Temperature Guage...I think

I have a problem with my temerature guage.... I think!

My 4.0L has an intermittent problem with my temperature readings. When I start it up, sometimes the guage climbs up to H (soon to be followed by the red Check Guage Light, and the onboard computer beep "check engine temp") it takes about 5 minutes to make the climb from L to H, but it is disturbing just the same. I've replace the termperature sender (the one with the single lead, on the left hand side of the thermostat housing (when facing the firewall)) and it did not seem to have any effect. I did notice that when the lead is removed from the sender, that the guage goes down to L right away. The other temperature sensor (with 2 leads, on the right hand side) has never been replaced, could this have something to do with it??

Also, in my seaches I read a post about a fellow with an actual guage problem, he pulled out he instrument panel cluster and cleaned all the contacts.

Any Ideas???

Peter

There are indeed two sensors on the front of the engine. One does the gauge and the other goes to the computer. I would say if the two agree, gauge and computer beep, then the problem is overheating.

My first guess would be sticking thermostat, a search will yield much info.

Good Luck!

As a test, pull the thermostat and run without one for a short time to see if you still get over heating. If not, then its the therm. If you still get overheating, it is likely a flow problem / pump problem which needs attention.

budwich said:

As a test, pull the thermostat and run without one for a short time to see if you still get over heating. If not, then its the therm. If you still get overheating, it is likely a flow problem / pump problem which needs attention.

Click to expand...

I changed the thermostat and at first there was not effect. The truck was still showing hot, however from touching the hoses it was not actually hot. So I set off on a 40 minute trek and the temperature guage was pinned to HOT. Then about 10 mintues into the ride the guage moved back to normal temperature..right in the middle. I did add coolant just before I took off. Is it possible that from running low on coolant that the sensors are not imersed in coolant to accurately measure fluid temperature??

Anyway, so far so good. It's been 2 days and I have not had the temperature guage go wonky.

If you changed the thermostat and saw your problem thereafter, it is more likely a problem with air in the system. Potentially, it means that it needs to be "burped". A few "runs" will eventually get rid of this if it is a problem.... make sure that your overflow is filled appropriately so that the system can draw fluid in to take that airs place.

Note: running with a new therm isn't the same as running without a therm as without you are checking that indeed the system is "free flowing" well enough to keep your truck at "cold" which is where it should be with no therm. If that doesn't happen then you have some issues not thermostat dependent. Putting in a new thermostat doesn't necessarily help testing directly as a new thermostat can be bad also. Anyways, it sounds like you solved your problem.

budwich said:

If you changed the thermostat and saw your problem thereafter, it is more likely a problem with air in the system. Potentially, it means that it needs to be "burped". A few "runs" will eventually get rid of this if it is a problem.... make sure that your overflow is filled appropriately so that the system can draw fluid in to take that airs place.

Note: running with a new therm isn't the same as running without a therm as without you are checking that indeed the system is "free flowing" well enough to keep your truck at "cold" which is where it should be with no therm. If that doesn't happen then you have some issues not thermostat dependent. Putting in a new thermostat doesn't necessarily help testing directly as a new thermostat can be bad also. Anyways, it sounds like you solved your problem.

Click to expand...

Thanks Budwich! If I get the H temp readings again, I'll run with out a thermostat to verify the engine runs cold. So far, every problem I've had with my truck has your name in the threads that I've searched (or posted) Thanks a ton!