Help!!! Engine Coolant boiling over!!!

[jelly]

My GTI's engine just started overheating stupidly today.

The temp rocketed in traffic in town so I parked up and checked it. Coolant was pouring out of the header tank cap valve. I decided to leave it whilst i went shopping. When I got back there was a huge lake of coolent under the car and none left in the system whatsoever. It was under that much pressure!  :-[

I think it may be a blockage in the system somewhere, but not sure.
Does anyone have any suggestions?

Need to get sorted quick, got MOT on wednesday....

Cheers

JELLY

[richandhazel]

If you were stuck in traffic, your radiator fan should have come on...........did you notice whether it was working or not?

[jelly]

Yeah, radiator fan was working fine.

I have since taken the whole cooling system apart this weekend.
Water pump, radiator and all pipes have been flushed and no sign of blockages.
I obviously couldn't check the veins through the cylinder head, apart from flowing water through it and that seemed ok.

My mate suggested that it may be a faulty head gasket blocking flow through the cyclinder head, but it still seems to flow.

[richandhazel]

Hmmm, could be a number of things.
I'd test the thermostat, make sure that's opening at the required temperature.
Also make sure the reservoir cap is sealing properly.
If that's all OK then it sound like your head gasket may have gone. I believe you can get the coolant checked to see if there any trace of combustion gasses in there.

[ManicGTI]

Arrrrggghhh I've got the same problem.

Had to stop and add water 4 times between home and MOT place today.
(N London: Potters Bar to Edgeware should have been a 25min journey)

Ok, so it passed, but thats bugger all use when I cant drive it anywhere. Engine seems to be running really well other than that  :-[

Ok, so my fan doesnt seem to be kicking in, but that surely doesnt account for the extremeness of the coolant boiling over.

Havent got a guide for it yet, wheres the thermostat?

Reservoir cap....hmm, i'll have to get me a new one or something. I doubt it very much thou, the coolant is under pretty high pressure.

Head gasket....ooooer, difficult to change? How long should this take?

I was hopeing not to spend money on this car, engine looks like its fairly recently been sorted out, very clean.

oh yeah, Its an '83 mk1 1.8 GTi.

Dave

[fitz2282]

i had the same problem, the cylinder head is knackered. on mine the coolent pathway had coroded too close to the cylinder bore so combustion gasses pressurised the system.
either get head welded or buy new one, but if you are getting a new one might as well get one thats been gas flowed

fitz

[mk1]

Or get one from the scrappers and port it yourself .
Steve.

[lewis]

Hi Steve,

When you ported your own head did you use a flow bench or just widen the ports to there limits? Have you had any problems with air speed through the ports as I was thinking of flowing my own head but have heard if you widen the ports too much you can affect the air speed through the head which can make it worse than better? Any tips you have would be much appreciated as my heads off now wile I?m changing my pistons to G60 ones.

Thanks

[mk1]

I don't have access to a flow bench , I made sure the ports on the head and manifolds matched the gaskets port size. Used a die grinder (that we have at work) to clean any casting marks etc from the ports. Then pollished the port walls with some fine stones. I Didn't want to go to far and scrap the only head that I had at the time. There is a lot of info on www.vwvortex.com
on this.

[Davo13]

I had the problem of the coolant boiling out of the overflow.

couldn't get my head around why! thought it was the head gasket, but there was no evidence that that had gone.

It was something dead simple the rubber O ring  in the filler cap had slipped out of its groove and was pushed to the top of the filler cap, moved it back up to it's rightful place and hey presto problem solved.