94 cooling troubleshooting help please

[Thor]

I have a 94 6.5 TD in my 3/4 ton 4x4, have owned the truck for 6 years and it has always cooled fine, towing and in hot weather. It recntly started to run warmer so I bucked up and put in the SS diesel supply cooling upgrade along with a turbo clamp on air filter. All the work and parts did not sem to change much at all. I tried a Gm fan clutch, and radiator cap and this did nothing also. 250,000 miles on the truck, 150,000 on the engine. Got $600 in parts and it has not fixed it. Do those aluminum radiators go bad? Any help would be great. Thanks

[BUZZ]

HAve you cleaned the area between the radiator anf the AC condenser? Collects a lot of debris, Rad could be plugged in the tubes.

[a5150nut]

Like Buzz said, clean the radiator and the ac condensor. Pull the fan, shroud and radiator. I use a small brass nozel, looks like a mini fire nozel, and Simple Green in a weed sprayer.

After you get everything nice and clean, cover your radiator/condensor with black nylon window screen to keep the bugs and trash out. I have my grill holding the screen in. I clean mine every couple years. It is amazing how much dust and trash gets into the fins.

[Iain]

Never hurts to check your water pump as well. My 1994 ran perfect and never overheated when I first got it. 3 years later it started to run warm, especially in the city with the AC on. I changed the water pump (which was not leaking yet but had a loose shaft) and put on the HO 1997 model pump and crossover and now have no problems at all. Your pump may just be starting to wear out.

[markrinker]

I battled moderate overheating with truck #1 (stock '94), even after a water pump failure took out the radiator and both were replaced.

Still saw temps of ~230 in hot weather while towing.

Finally I pulled the thermostat as a 'test' last summer, and never saw temps over 190 since, running without one. I now run the truck without a thermostat in the summer, and drop one back in for the winter.

There is probably an underlying cause (scale and corrosion in the heads most likely), but the increased water flow solved the problem.

The engine has similar miles to yours - about 145K.

[Kennedy]

Provided the air path thru the rad is good andeverything else is in working order, I'd say fan clutch.

[Kennedy]

Originally posted by kennedy:
Provided the air path thru the rad is good and everything else is in working order, I'd say fan clutch. The aluminum radiators typically stay clean,especially with Dex Cool.

[markrinker]

I failed to mention that the fan clutch was replaced when the water pump and radiator were replaced. All OEM stock peices. Certainly the truck could have benefitted from JK's fan clutch.

I have one on #2 and it makes a huge difference when towing.

[Kennedy]

I'll also add that the afformentioned kit appears to use conventional reverse poppet stats rather than the balanced flow units that allow for increased flow and do not open directly against coolant flow.