Just bought a Golf GTI 1.8T and have some questions

[JonesyA6]

I have just picked up a late 2000 on an 'X' plate Mk4 GTI 1.8T. It has mega miles but I paid very little money for it so couldn't resist. It all seems remarkably tight considering it's done nearly 170,000 miles but it does have some issues. It had been sat for several weeks and the battery had gone flat but it jumped relatively easily and ran ok and engine temp went up to 90 degrees and it sat there. But when I drove it home the temp gauge went practically back to cold and never really moved again until you let it idle and it climbs to 90 again. Does this sound like the thermostat is jammed open? I'm not sure it's the temp sensor as it moves fine when idling. I'm also pretty sure it runs better when the needle has hit the 90 mark and not as well when it goes back down.
I have run VCDS on it and it came up with a few errors which I have cleared and scanned again and it did not come back with anything immediately, is this normal?
There is definitely something amiss with the engine as when accelerating it hesitates but once cruising it runs very well indeed and is quiet and smooth.
What I did notice though is once I reset all of the error codes the idling got worse and will generally hold about 760 revs but then it rises to about 850 momentarily before going back down again. Why should resetting the DTCs do this?
That's about it for now and apologies for the rambling, I will have more soon!
Any help much appreciated.

[Crasher]

Standard fault on this engine, stuck thermostat. It will bring up a rich running code.

[JonesyA6]

Crikey Crasher, thanks for the speedy reply! Ok I'll get one ordered up, is it ok to do or a bit of a pig, presumably it's in a plastic housing? Thanks agin.


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[S3ohyeh]

I had this issue on a gti I had (2000 w reg) got the thermostat changed only cost about £20 and it was fine after that for a while. Affected the heating etc in the car as well, have you had any similar issues with heating?

The car ended up with one of the valves bending and serious running issues think coz I used to run it on nearly empty all the time (was broke back then) and recently I've heard that can cause issues because the particles from the bottom of a tank of fuel get clogged up in filters etc

So one thing I'd say is alway have at a least around half a tank of fuel in it with it being a high mileage!


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[JonesyA6]

Btw you are spot on it did have a rich running code.


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[S3ohyeh]

Yeh had the juddering issue at low throttle too!used to have to take it and redline as it felt like it needed components clearing up but obviously looking back now I was probably making it worse!


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[Crasher]

It is a bit fiddly as it is behind the alternator but you can do it without removing the alternator. The bolts are 10-mm external hex/5-mm internal hex and I tend to use a 10-mm 1/4 inch drive socket on a wobbly end as a 5-mm hex (Allen) key would need to be ball ended and would probably slip. Personally I will fit nothing but genuine VW thermostats, I don't trust any of this white box Yingtongiddleipo rubbish we get foisted upon us, unless I can get Behr or Whale.

[JonesyA6]

Thanks for the fitting info. Will order OE, think that is sound advice. Will report back once fitted. Appreciated.


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