Temperature rising, heater cold, idle speed fluctuating

[kailear]

Any ideas?! I was driving through town tonight and the Chim started exhibiting some strange behaviour. First off, the air coming from the heater was intermittently stone cold and lukewarm whereas it is usually like sitting in an Aga (and it is damn cold this evening). Secondly when at traffic lights, I noticed the temperature guage rising to c.95 even though both fans had kicked in. Then the idle speed began to fluctuate between the normal 800 and c.1500 rpm. Finally, I cannot recall what oil pressure the engine normally runs at idle but the needle looked unusually low to me (below the first marker) but rose to the normal mid-point once moving. Any thoughts gratefully received!
Thanks,
K

[GreenV8S]

Any time the heater goes cold is a big worry because it's a clue that there may not be coolant circulating. At that point you can't really trust the temperature gauge because it only tells you the temperature around the sender, and if the coolant isn't moving the temperatures elsewhere could be *much* higher. Obviously the first thing to do is stop and get it cooled down, which obviously you've done. The second is to check the coolant levels. It could be that you had an air lock in the pump, or in the engine, stopping coolant from circulating. In that case hopefully it's been dislodged now and if you top up the coolant it'll be fine from now on.

[kailear]

Topped up the coolant which was a little low. Ran the car and now the fans are kicking in at an indicated 70 - 75 on the temperature gauge as opposed to the normal 90. Heater still stone cold. No obvious signs of leaks and I couldn't see any steam or spray while running the engine. Needless to say I am a little concerned. Not much I can do on the street and I suppose I can't risk driving it so sounds like a recovery to the dealer.....

[MADMAX2]

Is your thermostsat opening might be stuck closed its a diy job easy to fix

[GreenV8S]

I assume the heater is on 'hot'. On my car the hot/cold control operates a valve that shuts off the water flow through the heater. I guess yours is probably the same. See if you can locate the valve and check it's opening. On mine it's in the engine bay at the base of the windscreen directly in front of the passenger. Probably somewhere else on yours, but see if you can follow the pipes round the back of the engine and track it down. Also feel whether either of the heater pies are actually hot.

[WOO5IE]

Heater Valve is in the passenger footwell behind the carpet just in front of the passenger door. about 12" off the floor.

There are 2 cables that operate the valve that go to the temp control under the dash top.

Yoy may of course have an air lock .

Not the weather for heaters not working

How much water was replaced as it is unusual to loose a lot of water if the there is no leak.

Trev

[kailear]

Thank you for all of the tips. Will check the heater valve. The expansion tank only had about an inch of water in it when I topped it up to c. 2 inches from the top. It usually runs at about the weld line. What I am less clear on is why, if it is indeed just the heater valve, the temperature gauge now shows an indicated 70-75 when the fans kick in which suggests the actual temperature may be closer to 90. Does this indeed suggest that the temp sender is not immersed in coolant? I guess, as GreenV8 noted, that this, combined with the suddenly cold heater may indicate a more serious problem. Will have another look for leaks although couldn't find any indication last time. I was thinking that with anything less than a major leak, which I should be able to see, the heater should at least run hot for a while having topped up the coolant. Could the water pump be a culprit?

Thanks again,
K

[V8 Animal]

kailear said:

Thank you for all of the tips. Will check the heater valve. The expansion tank only had about an inch of water in it when I topped it up to c. 2 inches from the top. It usually runs at about the weld line. What I am less clear on is why, if it is indeed just the heater valve, the temperature gauge now shows an indicated 70-75 when the fans kick in which suggests the actual temperature may be closer to 90. Does this indeed suggest that the temp sender is not immersed in coolant? I guess, as GreenV8 noted, that this, combined with the suddenly cold heater may indicate a more serious problem. Will have another look for leaks although couldn't find any indication last time. I was thinking that with anything less than a major leak, which I should be able to see, the heater should at least run hot for a while having topped up the coolant. Could the water pump be a culprit?

Thanks again,
K

I'm surprised it stays at the weld line mines a couple of inches above the bottom of the tank.
I would change the stat first as it's easier and cheaper and there are two degree types available i think.
Fans kicking in about what you say appear right to me.
The heater valve is operated by a cable cord connected to the wheel and can get stuck mine was i just squirted some WD over it and now ok.
V8 Animal

[paulathome]

The first thing to check is your swirl pot level. (the big ally pot at the front of the engine)
This should be full to the brim with no air gap. If low fill to the brim and refit the lid.
Then with the engine still cold check the radiator is full by removing the plug top right fill and refit.
If any of the above are low, start looking for leaks, unless you have not checked levels for a long time.
Paul.

[AlexanderV8]

The expansion tank level varies from car to car. Mine runs perfectly about an inch from the bottom - any higher & it dumps it on the floor via the cap.

If I were you I'd check the level in the swirl pot. That needs to be full. There is a correct procedure in the bible on how to prime the system and rid it of air via the plug on the rad. If the level is low in the swirl pot, air will enter the system and prevent circulation.

[V8 Animal]

AlexanderV8 said:

The expansion tank level varies from car to car. Mine runs perfectly about an inch from the bottom - any higher & it dumps it on the floor via the cap.

If I were you I'd check the level in the swirl pot. That needs to be full. There is a correct procedure in the bible on how to prime the system and rid it of air via the plug on the rad. If the level is low in the swirl pot, air will enter the system and prevent circulation.

Bang on!!!
Refilled my radiator this weekend after refitting heater pipes in a rush to start her up i only filled the expansion bottle up.
Completly forgot about the swirl pot.
When car warmed the noises from the expasion tank were frightning.
It then dawned on me what i had forgot to do.
Next day sorted it and now ok.
V8 Animal