Recently I had a new block installed in my 2003 WRX. The previous engine block blew up for some unkonown reason. The temp gauge shows normal then increases rapidly to hot then back to normal. Could it be the temp sensor or gauge or is it the normal water pump or thermostat?

Recently I had a new block installed in my 2003 WRX. The previous engine block blew up for some unkonown reason. The temp gauge shows normal then increases rapidly to hot then back to normal. Could it be the temp sensor or gauge or is it the normal water pump or thermostat?

 

Quite likely you have air trapped in the coolant system. Could be something else I suppose - do a search here on radiator filling/verheating etc. and you will find many threads that will guide you on checking for proper filling.

 

Carl

I hope this is not a sign of a bad head gasket. Hopefully it is just a sticking thermostat. You may want to get a block check done to see if any exhaust gases are in the coolant.