GTI running too cool?

[Stuwey]

In traffic, my car runs at a steady 90C. Oil temp 180-210F.

Lately however, if I'm belting along the freeway at 110kmh late at night when it's really cold then the coolant temp drops away, and shortly after the oil temp too.

I'm thinking thermostat staying open?

Where exactly is the thermostat on these??



Cheers

[Lito]

There is a housing that comes of the block under the intake manifold which the thermostat sits in. My car used to take ages to come up to temp and the temp would drop when cruising in a cold night, fitted a new thermostat and it's much better. Can be a bitch to change though, I would recommend taking the IM of for easier access, some people also recommend removing the alternator for more clearance but you can remove the t-stat with the alt in place, just a bit more fiddly

[nightphotographer]

Before touching anything big I'd look at your coolant temperature sensor (CTS) they're about $15 for a new one and are quiet common failures (or were on the MK4 platform anyway - I went through 2 on my MK4) - but that created similar problems - it'd take 15 mins of driving to get anywhere near 90 degrees etc. I dunno - see what Gav says

[Martin]

Yeah, sensor or thermostat

Check how much heat you can get out of the heater when at 90 degrees and again when running cooler temperatures
If the heater can't produce hot air then it's a good indication that the thermostat is the problem

[Stuwey]

If it were just the sensor then the oil temp would remain higher.

With the coolant coming down so low, it cools the oil too much through the heat exchange.

My thoughts anyway!

<edit> the heater cools off, too. So yeah, I'm definitely thinking t'stat. I just have to find it and get one I guess!

[Martin]

Good point about the oil

So you need a thermostat - may as well take the opportunity to change the anti freeze at the same time

[h100vw]

If you do the stat, I reckon you should prepare yourself with a spare plastic pipe. Just on the off chance that you break it. Ball ended allen key socket is a winner for doing these in situ without pulling the alternator or manifold off.

Temp sensors not so bad on these, I'd look at the measuring blocks with VCDS if you can though. soon see if its cooling off in the breeze.

Gavin

[Stuwey]

If you do the stat, I reckon you should prepare yourself with a spare plastic pipe. Just on the off chance that you break it.

Gavin

Do you think the new 034 billet housing is worthwhile then?

Metal Thermostat Housing, Audi/Volkswagen 06A 1.8T Transverse, Aluminum - 034Motorsport | Performance Parts for Audi, Porsche, and Volkswagen

[h100vw]

Do you think the new 034 billet housing is worthwhile then?

Metal Thermostat Housing, Audi/Volkswagen 06A 1.8T Transverse, Aluminum - 034Motorsport | Performance Parts for Audi, Porsche, and Volkswagen

I like the look of it but tbh I wouldn't spend $100 odd plus shipping for it. A new std one would last for ages if you did have to replace it. For a fraction of the cost.

I keep one in my cupboard just in case, I reckon it was under $30.

Gavin

[h100vw]

Do you think the new 034 billet housing is worthwhile then?

Metal Thermostat Housing, Audi/Volkswagen 06A 1.8T Transverse, Aluminum - 034Motorsport | Performance Parts for Audi, Porsche, and Volkswagen

I like the look of it but tbh I wouldn't spend $100 odd plus shipping for it. A new std one would last for ages if you did have to replace it. For a fraction of the cost.

I keep one in my cupboard just in case, I reckon it was under $30.

Gavin