Overheating issue??

[Promark80]

Just wanted to throw this out and see what feedback I Get, thanks in advance to anyone who replies.

Just finished up a head gasket job on my 4.0 Ranger, also replace radiator, t-stat, water pump, and hoses. I have about 30 miles on the fix and while driving today I noticed that the temp gauge never showed hot, but fluxuated quite a bit, also the air out of the vents never got real hot either. After it was parked it didn't leak any coolant at all. Thought maybe it would regulate after some more miles, what do you all think??

Thanks again

 

[Craig0320]

Sounds like bad thermostat. It is opening up to quick or it opened up the first time and stuck there.

 

[Uncle Gump]

Kinda sounds to me like the cooling system isn't full. You sure you got all the air burped out of it?

If it's full... what Craig said.

 

[Denisefwd93]

Check with external thermometer infrared handheld, good chance the sensor is bad on the on the engine block and the gauge is fluctuating happens in my truck all the time will get around to it someday

 

[Craig0320]

Check with external thermometer infrared handheld, good chance the sensor is bad on the on the engine block and the gauge is fluctuating happens in my truck all the time will get around to it someday

Temp sensor is probably less likely since op posted heat is warm at best. Rangers will burn you out when engine is at correct operating temp under normal circumstances.

 

[Denisefwd93]

"Fluctuated"

 

[RonD]

I also have a 1994 4.0l Ranger

Your heater core is clogged up, and that causes the fluctuations

If you look at the heater hoses in the engine bay you will see there are no valves on them, this means the heater core is the Bypass for the water pump when thermostat is closed and when open as well.
Heater core always has/needs coolant circulating thru it, so heater works, lol, and so water pump can have full circulation thru the engine all the time.

When Bypass is blocked, partially or fully, you will get the up and down in temp on the gauge because thermostat is opening and closing alot because flow thru the engine is not stable, and can't stabilize.

Good news is the heater core is not too expensive and very easy to change in 1994
2 hose clamps and 4 screws, and you don't need to drain alot of coolant out because heater core hoses are high up in the system.

You can test for this blockage by taking heater core out of the flow.
Remove the two heater hoses and connect them together, or route one heater hose from lower intake outlet to water pump outlet

Then go for a drive

But with the symptoms described, little heat in cab and fluctuating temp gauge, I would bet money on the heater core only having partial flow.

There are 4 screws holding on a plastic cover under glove box area, 3 are lower down, 1 is higher up, you can fold down glove box all the way to see this one.
Cover will drop down/come off after screws are removed, heater core will be visable
Put a towel down under the core
Assuming hoses are removed at this point
Pull heater core back and tilt it, you need to tilt it to wiggle it down and out and coolant WILL spill out, which is why towel should be there.

If core is blocked it will be HEAVY, compared to new core

Have some 3/8"-1/2" weather strip handy, the old stuff usually doesn't come off the old core.
Weather strip is NOT required, but you will get some air leakage around the core without it

 

[Craig0320]

"Fluctuated"

Flux capacitor.