Just about a 1/2 mile from home, suddenly the truck makes a very loud rapid knocking, and pours white smoke from the exhaust.

This seemingly came from out of no-where.

It's a 92 f250 7.3 with 250,600 miles.

Any suggestions on what could be going on, and/or steps of how to self diagnose?

Thanks.

 

Checked the oil: very low.

While filling it, there was water-type vapor on the funnel.

Though- it never showed signs of overheating. Always running at normal.

I ran it and cracked each injector and there was no change for the better.

Ideas?

 

sounds like you popped a head gasket.
or worse.

 

Yeah a mix of coolant and oil is coming out the exhaust.

Is there some sort of procedure, or an online reference of how to get to the heads/head gaskets?

 

Or,
What are the chances it is the oil cooler?
I happen to have a set of those gaskets around.

And, what would that knocking physically be?

It seems like it's coming from the bottom of the engine.

It's a 5spd

 

Do you know if the coolant has been treated with SCA additive and for how long? 250K on a 7.3L IDI without SCA additive in the coolant it might be cavitation (hole rusted though water passage into the cylinder).

It would explain the white smoke (coolant burning off in exhaust), the knocking (damaged rod/bearings from vapor lock), water in oil (running down past the rings), and the abruptness of the onset.

 

No there haven't been any additives in the coolant.

What should I do? I have some mechanical skills- though i've never taken apart the engine. I'm up for it-

Is there any way to determine if it could be the oil cooler, since that seems a lot easier? Or would there not be knocking if it was the oil cooler?

 

I've read that without SCA additive most 7.3L IDI engines don't make it much past 150K without running into cavitation.

 

not true. i know of at least 5 that never had any additives added to the coolant other than what was put in at the factory, and they all have over 400,000 miles on them.




an oil cooler is easy to take off.
the noise in the bottom end is probably a rod knock from the water in the oil, or a hole in a piston.

it sounds like you may be looking at replacing the engine.

 

The knocking seems to be coming from the bottom of the engine, near the oil pan/transmission. Any hints on to what it might be? Or, is it fairly certain that such knocking comes from vapor locked and damaged rods/bearings.

I am ignorant, so I don't know where the rods/bearings are.

 

vapor lock is a condition where the gasoline in the carburetor turns from liquid to vapor because of high heat. so that is something you will not see in a diesel.

the connecting rods go from the pistons to the crankshaft, the bearings are on the crankshaft in the rod connection.

the fact that you have oil and coolant pouring out of the exhaust tells me that engine is most likely toast.

 

That is correct, I meant to say hydrolock.

I still think it's probably cavitation.

 

but cavitation would cause a hydro-lock condition.
his engine still runs, and is pushing coolant and oil out the exhaust.
cavitation normally only puts coolant out the exhaust, not oil.

 

Best case senario it's a head gasket, right?

So then, the knocking seems like some mechanical part is hitting some other part. What would that be?

Or, is it just the sound of an awkward explosion due to oil/coolant getting into a cylinder and could disapear with new gaskets?

 

this is one of those thing you really will not know until you take it apart. after removing the head you will either see a section of head gasket missing, or a hole in a piston.