7.3 IDI Turbo - Knocking - Rough Idle

[94turbocrewcab-lb]

Hello, I've had many diesel trucks but this is my first IDI truck. I've owned it for 2.5 years. It's been extremely reliable. But lately I've neglected it just a bit. I know it needs the front axle overhauled. Planning on doing that after my spare truck is up and going. It is getting oil changes and fuel filters though. My son and I had a break down in it the other morning but made it close enough to home to get towed back by my wife! 7:15am

The truck was making a slightly off noise sort of like a loud knock coming from the intake. I didn't think anything of it and left for a meeting. Shortly after getting down the .5 mile drive way it really started sounding odd. Turbo Squealing when you give it 1/2 throttle and the injection sounded awful. So we turned around after a mile. Raced home..after about a mile I was giving half throttle to get down the road at 25mpg. Then it just gave up...I coasted over to the side and ran home to get the family. I tried turning it over when I got back ( about 10 minutes) and it was slow turning over and batteries seemed dead like they were dead. We towed it home and left it there on the battery charger.

Next morning I added some oil to the engine it was lower than the night before. It cranked over fast with the freshly charged batteries and it fired up. Sounded horrible and knocked and shook. I turned it off and changed the fuel filter. It was 9k miles old and had very little water in the bottom. I topped the radiator off with water. It took about a gallon?! I was planning on a coolant flush but it's been low on the list unfortunately. Im thinking a need a thermostat but I only drive 20 miles at a time and it never gets that hot. It's about 30 degrees here. So anyways. I filled the filter with straight atf. Put about half a gallon in the tank and fired it up. It ran a bit better and stable.

So currently the truck has the turbo inlet exposed. no air intake or intake box. Ive removed the belt so I can hear just the motor. My power steering pump makes a gear grinding noise when spun by hand. There is one injector that does account for most of the noise. But I still hear a loud knocking noise. It will run but knocks and sounds like a gas job with cracked exhaust manifolds when you give it throttle. And oddly enough steam and WATER drip from the CCV tube. Lots of steam from the oil fill.

So...do I have cavitation or maybe blown head gaskets?

I can only find normal non turbo 7.3 IDI engines.

Thanks! I need to get this figured out. I tow my tool trailer to job sites with this truck. It might be easier to park this one and get floor pans in my dodge and use that for a while.

This truck is a 1994.5 7.3 factor Turbo IDI. Front axle from a 97. Minimal rust and 269K Miles. I'd like to keep this truck going but don't need to daily drive it.

 

[TNBrett]

I think the next step should be a compression test.

 

[Big Bart]

Ditto on a compression test.

However sounds like a head gasket VS oil cooler because it is running rough. But it could be cavitation, but that is a rare problem.

Be careful not to hydro lock it and bend something in the bottom end. Most have been able to do head gaskets and get underway. With that said you may want to have the heads gone through by a reputable machine shop.

From pics of folks with cavitation there is often a stain around the cavitation hole in the cylinder wall.

Some thoughts
1) Drain the oil, change the filter, and refill it. Get the water out.
2) Do not add any more coolant to the radiator. It may just leak into a cylinder.
3) Do not drive the truck to prevent damaging it.
4) OTC makes a decent compression tester, they are on Amazon. Harbor Freight has a inexpensive kit for around $90. Some said they had to cut the glow plug adapter down so it would thread in a ways. You just cut some of the tip off, when you see it you will understand what to do.
5) When you do the compression test start by removing all the glow plugs, that should prevent you from hydro locking while cranking it over.
6) Do 6 compression strokes per cylinder, the needle will wiggle and move during each compression stroke. I record the first two compression stroke readings and the last. Then compare all the cylinders. Ford did not have a compression psi guideline, just that no two cylinders should be more than a 20% difference.
7) Cavitation from what I have seen happens mid cylinder and down. So if you have low compression more likely a head gasket. If your compression is good across the board, then it could be cavitation.

send some pics and

 

[IDIBRONCO]

If you have the funds, you may be better off to buy one of those N/A 7.3 and put it in the truck so that you can take your time pulling the heads off (and possibly more). Unless you're running quite a bit more than stock levels of boost, a N/A engine will hold up just fine.

 

[captain720]

If you have the funds, you may be better off to buy one of those N/A 7.3 and put it in the truck so that you can take your time pulling the heads off (and possibly more). Unless you're running quite a bit more than stock levels of boost, a N/A engine will hold up just fine.

I second this. But I would compression test before spending big bucks.

 

[94turbocrewcab-lb]

So the only ways to have steam and water drips out of the ccv tube is either HGs or cavitation?

 

[TNBrett]

So the only ways to have steam and water drips out of the ccv tube is either HGs or cavitation?

From what I understand, that’s the most likely. Especially with the running rough.

Oil coolers tend to put oil in the coolant. Oil pressure is higher than coolant pressure there.

Head gaskets and cavitation put coolant into oil because both leak coolant into the crankcase.

If you do a compression test, that will give a little more indication as to whether it’s cavitation or head gasket. No compression is more likely to be head gasket.

I would not turn the engine over any more though without first removing all the glow plugs. The last thing you want is to hydro lock it and bend a rod or crack the block.

 

[94turbocrewcab-lb]

I've found a few non turbo engines local for around $850. could I just swap that in and bolt on my turbo parts?

 

[TNBrett]

I've found a few non turbo engines local for around $850. could I just swap that in and bolt on my turbo parts?

Yes sir. There are only a few things you’d need to change. First, is the oil feed for the turbo. Where it feeds on the turbo block is 1/4” npt. That same port on an N/A block is 1/8”. Other than that there is no difference that I have found between the two blocks. The remaining differences are all in the rotating assemblies. The factory turbo engines have larger wrist pins, and slightly different pistons. They are therefore balanced differently and use different harmonic balancers and flywheels. I’m not sure but I assume flex plates are different too if yours is an automatic.

 

[IDIBRONCO]

First, is the oil feed for the turbo. Where it feeds on the turbo block is 1/4” npt. That same port on an N/A block is 1/8”.

For this, I've used a 18"NPT male/1/4" NPT female adapter MANY times in the past. It will work just fine. Most, if not all of the aftermarket turbos get their oil from a 1/8" NPT hole.

 

[94turbocrewcab-lb]

I’ve never gotten this far into a truck before. Any rough estimates on time to swap motors? I’m thinking I will just get the stock idi motor and my son and I will rebuild out stock turbo.

I have the c6 auto. Wanting to swap for a 5 speed. But that can come later when it’s running again.

Would a 12v Cummins swap be much more complicated?

 

[TNBrett]

Time wise to just pull one out, and put the other in is probably a long day maybe two for your first time. That’s assuming you have an engine hoist, and a transmission jack. What adds time for me is all “while I’m in here” things. Water pump, thermostat, oil cooler, lift pump, front and rear main seals. I’m not very good at reining myself in on stuff like that so I spend more time and more money.

 

[94turbocrewcab-lb]

I’d just think I’d spend the extra money on rebuilding my turbo motor.

I also found another 7.3 idi 1990 dump truck really clean down south. Might buy that and rebuild my turbo motor.

 

[Big Bart]

Would a 12v Cummins swap be much more complicated?

Yes, it’s a lot more involved.

 

[94turbocrewcab-lb]

I’m waiting to find a quality compression kit to borrow. My mechanic seems to think the steam I’m seeing is oil vapor/smoke and not steam. When I crack number 5 injector the knocking does go away to a certain point..

When this all went down my turbo was squealing as well. And I used maybe 1/2 a quart of oil quickly. So he’s also leaning towards turbo rebuild.

So I have the factory garret turbo. Does anyone know the number so I can find a rebuild kit for the turbo? There is minimal play in the shaft.

I’m also trying to understand how that turbo snail thing comes off. I undid the big bolt on top and figured it spun out of the way but maybe im
Missing something.

Can you rebuild these injectors at home or is it best to just buy remand?