jacobs4x4

Ok so my coolant temp gauge stays as high as it will go all the time when my truck is on. When I brake accelerate realy fast it goes back to normal. My instructor at my school says that I need a new thermostat.

What do you guys think?

wde3477

The thermostat would be a little further down on my list of suspects.

First - does the truck seem like it is running hotter than normal? If so, might explain the high reading but not the normal one.

Next - are you sure you have enough coolant - sensors don't measure air temperatures very well. Your description of going to normal during accel/decel has me wondering if the coolant may not be getting sloshed/pushed up on the sensor during these moves.

Next - check the gauge. If you pull the connector off the sensor, it should read Cold. If you ground the sensor wire, it should read Hot. Maybe it's the other way around - but at least you'll know that the gauge is probably working as it should. Not sure how your truck is configured - my model year used two coolant temperature sensors - one for the computer and one for the gauge. Needless to say, find out and then be sure you're on the right one.

Next - if the gauge checked out - suggest the sensor is bad. A bad sensor on the computer coolant sensor side should have yielded a 'check engine' light. Again, be sure you chase the right problem.

jacobs4x4

I don't think it's running hot. I'll check that next time I run it for long enough to heat up. I definitly have enough coolant I've changed it once and taken it out and put it back in one since this has been hapening. I found a picture of the sensor on alldata I'm off work tomorow so I'll check it in the morning. It's easy to get to it's mounted on the top front of the upper intake manifold. If the water pump was bad would that cause there to be no water at the sensor since it's at the top of the engine.


I don't think the engine is runing hot because of this feture. Acording to this if the gauge is all the way on hot which it is most of the time then the injectors should be disabled by the computer.

The Cylinder Head Temperature(CHT) sensor:

- Is mounted into the wall of the cylinder head and is not connected to any coolant passages.- Sends a signal to the PCM indicating the cylinder head temperature.- If the temperature exceeds:
126°C (258°F)</B>
the PCM disables four fuel injectors at a time. The PCM will alternate which four injectors are disabled every 32 engine cycles. The four cylinders that are not being fuel injected act as air pumps to aid in cooling the engine.


- If the temperature exceeds:154°C (310°F)</B>
the PCM disables all of the fuel injectors until the engine temperature drops below:


154°C (310°F)</B> - If the engine reaches critical temperature, the following happens:- The coolant temperature gauge pointer will read fully hot at 121°C (250°F). - The check gauge warning indicator will illuminate.- DTCs are set.


Sorry I don't feel like checking the sensor at 11:20 P.M. so i'm just talking about all you sugested.

blackbetty

i would think it would be air in the system since the fluid is new, then i would check the sensor, also check the guage, but sensor is first in my book...

also a fail safe thermostat is the best 10 bucks you can put in your coolant system imo

jacobs4x4

The way to get air out of the system is to take out the sensor isn't it.

blackbetty

take off the coolant cap, start it up, let it warm up, it will burp out all the air and when coolant starts to come out the hole put the cap back on...thats how to burp a system

Ty

I thought that the system was designed so that the radiator cap was the high point of the system, so that it would blead its self?

blackbetty

it is designed to be high point, your right....however i am not sure if his is like our newer ones, i should have said that is for a radiator type cap and not one where we have the bottle....my bad

Ty

His would be the same as mine. I am trying to find the thread I had when there was some air in my system, I think there was some good info in there.

jacobs4x4

My radiator does not have a cap.