GTI MK5 temp / boost

Changingtime

My mk5 gti is not heating to 90 degrees, gets to about 70 or so. I'm pretty sure thermostat gone. It's still driving fine but as it's been like that since I've bought it, I'm not sure if performance is impacted. Never drove another gti to compare either.

Does the ECU limit full boost until the temp is 90 or so?

Thinking I should get the thermostat done but seems a big enough job 2 hours labour and parts. Prob 300-400? Would hope i notice difference if spending that.

I have torque set up on phone and a bluetooth obdii so could check boost but no idea to be honest what readings should be.

Advice greatly appreciated!!

rex-x

You will be doing damage driving the car around with a faulty thermostat. Nothing will get up to operating temperature and it will be overfuelling. Get it done, pretty urgently

Moanin

Changingtime wrote: »

My mk5 gti is not heating to 90 degrees, gets to about 70 or so. I'm pretty sure thermostat gone. It's still driving fine but as it's been like that since I've bought it, I'm not sure if performance is impacted. Never drove another gti to compare either.

Does the ECU limit full boost until the temp is 90 or so?

Thinking I should get the thermostat done but seems a big enough job 2 hours labour and parts. Prob 300-400? Would hope i notice difference if spending that.

I have torque set up on phone and a bluetooth obdii so could check boost but no idea to be honest what readings should be.

Advice greatly appreciated!!

Is it DSG or manual? DSG cars have a second thermostat for the gearbox oil cooler which is very cheap and easy to change. So what you could do is get that replaced first and see if it fixes the problem.

Changingtime

Moanin wrote: »

Is it DSG or manual? DSG cars have a second thermostat for the gearbox oil cooler which is very cheap and easy to change. So what you could do is get that replaced first and see if it fixes the problem.

It's a DSG. They have three thermostats, the manual has two! Am considering the easier ones first and do myself but the main thermostat seems too big a job for me. Will get it done either way just wondering if more performance to come.....

rex-x

Does it feel particularly slow? They were never a rocketship really

Tea drinker

Changingtime wrote: »

It's a DSG. They have three thermostats, the manual has two! Am considering the easier ones first and do myself but the main thermostat seems too big a job for me. Will get it done either way just wondering if more performance to come.....

Well start with which ever one feeds the dash temp. At least on the older VAG engines they can go wonky (on the dash) but still fuel OK. I think they had 2 thermostats in one or something.
As regards using torque someone who actually knows what they are talking about might chime in but you could try log requested vs actual boost on a wide open throttle run.

George Dalton

You won’t notice any major performance gains afterwards.

You should consider having the intake ports cleaned at the same time as the thermostat replacement job as the intake manifold will be off in any case.

Notch000

If you not boosting the most like cause is a torn diverter valve on the turbo, review replace this first for the lask of power. These are rubber diaphrams that split over time and long term owner tend not to notice. I got a 2005 GTI last yr and knew it was realy down on power, previous owner hadnt a clue. While not rocket ship fast the 200 BHP should be able to push you back into the seat and put a smile on your face.