Coolant Temperature

[Tallyman]

OK, this isn't exactly a problem, more a case of "anyone else noticed this".

Decided to replace my radiator this week, as I'd noticed a few tiny holes in the header tank where it had been repaired at some time in the past. Up until a few months ago it usually got up to temp quite quickly and stayed in the 80-90C range most of the time, except when towing up hill, when it would climb to about 115-120C.

I've noticed over the last few months that the coolant temperature shown on my additional temp guage was fluctuating quite wildly at times, from 80C, down to 60C under acceleration and then back up to 80+ at idle or on overrun. Now this might have been because the coolant wasn't pressurising properly because of the pin holes but that should have caused it to overheat, not run cold. And before you ask, it had a full service from our dear TonyN last year / 3300 miles ago.

Anyway, I repaced the rad with a reconditioned unit from Roughtrax on Friday (apart from not having exactly the correct extension bars on my socket set to move the rad fixing bolts easily, I found it quite a simple job to do). Having run it for a while and topped up the rad with about an extra 1/2 litre of new red coolant since then, checking it when it's well cooled down, I'm finding that the engine seems to be running at an indicated and very steady 70-75C now. I'm not complaining, as if it's running cooler then I might get a very easy tow down to Cornwall in a couple of weeks.

What I'm actually interested in is this. Has anyone else who has changed their rad for a new/reconditioned unit noticed anything similar? I know if you only have the normal temp guage then you are unlikely to notice anything, as mine shows "normal" anywhere from about 40C to 120C. But if you have an auxiliary guage fitted, I'd be interested to know if you have noticed anything similar.

Thanks

[nero279]

did you replace the stat at the same time?

i noticed when i ran without a stat i had huge fluctuations according to my modified temperature gauge, sounding quite similar actually in that it seemed to cool a little under acceleration, and then climb again when cruising. I think modern stats are designed to fail 'open' after an overheat, so i was just wondering if the stat had been replaced at the same time maybe it wasn't so much the rad that had the effect as the stat?

[europa88]

Might be a long shot, but is the temp gaugue an electric one? It's possible that It could be an earth problem or failing sensor.I had similar probs and It was a broken earth wire!

Neil

[Tallyman]

Hi Guys,

No, I haven't changed the stat but I presume TonyN checked it when he did the full service last year (may even have changed it then... Tony?). It certainly still warms up very quickly, far quicker than my wife's 1.7D Corsa, so I presume the stat is working fine.

I did notice the connection on the temp sensor was a little loose (ring connector and nut), although I've tightened it as best I can. I may well look to buy a new sensor with a spade connection and fit that to see if it makes any difference. Other than that it just may be that a clean shiny new rad is cooling far better than the old one.

[MattF]

And the coolant level is okay and no airlocks? Must say that Nero's 'stat theory does sound the best possibility if so.

[Tallyman]

And the coolant level is okay and no airlocks? Must say that Nero's 'stat theory does sound the best possibility if so.

No, checked it a few times now. The air is bleeding out in little bits. I've put about 1/2 litre in since the initial refill and as it's not overheating I can't see any problem with airlocks. Both heaters working fine and giving out good heat.

So maybe it's a dodgy sensor! Will try replacing that first, as I've bought a proper sensor adapter now instead of the bodged bit of bent 35mm copper pipe the local radiator guy made up for me a year or two back. Oh, and I bought the adapter on fleabay from a car parts dealer in Hong Kong. £10 delivered including two jubilee clips and it arrived within 4 days. Far cheaper than anywhere else in the UK.