6.5 non-turbo overheating with no load.

[Thor]

I have a 89 K2500 that had a crate 6.5 non-turbo replacement motor put in it in 93 from the prior owner, my question is how to troubleshoot my cooling problem. This truck will heat up quickly to 200 degree's whether it is 90 or 40 below zero. We had weather here a month ago that was 50 below with windchill it it got up to 200 in a about 5 miles. The prior owner cut air holes in the bumper to try to improve air coming in but it is not helping. If I pull even a small load it will get over 200. I can not find a smaller thermostat than a 190, I want to no if I can get a coller stat, recore the radiator, or if I have to look at a performance water pump, need to know where to start so I fix it right the first time. Thanks

[britannic]

Presumably you've eliminated the radiator, thermostat and water pump as being the cause?

Where's the timing at?

Do you get any black smoke under load?

[rhill2901]

Make sure you are using a high flow Robertshaw or Mr Gasket thermostat. I would recommend one that flows at 180 degrees. If not available in your area, I would check at your high performance car shops are web sites, likes jeds.com.

Lower the fluid in your radiator and check with a flashlight if you have white corrision (crud) in (or on) the crossover cooling tubes. If so, a flush/repair/replacement is in the works.

If the radiator cap isn't working properly (ie, building pressure), it makes it harder for your radiator to keep your engine cooler. I'm assuming your coolant level is full...

Idle the engine for 15-20 minutes with the radiator cap off, the water in the radiator should be getting hot. If it stays luke warm, something could be up with your thermostat or waterpump.

If there is lots of air bubbles venting from the radiator when you have the radiator cap off and the engine is running, this is bad. It would indicate a cracked block or head, or blown head gasket. If your water level is constantly low, you will have to find the leak, probably a hole in the radiator.

Hope this helps...