6.2L Diesel problem

[paradigm]

Hello everyone
first time post... but long time reader here
this morning , I noticed a strange problem.
I saw a little drip of my transmission cooler line so I tightened it and started the truck to check it the leak was still there. Then engine ran normal and I let her idle for a minute or two.
Then I turned the truck off. Upon restart right away I knew something was wrong. The engine didn't run right. i could hear what i thought was misfiring.
there was a slight popping noise through the intake. So i turned the truck off right away. I noticed a Glow plug wire was off. I put the wire back on , but when i started the truck, the noise was still there. I had the impression as if it starts maybe a second after the truck fires up (but that could be just my impression). I have an external fuel filter and bleed it to see whether there was air in the filter. was none in there.
I hope , I don't have a more serious issue. but how should I go ahead with troubleshooting?
thank you for your help , guys

[More Power]

Welcome to the board!

Have you driven it since? I would drive it around the block to get a better feel for how it's running. How long have you owned/driven this truck?

Jim

[paradigm]

Welcome to the board!

Have you driven it since? I would drive it around the block to get a better feel for how it's running. How long have you owned/driven this truck?

Jim
Hello Jim. I own this truck since 2 years almost.
I heard a week ago a noise that sounded like an exhaust leak. since I had to have the exhaust worked on I didn't think it could be much else. And I haven't been driving the truck anyway.
When I got her back from the shop the noise was still there, maybe a bit less. So I didn't think much of it.
This morning happened what i described in my last post.
I just took her around the block and apart from less power, I could also hear a metallic noise, never heard that before. that noise prompted me to get right back to the house with as little RPM's as possible

I did some more reading on this forum then and checked the injectors for air blockages. when I loosened an injector I could notice a change in how the engine acted on all 4 injectors of that bank. but the tapping noise in the intake was still there.
Then I thought maybe I should spray something in the intake, so I did that. I noticed there was fluid moving away from the intake runners.
I thought that must be air being pushed up the manifold rather than down... I could also feel a stream of air blowing, not sucking.
I , then tried some transmission fluid as a replacement ofr a quart of oil (read it here somewhere) and started it for a second and let it idle for maybe five... then I turned it off and let her sit... I probably will walk down to the autostore and get some sea foam? what do you think and pour it in the crank case and intake and see what happens.
I hope to be able to release the lifter. but I also fear that it may be bent or the valve might be bent/stuck
thank you for your fast reply, Jim

cheers
~michael

[More Power]

A stuck open EGR valve might cause this, if this is a light-duty EGR-equipped engine.

The EGR valve sits at the center of the intake manifold, and has a hose barb for a vacuum hose. If your engine has an EGR valve, make sure the it's closed. If you have the HD version of the 6.2, it won't have an EGR valve.

If it's not the EGR, you may have an intake valve problem. A loose piece of debris (i.e. small nut, bolt, screw, pebble, etc.) could be jamming a valve. Also, a rocker arm or pushrod could be at fault.

You can locate the cylinder by loosening one injector fuel line fitting at a time, while listening for a change in sound. If you can identify which cylinder is at fault, pull that valve cover so you can check the valve train components.

Jim

[paradigm]

I believe it is the last cylinder on the passenger side bank.
That is where I heard the slight tap before and that's where si think i can feel air pushing out.
I forgot to mention it is a mil spec 6.2L, so you are right , there is no EGR

i'll try to see if i can pin point the cylinder by the way you desribed.

[paradigm]

This is what it looks like under the valve cover... I was like :eek:
http://i376.photobucket.com/albums/oo208/bmdoublesyou/62l%20diesel%20conversion/IMG_20120319_174206.jpg
http://i376.photobucket.com/albums/oo208/bmdoublesyou/62l%20diesel%20conversion/IMG_20120319_174150.jpg
http://i376.photobucket.com/albums/oo208/bmdoublesyou/62l%20diesel%20conversion/IMG_20120319_174140.jpg

[paradigm]

SO it looks like i got a broken intake valve spring...
any hints on how to pull the spring off with the head still on and not lose the valve down the piston?

[paradigm]

this is what looks to be the problem here

http://i376.photobucket.com/albums/oo208/bmdoublesyou/62l%20diesel%20conversion/IMG_20120319_191723.jpg

[paradigm]

I am trying to find out what parts I should need to replace now.
ordered springs and stem seals (i think i have some , as I found pieces of a tiny steel spring...) i got a 1990 6.2L mil spec diesel
I ordered a set of valve cover gaskets and intake gasket.
but what else will i need?

[DmaxMaverick]

It's simple to replace the spring w/o head removal. You should have to replace only the spring, retainer and seal. Get/make an adapter so you can apply shop air to the glow plug hole (use an old glow plug, gut it and braise/weld a shop air nipple to it). Rotate the engine so both valves on that cylinder are closed, and piston is BDC. REMOVE the engine oil fill cap (VERY important). Apply about 60 PSI continuous to that cylinder (don't shut off the compressor, it WILL leak some). Make sure you are clear of engine moving parts at that time, as the piston will bottom out with the pressure. Use a "top end" valve spring compressor to remove (if necessary) and install the spring. I have one in my barn I haven't used in 20 years. It may still be usable, if you can't find one (I can send it to you if it's still any good), or need a picture of one. KEEP shop air pressure on that cylinder during the entire R/R of the spring. Once the spring retainer is off, the air will be the only thing keeping the valve up. The job is easy and doesn't take long, but you need the right tools to do it.

[paradigm]

Thank you for your help, Dmax.
i got a tool to get the spring off
but can you or anyone confirm what this little spring may be from?
http://i376.photobucket.com/albums/oo208/bmdoublesyou/62l%20diesel%20conversion/IMG_20120320_084731.jpg

[DmaxMaverick]

Hard to tell without something to scale it, but it looks like a glow plug tip. Where'd that turn up?

[ginger743]

That long " spring looking part " is probably a glow plug heating element .

Jerry

[paradigm]

Hard to tell without something to scale it, but it looks like a glow plug tip. Where'd that turn up?
I found it while i was cleaning out stuff around the valves.
while looking online for parts I need to fix the problem
I found a small photo online the top of it looks like it could be a spring.
The photo is of a exhaust valve stem seal.

[paradigm]

I have never taken the diesel lift valves apart before.
does anyone have some pics of what the parts that are supposed to be on the intake valve look like? I bought new springs and some tiny looking valve stem seals, there was a washer like spacer between block and spring,
a cup , a washer like retainer and the clip... am I missing something?

[DmaxMaverick]

If the spring is the diameter of a pencil lead, and found under the valve cover, it's most likely from a stem seal. The picture "looks" like a GP tip, with the element pulled out of it. However, having nothing for a scale comparison (next time, drop a coin next to it for the pic), and the appearance of a "tube", with the spring pulled out of it, I took a guess. The smaller piece at the bottom of the pic "looks" like a Heli-Coil deep thread insert, again, with nothing to scale it.

That said.....
Broken valve springs happen on occasion, but isn't common. This is the same for any engine, and none seem to be more prone to it than any other. It's just one of those things that just happens. Replace the broken/worn parts and you should be good to go. Make SURE the pushrod goes in like it came out, with the copper colored end at the top. In order of assy: Washer; spring; seal; cap; retainer.

Good luck!

[paradigm]

Yes , I would say it is the size of a pencil lead.
And my apologies , I didn't mean to make it a guessing game. Next time I take something in the photo to be able to scale it...
both pieces are spring fragments. I don't know how much is missing from the original size, though

[paradigm]

I attached another photo of the fragments

[DmaxMaverick]

Much better pic. It looks now like it is a seal spring. Unfortunately, there's no way to know that is all of it. I suggest not worrying about it. Look and clean where you can, and if other parts don't turn up, they are small enough to not plug anything, and large enough the screen or filter will catch them. What's left to worry about, is too insignificant to worry about.

[paradigm]

Those seal springs are only on the exhaust valves, is that correct?
if so do i need to replace the seal with that missing spring or is it nothing to worry about?

[DmaxMaverick]

You'll have to get in there and have a look. It depends on why it failed/broke. If the others look good, it could be only one that failed, and there's no telling when it failed (could have been on its first run). Could be only the spring failed, and the remaining seal material is still intact. If thats the case, I'd replace only that one. Otherwise, I'd be inclined to replace all of them on the bank you have open. It's a difficult call, considering what I can see from here. Without reason, I wouldn't be concerned with the other bank, at this time. They may have been assembled by different persons, or shifts/days apart. Keep it as simple as you can.

[paradigm]

got it working...thank you all for your advise (:

[paradigm]

the truck behaved all strange again... I limped back to base.
Took the intake off and I got the feeling the same valve spring broke...
I'll check tomorrow morning to be sure. But if so, what could be the cause?

[paradigm]

it's a different spring

[DmaxMaverick]

That's interesting. There's only a couple things that cause springs to fail. Fatigue, defective, or debris interfering with their movement. If the (late) broken spring is on the same bank as the previous broken spring, a piece of the previous broken spring may have damaged it. Possibly before you sealed it up the last time. At this point, I'd toss out the band-aids and replace all the springs on that bank. If it's fatigue related, the rest may leave you at any time. Unless you really enjoy pulling the covers and spending your time humped over the fender.

[engineeradam]

I pulled the heads off my one of my 6.2 s and grinded the valves with a cordless drill and some grinding compound, and replaced all the valve stem seals as a sorta top end tune up. The thing purred like a kitten. SOO SMOOTH. Just an option since you probably already have the intake and valve cover off and the 6.2 heads come off with manifold attached. So 80$ headgasket and time. But with that said, i def recommend replacing all springs and glow plugs since there is no clearance in the 6.2 cylinder for any debris. Tip: spray the glowplugs with diesel and let soak, its a sorta natural wd-40.

Springs break under three conditions only; an impact load, a stress concentration riser or past the fatigue life. With that said Dmax has been right with all the advice he s given me. and that the spring has either been damaged or past there life span, and if your anything like me, if you dont replace them all, every time you drive the truck youll probably be wondering when the next one will fail.

Ps. Dmax i fixed my 700r4 that had no fourth gear. Stuck 4th valve in the valve body. Added a corvette servo too and love it.

[paradigm]

so, here is an update on my situation:
A few days ago I noticed a strange noise coming from the passenger
bank. I thought it could be an exhaust leak and was going to have a closer look after I get my exhaust welded.
The noise was still there. And when I started the engine to check on the transmission fluid.
She ran very erratic , right after start up.
Anyhow it turned out to be an intake valve lifter spring.
I asked around and everyone seemed to be very surprised that it broke... so I replaced just one.
http://i376.photobucket.com/albums/oo208/bmdoublesyou/62l%20diesel%20conversion/IMG_20120319_191723.jpg
Then 150 miles later another intake lifter valve broke on the same bank.
I also noticed some spring fragments from a exhaust valve stem seal laying around in there.
http://i376.photobucket.com/albums/oo208/bmdoublesyou/62l%20diesel%20conversion/IMG_20120320_153205.jpg
so I went and replaced all springs on that bank and found two more broken ones.
http://i376.photobucket.com/albums/oo208/bmdoublesyou/62l%20diesel%20conversion/IMG_20120331_185500.jpg
Now, The engine is a 1990 6.2L J-spec from a hummer. it is supposed to have between 10k and 40k miles...
she looks very low mileage as it's very clean in there.
But I also found quite a bit of rust in the rear portion under that valve cover and some on the rockers and springs...
http://i376.photobucket.com/albums/oo208/bmdoublesyou/62l%20diesel%20conversion/IMG_20120319_174206.jpg
http://i376.photobucket.com/albums/oo208/bmdoublesyou/62l%20diesel%20conversion/IMG_20120319_174150.jpg
http://i376.photobucket.com/albums/oo208/bmdoublesyou/62l%20diesel%20conversion/IMG_20120319_174140.jpg
could that be the reason why those springs broke?

[john8662]

Rust is as good a reason as any.

On the other springs, was there any indication the spring was broken when you had the rocker arm shaft off? Or was the only way to tell by taking the springs loose?

[paradigm]

Rust is as good a reason as any.

On the other springs, was there any indication the spring was broken when you had the rocker arm shaft off? Or was the only way to tell by taking the springs loose?
I could tell by being able to twist the assembly and push in a little...
the 'healthy' springs didn't budge at all

[john8662]

Thanks for the tip. I haven't run accross anything like this before myself. So you got me checking my used heads I bolt on stuff.

I have a HUGE box of springs, but who knows about their actual condition. My machinist has been picking through them based on spring pressure. I gotta figure weak ones that might fail will show up that way.