So my wife started the car and drove to work (about 12 miles) and the engine overheated, but the heater blower was cold when she arrived at work.
She drove it home, the same happened. I felt the top radiator hose and it was cold. Im guessing the thermostat failed in the closed position hence not letting the water flow thru the radiator to cool the engine.
Can anyone confirm the thermostat fails in the closed position, causing the engine to over heat?
Thanks

 

Seen them fail in both buy mostly closed position.. working on vans and cabs see this quite often.
Id advise a compresaion test and a block test which local garages can do and by putting the solution in the coolant it should change colour if headgasket failure. Worth checking these before going out on taking motor apart.
Also remove thermostat and put in a cup or boiling water and see if it opens..

 

Ok thanks

 

Check you haven’t got an airlock. Heater blowing cold is a classic symptom of this on the s2k.

 

^^ yep. Did you do anything recently to the cooling system? When you first refill them they will even seem fine up front, then suddenly the air bubble will hit, heater will blow cold and the car will overheat quickly.

 

So I got the thermostat out of the engine block yeaterday, and tested it in boiling water and it open about 2mm. I guess it should open alot more than that to let the coolant flow to the radiator.
Does the radiator for the air-con have coolant flowing through it, or is it a seperate system?

 

that piece is called a condenser and is not part of the cooling system. It contains refrigerant for your AC.

 

Thanks for the info clubhopper

 

there are a few points to bleed it but assuming you didnt touch anything that would mean a leak.

a new thermostat then follow the bleed approach in the service manual.. its messy if you dont have a spill free funnel

 

This is info from the service manual on the stock thermostat.
Lift height: above 10.0mm / 0.39in
Starts opening: 169-176F / 76-80C
Fully open: 194F / 90C