OVERHEATING PROBLEMS

[70f350]

I just got this truck running and know it overheats but not all the time. It will overheat when I drive it for more than a 1/2 hour at a time, I pull over, wait about 10 minuetes and then it's fine again for another 1/2 hour or so? The truck has an FE. I changed it over to duraspark, it has a fan clutch, no fan shroud (never had one), new tstat, the initial timing is set at 6* btdc, I think that's all.
It really makes know sense. Any help would be great.

[fordman]

it could be a incorrect timing issue. i have a truck with abd timing chain. well is was loose and sloppy. so it got hot when driven so far a distance or even sitting still after so long of a time. it was timed with a static settign. it ran perfectly. but it got hot. i changed the timing by moving the dist. it hasnt gotten hot since. i does run like junk though because of a sloppy timing chain but it doesnt get hot. or your new t stat is no good either.

[70f350]

Thanks Fordman, I though I should try a new tstat also. The timing chain is tight though. I was thinking it may have something to do with the fan clutch too. It seems to get hot when the rpm is above 2000 for a bit of time. I know the clutch is good though. Maybe the tstat is sticking.

[BobbyFord]

Pull the radiator and have it rodded out. The radiator shop will be able to tell you what percentage of it was plugged.

[NM5K]

Yep, I'd have to place my bet on the radiator also..
I would check the fan clutch for good measure too though.
But I would think a bad clutch would show more at idling,
slow speed traffic where air flow across the radiator is low.
If you are keeping a steady driving speed where you have decent
air across the coil, I'd be blaming the radiator.
I doubt the T-stat is the problem, and it's new according to
the first post. So I wouldn't bother with it. I also doubt it's a
timing problem per say. No amount of minor timing variation
should cause overheating if you have a good radiator.
If you have to change timing to avoid overheating, that tells
me the radiator is about half shot or undersized. With most all,
it's the right size, so usually means it's half shot and clogged up.

[willowbilly3]

If it's a V8 truck it did have a shroud at some point and you should get one back on there. Some people will claim they get by without it but it can make a big difference.

[whisperer]

NM5K is right on the money - radiator. The only other 'normal' thing that causes this is the lower radiator hose collapsing. Make sure that the lower hose is either the ribbed type or has a spring inside of the smooth type. You can test this in the driveway just by sticking something in the throttle stop to keep the engine above about 2500 RPM's and keeping youe eye on the lower hose. If it is the smooth type with no support spring then you will see it suck down flat before your eyes. Obvious problem.

[70f350]

Thanks guys, I'll check that hose and the tstat that would explain alot. I'll start there. You can be driving down the road and watch the gauge go from normal to hot in less than a minute like somethings shutting off. But I haven't been able to recreate it yet.

[sgs]

70 F350,

A have a very basic question for you. Are you sure that you are overheating? That has to be step 1. All of the above mentioned possibilities with the exception of timing would be suspect in my book however, It is really unlikely that with a bad radiator,thermostat, or fan clutch you would be able to drive your truck in the normal range and then one minute later be overheating. I would verify that you don't have a gauge issue first. Are you using an electric gauge? Try hooking up a mechanical gauge so you can watch them both in tandem. If one goes up and the other doesn't, you will know it's the gauge.

sgs

[70f350]

It actually boils over. I have a mechanical and the stock gauge.

[fordman]

when you look down into the radiator how does it look inside? is there any white build up around the inside tubes? do they look to be open are any other color of build up insdie of the top of the radiator? what color is the fluid in the radiator? is it yuky looking or is it a good clear color?

[70f350]

Thanks again guys. The coolant is clear and it looks like the radiator is clear also. It is like something is sticking. I won't have time to look at it until later this week. It is starting to warm up around here and work is getting busier, refrigeration never sleeps! I will post a conclusion if I find one.

[BobbyFord]

Generally, if a vehicle overheats in stop n go city traffic, but cools back down after steady driving, you have an air flow issue; shroud or fan related. If a vehicle overheats at a steady highway speed and continues to get hotter the farther you drive then you have a water flow issue; clogged radiator, compromised thermostat (restricting flow) or a sludged up block.
Yours sounds like a water flow issue. I would pull the radiator, as I stated above and have it rodded out. (not expensive). I would also pop a few accessible freeze plugs out and flush out the lower end of the block. I have a special tool that I made that hooks up to a garden hose that has a bendable tube that I stuff into the freeze plug holes and force out any sludge and contamination. You'd be surprised how much junk is in there.

[D.J. Wyman]

I completely agree with Bobbyford. Nuf said.