Blown head gasket or cracked head???

[GRY9273IDI]

I have a 7.3L IDI with an 093 ATS turbo and a ZF5 Transmission on a 1992 Ford F250.

This is gonna be a longer post so I apologize in advance but I am at a loss of what I should do next.

While driving home from work I had zoned out on a long stretch of highway and realized I was still in 4th gear going 45-50 MPH and 2500+ RPM, without thinking I shifted into 5th.. except instead of 5th gear I had some how managed to accidentally down shift into 3rd gear. As I let off the clutch I realized due to the immense increase in RPM and I ripped the shifter back out of 3rd and up into 5th (I have no idea how high my RPMs got. I’m not even sure I fully let off the clutch as I pulled the shifter back out of 3rd as soon as i heard the RPM increase). I continued my drive home silently kicking myself for what I did and made a quick stop at the store for groceries. The truck was shut off for 30 minutes at most. When I came back out to the truck I tried to start it up and the engine would begin to turn over from the starter but would then sound as if it was hydro locked or something… I gave it a couple minutes while I tried to think of what could be happening and then gave it another try. Once again the engine began to turn over but then immediately sounded like the piston was getting stuck and unable to move. After a couple more tries all of a sudden the engine turned over (sluggishly) and fired up. Once I got home I noticed the oil leak from my dipstick tube had gone from an occasional drip to now spraying oil over the entire passenger side undercarriage. I decided to give the engine a Quick Look over before I went to pick up a new O-ring for the dip stick tube and that’s when I noticed my radiator had drops of oil floating inside of it. I drove the truck to work the next two days and when I checked everything again that weekend to no ones surprise the oil and coolant were both milky.

I dropped the oil and coolant, flushed both systems, rebuilt the oil cooler with new O-rings hoping that was the fail point and had no change. When I refilled both systems and ran the truck with the overhauled oil cooler I once again had an engine full of milkshake. I have since pulled both heads and found no obvious head gasket failures (one of the gaskets got warped as I lifted the head so I can’t definitively tell if it failed or not) I have however found 2 cracks on the passenger side head, going between the front 2 cylinder intake and exhaust valves (see Photos the pistons were also black with carbon rather than clean). When removing the heads I also noticed that the pistons in the rear cylinders of the engine looked completely clean; like it had been steam cleaned however the mating valves and head looked black with carbon and normal with no cracks.

My current thinking is that the crack in the head might be so deep that it allows coolant from the cooling jacket above the valves to leak down and into the cylinder causing the sensation of a hydrolock during start up and then leaks down past the piston rings and mixes with the fuel.

Does that seep possible? Can the heads be repaired? They don’t seem to be warped. Is it more likely that my coolant mixture PH may have been off causing cavitation or maybe a crack in the block that I can’t see? Could it still have been the the head gaskets even though there wasn’t a clear blow in the seal anywhere?

Thanks so much for the help, sorry it’s so long.

 

[GRY9273IDI]

Here are photos of the old head gaskets (keep in mind one got a little twisted when removing the head) and a photo of how dirty the other pistons are in comparison to the rear pistons that look steam cleaned.

 

[IDIBRONCO]

I want to lay some things out first.
I think that it's pretty unlikely for a cylinder to be burning coolant and not having both the piston and the underside of the head being pretty clean.
Yes it is possible that it could be a head gasket without seeing a clear indicator of where it's leaking. You didn't drive it very long like that.
I don't believe that it's possible to overrev one of these engines enough to do any damage and still have it drive normally on the way home. You didn't mention anything out of the ordinary so I have to assume that it seemed fine.
These are extremely high compression engines. I doubt that it's possible to have a leaking head or head gasket and then not have coolant being pushed out everywhere during the drive home. There's MUCH more pressure in the cylinders while the engine's running than is possible to get in the cooling system.
Cracks in our heads, especially on 7.3s, is not out of the ordinary and can usually be repaired.
The fact that you said that you had "drops of oil floating in there (your radiator)", but then had milky oil and coolant is unusual, but could happen if your oil cooler was leaking.
Overall, I think that your oil and coolant mixing is probably from the oil cooler. A cracked head, a bad head gasket, or even cavitation could put coolant in the oil, but not oil in the coolant. There is the possibility of something happening to one of the iron parts of your engine and the oil cooler leaking at the same time. The chances aren't very good, but I won't say that it's impossible.
Now for the bad news. If you did experience hydrolock, and did try to start the engine with coolant in a cylinder or multiple cylinders, there's a very real chance that you have a bent rod or more. Coolant doesn't compress like the air/fuel mixture does, so that's what causes bent rods from doing this.

 

[GRY9273IDI]

I want to lay some things out first.
I think that it's pretty unlikely for a cylinder to be burning coolant and not having both the piston and the underside of the head being pretty clean.
Yes it is possible that it could be a head gasket without seeing a clear indicator of where it's leaking. You didn't drive it very long like that.
I don't believe that it's possible to overrev one of these engines enough to do any damage and still have it drive normally on the way home. You didn't mention anything out of the ordinary so I have to assume that it seemed fine.
These are extremely high compression engines. I doubt that it's possible to have a leaking head or head gasket and then not have coolant being pushed out everywhere during the drive home. There's MUCH more pressure in the cylinders while the engine's running than is possible to get in the cooling system.
Cracks in our heads, especially on 7.3s, is not out of the ordinary and can usually be repaired.
The fact that you said that you had "drops of oil floating in there (your radiator)", but then had milky oil and coolant is unusual, but could happen if your oil cooler was leaking.
Overall, I think that your oil and coolant mixing is probably from the oil cooler. A cracked head, a bad head gasket, or even cavitation could put coolant in the oil, but not oil in the coolant. There is the possibility of something happening to one of the iron parts of your engine and the oil cooler leaking at the same time. The chances aren't very good, but I won't say that it's impossible.
Now for the bad news. If you did experience hydrolock, and did try to start the engine with coolant in a cylinder or multiple cylinders, there's a very real chance that you have a bent rod or more. Coolant doesn't compress like the air/fuel mixture does, so that's what causes bent rods from doing this.

Ok thank you! I will see if I can find any radiator shops In south florida to pressure test my oil cooler later today. Thankfully none of the pushrods appeared to be bent. I’m also going to see about reinstalling the injection pump today (I would really like to not have to time the engine on top of this) and then bump the starter to try and get a better look into all the cylinders for any cracks or cavitation.

Here are some photos of the coolant the first time I found it (coolant is green with oil mixed in) after the oil cooler rebuild (coolant is just water with oil mixed in) as well as the oil the first time I checked it on my finger (it got worse over the next couple days of driving but not as bad as after the oil cooler) vs after the oil cooler rebuild the entirety of the oil pan drained out as a grey milkshake.

When disassembling the engine I scraped out heaps of the grey gelatinous goop pictured on the rag from the valve covers.



Another note: When starting the engine I only experienced white smoke if the truck had sat 8 more than 8 hours without running. The white smoke out of the exhaust was also only present on the initial start up and then vanished after 3 seconds or so. If the truck was ran any sooner than every 8hrs the truck would start up with its usual small puff of black diesel smoke.

 

[IDIBRONCO]

Thankfully none of the pushrods appeared to be bent.

I meant your connecting rods. Push rods are fairly minor. Connecting rods aren't.
Overall, this post makes me lean even more to the oil cooler. You weren't clear on how long you ran the engine after doing the oil cooler. One thing I don't think you mentioned is whether or not you're still getting oil in the coolant.

 

[GRY9273IDI]

after rebuilding the oil cooler I ran the truck for maybe a total of an hour as i flushed the cooling system with water and then once the system was clean I continued to run the engine until I noticed more oil in the radiator which is pictured in my earlier post. At that point i drained the oil and that’s when i drained the entire pan of oil fully emulsified with water.

I think you’re right though. I’m going to pull the oil cooler tonight and have it pressure testing tomorrow along with inspecting the cylinders for cracks.

Thanks for the help!

 

[GRY9273IDI]

Update: I have inspected the heads further and it looks like i have cracks on the front 2 cylinders of the passenger side and the pistons below them. I know cracks in the heads are common and and easy fix however the cracks in the pistons is worrying me quite a bit.
I’m still waiting to hear back from the radiator shop on wether or not my oil cooler has internally failed, I’m hoping that will answer the question of wether or not my engine has suffered damage from cavitation.

Is it time to pull the whole engine, disassemble and overhaul the whole thing?

 

[IDIBOBS]

Is it time to pull the whole engine, disassemble and overhaul the whole thing?

Yup. I’d say so.

 

[IDIBRONCO]

I'd have to agree. It seems like it is. At least you could start thinking about a used, running engine to put in so that you can use your truck while you overhaul this one.

 

[onetonjohn]

What's an overhaul with machine work and new pistons and cost these days. Last engine I rebuilt I want to say was 4K for a V6 ranger (needed new heads). I paid 1Kish for the heads on project little foot a few years back. With machine work gaskets and parts is 5K reasonable? For these old trucks - unless you plan to keep it forever, seems like used engine may be the way to go.

 

[ROCK HARVEY]

I noticed your current pistons are already .030 oversized, so you’d probably have to sleeve all 8 cylinders if you rebuilt this engine. If I were in your shoes I’d be shopping for a good used engine rather than rebuilding this one.

Sorry this happened. It happens to all of us eventually but it sucks.

 

[Jesus Freak]

I noticed your current pistons are already .030 oversized, so you’d probably have to sleeve all 8 cylinders if you rebuilt this engine. If I were in your shoes I’d be shopping for a good used engine rather than rebuilding this one.

Sorry this happened. It happens to all of us eventually but it sucks.

I'm with this guy. Sleeving would be awesome, but $$$$$ woooooo..... so id save that money to buy an old Honda 3 wheeler and a "ought to run" 7.3 from a junkyard.

 

[catbird7]

What's wrong with throwing a new set of heads on it? How many miles are on the rebuilt bottom end with new rings, pistons, bearings etc?

 

[Nero]

I mean, as long as the pistons are good, and hones are okay, I'd send a bottom end. But you already have a cracked piston so.....

I know Justin at R&D his base engine rebuild is $6500, so I'd use that as a baseline for cost for like-new engine ready to go. Less for more used of course. When I can find a good running core, it's usually around the 150k mile mark and pick them up for $400ish.

 

[GRY9273IDI]

I noticed your current pistons are already .030 oversized, so you’d probably have to sleeve all 8 cylinders if you rebuilt this engine. If I were in your shoes I’d be shopping for a good used engine rather than rebuilding this one.

Sorry this happened. It happens to all of us eventually but it sucks.

When you say a good used engine you’re referring to buying another truck with a solid engine and swapping the engines right not a remanufactured engine correct?