Temp going down then back up again?

Ive noticed recently a few times where my temperature gauge is dropping from half back to quarter for a while then rising back up, what could be causing this??
Thanks in advance!

jimbo-td5 said:

Ive noticed recently a few times where my temperature gauge is dropping from half back to quarter for a while then rising back up, what could be causing this??
Thanks in advance!

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Thermostat......put a new one(genuine recommended)

try bleeding the cooling system, then as the man says change the stat

Afraid a mates did that before head gasket went .

Sounds like a low coolant level/air lock problem or possibly a duff thermostat . Best to sort it asap before it causes a big problem . Regards Jonathan

When I had mine MOT,d this year, ( Jan ), after the car had been stood running for 15/20 mins, ( while the emmisions were tested ), the temp gauge went back down to the quarted mark.

Had,nt done it before and has,nt done it since !.

Del.

jimbo-td5 said:

Ive noticed recently a few times where my temperature gauge is dropping from half back to quarter for a while then rising back up, what could be causing this??
Thanks in advance!

Click to expand...

when driving or at standstill? How quick is it rising and falling?

It could do it a few times but ive only noticed it once reversing onto my drive and today driving along a dual carriageway i looked and it was down, i looked again after about 10 secs and it was back up (steering wheel blocks my view). Ive just checked the water level and theres plenty of water in it and no signs of water/oil mixed so im hoping its just a thermostat!

could be a duff conection in the gauge or sender if it jumps up n down fast

see if this makes sense, when you first drive discos the gauge goes slowly to about quarter, then quickly up to half when the thermostat opens. when my gauge falls back, its landing in the position where im assuming the thermostat is closed, then rises back to the middle (thermostat open) after a few seconds so it sounds to me like the thermostat is unecesserily closing, then opening again, pointing to duff thermostat?? or am I wrong?? anyone?

could as already said be just a dodgy connection. It could be waterpump, air lock, overpressurisation of the coolant system, pockets of steam, HG, thermostat, temp sensor,

ok so how can i diagnose it?? should i just leave it and see if anything else materialises??

jimbo-td5 said:

ok so how can i diagnose it?? should i just leave it and see if anything else materialises??

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Do you know anyone with a diagnostic computer. A quick plug in and test drive may yield your answer.

I know someone with A diagnostic computer, dunno if it does LR though, Ill give him a ring! Just wondering could it have anything to do with a bar seal that I used about about xmas time? I had a small coolant leak around the diesel preheater (I think it was) and it cured it!

jimbo-td5 said:

I know someone with A diagnostic computer, dunno if it does LR though, Ill give him a ring! Just wondering could it have anything to do with a bar seal that I used about about xmas time? I had a small coolant leak around the diesel preheater (I think it was) and it cured it!

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Does it seem to alter as and when your revs exceed 1500rpm?

dont think so, usually once its up it never moves at all

I gave it a good going over on the weekend and there seems to be nothing pointing to HG or overheating, the fan is fine, the water level is clear and correct, the oil is fine, driving with the heaters on flat out when the gauge plays up makes no difference to the temperature, and ive noticed a few times its starting to do it when i come to a standstill. i drove it about 7miles in country lanes and it didnt do it, but as soon as i pulled in a mates drive it dropped slowly, i drove off and it came back up. I stopped at another friends and it slowly went down again. I then went home and when reversing onto my drive i notice it start to move slightly again!
will this info shed any more light for anyone?
thanks to all thats helped so far!

"water is clear" - yu mean yu have no antifreeze/coolant in there?

yeah sorry i do have antifreeze, i mean theres no signs of anything in there like oil or anything! my bad:frown:

found it! seems the water pumps on its way out! small pool under it when I parked it home! new water pump time!