[six5turbofan]

We bought a '94 6.5TD it is pumping back thru the intake and turbo. Just to make sure we disconnected the hose from turbo to intake and it is definitely coming out of the intake.
What normally goes on these ? Valve, rocker arm, cam, lifter, possibly head gasket between cylinders ? It definitly has exhaust from one cylinder coming back up thru the intake. Tomorrow we'll do a compression test on it to determine what cylinder, but I hope to get an idea of possibilities before we dig in. I'm figuring if it is a exhaust valve not opening the compression should be good only if it has a burnt intake valve or bent would I have low. The garage that they had it told them it had a bad turbo...
I know on gas engines (same theory) it usually is a exhaust valve not opening, due to cam lobe wore off...
I'm hoping rocker arm broke...
Any help will be appreciated

 

[DavidPhillips]

Does it have an EGR valve?


Is it running rough?

 

[six5turbofan]

Non EGR engine

 

[six5turbofan]

I guess before I answer that where is it located ? I thought it could be seen either on top plentum or at least inside of it incase they put on the wrong top. Is that correct ?

 

[DavidPhillips]

If it has an EGR lower intake there is a snorkel tube that has exhaust in it. It has a gasket between the tube and the top.

 

[six5turbofan]

It's a F engine, We pulled the upper off and looked down in and it is smooth in the lower half no hole for exhaust. Just wanted to make sure they didn't just put a non egr upper on a egr lower.

 

[DavidPhillips]

Running with the top off can you tell where the problem is?

 

[six5turbofan]

I'll try that tomorrow, I didn't fire it with the top plenum off so I'll try that. If that at least shows me what side or cylinder it is, it will limit my search. I figure I might as well work down from the top, look at the rockers see if one isn't working or is broke or push rod. If I don't see anything there then I'll pull head off and look at valves and head gasket. I was hoping someone would pop in and say they had problems with broken rockers or something simple, but I should know my luck...
P.S. I was searching more and more here and found the threads on the plastic retainers or guides on the rockers. Someone actually had a pushrod pop out of the rocker... I hope this is our problem it would be great to get that lucky. I'll report back tomorrow with our findings and will try to take some video and post a link to it with how it sounds.
One thing I did find today was the frost plugs have tags on them saying something like warranty void if removed... I'm hoping this has a new short block in it. It does have over 50psi oil pressure.

 

[TedReminder]

Had something very similar with my 94 two times. First time was intake valve spring broke, second was exhaust valve spring. Pretty easy fix with heads on. Run it with upper plenum off, stick hose in your ear and find out which cylinder is huffing back. It will get pretty loud when you get in the effected intake runner with the hose if it's an intake valve hanging open. If it is exhaust it will sound more mechanical, like real big valve lash, but won't huff back through the intake runner. Hanging exhaust valve will make lots of smoke out the exhaust. I'm going to guess yours will be an intake valve hanging.
If you find a broken spring, it is pretty easy to replace. You can turn the engine over with the pulley nut on the alternator till the piston is at the top. Valve only moves about .080" or less before contacting the piston, that will hold the valve in place for spring replacement. I drilled two holes in a hunk of pipe to bolt where rocker shaft bolts and used a real big open end wrench to compress springs. A magnet helps with getting the keepers out. Once the spring is off you can position the piston TDC in the bore to hold valve up.
Let us know what you find, I'll watch this thread.
Ted

 

[oil burner]

Some common problems are broken plastic rocker arm retainers, broken valve spring, sticking valve in valve guide. Broken rocker arm retainer usually causes constant miss/popping through intake[sometimes will clear up slightly if RPM's are raised past 1500 rpm's or more], broken valve spring or sticking valve can be intermitant miss/popping through intake. I would isolate which side has the problem and pull that valve cover and look for broken rocker arm retainer or broken valve spring.

Looks like I was typing slow while Ted was posting.

 

[six5turbofan]

Exhaust coming back up thru 1 or 3 coming up thru so bad can't tell which. Pulled off the valve cover and no broken parts up there. Disconnected injector cranked over valves are opening and closing. Tomorrow we'll fill the cylinder with air and also take a compression test and see where it leads. If the air blows back up thru the intake with the rockers off and air in the cylinder I guess we pull the head. Didn't have much time to work on today...

 

[TedReminder]

When you get the rockers off take a real close look at valve springs. Pretty hard to see a broken spring. Grab spring with hand and twist, broke one will feel loose. Another way is tap the top lightly with a small hammer. Bad one will sound different. Kind of like a tuning fork, all should sound crisp.
I really do hope you find a bad spring. Pulling heads in January sucks.
I'm looking at starting mine for work in about an hour in 10º Ohio cold.
Ted

 

[six5turbofan]

We pulled the rockershaft off and filled the #3 cylinder with air. It poured out of the intake proving a problem with the intake valve not closing or ??? Brought the piston up to TDC (because cylinder wouldn't hold enough air pressure to allow us to take the spring off and air hold the valve) we had to let the piston hold the valve. Removed spring checked it out spring is ok, so hopefully tomorrow after work we'll remove the head and find ??? Bent valve, bad seat, burnt ? we'll post what we find when we do...

 

[DavidPhillips]

maybe a crack in the head.

 

[Dan Hunter]

I'd be curious if the glowplug is intact.

 

[six5turbofan]

Glowplug is intact... and they are new which makes me think maybe it had a problem broke off and hit the valve. That might be why they did the short block (damage to the piston).
I was thinking of the cracked head, but no bubbling in the coolant and I pressure tested the system and it holds... They usually crack between exhaust and intake valve don't they ? and that usually leads to coolant bubbling doesn' it ? Hoping for the valve or something easy...

 

[six5turbofan]

The dumb @$$ that put it together dropped one of the hose hold down brackets into the plenum when they put it together. The whole bracket stayed above the valve just a small corner of it made it down to hold the valve open about .010" I guess it's a good thing they did it or we wouldn't have gotten it so cheap... Tomorrow we'll grind the valves and seats and throw it back together...
Thanks for all the ideas... they were all good, but human error played a part in this one. That's the second easy fix on a 6.5TD that we got lucky enough to get cheap due to dumb little problems.
I'll post a few pics of what we found tomorrow in our garage page.
Also the heads on this thing are casting number 10137567 are they ok heads ?

 

[six5turbofan]

Back together purrs like a 6.5TD should... picture of the intake valve in my garage under 94 Suburban. Thanks for all the info it was much appreciated this group is a great place for knowledge... I have many many years of rebuilding probably a 1,000 engines or so (mostly S&BBC) but only a few diesels, so I'll be asking dumb questions in here to help narrow down the possibilities.