1995 F-150 with 4.9L engine with approx. 170k miles on it. I just changed the water pump, thermostat, radiator hoses, radiator cap and have confirmed that the coolant temp sensor is good, the guage is fine, and that there are no problems with the resevoir. It also shows no evidence of water in the oil. Even with all of this my engine still overheats under these conditions: 1. When I drive at hwy speeds >55mph. 2. When I run the a/c. However, I am able to keep the guage in the high end of the normal range when I cruise at between 25-40mph by driving easy. The only thing left seems to be the radiator, but it looks to be in good condition. Any ideas? Could heat be sinking into my cooling system via the head gasket without showing signs of water leakage? Or, how can you tell if the radiator is shot?

 

I don't know of a way to tell about the radiator yourself, but if you pull it yourself and take it to a shop they should rod it out for less than 50 bucks.
One more thing- on my mustang there is a tiny hole in the thermostat that lets air escape, that needs to be on top when you install it.

 

Well I went back and checked for a pin hole in the thermostat and there wasn't one.

 

Yours may not have one but mine was very hard to see. It wasn't on the flat part it was hidden between the inner lip and the spring loaded plunger right in the crease. Probly not your problem anyway. good luck

 

I think that your truck has a cooling fan with a thermostatic clutch. With the engine off and cold see if you can turn the fan by hand - there will be some resistance. When the engine is hot, turn it off and try turning the fan by hand. It should be harder to turn when hot.

The right way to check the fan is to read it's speed with a strobe and compare it with engine speed, but this check might help.

Lou Braun

 

sometimes it's the basics that we over look

It's a clogged heater core...

 

I'm not so sure about the heater core being clogged. I can actually use the vent to cool the engine down a little. However, at this point I'm willing to give almost anything a try if I can avoid pulling the head. If I hook up a garden hose to the intake I should get flow on the other end, right, and that would tell me if the core was blocked or not? Oh, by the way I forgot to mention in my original post that the fan was OK, so that's not the issue. Right now, still leaning towards a new radiator. ???

 

Probably a clogged radiator. Heater core shouldn't affect your engine temp. Also, I wouldn't pay someone $50 to inspect and clean my radiator only to find out it was no good, I would rather spend $150 for a new radiator. But before you buy a new one, remove the lower hose and drain, fill the radiator and check for flow. The water should drain as fast as you fill.

 

check the cluth fan it operated by heat and it will get packed with road dirt and thing sometimes it just weatrs out and bids or does engage at all good luck
barkeater out

 

Yes if you run the hose in the inlet it should run out the outlet.

I had a simuler issue with one that makes me think the heater core.

it would run a little but NOT a great flo...