I really need some help with this, my temp gauge is going from very hot to ice cold then back to normal operating temp. The motor didn't seem to over heat, I changed the thermostate but have the same problem. Any suggustiions on a repair. My truck is a 2000 Ranger. 3.0 V6

Thanks

 

Is it just moving around randomly or is there a pattern to it?

 

When I start the motor for the first time the gauge shows cold (normal) it will move to normal operating temp on the gauge for a short time then move to cold again for a short time. Then back to normal. Seems like it changes when I am stopping or turning.
Thanks

 

Hello again everyone
I have been away from my turck for a while and would like to get this problem of mine taken care of if any one is willing to help.

I changed the thermostate, checked the rad cap and it holds pressure,that did not take care of the problem, I also checked the inside of turck, there are no leaks, then I was reading some posts and found that part of the problem might be air in the system, so I blead the system as suggested. The motor got up to temp with the rad cap off and the heater on, the only thing that happened was the coolant was flowing out of the top of the rad rapidly, even more so when I reved up the motor. I shut the motor off and filled the rad again. The same thing is happing still. The motor when driving will get up to temp, sometimes the gauge will go back to cold then back up to normal operating temp, when I turn on the heater the gauge will always go to cold.
Does anyone have any advise as to how to repair this problem.
This is a 2000 Ranger 3.0.
Thank you so much for all of your help on this.

Jim

 

Does the temp gauge drop quickly and or jump erratically or does it drop slowly? When you turn the heat on does it get hot?

 

The gauge drops slowly and returns to normal slowly and heater air is cold
sorry I forgot that part about the heater getting hot.

 

It almost sounds like you don’t have sufficient coolant in the system.

Note with the radiator cap off, as the engine is warming up, the coolant shouldn’t start flowing out the top rapidly. It will slowly start to come up. Once the thermostat starts to open it will start to run out. However, if you rev up the engine it should be sucked back down and you should see it flowing rather rapidly through the radiator. Once you let off the gas it will rapidly rise back up and start to overflow.

If while revving the engine the coolant lowers to the point you can see the core tubes, your probably low on coolant. If you don’t see any flow or its very slow either the core is partly obstructed or the water pump may be on its last leg.

Try this, with the engine cold, start it up, allowing it to idle with the heater set to full hot. While its warming keep checking the heater hoses that go to the fire wall to see if they start getting hot. If both hoses start getting hot, coolant is circulating through the core.

Once the truck is up to operating temperature, the upper radiator hose should start getting hot as the thermostat starts to open. Shortly thereafter the lower hose should start getting warm as well.

Note, it may take a while for the thermostat to start opening. I know my 2001 w 3.0 outside on a cool or cold day will take forever unless I constantly rev it up.

PS: it can be a PTA to purge the air after fully draining the coolant. I had to park mine on steep incline, while running it to get most of the air out. I did find you could get more of it out with a flush tee installed in one of the heater hose allowing it to burp out the tee cap. Even then the next day I still had to add some more coolant directly to the radiator.

 

Thank you, I'll try that this morning.