Lazy stat?

[MJS]

During the cold winter months I had overheating problems which I deduced was caused by overcooling. Now that the weather has turned warmer, I have a similar problem. When driving at any speed engine temp is fine and never budges from 80°C, however if I come to a stop, or near stop, after a run the temp rises quite rapidly to around 100° and it blew some water out of the expansion tank yesterday. It kept repeating this for the remainder of my journey due mainly, I think, to there being less coolant than was required.

 

My question is: surely the cooling system should be able to cope adequately with this heat soak situation and even though the temp is reaching 100° surely it shouldn't start venting off pressure? I have been advised before that Rover fit cheap thermostats as standard, so maybe a change would help things. Things is though, if I go to Unipart won't I be sold one of identical quality? Does anyone know of a superior quality stat I could try?

 

Matt.

[Fred]

DONT UNDER STAND THIS PART I had overheating problems which I deduced was caused by overcooling question.gif IS THE FAN CUTTING IN OK HAVE YOU A AIR LOCK TEST THIS FIRST IS THIS A ROVER ENGINE 100 is to high most thermostats are ok

 

fredid=blue> smile.gif

[MJS]

My cold running problems were deduced by having repeated high readings on the temp gauge which was only cured by partially blocking the nose cone aperture. Stat was checked, and filling of cooling system was done VERY CAREFULLY to avoid air locks. Once piece of card was used behind the grill (to reduce the very icy blast through the rad, causing overcooling of the stat and hence incorrect operation) problem disappeared. Now this recent problem has occurred it has made me wonder whether it is a dodgy stat after all. The fan is definately cutting in, but cannot say for certain when due to the difficulty in hearing it.

 

You say 100°C is too high, but in my brother's Elise the fan doesn't kick in until he has a reading of 99°.