I have been having a problem with temp gauge for about 2 weeks and from reading some of the posts on this forum, I have so far replaced the temp sensor and the thermostat but its still not working 100%. The problem started when the gauge failed to move and I had been driving on the motorway for about 1hr. As I kept an eye on it I did notice it "float" between 60 and 90, it would normally stick at 90. Since the problem began I did notice 1 strange think, the pipe coming from the rad to the themostat housing was always cooler than the top hose which was coming from the engine. This is normal as the thermostat would only open once the car had reached a certain temp. I also checked the sensor readings via the cilmate control system and reading 49 would always reach a max of 30oC and 51 would be max 75oC.
Today I wanted to check if the rad fans were operating so after driving for about 20mins I left the car running and monitored the pipes and readings. Checked the pipe to the thermo housing and it was considerbly cooler than the top one, 49 was still sitting at 30oC and 51 at 75oC. After about 20mins the housing pipe started to get hotter and as it did the 49 reading started raising and then stopped at around 96oC when the fan kicked in and started dropping.
Now my question is that could I have a block in the rad ? which sensor is responsible for the 49 reading ? could I have an air lock ? where does the gauge on that dash get its reading from ?
Another stange thing I've noticed is sometimes when I turn on the ignition, the temp gauge jumps over and above the max reading and then comes back down to 90 then slowly to 60, not sure if thats normal or not.
I hope you guys can help me out.