Sudden Overheating Problem

[Sean Flanagan]

I got a call from one of my buddy who was pulling his car hauler from Phoenix to Denver. He said, all of a sudden he is having a serious overheating problem. He swapped out the thermostat with another and still no improvement. Even swapped it with and old one with the guts removed (wide open). Is it possible that the radiator is plugged? The truck is only 4 years old.



The truck is a 98. 5, has 185k miles, and has had the coolant flushed once a year. By the way his gross combined weight is 28-30k! This is at high altitudes (9000-11000 ft)



He said he could easily peg the coolant temp at 240F.



Any ideas?

 

[JR2]

Is his radiator full of dead bugs and muck? I read a post about a guy that had to remove his rad and pressure wash it to get all the crap out to solve his over heat problem.

 

[Texas Diesel]

I had this happen to me: The impeller comes loose from the shaft.

Not much water flow when this happens, but it was not a CTD just a regular truck.

 

[WeirCummin]

Sounds like a bad fan clutch. I've got a truck in my yard that has 121K and needs one along with injector and lift pumps.



Dean

 

[BK]

I agree with all the above thoughts. .

another one... bad radiator cap.

If the clutch fan is marginal, the thin air could be a hint. . does it happen at lower altitudes?

 

[TowPro]

Any chance this guy has a exhaust brake, thats stuck on?

 

[Sean Flanagan]

How do you check the fan clutch? I think his fan clutch crapped around 30k (under warranty), but that was over 150k miles ago. Can you still spin it when it's hot?



I doubt it's the radiator cap because it wasn't blowing steam or loosing water until he pegged the gauge at 240F for a long time.



He doesn't have an exhaust brake, even though he should with that kind of load in the hills.





Thanks for the ideas...

 

[PCrable]

Hey Sean !

Sorry to hear about your friends truck troubles.



The stock fan clutch is a fluid coupling. As the fluid gets hotter in the fan clutch, the fan is engaged more. When the engine is cool, it still will engage about 15%... When the engine is hot, it should be spinning at about 85% of the engine speed.



I have the Horton Fan clutch... it's either fully off, or fully on.



--Phil

 

[fest3er]

Originally posted by Sean Flanagan
I got a call from one of my buddy who was pulling his car hauler from Phoenix to Denver. He said, all of a sudden he is having a serious overheating problem. He swapped out the thermostat with another and still no improvement. Even swapped it with and old one with the guts removed (wide open). Is it possible that the radiator is plugged? The truck is only 4 years old.

The truck is a 98. 5, has 185k miles, and has had the coolant flushed once a year. By the way his gross combined weight is 28-30k! This is at high altitudes (9000-11000 ft)

He said he could easily peg the coolant temp at 240F.

Any ideas?

Hmmm. I'll bet his fan clutch is shot. Ask him if he ever hears the fan engaging - it should be *real* loud. It should engage when he first starts it cold and roar for 10 seconds or so. In hot ambient with the A/C running, the fan should also engage when crawling in stop-n-go traffic. . If he *never* hears the fan engage, the clutch is bad and needs to be replaced.

It wouldn't hurt to replace the t-stat as well.

IIRC, isn't the Cummins t-stat 'reversed' from normal. That is, doesn't it close off the radiator by opening up, and open the radiator by closing? I thought that's what I read here a long time ago... .

N

 

[Sean Flanagan]

I talked him about checking the fan clutch. Now that he is back in town, the hard part is trying to get it hot enough without pulling a load.



He told me that he pulled E. B I70 from Silverthorne to Eisenhauer (9,000 to 11,000ft) with the temp gauge pegged the whole way. He pulled over on the down hill side when the check engine light came on and the thing wouldn't cool off. He said the radiator was DRY! Having the temp pegged for 10 miles boiled all the water out of it. These motors are damn near indestructible. He's lucky he didn't toast it. If you see a green 98. 5 4x4 quad cab with high miles and from Colorado, for sale, DON'T BUY IT.



He ended up filling it back up with stream water and made it the reset of the way home (all down hill).



Unloaded, the thing still runs fine

 

[fest3er]

Originally posted by Sean Flanagan
I talked him about checking the fan clutch. Now that he is back in town, the hard part is trying to get it hot enough without pulling a load. ...

Put a piece of cardboard in front of the radiator. *That'll* get the engine to heat up but good!

N

 

[dmurdock]

Yo dean, i thought the city got onto you about all those trucks and dishwashers in your yard??