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Strange temperature behaviour...

My creaky old Mondeo has a strange issue with the temperature - it goes up fairly quickly when starting off (to about 1/4 of the scale within 2-3 miles) but then either stays there or goes right down to cold again, even on long trips.

If the stat was stuck open, I'd expect it to warm up very slowly or not at all in this weather. If it was stuck shut, I'd expect a nice warm car or permanently cold, depending where the sensor is.

I do get warm but not hot air from the vents, even when it is showing cold (except when first started up, obviously).

Any ideas? Or should I just fit a new stat and see if it fixes it, since it's relatively easy to get to on these?

Reply to
PCPaul
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stat is definitely the first thing to try.

Reply to
Mrcheerful

Replace the stat and whilst at it, make sure that there's no air locks. I had a similar issue with a Mk1 and the water would migrate around the system - sometimes giving warm air at the vents and at other times actually trying to cool down the engine like it should.

Reply to
marpate1

OK, Fair enough. I've got a stat with an air vent (goes at the top, I know...) so I'll stick that in at the weekend and see how it goes.

I haven't heard of a particular problem with airlocks on these, as opposed to, say, almost all Peugeots... do you know of one, or is that general advice?

Reply to
PCPaul

I can only speak from my own experience with the Mk1 Mondeo - and, I did have an air lock (how it got there, I have no idea).

If a Mk1, then also check the steel water pipe under one side of the engine. If this rusts through (as did mine during an MOT) then it's worth replacing at the same time. I swapped mine with a short length of microbore, I think - it was many years ago.

Reply to
marpate1

Useful info, thanks. I'll check it out.

Reply to
PCPaul

Replying to my own post. Johnny No-mates, that's me

For the benefit of futureGooglers...

I replaced the stat and it all seems absolutely fine now.

My theory is that it was working up to jamming open, but hadn't got there yet. So it was closed at startup, opened normally, but was very slow to close again. So for the whole trip it was holding the maximum open it had seen for a while (hence overcooling), but after I stopped it could shut slooowly so it was closed again the next morning.

That's believable enough for me, anyway. And it works.

Reply to
PCPaul

I will file those symptoms for future reference.

Mrcheerful

Reply to
Mrcheerful

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