Thermostat

I had issues with my engine heating up quickly when I was stationary in traffic. The temperature gauge goes quite far up then the fan kicks in bringing it back down a bit, then it just keeps repeating this process until I get moving. The engine bay gets quite hot too.
The engine was fully stripped down and rebuilt about 3 years ago with new radiator and hoses, however I never replaced the water pump.
I have now bought an upgraded alloy radiator and new water pump but Im not sure whether to fit a new standard 87°C thermostat or the lower activating 71°C thermostat. Will fitting the 71°C stat cause any problems when running the engine?
I dont drive the car too hard.

Hi Macca
If you're talking about the mechanical stat defiantly stick with the 87deg stat, 71deg is far to cold to run your gti engine as your oil temp in turn will also be holding aprox 71deg when in motion. The electrical stat that brings the fan in is what keeps your car cool when idling & you used to be able to buy two versions I bought the one that cuts in at 92deg  I think from memory & never have any problems when idling in traffic but of course whatever you but it needs needs to cut in a few degrees above 87deg & then off on 87 or slightly higher. Very sensitive the water temp needle on the gti just a few extra deg cam make you think its cooking.

hope that helps
cheers
barry

Cheers Barry.
Ive got the new racing radiator and a new water pump to fit so I shall order an 87° stat.

Hi Macca
Yip the 87deg mechanical stat is defiantly the only one to fit as VW intended. It will throttle open & close to maintain this temperature with the airflow through the radiator. When idling it will throttle open & the electric fan then produces the wind. The racing radiator will not make any difference to the actual temp the car reaches when idle.
cheers
baz

macca the symptoms you describe are exactly how the cooling system should operate while the car is stationary, are you sure there is even a problem?

I changed the rad stat for the fan for the correct one and it cured this. my car came with the wrong one, think it was a mk2 one for a two speed fan, it had three terminals. my temp gauge would go right up before the fan would kick in.

John i think that it is getting too hot though. If the fan kicked in at a lower temp and kept it down then that would be fine. 
It never did this during the first year that I had it on the road. It just started last year.

Could be the temp sender, but if when driving its sits bang in the middle probably not. But by simply pulling the connection off & on can help if its a corroded connection as its done by resistance. Ive had my temp sneaking up a bit of the middle before under normal driving & this was all the problem was

Does the water temp sit bang in the middle when driving?

as above where does it sit while driving along, and where does it get to when the fan kicks in?

It sits slightly higher than halfway when normal then gets to about 3/4 when fan kicks in. It doesnt just creep up when sitting in traffic, it gets hot quite quick.

sounds ok to me then, as logn as fan catches it at 3/4 and pulls temps back down all is workign as it should. 1/2 is where you want to see it really but just over 1/2 isnt so bad either, could just be sender reading slightly out.

whats the mfa oil temp say when its just over 1/2 and when fan cuts in?

have a look at your rad though, if its qute grotty or only a single core bin it and fit a new one, no need to go alloy really but if you have one now may as well fit it!  I'm using a bog std 1.8 8v gti hella made rad in my abf mk2 and its perfect

Cheers John