Attached is a picture of my dash coolant temp. gauge. While driving my 1996 ford f250 7.5 v8 my gauge reads around the "N" to the "O" but while stopped at a stop light, drive through or idleing like in park gear it rises to the "M" to "L" but when i start driving again it drops back down to the "N" or "O". it is 90 degrees out side with the AC on and i wasn't towing or traveling up hill it was city driving and i also can here a difference in the engine as i step on the gas it feels like it take more pressure to push the gas petal also. any ideas or it that normal?
Thanks

 

Do you have a fan clutch? That could be weak or worn out. You're getting enough air flow as you drive but your fan isn't pulling enough air through the radiator when your stopped.

 

Yes i do have a fan clutch and i can see it moving and spin. I also have a K&N cold air intake on that been on for about 3 years but the heat problem just started. Is there any way i can check to see if the fan or clutch are working right?

 

The fan will still spin with a bad clutch, it just won't move enough air. When the engine is off try spinning the fan. Just give it a push or pull and it shouldn't rotate very far after you let off. It should resist your effort and not turn any more after you let off.


A fan shroud is also very important, but you said it was cooling just fine as you have it set up before.


I'm wondering if you shine a timing light at it while the engine is revved up if you will be able to see it slipping. I haven't tried this before. The fan should be rotating at the same speed as the shaft that it is on that is hooked to the water pump.

 

Thanks for replying again. I moved the fan and it stopped as soon as my hand moved away from it and when the truck is running the fan spins fast.

 

Ok, that's about right for the fan clutch. Should of had a good feel of resistance when you where turning it. Kind of only way to know is to compare it to a known good one.


Otherwise...have you checked the coolant level?

 

There is good resistance to the fan. I just had my intake manifold gasket replaced about 3 weeks ago and the antifreeze was at the normal level then but when i went to try and spin the fan i noticed that the anti freeze level was way below the cold line, so i added anti freeze to the cold line. so Im hoping that was the problem and not another leak. I checked the oil and oil cap and there was not sign of anti freeze in or on them and there is no anti freeze smell coming from the engine like before. but i did notice on one of the pulls there is a triangle piece of metal that usually spin but it doesn't do it all the time and the fan would spin faster and today i had the truck running for about 30 mins and it didn't spin of move once that im aware of.

 

I'm not sure of what you mean by the 'triangle piece'.


The next step is to start the engine with the radiator cap off. Put a thermometer into the neck of the radiator far enough so it is in the coolant. Watch the temperature and see if it is as high as the gauge on the dash. This will let you know if the sending unit is working correctly. The engine should be able to manage to stay at about 180 degrees.

 

Triangle piece is probably the electric clutch for the Air Conditioning Compressor.

It is normal for this to cycle on and off depending on demands of the climate control.

 

I did figure out that the truck starts to over heat when the AC in on and that Triangle piece is the AC electric clutch ( thanks ArdWrknTrk for the pic and help) and as soon as the AC comes on the truck drops in rpms and when u step on the gas its harder to push and the engine sounds like its under a large load. still not sure whats going on.
Thanks Turbo Dog also for the help

 

If your truck was old enough to have a carburetor, I would say the throttle positioner solenoid was bad or disconnected.

I'm not sure how your fuel injected engine deals with the compressor load.
Maybe the computer is supposed to adjust the IAC, or something...