Hi, I'm a newbie, so forgive me for any stupidity. I have a 91 E150 4.9 I6 w/ 190Kmi. This is my first car, I've had it since 110K and I never want to get rid of it.

Last September on the way to the Holland Tunnel in NYC, I overheated and boiled over. I've tried tackling the problem by replacing the plugs & wires (quick tune-up), radiator (this was fun, ugh), upper & lower radiator hoses (they were melted on & i think original), radiator cap, thermostat (190; twice since), tried cleaning the fins of the a/c condensor? and the radiator with a hose and I've installed an overflow tank b/c it never had one when I bought it. This has solved the oveheating problem unless I run the a/c.

My question is:
I'm not sure where the needle on the temp gauge should be for normal or for that matter what normal operating temp should be on that gauge. With the a/c off on a hot or cold day, the needle sits btw the R & M of normal on the gauge, leaning more towards the R. Today was 88-90degrees & humid and with the a/c on, the temp with no cargo hit the L only after city driving for maybe 45min. I turned the a/c off and it went back down to btw the R & M within about 5 minutes. The a/c is still r12 and blows cold even with the engine temp that hot. I've tested (to my knowlege) the fan clutch, by turning the fan by hand when cold. It turns by hand but stops spinning when you let go of it. There's no coolant dripping. The water pump and fan clutch are both original; are they the problem?
any suggestion is welcome no matter how dumb or small or whatever? I wanna figure this one out.
Thanks for your help,
-jeremy

 

You need to turn the fan when its hot to check the clutch. It should be tight.

As far as the temp guage, they're not calibrated or anything so it's anyone's guess as to where it should run. My 89 E-150 runs right in the middle all the time but my 88 E-350 RV runs at the top end, and once it goes over High the fan clutch kicks in and roars until it kicks out. Of course it's got the 460 so the fan is lould when engaged.

What did your gauge do when you overheated?

 

I'll bet anything that your fan clutch is gone...if the problem is only when slow traffic or idling and not when you are driving at highway speeds the fan clutch is most likely the problem...only about $50 for a new one...that many miles on the original and I'll bet it's it.

 

I have a simular problem, when on the highway say doin 60 my
460 heats up to around btwn the r&m in normal and in the city
it cools to just below the n . I also have a new water pump and
thermostat so my conclusion was also the clutch on the fan which
i have'nt got yet but soon, when hot the fan would rotate easily
cold it was hard, so therein lies the problem the clutch part of the
fan is bad. good luck, let us know if that works.

 

Thanks on the fan clutch info. I guess I misunderstood how the fan clutch test worked. The problem is definitely with the fan clutch. I'm replacing that tomorrow along with the water pump which is functioning fine, but after 190K i guess it's better safe than sorry.

As far as the temp gauge:
It went up about to where the normal range ends, I pulled over, let it sit running for a minute or two and then shut it off. The gauge at this time went up into the red. I didn't have an over flow tank at the time so it boiled over. I let it sit for about two hrs and then filled the radiator back up. By this time there was no traffic and night time kept the air a bit cooler. I guess I should install an aftermarket temp gauge so I know where the temp should be.

 

thanks for your help everyone

 

I read a little article on overheating and they basically said if you overheat at speed it is likely the radiator to look at, if you overheat at low speed it is likely the fan clutch. Now I know this doesn't address the thermostat, radiator, radiator cap, etc. but it does make sense.

I had an overheating problem a couple years ago on a trip to Colorado. Had a radiator shop run the "borescope" in the radiator and find no problem. He suggested replacing the thermostat which I did. It still overheated on the way home so I sprung for a new Transpro HeatBuster four core radiator from RockAuto.Com. As I was lifting out the old one, with the trouble light under the hood behind it, I saw that almost 50% of the core was full of mud, bugs, etc.!!! We'd all missed it because the AC condensor was clean. The old radiator was probably OK but I put in the new one anyway. No problem now; pulling a fifth wheel, upgrade, at altitude in 90*+ temps. If I turn on the AC it goes up as high as ~225*. Warm, but still acceptable for a hard working 460.

Pull the radiator (if you haven't already) and make sure it IS clean ...

Roger