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

[louis19]

I think I'm having the same issue as stated above. What would you guys call running "too cool"? My GTI cruising along in the current weather at night (12-15 Celsius) is sitting on 70 degrees as opposed to 90 degrees when around town at lights or during the day. I must admit it does seem like it takes a fair while to warm up to 90 degrees (probably 10-15 mins on average) during the day when it's warming aswell. Is running at 70 degrees at night and the time it take to warm up an issue worth worrying about or should it be corrected? And if so, should I first look at the sensor mentioned above or just go straight for the thermostat?

Thanks!

[Stuwey]

Definitely too cool there mate. Ideally, water should be 90C ad the oil should be around 95C before giving it a real hard time.

I'm not gonna scan anything... Straight to the thermostat for me. Next weekends job!

[louis19]

Definitely too cool there mate. Ideally, water should be 90C ad the oil should be around 95C before giving it a real hard time.

I'm not gonna scan anything... Straight to the thermostat for me. Next weekends job!

Thanks mate! I thought it was odd. How quickly should the car warm up in normal driving conditions? Surely my 10-15 mins is to long aswell. By the sounds of it replacing the thermostat is the best way to go for me aswell? How are you guys reading the oil temp? I've only got the 1 gauge up the top next to fuel which I presume is the water temp?

Also where's the best spot to get a new thermostat and how much I'm looking at price wise?

Sorry for for all the ?'s!


Edit: I now strongly believe it is the thermostat as I drove the car and got it to the normal 90 degrees this morning then just cruised along when it was 15 degrees outside and within 1-2 mins it had already dropped back to 70-75 degrees so I can only assume it is staying open.

[h100vw]

Thanks mate! I thought it was odd. How quickly should the car warm up in normal driving conditions? Surely my 10-15 mins is to long aswell. By the sounds of it replacing the thermostat is the best way to go for me aswell? How are you guys reading the oil temp? I've only got the 1 gauge up the top next to fuel which I presume is the water temp?

Also where's the best spot to get a new thermostat and how much I'm looking at price wise?

Sorry for for all the ?'s!


Edit: I now strongly believe it is the thermostat as I drove the car and got it to the normal 90 degrees this morning then just cruised along when it was 15 degrees outside and within 1-2 mins it had already dropped back to 70-75 degrees so I can only assume it is staying open.

You can check the temp sensor with VCDS, compare the ECU input with the dash. Does sound to be 100% the stat to me though. Are you still running pink coolant?

Gavin

[louis19]

You can check the temp sensor with VCDS, compare the ECU input with the dash. Does sound to be 100% the stat to me though. Are you still running pink coolant?

Gavin

Hi Gav, yes I am still running the Pink coolant. Sorry for the noob question, what's the VCDS and how do I compare the ECU input on the dash?

Should the car sit at the optimal 90C even when it's cold outside or is it normal that it's sitting at 70C given the fact that the air would be a contributing factor?

Thanks mate