Overheating Issue

[tinner12002]

I noticed, now that its getting warmer and that I'm driving it more, that my 91 318 with 147K is getting a little bit to warm when sitting at idle or in a lot of stop and go traffic. I've flushed the radiator, changed the stat, it was stuck open, and put on a new radiator cap. I even changed the upper radiator hose after it blew apart, but its still getting hot when idling for a period of time. Anyone have any ideas?

[USN78W150]

overheating

Check your fan clutch. It may not be engaging like it should.

[tinner12002]

Guess I didn't think of that since it looks like its turning okay when idling. How would I check it, try and hold a blade with a screwdriver while someone starts it, or is there a safer way to check it?

[Gordon Maney]

Guess I didn't think of that since it looks like its turning okay when idling. How would I check it, try and hold a blade with a screwdriver while someone starts it, or is there a safer way to check it?

No, do not try to hold the blade and have someone start the truck!

Check the clutch for looseness as you would a water pump shaft.

My concern is your radiator may be dirty — tubes internally coated with residue — preventing heat transfer. Flushing the radiator and cooling system would be a good start. Then you might even remove the radiator and have a radiator shop clean it.

Can we get a shop light down behind it to see if you can see through the radiator? You would be surprised how much particulate matter, grass, and dirt can accumulate in a core, external to the coolant circuit.

Ideally you would get behind it with compressed air or water under good pressure, driving whatever is in the core back out the front. If you have air conditioning and a condenser your situation is more complicated.

Another, messier, method [assuming no A/C] is to take it to the car wash and use the wand to direct high pressure water through the core from front to back, blowing all the evil onto the engine.

I am guessing at your odometer reading your radiator is dirty, inside or outside or both, and needs cleaning.

[tinner12002]

Changed out the radiator wednesday, seems to be staying cooler. I will know more today when I drive it to the shop though its only suppose to get in the 50s and shouldn't get into any traffic. Appreciate the help.

[Deathdeelr]

This may be too late since you changed it already but I've had unbelievable results with the all-aluminum radiator I picked up off Ebay. Under $200, all aluminum core, welded tanks, brass inserts for the trans cooler line fittings. I can idle that truck all day long and the needle doesn't move much past the first little mark. I use a 180 thermostat, 7 pound cap and no fan clutch.

Keep in mind that this is in my '77. I tried something similar on my '99 Jeep when I changed the radiator and once in a while she throws a code for the engine temp sensor but that's because unless it's 90 degrees or above out she doesn't run over 190 degrees. I learned to live with it for the peace of mind knowing my wife isn't going to call me because she overheated somewhere.