1998 6.5 T/D Bought for parts

[Aftermath]

So I just bought a complete drop in already removed from the truck and the owner installed a 454. I think it's a 504 block. The crazy thing is that this truck has 17k on the clock. So I only paid $150 for the complete engine, worth that in parts for sure.

So here's the story I got: it started smoking white smoke and skipping all of a sudden. There's fuel in the oil. He thought it was Injectors, replaced a few injectors and no change. Without further investigating, and literally immediately he pulled it out and installed the 454 and sold it to me.

So I've had lots of these engines, mostly ended up cracked heads and blocks when I buy them for the parts. Before I strip this one down, I wanted to get some feedback. Does this sound like it could be a bad pump, or most likely cracked heads?

Thanks in advance

[More Power]

It's somewhat rare, but I have heard of a few instances where a bad seal in the fuel injection pump caused diesel fuel to leak into the crankcase. The injection pump housing is under constant pressure, so a seal leak could cause a lot (depending on the size of the leak) of fuel to leak past and into the oil.

A stuck injector usually causes other problems... like a dead miss, white smoke, a hard combustion knock.

These fuel injection pumps are the "fixed displacement" types, meaning the fuel injection pump and its pumping plungers determine the volume of fuel delivered to the injector. At light pedal, only a little fuel is delivered to the injectors - not enough to cause a diesel fuel in oil problem... unless there's a dead cylinder (lack of compression - bad piston/rings). In that situation, the fuel won't combust, allowing some of it to move past the piston and into the crankcase. Jim

[DmaxMaverick]

The injection pump is double-sealed (double-double, actually), with a weep hole between the seals. Each seal is a double-lip type, one at the pump end of the input shaft, and one at the flange (cam gear) end, with a trust shim at each end. The weep hole is at 6 O'clock on the input shaft housing. In order for the IP to allow fuel to get into the crankcase, it would have to leak past the pump-end seal, pass a weep hole (it would have to be plugged, or flow so high, to maintain some pressure), then leak past the oil seal at the flange-end. Add to that, housing pressure of the pump is limited to the "return line" pressure, which would mean that is plugged, too. A leaking weep hole will leak fuel into the engine valley, and drain down the back. Difficult as it may seem, it's happened a couple times in my recollection, but only on DB-2 pumps. DS-4 pumps are basically the same at that end so it could happen just as often, but I haven't seen/heard of one. I suspect that is due to the DB-2 having HPCA, which increases the case pressure (to advance timing) during cold starts.

There is a slight possibility for fuel to leak into the crankcase from a mechanical lift pump, but it has triple redundancies, too. It's happened. Not an issue if your engine doesn't have one.

All that said, white smoke and missing with fuel in the crankcase screams broken piston. It should also have very high blow-by.

[Aftermath]

So I lierally just picked this engine up and was able to talk to the company "mechanic". Sure enough 17k Miles on the odometer. This guy is as country as cornbread and admittingly knows nothing about diesel engines. So here's the real story; after sitting for "some time" they went to crank it up and noticed there was a mis, and white smoke coming out of the tail pipe. He removed the injector lines one by one and the only non-working hole was coming from #6. All other cylinders were working. He replaced #6 injector with no change. They immediately pulled the engine and installed a 454 crate motor. No excess fuel in the crankcase. I asked about codes and they couldn't remember although this all happened within the past month.

The owner of the company just told me that between 95-98 they had (8) 6.5's in their fleet, and they had problems with all 8 and he wasnt going to spend another dime on this last 6.5 truck. Had I been there a month ago, I could have bought this truck complete $1500. HD too....dang it!

[DmaxMaverick]

You may get away lucky then. Maybe only a head gasket or something simple.

[Aftermath]

I know, too bad I didnt get the entire truck, man that thing is super clean 17k miles though.

So pull the valve cover, all looks okay, pull the head?

[DmaxMaverick]

Pull the head? Absolutely. Now or later doesn't really matter, but it will be now or later. I'd do both, even though 17K miles. I'd pull the pan and get a good look there, too. Depending on the type of service, it may be a little, or a LOT of miles. Some of them idle all day and only make occasional trips to the doughnut shop.

[Robyn]

Another thing I would suggest is to get a starter on that thing and battery it up and get some basic compression readings.

One good battery will suffice to spin the engine fast enough with the glow plugs out and only one cylinder being allowed to make pressure. (Start with #6)

Yank the glow plugs and check each cylinders pressure through a few good spins on the starter.

The readings are going to give you some real good ideas as to Waaaaaasup in the engine.

I agree with Maverick....GET THE TOP OFF.

But some pressure readings will certainly get you to any suspicious spots quicker...

[Robyn]

With the low miles...what was the "Fleet" used for ????

[Aftermath]

With the low miles...what was the "Fleet" used for ????

Marble company. The owner said there were no additional run times on any of his trucks, he pays for the fuel. The truck is super clean, but who knows. I'll try to get cold compression info and report back.

[DmaxMaverick]

Just a note on cold compression tests, specific to GM Diesel engines:

They will not be accurate, and only good for tracking a trend. Even then, the values can swing wildly. However, any cylinder that will not fire (due to compression) when the rest do, should show a significant difference, although it may not in every case. The compression test should only be considered diagnostic (for pressure) when the test is done near operating temp (140F+).

[Aftermath]

Cold compression readings:
1-400
3-395
5-390
7-375

2-395
4-385
6-0
8-390

[DmaxMaverick]

Looks pretty close. Better run it again.....

Seriously, that's fairly conclusive. At least they identified the correct cylinder. When you pull the valve covers, check for valve movement before pulling the rack. Even with a blown head gasket, the compression test will show some minimal pressure. It's just guesswork until you get a look inside. Post som pictures so we can share in your misery.

[Aftermath]

I will pull the valve cover tomorrow afternoon. I'm guessing a broken spring but we'll see. I will post some pics. Thanks for all the help !!

[DmaxMaverick]

Possibly broken springs. There are two each. Inner and outer. The engine is zero clearance, meaning, even if it is only a broken spring, there may still be piston damage. It's about 50/50. Just keeps getting better and better, eh?

[Aftermath]

Valve cover off. Everything looks normal, rotates normal etc. Time to remove the head.

Does anyone know the thread specs for the bell housing bolts so I can get this sucker on an engine stand??

Thanks

[JohnC]

Blow air in the glow plug hole and see where it comes out...

[Robyn]

The bell housing bolts on early block are 3/8-16 thread.

About 96 they went to metric thread there too.

Get a bolt out and get eyes on it.

The metric block will allow a 3/8" bolt to screw in BUT IT WILL NOT BE SECURE

LOOK AT THE HEAD OF THE BOLT See what is stamped on the head.

Try a 3/8-16 nut on the bolt

The metric bolts are slightly bigger than than 3/8" and a standard 3/8-16 nut will not screw onto the metric bolt.


Once the engine is out you can scope out the bolt holes really good.

I have seen 3/8" bolts used where they should not be.

The 6.2/6.5 were all metric, accept the bell housing bolts in the early ones.

Like John said

Blow air in the glow plug hole...

Turn the engine to get both valves closed and then blow in the hole.

Burnt valve...or otherwise damaged

Hole in a piston from foreign object FALLING IN

Hole burnt through piston due to ????????

[arveetek]

I've got a '97 6.5L sitting in my shop that had zero compression on cylinder 1. I mean zero. With the engine running, I was able to remove the glow plug and keep my finger over the hole with little resistance. The owner didn't want to fix it, so I bought the whole truck for parts. Still have the engine. I have yet to tear into it to see what the actual problem is. I suspect broken piston or rod... I had a gas engine bust a rod in half one time that left the piston shoved up in the bore, but not enough of the rod was left on the crank to cause it to get wedged anywhere and lock up the motor.

Casey

[Aftermath]

Compressed air to the glow plug hole and it come out the exhaust as if there were no resistance whatsoever. I could have used a straw.

[Robyn]

Burnt valve

[Robyn]

You may get by easy on this one.

Get the thing on the stand and rip the heads off.

A fresh set of AMG heads would be sweet...but the aftermarket ones will get you going if you are on a budget....

I would not recommend rebuilt heads on these engines.

I have used the Clearwater heads with good luck as well as the AMG heads
A fresh set of Felpro head bolts and head gaskets and you're set.

I am very interested in seeing what you find when you get that head off.

PICCY'S PLEASE :D:D

[Aftermath]

Piece of the valve is missing

[Aftermath]

I don't see any issues with the head. I think I'm going to lap a new valve in, new gaskets, reassemble, compression test to confirm, then send it