Engine trouble

[93_Burrito]

'95 Tahoe 6.5L TD
100k miles

I think I developed a problem this past Friday night. Fired the Tahoe up, engine was cold, and it idled rough for about 10 seconds. Seemed like a cylinder didn't want to come online. After that initial 10 seconds, all was well.

Fast forward to last night. Fired truck up on my lunch break and it idled rough for 10 seconds or so. Drove it about 15 miles to get some lunch, turned the engine off when I reached my destination. 5 minutes later I hop back in and fire the truck up, and it really struggled to smooth out. White smoke was just billowing out. It cleared up, and I drove it back to work without a hitch. This morning when I got home I popped the hood and saw some smoke from the dipstick.

What really caught my eye was what I saw just below the driver's side valve cover. The surface of the cylinder head around the injectors was wet. I know this area was dry Friday morning/afternoon, I put an 'F' intake manifold on the engine then. I've uploaded a picture to show what I'm trying to describe, it's in my member gallery.

When the engine cools I will check the coolant level and report back. I've got this sinking feeling...

[john8662]

Looks like oil in the picture, but can't be 100%, maybe a the result of the increased blow-by.

Valve covers on these engines don't seem to need an excuse to leak anyways...

Are you getting any codes?

Just be curious if you're seeing any cylinder balance codes, might help identify the offending cylinder.

I'm going to sound like a broken record, buy any time you're getting blow-by that is excessive (out the dipstick is on example with the dipstick inserted) it's time for a compression test.

Is this engine otherwise stock, what about computer programming?

J

[93_Burrito]

I haven't received any codes up to this point. The fluid level in the coolant overflow tank looks to be where it should be, though I can't get a good look at its color at the moment.

I just installed the 'F' intake, an 'F' chip with factory programming, and I removed the vacuum pump since I installed a TurboMaster two weeks ago. Aside from Kennedy's lift pump and pump harness, all else is stock. Well, I also replaced the AC 9G glow plugs with 60G's. That had pretty much eradicated any smoke at startup.

Guess I'll go with a compression test to see what's going on... thanks.

[john8662]

Yep, report back on what you find.

What kind of boost are you running with the TM? Just trying to figure out why the change has affected the engine so dramatically in the wrong way.

I'm sure you've got gauges (the subject of many of my off-site emails). ;)

Of course, the more free the intake is, the more blow-by you will see, but from the sounds of it, you shouldn't see that much.

Any big globs of sut/oil fall down the intake ports during install, possible debris...

[93_Burrito]

Well, someone had the intake manifold off the engine before I purchased it. I could tell as soon as I popped the hood before I bought it, the gaskets looked spooky clean. Sure enough when I took the original manifold off, the gaskets slipped right out. Fel-Pro...

The FSD looks like it may have been replaced.

There was a little bit of debris around the ports, but I sucked that all out with the ShopVac.

Boost peaks ~ 10psi. Not experiencing a loss of power. Retarded fuel injector?

[93_Burrito]

I drove the Tahoe around for a while today. The low coolant light came on for a second, two different times. I popped the hood when I parked it, and I could hear hissing. It was coming from the rubber vent tube of the coolant overflow tank. Some coolant was forced out the tube. Had a few drops of coolant make it down to the blacktop.

I didn't observe any smoke coming from the dipstick today. Anyone have any recommendations for a compression gauge? I've been unable to find any locally, the one hit I managed was for a MityVac, and it's on back-order until June 26th. I didn't want to take this to a garage if possible. Thanks.

[JohnC]

Take off the crossover tube with the thermostat housing, and the fan belt. Start theengine and watch the ports on the heads for bubbles (or gushing water...)

[john8662]

There are typically a few Matco Compression tester sets on ebay.

That's what I have, cheap enough, and with the adapters. Some say they're not good, but mine has worked for over 10 engines so far...

Might also search for the general "diesel compression tester" on ebay, or something along those lines...

I don't like the sound of your coolant overflow hose situation, does sound like you're getting compression into the cooling system.

The advice by JohnC is sound concerning removing the coolant crossover, although this is a bit messy.

The compression tester will be a great tool to add to your toolbox.

[93_Burrito]

For the MityVac MV5534 (analog) I was quoted $68, and $8.82 for the MVA5604 6.2/6.5L glow plug adapter. But like I said earlier, it's on back order until the 26th. I'll take a gander at eBay to see what it has to offer.

I've been going back and forth debating on tackling this job myself, or letting a garage do it. The local garage I trust doesn't have anyone who ever worked on a diesel. I spoke to a service writer at Forbes Chevrolet, where I buy parts on a regular basis, and he refused to get involved with heads on a 6.5L TD. He claimed that the dealership bleeds money when it comes to doing head gaskets and the like on these engines. I got the names of two diesel mechanics who work there from my buddies at the parts counter, so I may call back in an attempt to speak with them directly... see what they think, or maybe see if one would be interested in doing a repair on the side at another location. Another dealership nearby, Lefever Brothers, has a truck center but no longer have a diesel mechanic.

Sutliff Chevrolet in Harrisburg is the only shop I came across that is willing to take on the job. The guy I spoke with there asked about the symptoms of my problem, and I told him about the white smoke coming out the exhaust. He followed with a question, wanting to know if compression was blowing coolant out the overflow, which I replied with a yes. He said with all the 6.5's they work on there, he's almost certain the driver's side cylinder head is cracked. And he'd bet money that the gasket is fine. In any case, if we were talking about just head gaskets he said they replace both gaskets regardless... ~ $1600 labor. Parts and supplies extra. 15 - 16 hours at $95 per hour is what the dealership charges when they get into engine internals, he said.

I have the 6.2L/6.5L Diesel Troubleshooting & Repair Guide, and I believe it's a job I can do. It doesn't look overly technical, just time consuming because you have to remove everything from the intake manifold to the kitchen sink before you can pull the heads off. Instead of paying all that money for labor, I'd rather invest some of it into the '97+ cooling mods.

What do you guys think? Am I cruisin' for a bruisin'?


Andy

[Warren96]

Have you done any serious engine work before? Do you have the tools onhand ? You can get a lot of help and advice here if you get stuck, just dont try to rush.Do you have another car to drive?

[93_Burrito]

1. I have access to another vehicle or two while the Tahoe is down.

2. In addition to the Troubleshooting & Repair Guide, I have the Helm manuals for 1997 (had a '97 pickup with a 5.7L a few years back)

3. Have a digital camera to document progress

4. Got the tools, love my torque wrench...

5. About the only thing I've really done with any engine is change a water pump (on a 5.7L Vortec). I've swapped the intake manifold on my Tahoe, removed the vacuum pump, installed Greg's oil cooler lines, new starter, glow plugs... just haven't jumped into the engine.

6. Got a recommendation from a neighbor for a good machine shop that could check the heads out, if necessary. Neighbor has a race car...

I understand the most important aspect of working in an engine is to take your time and keep it clean. I'm not afraid to jump in, just never had an opportunity to do something like this.


Andy

[john8662]

Gotta love those first times...

It's doable, although I haven't done it in chassis, always with the engine on a stand.

I'm betting if it is bleeding compression that it's the gasket. The gaskets used on these 6.5's in a way kind of suck. The updated Felpro 6.5TD gaskets are the only way to go.

You'll likely find cracks, but ignore them if they're the little ones that just appear between the intake and exhaust valves. It's the cracks that start at a valve and travel accross the head surface that make the heads anchors.

Are you planning on doing them both?

It would be wise!

[93_Burrito]

I think the service writer at Sutliff Chevrolet was trying to spook me. From what I've gathered through The Diesel Page, it is likely that a gasket failed. I mentioned that with the high volume of 6.5L's going through their joint, he has to know about The Diesel Page... of course he'd never heard of it.

The plan of attack would definitely involve replacing both head gaskets. I'm sure it would be a lot easier to do with the engine on a stand, but it's going to stay in the truck unless something really bad is discovered.

First timer for sure... but I've watched enough episodes of Trucks! on Spike that I should be able to fix this problem, install a lift, add a sunroof, and upgrade my flux capacitor in about a half hour.

Back to reality, my dad has torn into a few engines, so he may be involuntarily volunteering to lend a hand :-)

... I should have named this thread 'hoe Down

[JohnC]

Whatever you do, don't let a single spec of dirt get into the injectors, pump or lines!

;)

[trbankii]

If you need an extra hand, give me a shout. I'm up in Lemoyne.

[Warren96]

Tools,a second car lots of free help...Go for it!!

[93_Burrito]

Just started working on the Tahoe today. Put about 2 hours or so into it.

Managed to remove:

1. crossover exhaust pipe
2. air intake/filter
3. upper fan shroud and engine fan
4. serpentine belt
5. alternator
6. intake manifold
7. glow plugs

Items of note:

1. The top alternator bolt, which fastens it to the bracket with the belt tensioner, was cross-threaded. Ended up snapping it in half. My dad was around to watch all the excitement, and he decided to take it upon himself to drill out the piece stuck in the alternator, then tap the hole. Woohoo, thanks dad.

2. Crossover pipe came out super easy. I was totally suprised, figured I would snap a bolt or two while at it. Used a Craftsman Professional 1/2" drive impact wrench of the lowest power setting... like butter. Gotta love air tools.

3. Glow plug #7 (driver's side, nearest to firewall) had green soot on it. The rest had the usual black soot. I think I'm on to something...


Will have more time tomorrow, so it looks like heads will be coming off then.

[93_Burrito]

I'm back...

I got the cylinder heads off the block, and added a few pics of the heads to my photo album. Please take a gander.

When the driver side head freed from the block, it slipped back somewhat. I think that is why the gasket looks so bad at the #7 cylinder, but I can't say for certain. As I said in an earlier post, the #7 glow plug was covered in green soot when I removed it. All other plugs had black soot.

My other concern is with the valves for #3 and #6. They have lots of pits, and I recall someone mentioning somewhere that that's a possible sign of antifreeze being cooked in the cylinder.

I am not going to do anything else with the engine until I get a few opinions from here. And I realize that I may find more things to look at once I clean the surface and remove the old gasket remnants. I took pictures of each cylinder and piston, but they came out rotten... will have to try those again. It's tough to get good pictures of them, especially towards the firewall, with the engine still in the truck. Thanks in advance.


Andy

[john8662]

Well, it looks like the gasket was blown, and in the traditional place, at the end near the coolant passage.

What I can't figure out is why all the pitting on cylinders 3 and 6. I guess the pitting is not burned surface junk that can be scraped off (actually not a pit).

You're right though, antifreeze/water in the cylinder pits the head badly, I had a head that had blown between cylinders 3 and 5 (opposite side as yours) and the head was not usable, because the material between the valves was eroded badly.

I can't see any cracks in that spot. Go ahead ad remove the gasket and do some scraping and see what comes off.

If if were me, I'd replace that head, got to figure out where the coolant was coming from though..

The areas for a leak like that could be head bolts, or some of the cooling passages in those areas, but the sealing ring / fire ring would have to had failed already to get the coolant into the cobustion chamber.

J

[93_Burrito]

I cleaned the gaskets and residue off the cylinder heads today. After taking another look, I spotted a cracked valve for cylinder #3. I uploaded a picture, in the member's gallery, but it didn't come out too clear. I circled the crack in the photo.

As for the passenger side head, I didn't see anything obvious. Not to say there isn't something wrong with that with the way #6 looks. My racecar neighbor's connection said he can't test diesel heads, for whatever reason. Guess I'll have to call my buddies at Forbes Chevrolet to find out who/where they test this stuff.

While we're talking about this stuff, someone recommended replacing the nylon valve rocker fasteners... any particular reason why?

[john8662]

Yes, hard to tell the crack is there, I'm going to take your word for it.

My favorite way to clean up stuff like this is those red scotch pads accross the surface, that cleans off rust and the like, and lets me see those nasty cracks.

The recommendation to replace the nylon buttons comes from the fact that over time the existing buttons become harder and more brittle. This just goes under the category of "since you're there" kind of stuff.

The only side i'd really WORRY about is the turbo side, as there is really more heat there. Just inspect them carefully.

You can probably have the good head pressure tested at a local engine machine shop. I know this will be a pain, but since you're going to have to get another head, it'll likely need freshening up, or if you buy new, match your existing one to it by having it rebuilt.

J

[trbankii]

So, how are things going? What is the prognosis?

[93_Burrito]

Hola,

Been busy with this and that, but here's what's transpired.


Called Penn Detroit Diesel Allison in York Haven, and spoke with one of their mechanics. Turns out the mechanic had several years of service in the Army, has a lot of experience with 6.2L and 6.5L engines... pretty much told me to get new heads after I told him how cheap I could get them through Clearwater. I asked if he would be able to check the heads I had, and he said his shop doesn't work on engines smaller than 8.2L. He could rig something up to test them, but it would not be cheap and I would just be better off finding a capable dealer to check 'em out.

Hauled the heads over to Forbes Chevrolet, and had one of their mechanics take a gander. He spotted the cracked valve and said that was the cause of the white smoke out the exhaust. Also said the pitting looked too deep to clear up by machining... the dealership doesn't do any kind of work like that, need to go to a machine shop. I was told that all local dealerships use Feeser's in Harrisburg, at least for diesel engine work. But in comparing the cost of repairing my heads versus getting new heads from Clearwater, the mechanic told me to go with Clearwater. Was told it would be a minimum of $100 to pressure test each cylinder head at Feeser's... valve $40...

So I went ahead and ordered a pair of cylinder heads on a Friday, and they showed up the following Wednesday. When I placed the order, the guy taking the order was cool. He said right off the bat that all 6.5L's have the same head casting (567). That's good, because I found way too many numbers on my old heads, and turns out the ones I were going to give him were wrong... The new heads have the diamond precups, whereas the originals have square precups.

I just put the new heads on today. Was delayed a few days because I needed new alignment dowels. Unavailable at the local parts store, and had to order them at Forbes. I was surprised the dowels didn't come with any of the Fel-Pro gasket kits I bought... oh well. Hopefully I'll have this together before too much longer.


I picked up another 6.5L TD in the meantime. A 2000 K2500 extended cab long bed. Had 49k miles on the ticker when I got it. Need to get it checked out... but that is for another thread.

[Robyn]

I used a set of heads from Clearwater on my 94 rebuild and I am happy with the price the service and the quality. They pay the freight back on the old ones too and I am about as far as yyou can get from Florida here in Oregon.
Great people and fine service
Robyn

[93_Burrito]

Clearwater would have never crossed my radar without this forum. I have to thank the other members here who dealt with them before me.

[Bnave95]

Clearwater would have never crossed my radar without this forum. I have to thank the other members here who dealt with them before me.
And I would of not been able to know or work with the 6.5 with out The diesel page and learning from other members.:)