Engine temperature query

[Roverageous]

Chaps,

 

i'm not terribly mechanically competent, so would appreciate some views on this.

 

Going into winter I noticed my 75 struggling to keep the cabin at a decent temperature when stood stationary in traffic. I have been running it with the onboard diagnostics on and have observed the following:

 

1. Normal driving sees the car achieve 87'c and stay there - whether I'm pushing it hard or feathering it. Cabin remains toasty.

 

2. After about 10-15 minutes of sitting in traffic, engine temperature creeps up to 90'c - this coincides with the heater cooling down. It never goes cold, but decidedly luke warm.

 

3. Holding the revs at 1500 rpm while stationary brings the heat back to the heater, and brings the engine temperature back down to 87'c.

 

4. One driving again all is honky dorey.

 

To my (very) simple mind this could be symptomatic of a failing water pump, which is not circulating water well enough at idle? Or perhaps a characteristic of the engine? other 75 owners have found the cabin struggling to maintain heat when idling - but I can't find any references to engine temps increasing too.

 

 

[fatharris]

Is it a diesel?

[cobblers]

Yeah I would say that it's either a diesel or it's got a slightly crap thermostat. My Mk3 Golf 1.9D used to go stone cold whenever I went down a hill and that was with a brand new VW stat. Just a symptom of the engine creating less heat than the heater takes out.

[Roverageous]

'tis a diesel.

 

I know that diesel's are renowned for not keeping their heat - but when the heaters got luke warm, the engine temperature is actually higher than when at speed?

[fatharris]

You can fit a lower rated stat, it's a common modification. Believe they use an 82c one from a Renault 5. Worth a trawl on owners forums.

[Roverageous]

You can fit a lower rated stat, it's a common modification. Believe they use an 82c one from a Renault 5. Worth a trawl on owners forums.

 

Yes, I've done this on one I had previously when the thermostat failed.

 

But what I'm getting at, is the loss of heat in the cabin coincides with increased engine temps. Both return to normal if the engine speed is held at 1500 rpm or by driving off.

 

Does this not sound like a failing waterpump?

[fatharris]

It's entirely possible, not sure how easy a job they are.

[cobblers]

Ah Ignore what I said above, I didn't read it right cos I'm a pillock. Does seem as though flow is suffering somehow, be it pump/silt/random bit of rubber floating round etc.

[AMC Rebel]

The heater matrix on these is notorious for silting up, too.  If it was a pez, the Rover forum would tell you to try bleeding the system and ask if anyone's been near it with the K seal.

 

I assume you're getting the temps from the IPK readout, seeing as how the gauge is so wank (and that really is a "thanks BMW").

 

Heater matrix is a bastard to flush too

[egg]

got a lukewarm cabin on the Mondeo. I haven't had a stat change - so might get that done first and then progress to the dreaded heater matrix flush or replacement. All the time worrying that it might be OMGHGF 

[sierraman]

Unlikely HGF, the Zetec very rarely suffers from this. The problem you'll have got might be a failed stat - genuine ones stick open upon failure. Ford do 2 types an 88 and a 92 stat. I'd put a 92 stat in. Quicker warm up, better heater etc.

 

Fortunately on yours it will be steel thermostat housing not the leak prone plastic you get on the black tops. Curiously it not the housing that leaks it's the rubber o ring that sits in the housing.

[egg]

Yep, I had a (supposed) leak on my black top (well, Duratec) Fusion - and had housing replaced (in the end it was the water pump I think I got a bit done there). 

 

Sorry for fred hijack.

[Roverageous]

Ok panic over chaps. Apparently it's due to the stat closing at 86'c (no load on the engine & heat being taken out by the heater) hence the engine temp rising then coming back down.

 

Common on plenty of diesels it seems.

 

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