Strange overheating problem

[wai]

So... both radiator and head gasket seem to be ok, now I really don't know Could it be some rubbish circulating in the system, which sometimes get stuck somewhere, sometimes not - that would explain why does the overheating problem not happen every time?

You can get mineral deposits coming out of the water being used unless you are using a pre-prepared coolant mixture. The only way to get this out is to reverse flush the system.

Basically, water is fed in under pressure in the reverse direction and then compressed air is added to this water to help dislodge any deposits. Any radiator workshop should be able to do this.

One other thing. Have you used a thermometer or proper temperature indicator to check the coolant temperature? Don't necessarily rely on what an instrument panel gauge says. Years ago, Holden simply replaced the temperature sender so that it read a lower temperature because owners were complaining because the gauge read higher than they were used to. The coolant was at exactly the same temperature, it just read lower on the gauge.

[smeghead]

Hi again, now the mechanic says it's probably the fan controller. But he said it would cost $450 - it seems to be a bit too much, what do you think? I saw it on ebay around $50, but that was a second hand... On another note - would a faulty controller cause that big overheating problem? I am just bit worried that I will buy the controller for 450 + pay for the work and it won't get fixed... But I don't know what else could it be - only thing I haven't done is to reverse flush the system... I haven't use a thermometer, but considering the coolant was really boiling and there was steam coming from the engine, I think the gauge is right

[wai]

"Probably the fan controller" is a bit iffy. Any good workshop should be able to tell you for sure by testing the outputs by using a sender in a container of boiling water and seeing how the fan outputs are.

I would get a reverse flush done first. Again, you do have to trust your mechanic as these days, it is all too easy to be spun a line that gets them more money.

Sorry, I am a bit cynical, but I have been caught out. I had my Holden Torana get a routine service on the automatic transmission. I had used the workshop for over 10 years, and it was run by an old guy who used to like you to hang around so that you could see exactly what was being done. The last time I went there I discovered it had changed hands. I should have walked, but I got them to do the service. They could not do it straight away so I had to get a taxi home. Then a couple of hours later I got a call where I was told I had a failed valve chest, and it would be $600 for a new one. I had no choise other than to pay for a new one. The transmission was in pieces, and I never new if I got a new valve chest.

Eliminate the basics, and then go for the expensive fix, unless you are sure you know what the problem is.

[smeghead]

Thanks wai, that's the problem I can't find a good mechanic - both I have tried have been like "let's replace this, lets replace that..." but without really testing it - so I ended up replacing a thermostat which was working...

Does anybody know a good mechanic who (ideally) specializes in Volkswagen cars, so he knows usual problems and would be able to really find & fix the problem...

Thanks!

"Probably the fan controller" is a bit iffy. Any good workshop should be able to tell you for sure by testing the outputs by using a sender in a container of boiling water and seeing how the fan outputs are.

I would get a reverse flush done first. Again, you do have to trust your mechanic as these days, it is all too easy to be spun a line that gets them more money.

Sorry, I am a bit cynical, but I have been caught out. I had my Holden Torana get a routine service on the automatic transmission. I had used the workshop for over 10 years, and it was run by an old guy who used to like you to hang around so that you could see exactly what was being done. The last time I went there I discovered it had changed hands. I should have walked, but I got them to do the service. They could not do it straight away so I had to get a taxi home. Then a couple of hours later I got a call where I was told I had a failed valve chest, and it would be $600 for a new one. I had no choise other than to pay for a new one. The transmission was in pieces, and I never new if I got a new valve chest.

Eliminate the basics, and then go for the expensive fix, unless you are sure you know what the problem is.

[wai]

You don't need a specialist VW workshop. What you need is a good cooling system specialist. Sometimes, the ones that have the mechanics write out the invoice with grubby hands (nothing wrong with that by the way) are more reliable and honest that the ones with pristine workshops that have a receptionist and customer service representatives.

A bit like when I had to organise some gas piping to be replaced for my mother. Some of the large plumbing outfits wanted over $100 just to come out and give a quote. I ended up using a guy who was a sole trader who came out, gave an estimate, called up the plumbing suppliers who delivered the pipes and fittings within the hour and who did the work straight away. He kept to his estimate.

You may have to do the rounds of cooling system specialists and find one that you can trust. You don't have to get them to do the work, just see what they suggest might be the problem. If they go straight to the expensive option, tread carefuly.

Heck, if you are a member of the NRMA, see what their service people suggest.

[smeghead]

Hey everyone,

First of all I would like to thank you for your help and patience

Secondly I wanted to record what was the problem for somebody who might be having a similar in the future as a reference. So cut long story short - the problem was 1) in the radiator - if I understood the mechanic correctly oil got in and damaged the rubber stuff inside the radiator and that stuff started to circulate and the coolant couldn't circulate properly. Another problem was that the radiator wouldn't switch the second speed on, so the mechanic has installed some kind of double sensor ensuring the radiator will turn on even if one sensor won't pick it up. And that's about it - using second hand parts the final price was a little over $700. Well it's a lot, but at least it's fixed

The mechanic is really really good - he really knows his stuff, so if anybody needs feel free to ask me for his number

Cheers!

Thomas