Hello everyone,
I'm new here and I'm very impressed with the site.

I do have a few questions about a 1990 7.3 IDI. That I have just purchased, (it sat for 2 years and was hauled to me) I have found a few problem. The oil level was over full and the coolant was low (not a good sign). I did a pressure test on the coolant system and it didn't seem to drop much after about 15 min. I then changed the oil and fuel filters. I got it running and it has a thud thud thud sound coming from the intake. I then did a compression test, found just about 380 psi in 6 cylinders. Number 1 and 3 are about 150 to 200 psi. My question is where should I go from here? And any idea's on what the problem might be. Any help would be greatly appreciated. Thanks in advance.



1990 Ford F-350 7.3 IDI 2 wheel drive pick up automatic.

 

Pull the valve cover and check the valve / watch movement to see that everything is kosher there. By 1 and 2 you are meaning the front two cylinders correct, or the first two on the left bank.

 

Yes, first 2 on pass. side. 1 and 3 I believe. All the valves seem to be moving all right. Thanks

 

I wasn't around personally for when my brother blew a head gasket on his '84, but he said it came out of nowhere and sounded just like that "thud thud thud" sound. He shut it down immediately, we tore it apart, and sure enough, blown head gasket. I'm going to put my bets on a HG for your problem.

 

OK, that would also explain the water in the oil too. Wouldn't it? Doesn't look like fun pulling pass. head off. Thanks

 

Yes, it would explain the water in the oil as long as the water wasn't there by leaking in from the intake. But your problem does sound more like a HG.

Anyway, head gaskets aren't THAT bad. You can do them with the engine in the truck if you follow a few "techniques". One, being that you'll want to pull out your A/C condenser to allow you the room to pull the head. Two, you'll have to loosen up the head bolts and then wrap a rubber band around them so they hold juuuuust far enough out of the block so you can pull the head out. You'll never get the back head bolts completely out of the head. I think the biggest problem you'll have though is that those heads are insanely heavy. I think they're around 80 lbs a piece.

 

Wow, Thanks for your help. I guess it's time to get my hands dirty and fix it. Other then the thud in the intake sound, it seems to run pretty good. Thanks you all again for your help.

 

Okay definately sounds like HG when you said 1&2 i wondered, but if theyre right next to eachother, 90% of the time its HG

 

Well, I pulled the pass. side head of today and to my surprise the head gasket was fine. What I have is a burnt valve. So the head will be off to the machine shop asap. Now my concern is how did the water get into the oil?

 

Well, we were close with guessing it was the HG. Lol. Anyway, if the intake bowl was loose, it can let water into the engine. Also, a bad oil cooler will do that, too.

 

I think maybe I should investigate the oil cooler, as the last time I had it running it blew the oil filter gasket. Isn't there a relief valve in around the oil cooler? Thanks

 

Yes, the pressure valve is around that area. Don't remember if it's actually in the oil cooler mount or the oil filter mount.

 

Ok, Thanks for all your help. Lol, I think you might end up rebuilding this motor over the computer for me.