86 F350, crew cab dually, 460/C6, "straight up" cam timing, 25 degrees ignition timing.

New water pump/hoses/t'stat,runs great towing my trailer (7K lbs). No overheating while the truck is in motion at all. But only when the truck stops, get out of the way of the boiling coolant! Once the truck stops moving, the "heat soak" is bad and the temp guage raises drastically.

I replaced the radiator cap with a 16lb, and replaced the fan clutch, as I could not tell if it was engaging. Made no difference! But, I could still not tell if the new fan clutch was engaging. I exchanged the fan clutch as defective, and now have another new one on, but how can I be sure that this one works?

Is there a way to test it? As a last resort I will take my trailer for a drive to heat it up.

Am I missing something? The fan and shroud are in good shape, and the radiator seems fine. If the overheating problem goes away once the truck is moving say, 30 mph or so, doesn't this point to the fan clutch? With the engine hot and off, I can not tell a difference in the resistance from when it is cold.

Suggestions????

 

Dan, I'm about the biggest dummy I know when it comes to timing, but there has been much talk in our group lately trying to help a guy with an overheating problem. What it ended up being was the vacuum line to the distributor had came off the back of the carb. I do know that timing that is too far advanced will cause heating problems. Something to look for anyway.

Good luck.
Ron

 

The extremely easy answer would be the raidator fan, but it's fairly obvious if that's not running (loose some blades maybe?).

Some guesses (off the top of my head--i'm nore of an engineer than a mechanic, so take w/ a grain of salt)

Other options could be low oil/water volume being pumped at idle. Low water would not allow heated water to circulate back to the radator as fast as it's being heated. Low oil would increase friction and increase heat from parts grinding together. You could also have an obstruction that is partially blocking flow, which is overcome at higher fluid/pump pressures.

I'm not sure if a vac leak could cause a lean condition at idle, maybe someone can shed more light on that idea

 

When it over heats is your A/C on or off?

 

[updated:LAST EDITED ON 22-Oct-02 AT 02:47 AM (EST)]A/C is off. Like I mentioned...on the road there is no problem even with the A/C on, and I mean workin'er hard pulling the trailer. When I slow way down is the problem. Running empty is no problem either, even slow.

When the fan clutch engages, it sounds like a roar, doesn't it? Is it possible to miss it? That is what I am not getting with a brand new fan clutch. Oh, and the water pump is new.

I am running my carb lean. In fact I had to richen it up quite a bit after I changed the cam timing just to keep it from popping through the carb. I am running an Edelbrock 750. Seems like this would be a problem at higher speeds though and not just at slow speeds.

Everything is perfect, except for this heating problem.

 

How old is the rad? Have you really flushed it lately, it may just be on the verge of capacity. Just a thought.

 

I second the vote for the radiator. And I assume you still have a factory fan shroud on it? Make sure the AC condensor is not clogged with bugs and dirt too.

 

I am going to be flushing the radiator today. The entire A/C system is all brand new so no problems there. I still want to hear that fan clutch roar though.

Fan and shroud are OEM and in fine shape. No cracks etc...

should I think about a bigger radiator? I think I have a 3 core, but I am not sure. Wish me luck...

 

I have found in my mechanical ventures this works sometimes when all else fails: Add coolent/water to a disconnected upper radiator hose held way up in air,then real fast and with good hand eye cowardenation put back onto thermostat housing. Forgive my spaelling

 

have same problem with my many mile FE. When I pulled the heads to replace them I found a coolant passage completely plugged on the right side! further investigation revealed extremely restricted coolant passages due to what looked like corrosion build up. chipped away at what I could reach runs 20 degrees cooler now. still warms up a bit at idle but what a difference. Professional shops have a process for this. It might be worth investigating.
just my $.02 worth.

 

If anybody has overheating Fords with heads off. Get a gasket and drill more holes in heads for coolent flow. You'll see many holes in gasket but not in head. GOD BLESS

 

Did you get the correct water pump? The 300 used a reverse rotation pump from around 87-on, with a serpentine belt. If you got that one, it would cause an overheat problem. The the opposite is also true: Serp. belt w/ v-belt pump.

Jared

 

The radiator "seems fine"? I think that would be the place to check. It doesn't take much clogging in a radiator to cause overheating at idle. My vote is "radiator".

 

Bad Fan clutch. Very typical. When the engine is hot - shut it off and try to spin the fan it should not spin around more than one or two times.
It wouldn't hurt to clean/flush the radiator like many of the other postings suggested. But I put my money on the fan.
Once the truck is moving down the road the air flow is increased so the fan doesn't have to work as hard. That's why it only overheats at idle.
Mike

 

[updated:LAST EDITED ON 04-Nov-02 AT 08:14 PM (EST)]The way I test the clutch is to warm the truck up so it SHOULD have engaged the clutch. Then, using a wad of rag to protect my fingertips, I push SLOWLY into the BACK BACKSIDE NOTTHEFRONT of the fan blades (where they're PUSHING, not CUTTING). It'll thump your fingers hard, but it won't cut you - just do it slowly. (If it grabs the rag off your hand, it's probably rotating backward & THAT'S your problem! ) If you can hear/feel the fan slowing down as you do it, then the clutch isn't REALLY engaged and you'll actually be able to stop the fan & listen to all the little noises your engine makes without the fan noise interfering. (You can do this with a good clutch when the engine is cool to diagnose other things.)

To test the radiator for blockage, warm the engine up & just hose the radiator core down for a minute or 2 and watch as the water dries off it. If it all evaporates at basically the same time, then there's hot water flowing thru the whole thing & it's OK. If (like the truck I learned this trick on) there's sediment or scale blocking some of the passages, there'll be a line that stays wet noticeably longer than the rest of the core and it'll feel cooler, too. You MUST hose it down for at least a minute so there's no residual heat in the water that's not flowing, or you won't see the effect - the heat conducted in from nearby passages when you warmed it up will evaporate the water you spray on even if it's clogged.