Early Mk2 Gti water temp guage, where should it sit at normal?

[Stu-dub]

I have an 85 8v gti, K-jet and the dash with the fuel and temp at the bottom of the rev counter.

I've changed and bled the coolant, new thermostat and made sure it was fully bled.

My question is where should the water temp needle sit?

Mine sits at 3/4, creeps up to just under the top thin line, then the fan cuts in. No lights flashing and this afternoon it was running for ages when I set the timing, mixture and idle, and it never seemed overly hot under the bonnet and the fan kicks in good and strong.

It just seems that it sits a bit too high. Most of my other cars even tuned stuff sit at 1/4 or 1/2.

Do I need a new fan sender or guage sender???  If I do where are they? I'm more used to digi PB engines in my watercooled vw's.

Thanks,
Stu

[rubjonny]

yeah does seem high, does the oil temp work?

[Stu-dub]

Oil temp seems fine, on the mway ata constant 60-70 mph it stays about 89degC, then off the motorway to town driving it rises to about 95degc fro a bit before dropping a few degrees.

Like I say the engine never seems overly hot, never smells hot and seems to perform fine.

I'm wondering if its worth changing the fan switch and guage sender. It has a new waterpump and theres always a strong stream of water into the header tank.

I suppose a new rad wouldnt hurt, its just the cost.

Stu

[rubjonny]

wont be the fan switch, completly unrelated to the gauge.  since the oil temp seems ok and the fan does kick in I'd lean towards a wiring/sender/clocks fault making the gauge over-read a bit.  the sensor is the black single pin one in the metal housing on the front of the block, give the area a damn good clean and check the wiring to the sensor is ok

[Stu-dub]

Thanks dude, I'll give it a whirl.

Stu

[Stu-dub]

Actually, could it be an issue with the header tank cap. Mines black and I think it may release pressure early as it hisses even after a short journey.

Am I right in thinking that pressured water takes longer to boil, therefore lower pressure means it will heat up quicker?

Just a stab in the dark to be honest.

Just trying the cheap things first.

Stu

[Dan34]

not sure if this help's but if you have a non-genuine temp sender in there some of them read 1/4 to high i have one in mine at the moment and reads like yours, ive ordered a genuine one from vw just gotta go get it.

Dan

[rubjonny]

well generally if it was the cap or something causing it to be too hot, the oil temp would also be elevated, so id still say its the sensor, wiring or gauge

[Stu-dub]

An update.

I thought, with summer on the way I'd go belt and braces.

I found the new stat was opening too late, so I sourced another cooler 82C one. Tested it and it open much earlier than the other one.
I also bought a new Rad, at £50 its cheaper than a headgasket!, I also flushed the system and added a 50/50 mix of coolant.

cleaned the original temp sender and the connector, bled it, and went for a spin. Driving around the guage still sits at just over 3/4, which is the same as my new non vw one. I went for a fairly hard drive for 10mins or so and then slowed it down a mile before home. The highest the oil temp went was 95C, and if I coasted down a 1 mile hill the oil dropped to 91C quite quickly and the guage went to just under 3/4.
Resumed normal driving to my street and the oil was 94/95 and guage just over 3/4. Idled for 2 mins and the guage went to the top and the fan came on. The switch for the fan looks quite new as well.

So I'm thinking the oil temp is what to go by, and if I clean and renew all the earths to the engine, possibly get a VW genuine sender, if its still the same stop worrying(?)

After 5 mins I stuck my fingers through the grill and I could feel warmth close to the rad, but not what I would consider cooking or even hot.

Opinions? I'm paranoid about not knowing exactly whats happening with the engine.

Cheers,
Stu

[danny_p]

my syncro used to do exactly this.  had new stat water pump and rad,   it religusly ran on 3/4 of the temp gadge gentel driveing or on track days.

decided the rad was to small so fitted an abf on and the problem developed and it boiled.   turned out the new thermostat wasent doing what it should,  it started to open at just off 100c and never fully opend.  fitted an old genuine vw one and it started opening bang on 82 C  and was fully open by about 95 C  engine runs at optimal temp now