Can anyone tell me if their temp gauge stays constant once it warms up or does it fluctuate. My 4.0 manual trans temp gauge fluctuates with no rhyme or reason. I have changed the temp sending unit. I have put on a new waterpump while I was replacing the timing cover gasket. I have a new thermostat, new coolant sensor, and put in an aftermarket gauge to make sure nothing was wrong with the dash gauge. I don't lose any coolant. I don't see any air bubbles in the resevoir which I believe tells me my head gasket is not leaking. I checked and there is about a 40 degree difference from the top rad hose than the bottom which tells me that the radiator and fan seems to be cooling it. The temp never goes into the hot range but it wanders up to hot down to cool and back to the middle. I just want to make sure that there is nothing else I should check. I don't want my son having problems with it driving from Cleveland to Columbus for school.
Any suggestions would be appreciated.

 

replace your thermostat.

 

I did two times. The second time I bought the more expensive heavier duty one and it did the same thing.

 

This may be stupid to take a look at... but just read.

I had a 2000 Daewoo Lanos, and part of routine service you have to have the valve cover gaskets replaced becuase they dry out and wear out. Now, on one of these services these suckers are easily messed up upon installation. The main thing that I noticed was not oil leaking or something very drastic.

Instead I noticed that the engine temperature gauge would go up and down. I suppose it was from oil or something leaking and cooling the block on the outside. I really never investigated it or anything too deeply since the shop that did the service had to redo this service free of charge... Plus the car was too small to work on.

I would suggest for looking for any kind of fluid leaks of any kind, just becuase there is a temperature problem does not just mean that it would be in the cooling system itsself. check around all gaskets where oil could leach, and check oil level. Also note if it happens ALL the time, or only in wet climates If it is just during wet times, maybe it is the water from the road just hitting the engine right or something.

In addition to this, check your fan clutch if you have a mechanical fan. It could be possible this part is not functioning properly, there for your fan would be changing speeds, changing cooling speeds of the engine eventually.

It is a more abstract way of looking into the problem, and is really just a guess to me. Best of luck to you, these problems can be very fusterating so just stick with it!