Join Date: Aug 2004
Location: Morgan Hill, Ca
Mentioned: 4 Post(s)
Tagged: 2 Thread(s)
Quoted: 111 Post(s)
Let me revisit the problem.
Temp gauge is always normal, except when it gets hot outside. Even then it stays at normal unless one of the following situations are also present:
1- Extended acceleration that lasts for several minutes.
2- Climbing hills for several minutes.
I have always slowed down or released the load on the engine at the first possible moment so I don't know if there is a point at which the temp maxes out. Frankly, I don't want to try it either.
Possible reasons for the problem:
1- Cracked head and/or blown head gasket - Ruled out because over heating happens only under load. Besides, I do not have contaminants in oil or water.
2- Low water level, leaking radiator, bad cap, plugged radiator - All of these ruled out by dealer when they pressure checked the cooling system.
3- Lean fuel mixture or incorrect engine timing - A possibility, but unlikely as I do not experience any of the other symptoms associated with those.
4- Low airflow to the radiator - Ruled out as both fans operate and there are no sir restrictions, other than my homemade lower grill which I don't think creates significant restrictions.
5- Bad water pump - I think I can rule this out too because when they go they make lots of noise and I do not hear anything.
6- Air in the cooling system - A possibility worth exploring
7- Bad thermostat - I agree with joe that thermostats are designed to fail in open position so this is probably not it but perhaps worth exploring.
Any other ideas?
Former owner of 2004 SL AWD