Thermostat

[Tatebailey1992]

For the first time ever my car has hit 90c today then soon plummeted to 70 again it seemed to get to 90 when I was in traffic or stopped, I've been told the next stage to find out my problem is the thermostat, but 110£ seems a lot to just check if that's the problem, anyone got any other suggestions?

[doylebros]

Have a read of this especially the link in the thread.

http://www.mk5golfgti.co.uk/forum/index.php/topic,76550.msg803139.html#new

[Itguy]

What year and gearbox do you have?

[Human Joist]

Your just described the main thermostat fail. Gets warm but drips down and gets hotter while stationary and colder when driving. The main thermostat for a mk5 is about £42 trade from VW as I just priced one up. You don't even need to replace the coolant to change  it out

[Itguy]

Your just described the main thermostat fail. Gets warm but drips down and gets hotter while stationary and colder when driving. The main thermostat for a mk5 is about £42 trade from VW as I just priced one up. You don't even need to replace the coolant to change  it out

Which engine is that on?

The main thermostat on the mk5 gti is bolted on the front side of the block just under the inlet manifold and needs the alternator removing first before access, then the main air inlet pipe from intercooler to throttle body removing. It definitely needs the coolant dropping before it can be swapped out.

If your car has one or two bypass thermostats as per my other thread I'd check the operation of these first before going to the hassle of replacing the main thermostat. I didn't and ended  up replacing my main thermostat for no reason. Ditto the coolant temp sensor.

Main thermostat change takes roughly 4 hrs DIY.

[Human Joist]

Just going on what the part guy told me At VW. He is normally spot on. Mine the early AXX engine if I have they right

[Tatebailey1992]

It's a 54 manual