From one extreme to the next

Mikep

Mikep

Active Member
As some of you may know I had issues with overheating which was cured by fitting an uprated three core radiator, coolant flush and change, new thermostat and I also fitted an expansion tank. All was fine until a week ago when I found that the temperature has gone the other way now and is too cold with the needle sitting at the top of the white section on the gauge. It will just creep into the green when sat idling but it took about 35 minutes when idling for the temperature gauge to hit the middle of the green section. Now I know the weather is colder now and that will affect the temperature but I would think this much, so that leads me to a faulty thermostat. Does this seem a likely cause? Bearing in mind I fitted a brandnew one a couple if months ago, can they fail after such a short time or could this lack of temperature be a caused by something else?
 
In the world of Lucas prince of darkness, anything is possible, Mike! But I think I'd start at the temperature sender. Or parhaps the voltage stabiliser in the instrument panel if the fuel gauge is also misbehaving.

I can't remember whether you have an electric fan or are still on the engine driven one? If the latter, then it will take a while to get up to temperature with the 3 row rad.


Chris
 
You should remove and test the thermostat, but if it's anything less than an 88° change it for one of those.
 
chrisyork said:
In the world of Lucas prince of darkness, anything is possible, Mike! But I think I'd start at the temperature sender. Or parhaps the voltage stabiliser in the instrument panel if the fuel gauge is also misbehaving.

I can't remember whether you have an electric fan or are still on the engine driven one? If the latter, then it will take a while to get up to temperature with the 3 row rad.


Chris
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My fuel gauge seems fine but I did think the sender could be a problem, it may be worth buying a new one if they are cheap enough. Also Im still on the engine driven fan and what with the colder weather I did expect it to take longer to heat up ewith my new rad but it never heats up while on the move.

harveyp6 said:
You should remove and test the thermostat, but if it's anything less than an 88 change it for one of those.
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I am going to test the thermostat to be sure. I can't remember what type I bought and fitted. I bought it from Wins and asked for the 'Standard' one, could that be 88 but 82 rings a bell? :?
 
Mikep said:
I bought it from Wins and asked for the 'Standard' one, could that be 88 but 82 rings a bell? :?
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I'd say 88° was the "standard" one, the 82° is a Summer stat (if needed). I suppose it depends who you ask, not everyone is right.
 
I think the first thing im going to have to do is take it out and test it. I take it that usually when the temp is too low the first thing to suspect is the thermostat?
 
Without your previous history of running hot, which you've cured without altering the guage in any way, (I assume as you didn't mention it) then rather than thinking the guage is giving a faulty reading, I'd go for the thermostat. How good is the heater?
 
To be honest the heater was quite good, I used to get quite hot feet but now its non existant which is why I suspect the therrmostat and not the gauge. I was out today and the car didn't get warm inside at all.
 
worth pointing out that the car doesnt get as hot for me in this cooler weather. if the same is true for you, and you're using 82 degree thermostat you could have similar issues... (I started on 74 when i got the car - no heater hardly, 82 when i first serviced it, some heater, to 88 where i get lots of heat after getting the correct temp for the stat from Harvey...)

Rich
 
Because they are cheap I think I will get an 88 degree stat and fit it. Interesting to hear your experience Rich.
 
Hi Mike,

If you find that fitting a new thermostat doesn't cure your engine's overcooling, you can always blank off part of your grille so as to reduce air flow. In cold weather and with a 3 core radiator, expansion tank etc, not getting up to temperature is not out of the question.

Ron.
 
The thermostat should always ensure that it gets up to temperature, unless it's so cold that it doesn't get hot enough for the stat to open, and I can't see that happening. If the cooling system is that efficient then the stat will just close again.
 
SydneyRoverP6B said:
Hi Mike,

If you find that fitting a new thermostat doesn't cure your engine's overcooling, you can always blank off part of your grille so as to reduce air flow. In cold weather and with a 3 core radiator, expansion tank etc, not getting up to temperature is not out of the question.

Ron.
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This had crossed my mind Ron, in my quest to cure my overheating I may have made the cooling system too efficient :LOL: The chillier days here at the moment won't be helping. My Dad actually said put some cardboard in front if the rad as my Grandad used to this this on his Morris Oxford during the winter to help it arm up.
 
Lucky is also a three row rad with wngine driven fan and the warm up and running temperature are exactly as per high summer in the recent cold mornings.

Whe you fit the new thermostat, don't forget to drill the bleed hole and locate it at 12:00.

Also check that you have flow into the top of the rad from the tower between the carbs on the inlet manifold. It could possibly have chosen now as the moment to block? (in which case the system won't be bleeding properly with unquantifiable effects on cooling behaviour)

Chris
 
The amount of radiator volume or surface area or outside temp is irrevelavant to engine temp that is purely determined by the theremostat, so I guess you onl;y hav 2 choices faulty thermostat or misreading gauge. I always suggest an IR thermometer to elliminate one or the other.

Graeme
 
chrisyork said:
Whe you fit the new thermostat, don't forget to drill the bleed hole and locate it at 12:00.

Chris
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The one I fitted had the jiggle pin which I made sure was a 12 o'clock.

Might sound a silly question but rather than ordering a stat from the usual suppliers and paying postage and waiting a few days as im using the car over the next few days, would local motor factors stock a suitable one; I take it they are all the same in the V8s obviously right up to the last ones in Range Rover for example, I just need to ensure correct temp?
 
Errr - they'll be the same up to the end of Range Rover Classic - the P38 starts the Serpentine engines. I guess that would be around 1991?

Standard thermostats as found in a factors won't have the hole or jiggle pin, but all you have to do is drill your own 1/8" (roughly) dia hole once you get it home.

Chris
 
chrisyork said:
Errr - they'll be the same up to the end of Range Rover Classic - the P38 starts the Serpentine engines. I guess that would be around 1991?

Chris
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Thanks Chris, it was the classic that I meant, I'm sure there is more chance them holding parts for early nineties cars than late seventies. Anyway I will only know when I call them, first job for the morning :)
 
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