in the car was reading just over 120 degrees. The temperature reading from the probe next to the otter switch was 73 degrees. The temperature reading from the probe next to the temperature sender was 106 degrees. 
 

I imagine that the exterior of the alloy cooling pipes will be slightly lower than the coolant flowing through them. Is that correct? And of course, only one side of each temperature probe was actually touching the metal surface. 
 

Whichever way you look at it, there is obviously a huge difference in temperature between the coolant flowing around the engine and the coolant entering the radiator which has been my suspicion all along. It also confirms my theory about why the fans haven’t been coming on i.e. the otter switch simply hasn’t got hot enough. 
 

What would be your next move? Do I do another test to make sure the temperature sender is accurate? It looked to be accurate with the old voltage regulator but I haven’t tested it against the new voltage regulator even though it’s giving identical readings. 

[ChrisJ]

On 08/05/2023 at 21:17, NG5 said:

I'm impressed it will idle smoothly at 750rpm !

I was wrong - it is idling smoothly lower than that - taken this morning just after I'd got the car out of the garage, so still cold, hence the oil pressure.

[ChrisJ]

@GreenGoddess - I'd check what the temperature is at the otter switch when you raise the revs in increments -  as it does look like you are not pushing the water round the pipes at idle - so this test would be to see at what temp it does get pushed around.

My fans come on when the needle is just below the right hand mark - but this will happen with mine if I just leave it idling on the drive - I'm not saying 120 as there is no measurement there, it is a mark on a gauge, rather than a specific temp).

[drdoom]

The temperature of the coolant pipes will be very near that of the coolant within, as the pipes are of thin aluminum which conducts very well.

[LotuStuart]

How hard is fitting a new water pump? If it’s easy and it hasn’t been done for a while I’d be tempted to do that. 
is it possible to fit a sensor in the engine area where the water rises to 106? To at least have a fan turn in at the right time.-id certainly fit an override switch until it’s resolved. 
 

I feel your pain…