Running Hot at Highway Speed

[gixxer]

Anybody have any suggestions on what would be making my truck run hotter than normal if i get on it on the highway. Im presently running the twin flex-a -lite fans , 160 hypertech thermostat and a radiator from a 1995 Suburban 2500 series. Its my understanding that the fans should not even be running while on the highway, that the airflow from moving would be enough.

 

Also the water pump was replaced with a new GM unit about 30,000 miles ago.

 

Its not like it overheats, but the temperature gauge can go to full. As for regular driving, the temp stays in the middle of the gauge.

[lrymal]

Warm only at highway speeds? Not hot at city speeds?

I think you have something blocking the front end, blocking airflow to the radiator.

[GM-Tech]

You are correct that you shouldn't even need fans when driving at highway speeds. Aerodynamics can play a big part in what you're experiencing.

 

For example, a number of years ago we had a similar problem in Camaro's. If you damaged or removed the little black deflector that hung down off the bottom of the radiator core support, they'd overheat the minute you got on the highway. You could run all day in 90 degree temps and stop and go traffic and never have a problem, but at high speeds, it overheated pretty quickly, even on days that weren't that hot.

 

The problem was that without that little deflector, the airflow characteristics where changed enough that turbulence upset the airflow through the radiator. That little piece didn't seem that significant, but everything is there for a reason.

 

So, depending on what you've changed/modified/removed in the front of your truck, you may have created a similar problem.

[gixxer]

The only change to the front of the truck was changing from an aftermarket bumper to a GM Z71 style (diesel bumper with the openings in it) I think that would allow even more airflow.

 

I gonna hook up the scanner to see what the temp is actually reaching tomorrow.

[100R1]

* lower raidator hose collapsing under higher vacuum while cruising ?

 

* cracked head or blown head gasket ?

 

* timing retarded?

[gixxer]

* lower raidator hose collapsing under higher vacuum while cruising ?

 

* cracked head or blown head gasket ?

 

* timing retarded?

 

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I wouldnt know if the radiator hose is collapsing ( i doubt it , they have the wire insert)

 

no oil in the coolant, no smoking out the tailpipes, no coolant in the oil

 

Distributor hasnt been out or touched and reads correctly on the scanner.

 

Any other ideas?

[unkleJ]

I had a similar problem with my 91 s10. The problem was a clogged radiator. I replaced it with a new one and the temperatures dropped to normal.

 

Jeff

[gixxer]

I had a similar problem with my 91 s10.  The problem was a clogged radiator.  I replaced it with a new one and the temperatures dropped to normal.

 

Jeff

 

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I thought of that, I put that radiator in brand new (GM) last May.

[gixxer]

Could it be that the shop that installed it originally filled up the coolant with the green coolant and I ran that for awhile before switching back to the dexcool?