Overheating for beginners

[manhoo]

Please could someone tell me what I could be in for with this problem: Fluid starts boiling then spraying out of the expansion tank as the temp gauge goes over 90. The fan had stopped working but after changing the fuse it now kicks in but does not solve the problem. It happened in traffic and I did have the A/C on, I managed to limp home in 3 stages after letting the engine cool. When I tried again last night after fixing the fuse smoke started coming out of the engine, yikes!

Excuse my ignorance, I’ve looked through a few old threads and I’m none the wiser. Had a BIG bill on a service a little while ago so if I can sort this out without resorting to a garage I’ll gain some brownie points.

Many thanks from a frequent (if quiet ) visitor to this forum
Stef

[chimhunter]

Stef,

In no particular order...

Do both of the fans come on? If only one comes on it's not doing the job. Check that there is nothing stuck on the radiator preventing air from getting to the rad. Try shorting out the temp switch (otter switch?) with a paper clip to leave the fans on permantently. Check the coolant level. Check for airlocks in the radiator. Check the coolant has the right mixture in it. Add some Water-Wetter. Get the Mod-Wise upgrade kit.

Right, I'm out of ideas. Someone else?

Rob

[alex200mph]

Sometimes you get steam flashing off if you have overfilled the system, however if you car is overheating is sounds like its not that. So;

If the fans come on as they should the first thing I would check is if you have air in the system or not. There is a screw on the drivers side top of the rad. Undo this and see if air or water comes out (Make sure that the reservoir top is off while you do this check) if air comes out re-fill you reservoir untill all air is expired. If only water comes out it could be a number of other thinsg but check the air in the system first.

NB I take it the fan belt is turning the water pump fine.

Hope this helps
Alex

[zzr1200]

Have you checked that the expansion bottle cap is actually sealing as this will allow the water to boil at 100C, whereas if water is under pressure it boils at a higher temperature. If it is not sealing properly change it (VW part I believe) then bleed the cooling system. Hope this helps.

Paul

[GreenV8S]

zzr1200 said:

Have you checked that the expansion bottle cap is actually sealing as this will allow the water to boil at 100C, whereas if water is under pressure it boils at a higher temperature. If it is not sealing properly change it (VW part I believe) then bleed the cooling system. Hope this helps. Paul

Second this, the pressure caps are not really reusable (well, they are supposed to be but in practice they aren't).

[manhoo]

Thanks for the suggestions - I'll have another look tonight...

[jtong]

Are you saying that I should consider changing the blue pressure cap if it's ever been "activated"?

I don't think mine ever has (even though I've seen temps up to 110C) but I did get a load of water dumped out of the RHS bonnet vent onto my windscreen when driving. The car was not overheating at the time...?

[metcalfer]

I had my Chim in yesterday for an MOT. Coincidentally I'd had an overheating problem the other day where one of the fuses had blown so only one fan was running.

Having replaced the fuse it still seemed to be running a bit hot - it seemed as though the otter switch was switching on at 92ish, but off again at a higher temperature, and hence the fans weren't having the necessary cooling effect.

New otter switch fixed the problem, but the main point of my post was to say that the blue cap on the expansion tank was also replaced by the dealer as a matter of course, as I had mentioned to them how hot it had got.

In fact, the car hadn't actually overheated in the sense of blowing out steam and water, but it had been at 110 degrees so pretty close.

So if the pressure cap has been 'activated' the dealer (or mine at least) will replace it.

[manhoo]

I've just been up to the VW garage and got a new cap so I'll try that over the w/e.

Am I being a complete spanner? I can't get the otter switch to short using a paperclip - I tried for ages but don't know the technique...

[dannyboyo]

manhoo said:

I've just been up to the VW garage and got a new cap so I'll try that over the w/e. Am I being a complete spanner? I can't get the otter switch to short using a paperclip - I tried for ages but don't know the technique...

I've just had to short mine out due to the weather and rush hour london traffic!!

At the bottom of the swirl tank (the one with the brass cap on it) or the expansion tank if you don't have a swirl tank (early Chimaeras i think) you'll see 2 spade connectors. All you need to do is join these two together and make sure they don't short out on the engine (earth). Just wrap a bit of tape round them, also make sure they can't wander into the belt next to the tank.

Hope this helps.

[dannyboyo]

manhoo said:

I've just been up to the VW garage and got a new cap so I'll try that over the w/e. Am I being a complete spanner? I can't get the otter switch to short using a paperclip - I tried for ages but don't know the technique...

I've just had to short mine out due to the weather and rush hour london traffic!!

At the bottom of the swirl tank (the one with the brass cap on it) or the expansion tank if you don't have a swirl tank (early Chimaeras i think) you'll see 2 spade connectors. All you need to do is join these two together and make sure they don't short out on the engine (earth). Just wrap a bit of tape round them, also make sure they can't wander into the belt next to the tank.

Hope this helps.