Cooling sytem problem 7.3

[js5020]

I am having a cooling system issue with a 7.3 IDI. The engine runs well, starts decent, and doesn't overheat. The issue is pressure in the system, enough that it opens the cap and releases into the overflow and on occasion will push more than the capacity of the bottle, pretty much pushes air 30 seconds or so after starting it up and will hold pressure in the radiator for hours ( I've seen a hard top hose for 8 hours). New water pump, 2 new thermostats, new hoses, new belt, radiator sent out and checked, much coolant spent on "burping" the system. Anyone have any ideas?

 

[DaveBen]

You may have combustion gasses in the coolant. Leaking or blown head gasket. This would cause the gasses in the coolant bottle you are referring to.

 

[js5020]

Pulled the glow plugs, no evidence of coolant, dry and slight soot deposits, no release of pressure at the top hose.

 

[ifrythings]

Simple test for head gasket, remove radiator cap, make sure rad is full, start engine. If it blows out and you see constant large bubbles you know it's time for a top end tear down.

 

[OLDBULL8]

Depending on what pressure the cap is, 13 or 16 PSI relief, the cap will close when it gets under either of those pressures. That's why the upper hose is hard.

What year truck and how many miles on it?

About three things can cause your problem.
Blown head gasket.
Cracked block.
Cavitation.

 

[js5020]

This engine is in a 94 F250 with an automatic transmission and according to the odometer has 125K.

 

[FarmerFrank]

You don't happen to have a craigslist ad looking for a IDI turbo engine do you??

My 94 was doing the exact same thing. After lots of fan changes, locking a fan solid, thermostat changes, and finally a thermostat removal my truck finally stayed cool.

a day later it threw a belt and I was 2 miles from home, hot and tired, I kept driving. when I got home I thought the radiator was about to explode from all the steam coming out of the cap. After resolving the belt issue I also replace a failing starter. After the new starter sometime when you hit the key I'd get a loud "thud" and it wouldn't turn over. after several repeats of this I realized I was a ******* and it wasn't a starter problem, it was hydro locking.

pulled #7 glow plug and I got showered with water. Because of my impatience and not wanting to get towed home I probably cracked the head. I'd like to think it had this problem all along and I finally sent it over the edge with crazy temps and no water flowing.

Now I get to change the engine this weekend (yay me)

 

[js5020]

No we haven't gotten as far as assuming the engine is bad and looking for another. At this point we have no conclusive test indicating that extent of failure. I've pulled the glow plugs, no coolant, I've pulled the oil drain, no coolant. No oil or fuel in the coolant, no coolant in the exhaust. Starts and runs as one would expect, seems to have plenty of power. I haven't found my compression tester yet and I'm not sure even that will give us anything conclusive. This is a recent purchase of my son and supposedly only needed a water pump, ha ha. Well atleast he bought it cheap enough. I guess we are getting to the point of just pulling the heads and take a look.

 

[DaytonaBill]

betcha the po overheated the engine and you have a cracked head... Just needed a water pump, huh?

 

[js5020]

Hard to say with these old smokers, most are old enough to have had many bad things committed against them.

 

[IDIBRONCO]

With no sign of coolant in the oil or on the glow plug, my vote would be a head or (hopefully) just a head gasket. Remember, there's A LOT more pressure in the cylinders than in the cooling system so you could be blowing compression into the cooling system, but not coolant back into a cylinder.

 

[riotwarrior]

Gasket...or......

But surely heads comin off

Nuff said

 

[js5020]

Yep, spent a good part of the day clearing out the bay in the shop in prep to pull the engine. I just want to be reasonably sure before I let young bucks have at it, I'm just the project manager on this one, it's time for them to start having all the hands on fun. I'm thinking its as said above,,, cylinder pressure seeping into a water port or cracked head. I'm not a Ford diesel guru, in fact its been 20+ yrs since I had a 6.9, in fact I think they were just putting in the 7.3's when I had one so I'm out of the loop with the little tricks.

 

[js5020]

Well was working on another truck today and needed a part so down to the local napa we go, so happens I run into a ford tech and we talked over our problem and symptoms, he tells me the 7.3 can be difficult to purge the air out of the cooling system and this sounds to be the problem not a head or head gasket. He suggested a visit to the dealership for a machine purge of the system before yarding out the engine,,,, hmmm a quick check on the web and I find a device that hooks to the system purges it and fills it with a vacuum. A hundy bux for the tool but IF it saves pulling this thing and it works the boy will be way ahead.

 

[junk]

Hate to say it i'm with the other guys and think its an issue in the engine that will require tear down. Try doing a pressure test on the cooling system overnight. See if it drops pressure. If it drops you got a leak. Being it isn't mixing fluids I'd say it's compression chamber. Could always do a block test using the fluid that changes color.

I had a subaru that we drove for a long time that eventually took head gaskets. We drove it daily for 9 months after we suspected a problem. Basically the only symptom was the cooling system never reclaimed fluid until it would get low enough it would spike the temp gage. Other than that it ran fine and leak down tests showed nothing. The only other tip off was it wouldn't consistently hold pressure in the cooling system when checking.

Good luck and I'm hoping it goes well for you.