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Overheating problem


cheet22
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Oh no, my baby is sick!

I have a 3.7QS (2000) and suddenly on Saturday she started overheating.

Normally, she runs at almost exactly 90degrees on the gauge, and for some reason on Saturday, on a shortish run, on a cold rainy Glasgow "summer" day, she went to like 110-120 and the electric fan ran constantly the 4 miles home.

I just took her out there again, after topping up oil and water to be sure these were ok, but shes doing it again.

She seems to rise normally to 90 degrees, then suddenly start to go up to 110+. I noticed if I idle, she dont seem to go up as quick as when driving. Also, if I put Air Con on full heat, it cools it down but still not back to 90.

Does this sound like a thermostat problem to anyone? If so, any ideas of effort / cost? I'm sure I saw a note once that to change this means removing half the front end, please tell me its not so.....

Any advice appreciated!

Paul

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It does sounds like a thermostat problem but just to let you know I had a problem with the Viscous fan not working properly. The symptoms were a bit different for that as it was fine whilst driving normally it was only when sitting still that the temperature went up a lot.

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do you have the ac running cold air when it starts overheating?

next time it starts to overheat make sure the ac is on full cold and see if it starts blowing out warm air, if it does then there is a high pressure switch behined the front bumper that shorts at its connector due to water ingress; might just need a clean out like mine did... just thinking...

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Thanks for the comments - especially the name of someone near glasgow.

Before I go to someone I'll was thinking maybe its time I got vag com working so i can at least try to have a look myself first. I bought a cable (Serial, not USB) off ebay last year, but it did nothing when I connected - maybe I should invest in a USB one to see if lets me do some basic diagnostics.

(Guess I should check out the vag com forum!)

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Yeah, im not using it just now to be safe.

I got old of a Vag com cable, and it recognizes it ok on the TEST button, but for some reason, none of the controllers can be found. Same things apply if I unplug it from the car too, so Im guessing its not connecting to the car at all. The OBD-II option reports that my car does not have the OBD-II interface?

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[ QUOTE ]

Yeah, im not using it just now to be safe.

I got old of a Vag com cable, and it recognizes it ok on the TEST button, but for some reason, none of the controllers can be found. Same things apply if I unplug it from the car too, so Im guessing its not connecting to the car at all. The OBD-II option reports that my car does not have the OBD-II interface?

[/ QUOTE ]

Make sure if your using a third party "dumb" interface, that your using vag-com version 409 or lower. The latest versions won't accept third party interfaces.

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VAG is very tempremental I find too.. Sometimes you need to have ignition on.. sometimes off, sometimes you need to unplug both end of the cable, quit the software and start again, or just keep trying to access it. Listen out fir quiet clicks behind the dash to see if it's accessing the car.

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Thanks guys,

Still can't get VAG COM to work. I took her out there round the block couple times, she got to 90 dead on. Sat on the drive for a while (15mins), no movement.

Turned on AirCon - started to creep and reached 115.

Turned it to full cold, was cold.

Turned it full heat, was hot - and this seemed to start to drag the temp back down - after about 7 mins, back to around 90.

Turned off AirCon, sat for 10mins, went back up to 115.

So lord knows.

All this time I was sat, I tried VAG COM, and no joy.

I guess I have to get it checked out, with the expectation this is the thermo or pump, or both.

One thing, when I turned the air con on, I did hear a screechy type sound (like a loose fan belt) but its been doing this a while now, couple jabs of accelerator and its away. Surely thats just a slack belt somewhere?

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What about the viscous fan coupling? I'm just trying to exhaust all the less expensive possible causes BTW.

If you try to stop the viscous fan whilst the engine is idling and at 90 degrees with say a pencil it shouldn't stop. if it does the bimetalic strip doo whacky in the coupling has had it so the coupling needs to be changed. Failing that then it looks to be the thermostat/water pump and a front off job, sorry confused.gif

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Ska (and anyone else!)

I took something of a guess that the viscous fan is one of the two fans attached to the radiator - the larger of the two, to the left as you look at the engine. The smaller one im sure is the eleccy fan - right?

It appears to be driven off the belt that drives lots of things, but it can be spun manually (engine off of course!)

Anyway, on this basis that I am on the right one, I got the car upto 90, and used a carrot to try to stop the fan - and, I can! It stops right away with really little effort, and then when I release the carrot as it where, it slowly starts to spin up again.

I would not say its spinning very fast at all either, not like the electric fan by any means.

Could this be it then maybe? (assuming I have the right fan!)

Not sure what this fan is supposed to do - ie should this speed up at normal temp and maybe its not? If it is this, is it a DIY job?

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You've got the right fan; if you left the engine for a good 10mins With bonnet closed and as the temp goes past 90 or even went for a quick spin to get the temp rising and then see if the same happens then chances are the coupling on the fan is knackered. As the temp increases in the engine bay the couple locks up like a clutch so there is no slip so cooling rate increases.

Another thing to see is when the temp rises does the smaller elecy fan switch to higher speed after some opperation of the a/c. Obviously you don't want to do this often just in case you BBQ you gaskets as mentioned. I'll have a look see about the proceedure to remove the viscous fan after the footy will post tonight. I hope for your sake it is the fan and not the water pump/thermo 169144-ok.gif

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  • 3 weeks later...

OK, after being away a couple weeks with work, decided I need to sort this.

Tried to source a new coupling, still trying - one place told me they can get this to me for £100 but will take a week from Germany.

I followed someones advice today and called Owen Ferry in Paisley (Glasgow) - the guy was VERY helpful and happy to chat about my problem. According to the symptoms I described he agreed the fan could be the culprit, but that I should check that if I run the car till it gets to 90, let it sit a while then drive a bit - if it only really goes up when I drive rather than just sit there, then he reckons its likely to be the pump as well/instead.

So, hes offered to take a look at it and give me his best opinion (check for head gasket leaks etc) within a one hour fee (£34).

If his thought leads to the water pump, then hes give me a rough guide that a new pump and cambelt fitted is around £350+VAT, which I think aint bad is it?

problem is, hes says they are mad busy so it might be some time before he can do that, if indeed its the pump.

Anyone any final advice on this price, and whether theres anyone else around Glasgow that can do this faster for same?

I'm a bit worried too about driving over there (15 miles or so) with the car like this too.

I really did appreciate his time today having said this, so I really hope the guy can squeeze me in sooner rather than later to be honest!

PS Im still hoping its the fan!

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From what you described before my money is still on that viscous coupling. What about getting one from the breakers I mean the price sounds great seeing as the front end has to come off, but checking out if a used coupling costs around £20 from say allaudi or motors in motion (ebay) or any of the other breakers may prove fruitful. When my water pump started going you could hear it almost sounds like the P/S pump is cavitating but it turns out it was the pump; like the V8s you may as well do the whole timing belt thing but costs far less as the front doesn't have to come off; cost about £150 +parts to do mine. good luck and keep us posted 169144-ok.gif

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