Strange overheating problem

[smeghead]

Hi everyone,

I have recently bought a Golf MK3 1997 2.0 Auto and from the beginning have had a strange overheating problem. The car goes well (gauge at around 90), but once I enter traffic after a while the engine is getting hot. I found out that the fans start working at around 110 degrees (that should be ok, right?) and cool it down. But why does it get to 110 in the first place? It seems that the previous owner had replaced the water pump, temp sensors and I have replaced the thermostat, but nothing helped... Has anybody had a similar problem?

Any help is much appreciated!!!

Thanks,

Thomas

[gldgti]

the fans should have a high and low speed setting... low speed should come on before 110 degrees, but the high speed coming on at that temp is OK.

There are a few possible causes - the fan controller, lives under/near the coolant filler bottle, can have a partial failure. Also check the fuses on top of said controller in the engine bay. Check the wiring plug going to the fan to ensure nothing is broken there.

defiantely sounds to me like the low speed is not engaging.

[smeghead]

Thanks heaps for your answer! I have already replaced the wiring plug, I will check the fan controller and the fuses as you recommend... But I kinda suspect they are new as the other parts... Isn't there something stuck somewhere so the engine doesn't get enough coolant? Or the fact that the temperature is ok while riding and only get bad when stopping at lights shows that it is the fan problem? (sorry if my thoughts sound silly, I am really new to this, it's my first car and I am learning Thanks again!

[gldgti]

Its pretty normal for the temperature to climb above 90 when sitting in traffic (though normally the fan will come on to prevent it going much further).

Its quite unlikely that there will be a physical blockage in the cooling system... in all the golfs I've ever had (thats about 7 or 8, i cant remember) I've never had a coolant system blockage.

Plenty of times I've had fan troubles though.

The fan controller is seldom replaced really, but I had one fail in my old car. They arent that easy to find either, and there are a couple of versions. The part number is on the upper side IIRC, but its been 18months since I sold my mk3 so memory is getting cloudy

Just how fast does the temp climb? I would expect it to take a couple of minutes at least of crawling traffic to get the temp up above 90.

Also, check that the radiator fans are turning on when the a/c is switched on (this should happen at any engine temp - if you turn on the a/c the radiator fans should come on right away).

[smeghead]

The temperature climbs rather quickly... So according to what you are saying to me it seems that the low speed doesn't work - so the engine overheats to 110 and then the high speed comes on and cools it down...

[smeghead]

Hey there,

So I have checked the radiator fans - they turn on when the a/c is on and also when I tried the plug using a paper clip and both low and high speed worked. But how can I test the fan controller? By looking at it, it seemed to be quite new and I didn't notice any obvious problem or damage. Is there any way how to test whether is it working? Or should I just check the number with a dealer to make sure it's the correct one for this model? And (sorry for the lame question) where exactly can I find the fuses you mentioned?

Thanks, your help is very appreciated!

[wai]

Have you checked the radiator fins to make sure they are not blocked?

[smeghead]

@wai: Thanks for your answer, could you tell me how to check it?

Have you checked the radiator fins to make sure they are not blocked?

[wai]

@wai: Thanks for your answer, could you tell me how to check it?

You will need to get a torch and have a look through the radiator grille. By shining a light through the front, you may be able to see light coming through on the fan shroud in the engine bay.

[gldgti]

Hey there,

So I have checked the radiator fans - they turn on when the a/c is on and also when I tried the plug using a paper clip and both low and high speed worked. But how can I test the fan controller? By looking at it, it seemed to be quite new and I didn't notice any obvious problem or damage. Is there any way how to test whether is it working? Or should I just check the number with a dealer to make sure it's the correct one for this model? And (sorry for the lame question) where exactly can I find the fuses you mentioned?

Thanks, your help is very appreciated!

The fan controller (being kind of under the coolant reservoir) can get wet pretty easily (when filling for example).... the fuses... well, as I remember it, there are a couple of fuses near the fan controller in the engine bay (big ones)..... for the fans.

I found an old photo of my engine bay... fuse location marked.

[smeghead]

Hey again, thanks for your answer. I have checked the fuses (there is just one?! but that one looks ok). I am getting desperate, I had the car checked by a mechanic this weekend and he said that it's probably blown head gasket or head itself But I thought that would cause constant engine overheating, wouldn't it? It seems the engine overheats only when it's idle... I don't know whether I should trust him as he said it would cost me around a thousand bucks, but there is no guarantee he will fix the problem... maybe I should let him to test it and see? Or do you guys think that the problem is somewhere else? And if it's really the head, how much should it cost? What is an ok price for a head/gasket replacement? Thanks for your help!!!

[thestu]

if the head gasket is blown it would generally run like a pig and there may be water in the oil.

[smeghead]

Thanks, that's what I would think! It seems I haven't been lucky with the mechanics, it's a second one already and neither of them looked really confident to diagnose the problem It seems to me like they are just guessing - it might be this, it might be that... Anybody knows a good mechanic here in Sydney? Thanks for your help guys, it's really appreciated!!!

if the head gasket is blown it would generally run like a pig and there may be water in the oil.

[wai]

A quick way to check if you have a blown head gasket is to do some pressure tests.

One is a cylinder compression test. If two adjacent cylinders are showing lower compression, then this would indicate a failure in the gasket between the two cylinders. If any one cylinder is low then this would indicate a failed valve seat, or a failure of the gasket to the water jacket.

The other a radiator pressure test. Basically you should be able to pressurise the radiator/cooling system and it should hold that pressure. If it cannot hold pressure, then there is a leak somewhere in the cooling system, including a possible failure of the head gasket.

Get the radiator pressure test done first.

Of course you need to make sure that the cooling system pressure cap is working properly before all of this.

[smeghead]

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?