850 Turbo overheating

I have problem with overheating on by 850 turbo, and I'm trying to decide how concerned I should be. Any comments would be gratefully received.

Whilst doing some work on the car on Saturday I noticed that the water could do with a top up so I filled the expansion tank from 'min' to 'max'. Then, after stopping the car after a 15 minute drive, the expansion tank filled up then leaked a load of coolant onto the floor. Later, I topped it up again and drove for an hour, this time planning to keep an eye on the car when it stopped.

I left the engine running, and looked under the bonnet to see a small amount of water leaking from the top of the expansion tank, then within a couple of seconds the electric fan kicked in. The water level in the expansion tank dropped so rapidly that I had to check later to see if there was an electric pump involved (there isn't, of course). I assume, then, that the amount of cooling was enough to make the water contract this much. This has lead me to thinking that perhaps the problem is linked to the car running too hot ?. (I've been considering the worst so far, that the head gasket has gone, but perhaps that is too pessimistic).

So far I've seen in these forums that there is an issue with the expansion tank cap (I have a grey one), and possibly the thermostat so I'd going to replace these.

I may have answered the question myself but if anyone can suggest anything else I should check I'd love to hear from you.

Best wishes,

Simon

Simon,

I would think your problem is being caused by the Cap leaking...get a green one...this has led to escaping water causing air locks.

I've just fully rebuilt my R, hence the engine was bone dry. On it's first start up, I let it get up to temperature, then switched it off. I had exactly the same thing happen to me. I too thought it went down so fast, it was like it was being pumped out!!

If your temperature stays around the 3oclock position on the gauge, regardless of driving conditions, then your thermostat is fine.

When you fill up, have the engine running at idle, with the heater on hot. Fill to the max mark, and fit the cap. Allow it to get to temperature, and then switch off, allow to cool and inspect the level. keep doing this until the level stays put.

Good luck!!!

[sholtby]

Change the filler cap as Nigel suggests as a first step. Your filler cap could have failed that would cause the coolant not to be pressurised. This would cause the coolant to boil which creates vapour bubbles/ air locks throughout the coolant system and loss of coolant from the filler cap. When the fan came on these bubbles would go and the coolant level would rapidly drop.
As long as the temperature gauge didnt get too high you should be OK.
The only other problem that comes to mind is if the head gasket has failed which would cause a lot of steam to come out the exhaust and over pressurize the coolant system which can even lead to burst radiators.
Lets hope its something simple like the filler cap which is available from Eurocarparts or your main dealer.

Simon

I changed the cap this morning and the good news is that, fingers crossed, I think it's fixed. I took it for a bit of a blast on the way to work then stopped it dead. The water level was only very slightly above the 'max' line, certainly not pouring out from the top of the expansion tank like before.

Thanks for the tips - you at least saved me the cost / hassle of a new thermostat.

On Sunday I was fearing that the head gasket had gone, so you can imagine how pleased I am to discover that it actually cost 10 pounds and 30 seconds to fix ...

Thanks again,

Simon.

Whilst being on the subject a lad down the road bought a 94-5 850 T5 and came to show me the car when he opened the bonnet the first thing i seen was the dredded grey cap. I gave him promt advice to get the thing changed straight away.

cheers Leigh