About a month ago my vacuum pump pulley decided to blow up on me, which in turn slung the serpentine belt. It was in the middle of the day on a busy freeway so I nursed her along another 10 miles to a shop.

I know the truck overheated. Regardless, got the vacuum pump replaced and filled her back up with coolant. 10 miles down the road she started to overheat on me, spraying out the coolant. I have a 16psi reservoir cap.

Got where I was going, unhooked my gooseneck and drove her for about 700 miles without a problem.

Loaded up the gooseneck with a moderate 15,000lb load and within minutes she was overheating and spraying the coolant out again.

Had 2 mechanics tell me that is could possibly be a blown head gasket that was pressurizing the cooling system under load causing the coolant to spew out... Put the truck in the shop, they pressure tested the heads and the coolant system up to 24psi and found zero leaks...... They did put a new thermostat in it just incase there was a problem there. They ran the truck for 2 days for almost 200 miles (without a load) and found nothing wrong with it...

I pick up the truck - drive it 600 miles back to my house (without a load) with zero problems....... hook up to my gooseneck and within 20 miles - overheating again.

So now - I am sitting here scratching my head. I just paid almost $400.00 to get the truck diagnosed and fixed to no resolution to the overheating problem. I am supposed to be leaving tomorrow to haul a couple more generators to a tower site but am afraid to back up to the gooseneck at this point.

Here is something I have noticed.... When I pull the cap after she's overheated, and all the water blows out, the bottom hose on the radiator doesn't have any pressure on it, but the top hose is still hard as a rock... I would think that once the reservoir is empty and all the pressure is released, that that top hose of the radiator would be able to be squeezed as if it were empty....... When I pop the top radiator hose off.... it pops off spewing steam....

Soooo

Heads been pressure tested - OK
Coolant System pressure tested - OK

Even if I am able to flush water through the radiator, could I still have something in there clogging up ?

HELP ! ?


JohnnyO - the bewildered

 

I am wondering if they put the right thermostat in for your year of truck.

http://www.dieselsite.com/index.asp?...ROD&ProdID=186

Read this!

 

It was doing it before they changed the thermostat.... Will it hurt anything to pull the thermostat completely ?

JohnnyO

 

I just pulled the thermostat from the truck.... The only #s I see on it says
64MM

JohnnyO

 

buy a new pressure cap from FORD. don't get one from auto zone they don't hold pressure. it makes a big differance controls more than you think it has two valves vaccum and pressure.

 

does it look nice and clean

 

i would geat a super stat or in other words a cooler stat. and check the fan clutch.

 

make sure your oil cooler is clean also it removes about 20 to 30 percent of the heat to. you can remove the stat and run the truck and see if it over heats but it will take alittle longer to warm up.

 

I would not get a cooler stat. But I would check your fan clutch. It should spin with some resistance when cold. it should spin about 1 turn or less when cold. if it spins free its junk. Also you need to doubel check and make sure you don't have dust and bugs plugging up your radiator fins. Its strange that it started when the belt blew off but I would bet that your fan clutch is junk.

 

Fan Clutch is fine.... I can hear that thing kick in and run all the time when going down the interstate... It's really loud...... I did do the spin test and there is plenty of tension on it. Also compared it to my other PS fan .....

I have the t-stat removed. Will do dog her out for awhile with a load on the gooseneck - it's really hot outside today so it shouldn't take long....

Any other ideas on what the problem can be ?

JohnnyO

 

is you truck auto or maunal

 

E40D - Automatic

 

your trans could be getting hot im not sure never seen it make that much difference but its posible. i would see how hot it is after you see if it over heats. good luck.

 

New Tranny built for this thing 2 months ago - spent 3700.00 on it... Built it bullet proof and have a monster *** tranny cooler that was added also.

I just ran the truck for 10 miles without a thermostat and she still overheated.... tons of pressure on the coolant system as I popped the cap off of the reservoir. Even after releasing the pressure from the reservoir, the top hose of the radiator is still rock hard.... popped off the top hose and plop off she came with a popping noise and tons of steam pouring out....

Water pump is working - tstat is working - no leaks in the cooling system....

What in the hell can be going on ! ? ! ?

JohnnyO

 

First let me say that I am no expert on the PS diesel, but I will share an experience somewhat similiar that I am familiar with.

On a 500 hp Cat engine it was running normal temp empty and even when loaded, but when loaded pulling a grade it began getting warmer than I like.

Found the culprit to be, not sure on the exact terminology, the vane inside the water pump was slipping just a little on the shaft. Replaced the water pump and everything back to normal.

I would think that unless your boiling her dry there should be some water in the top hose?? steam sounds like the water in the block boiled but no water was entering the block??

Are you sure the water pump is good? They don't always leak from the weep hole to be bad...............Since you have the thermostat out I would pull the top hose off at the radiator, start her up, and see if water comes out?

Your symptoms are very similiar to having a thermostat stuck closed or partially closed, run normal temp empty and heat up under load........since you have removed the thermostat something else is restricting the circulation of water????

Again, I do not claim to be an expert. Just throwing you a suggestion.

ra