My truck has recently started running a little hot. The needle used to sit on 'O' all the time, but now it rests sqaurely on 'M'. Up until about a month ago the temp needle has only risen above 'R' once and that was in the middle of summer pulling a really heavy and unaerodynamic trailer. The truck is a '92 F150 4wd w/ 4.9L, M5OD, BW1356, blah blah blah. I put a 195 degree thermostat in it a couple of years ago and flushed and filled the coolant last fall. A previous owner installed an F-SuperDuty radiator into the thing cause it would overheat when he pulled his fishing boat, so theres no problem there. I think the fan clutch may be bad: it really got toasty the other day while sitting in .5mph traffic. I became concerned when the needle made it to the top of the 'Normal' range and started smelling antifreeze. Is there any way to check the clutch before I go buy another one? Anything else it could be?

Also, I wouldn't be opposed to getting electric fan(s), if that would help. I've always liked the philosophy of 'If something breaks, replace it with something better'.

 

So, am I on my own on this one or what?

 

well the only way ive heard to check the clutch, is to start it, and pinch the upper radiator hose off, and wait for it to heat up and listen for it to kick in. i think you could take a propane torch lightly to the clutch, and see if it locks up, but im not sure.

 

Reading another thread in the cooling forum, I gather that if I can easaily turn the fan when the engine is off, the clutch is bad. I can. Should I sumise a bad fan clutch?

 

OK , before we start with the propane thing and heating up the fan clutch - not that I'm saying that it's a bad idea and all - I seem to remember some very detailed procedures in the Haynes manual on how to check the workings of the fan clutch - you DO have a Haynes or Chiltons right there by your hand - right?? Also, it's not totally uncommon for a t-stat to fail within a fairly short period of time - especially some of the jobbers from your local Wad-Mart, AutoZone etc, etc. Have you cheked your water pump to see if there is any a/f coming out of the weep hole(s) - if so you could be looking at a new water pump. Also, when was the last time that you changed out your rad cap? If the cap isn't holding pressure at the specified pressure (13?) then your motor will run hotter than it normally used to. If you could smell a/f when things got toasty in heavy traffic that leads me to believe that there had to be some a/f outside of the cooling system that was "cooking" off of the heat from the motor. Can you see any signs of external leakage on or under the motor? Also, you may want to check the condition of your heater core to make sure that it isn't plugged up which might screw up water circulation and potentially lead to a hot running motor. I'm not saying that your fan clutch isn't the culprit 'cause it could well be exactly what the problem is. All I'm trying to show you is that there is a plethora of other potential causes of a motor running hot that you might want to look at as well.

Keep us posted with your progress!

Cheers!

Mike

 

Thanks Mike. I'll check those things out directly after breakfast, with my Haynes manual by my side.

 

Alright, after following the Hayne's fan clutch check procedure, I have concluded that the clutch is good. It stayed on for about a minute upon initial crankup, then cut out. With a piece of cardboard in front of the condensor, the engine warmed up to 'A' before the fan kicked in and maintained that temperature. After pulling the cardboard out, the engine actually warmed a little more, almost to the 'L', but not any further. This is still much warmer than it used to run, i.e., never getting over 'R'. The thermostat seems to be operational (the upper rad hose is hot), and there's plenty of coolant in the system. The water pump feels nice and smooth, no bearing slop or roughness when turned by hand. I'll pick up a rad cap this week and see if that does anything. The one on the truck is at least 7 years old.

One other thing I've noticed: I seem to be loosing coolant at a slow rate. I've no idea from where its leaking, but the level is always a little low. For instance, I topped off the overfill tank and the radiator itself with about a liter of water before I started fooling around with it earlier. I last checked it about 2500 miles ago at the last oil change. Could a weak rad cap be letting too much water into the overfil tank where it evaporates? I did replace the heater core recently, but it was loosing coolant before that.

 

I had a similar problem overheating on my 1995 F150 5.0 , I installed electric fans and it still ran up to the "m" in town.
I replaced the thermostat ,cap and still ran hot, finally I replaced the radiator and it runs cool around the "o" . I could have had it rodded but the cost was about the same.

 

Make sure your bottom radiator hose has a spring in it. I'm in the process of replacing my hoses and the new one from O'reilly's didn't have a spring. I'm being told this can be a problem which makes sense if the hose collapses and water flow is restricted.

I'm going to Ford to buy the proper hose with a spring so I don't have to worry about it.

Just an idea...