1.8gti thermostat problems

hi, can any1 help, i have changed all the water pipes, thermo switch and themostat. all the pipes are getting red hot expect the one coming from the thermostat to the bottom of the rad, which means the thermostat is not opening which in turn means my fan wont kick in..... any ideas??????

The lower pipe should be colder than the others as the rad cools the water.

Is the car over heating and/or loosing water?

Did you put the thermostat in the right way round?

the car isnt losing any water, but the fan doesnt kick becuase the thermostat wont open to let water into the rad. i put the small end up into the thermostat housing.

The only time the fan normally runs is on hot summers days when you have just done a 10 point turn or sat in traffic for ages.

To check the fan side is working simply touch the two wires togther that connect to the switch in the rad. Becareful the fan will still turn even with the ignition off.

If the system is blocked and not allowing watrer into the rad it would over heat and boil up.

if i remove the thermostat at connect the fan wires the car stays at a nice temp perfectly, but if i put the thermostat in it doesnt work

This pic should help determine which way round the thermostat goes. Its always possible that you have a dud one.

errrr…. what was the orginal problem that you are trying to fix :dontknow:

If the car warms up reasonably quickly and doesn't over heat or loose water, sounds likes it working OK. :dontknow:

i have changed the thermostat 3 times, does the smaller plate go up into the water pump or does it point downwards?

the car orignal overheated so i changed the thermoswitch and thermostat and flushed the rad and it all worked fine 4 2 weeks then the fan stopped working so i changed the pipes and thermostat but still it isnt working

best way to check the thermostat is to place it in a clear glass full of boiling water and watch to see if it opens

tried that i put it in a pan and boiled it and watched it open and close

Mk1Fey said

tried that i put it in a pan and boiled it and watched it open and close

Check the electrics then. Check the fan spins, with 12V applied to it. And that the switch on the bottom left opens and closes when the car heats up/cools down. The connections here are quite unreliable, terminals corrode etc.

paul_c said

Mk1Fey said

tried that i put it in a pan and boiled it and watched it open and close

Check the electrics then. Check the fan spins, with 12V applied to it. And that the switch on the bottom left opens and closes when the car heats up/cools down. The connections here are quite unreliable, terminals corrode etc.

i will try that 2moro cheers, which way does the thermostat go, just double checking, the thiner end pointing up or down?

when you say the car overheated did it do any other damage? such as head gasket? otherwise electrics, done simple stuff things like check fuses and cracked wires?

hi,the thermostat cant be fitted back to front,,whilst the thermostat is out,look into the pump from underneath  to see if the impellor looks ok,and also try to move the impellor with a small screwdriver,ive had these come loose on the pump shaft and not pump very well.
Bert

all the pipes get red hot except that 1 coming from the housing to the bottom of the rad, which means the thermostat isnt opening, but it doesnt make sense y it wont work

Bert said

hi,the thermostat cant be fitted back to front,,whilst the thermostat is out,look into the pump from underneath  to see if the impellor looks ok,and also try to move the impellor with a small screwdriver,ive had these come loose on the pump shaft and not pump very well.
Bert

yep i'll second that thermostat will only go in one way, providing its the correct one!
 once you have fitted it and refilled the system you should run the car till it gets to normal running temp, (don't drive it thought) then let it tick over for about 10 minutes or untill the fan comes on whichever happens first, but watch the needle don't let it over heat ie needle all the way to the side. once the fan has come on let the car cool back down the refill the water, if it doesn't come on or the car overheats it could be the fan switch on the rad (if the rad is very hot to touch) if its still cold and the thermostat works it could be the pump or a blockage.

volkswarren said

Bert said

hi,the thermostat cant be fitted back to front,,whilst the thermostat is out,look into the pump from underneath  to see if the impellor looks ok,and also try to move the impellor with a small screwdriver,ive had these come loose on the pump shaft and not pump very well.
Bert

yep i'll second that thermostat will only go in one way, providing its the correct one!
 once you have fitted it and refilled the system you should run the car till it gets to normal running temp, (don't drive it thought) then let it tick over for about 10 minutes or untill the fan comes on whichever happens first, but watch the needle don't let it over heat ie needle all the way to the side. once the fan has come on let the car cool back down the refill the water, if it doesn't come on or the car overheats it could be the fan switch on the rad (if the rad is very hot to touch) if its still cold and the thermostat works it could be the pump or a blockage.

where abouts could the blockage be, cos the pipes get red hot and so does the thermostat housing unit execpt that 1 pipe

mmm… whats for dinner tonight then…  


This is an accurate way to make sure you're thermostat opens at the specified temp. Think I got this multimeter from Argos, was ages ago.