Hi my name is James, I remodel houses. Quit mechanics 20 years ago so being a little rusty at diagnosing mechanical problems I thought maybe some people here would be so kind as to offer there opinions on my overheating problem.

Just bought a 91 E150 cargo van with the 4.9 and C6 transmission, 186K miles. Clean and looks like its been taken care of. Great work van.

Right off the bat it starts overheating, especially when driving at highway speeds. Heres where I'm at so far.

1. Checked for blown headgasket/cracked head by filling radiator to neck while operating temperature and looked for bubbles, nothing.

2. Replaced thermostat, on checking old one in pan of hot water it only partially opened at boiling. Still no fixey.

3. Removed radiator and flushed, excellent flow. Cores I could see looked clean.

4. Replaced fan clutch and water pump. Still runs hot driving.

5. Put that stuff in radiator that is supposed to make coolant run cooler, it does a little but still runs hot.

6. Removed air conditioning condensor since I plan on total parts replacement of AC later anyway. Yep still runs hot.

Now I'm wondering if its running lean and causing this overheating. It hits solid on all 6 cyls but runs slightly rough at idle and idles a little too high. Dont know which sensor or other thing that might make it run lean.

Any ideas?

 

Welcome to the site!

How do you know it's running hot? As part of the divide-and-conquer troubleshooting process - have you determined actual overheating, or perhaps an instrumentation error?

My basic philosophy is that if one doesn't know what the problem is - start by eliminating the things the problem isn't.

I've had to replace the gauge coolant sending unit a couple of times due to erroneous readings. For my model year, there are two coolant temperature sending units - one for the computer and one for the gauge.

Good luck, and keep us posted.

 

Thanks, well it actually boiling over when it gets hot, even with antifreeze in it. So on this elimination process I'm down to two things, a compression leak under driving conditions (idling it appears fine) or its running lean and making it overheat. I replaced the thermostat with a 165 degree. Should run fairly cool with it. I have the same engine in a old F250, never had a problem with it, even running 75mph all day loaded down in 95 degree heat. Foot on the floor.

 

Check the radiator hoses, especially the lower radiator hose. It could be sucked closed if the spring inside is missing or damaged.

Also, make sure the fan is the correct fan for your vehicle. I had an '82 Mustang that some yokel had put the wrong fan on (the blades were angled incorrectly). So when you were sitting still, the fan was actually pushing air out of the front of the vehicle instead of pulling it in. This would have worked fine, except I did 99.9% of my driving going foward!

Also, did you check the heater core for leaks or clogs? When you turn on the heat, is it boiling hot heat (which it should be if the engine is running hot).

Good luck with the fix, I know those vans are kind of a nightmare when it comes to accessing the engine compartment.

 

Checked all that, yep very hot heater, can drive it longer sometimes without boiling over with heater full blast. But radiator is fine.

Just thought of something, a high idle could mean a vacuum leak, a vacuum leak could mean running lean right?

 

I would think it would have to be a pretty big vacuum leak to cause it to run lean, thereby causing it to run hot. That I am not sure about.

Have you checked the engine timing to make sure it is set to factory specs??

 

Did you check the hoses like was suggested? Also, is the fan shroud still intact? If it overheats more while driving it could be airflow, is there gunk in the fins of the radiator or the air conditioning thingy (I know, real technical term) in front of it? Also, did you flush the engine and the radiator, or just the radiator. When it is hot, are the hoses swelling? This would indicate a blockage of some sort if the hoses are building up excess pressure. Did you pressure check the system yet? If there is even a slight leak the coolant will boil over because it will not be able to hold the pressure.
Make sure that there aren't any air pockets in the system. Run the vehicle with the radiator cap off for a while, that way the air can work out.

Sorry to ramble, these are the things that I would check.

 

it sounds like the only thing you havent replaced is the radiator cap. if the seal is bad thatll cause it to overheat. and who is that guy from cape girardeau.

 

Checked everything, no vacuum leaks. PVC valve fine.

Let the van idle for almost an hour with the radiator cap off. No problem, took it out for an easy drive on secondary streets, no problem. Came back home and let it sit and idle for another 15 minutes, temperature dead in the middle of normal. Turn the heater on wide open and comes down slightly.

This means I have a flow problem right? Since I've replaced everything except the radiator, that has to be the culprit. Even though a garden hose flows through it fine, and the cores I can visually see look fine. So the next deal is a system flush I guess, then a radiator if that doesnt work.

Thanks for all the helpfull suggestions. Anybody got a swear by flush product?

 

Your problem is the radiator, its plugged up. Although what you can see in cap opening looks clean, its obstructed internally someplace. Doesn't matter which type of radiator you have, a down flow or a cross flow, remove fan and shroud. Run engine at idle and as water is flowing through it check with your hand the temperature all across the radiator to find the cold spot. Meaning no water flowing at those fins. My dime against your dollar, someone put stop leak in the system and f****d it up.