• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Trouble with the Optimizer 6.5

B

bobbiemartin

Author of The DB2 Conversion Guide
Messages
567
Reaction score
22
Location
Jacksonville, Florida
It's been a while since I posted. Lots of other projects going on, but now having problems with the Suburban. Some may remember the rebuild a while back, here is the link: http://www.thetruckstop.us/forum/threads/my-suburban-renewal-project.14685/

It's been running fine, but a while back it (almost instantly) developed a miss. It was so bad I had it towed home. My first thought was a bad injector, so I removed them and sent them to a local diesel shop that has 6.5 experience. Got a call a few days later that all of them check out fine, in fact good enough they didn't have to do anything to them.

Other projects kept me from looking further, but over the weekend I finally got around to doing a compression check. These are the results:
1-425 PSI
3-125
5-275
7-100

2-400
4-200
6-450
8-200

I guess the next step is to remove the heads and see what is going on. I'm thinking at best head gaskets. Not sure what else it could be or why both would go bad. It has never overheated or had any major problems. The block was checked over and the heads were new AMG's. I would hate to think one or both has a crack. Any ideas, let me know.

At this point we are really thinking about what to do. Come November, we will have owned it 20 years (we are original owners). If the engine is toast, I wouldn't put another 6.5 in it. It really depends, but thought about going 350 or newer LS type small block or possibly selling the entire thing. Once I get into it, I'll keep you posted.
 
How many miles? K&N air filter? UOA all been good?

Offhand I would say it ingested water or coolant and bent up some rods. The compression numbers - are we working on a gas engine!? :facepalm: Possible leaking valves from derbis: carbon came loose, glow plugs broke up, or turbo compressor wheel shrapnel? Last would be a HG failure, but, with studs and my FOD (ate a 1/4 worm clamp) engine failure I highly doubt it as the HG's were still holding.
 
With numbers like that, I would be doing a little more testing BEFORE pulling the heads. I would pull the valve covers off, remove the rockers so the valves should all be closed, then pressurize the cylinders with an air compressor and see where the compression is going BEFORE I'd pull the heads. This will give you an idea where to look after pulling the heads so you have a better idea what to look for. If it's valve, rings, or whatever, the air will tell you real quick.
 
Just curious does the oil in the cylinder trick work on a diesel? I know with a gasser you can squirt a little oil in the cylinder with low compression and retest- if it goes up it indicates the rings are bad.
 
Am with WW about the UOA. A $35 test can help isolate a bunch of things. Although at this point, will get sand-bagged results unless you want to fire-up the motor to let it come up to operating temp for the sample.
 
WarWagon said:
How many miles? K&N air filter? UOA all been good?
Click to expand...

About 60,000 miles, Yes K&N and been awhile on the oil analysis. I looked, 2012 was the last one on this engine, so not much help.
Offhand I would say it ingested water or coolant and bent up some rods.
Click to expand...
I know it didn't suck in any water, so not sure on that one.

I considered it could be a rocker, but not sure why it is low on multiple cylinders?
I thought about doing an oil analysis but doubt it would tell much at this point.
The turbo and injectors are off at this point, so getting it running would be a fair amount of work.

Probably I'll just take it out and then remove the valve covers and most likely the heads to see what is going on. I could take the valve covers off, but that means the intake and injector lines have to come off first. It's a lot easier to do everything on an engine stand than in the car, but taking the engine out is no picnic either.
 
Last edited:
Hi Bobby, I don't think I've ever talk to you before. Excellent work on your instructions for DS/DB2.

Yes oil in cylinder test - wet vs dry compression test works exactly the same in diesel as gas engine.

Unfortunately some people out there are against it because the oil in your cylinder can act as a fuel and let the engine run. Oh no! What to do?

You remove all 8glow plugs as step number one. Next, do your dry test on all eight cylinders. Finally, squirt in the oil one at a time as you testing shoulder for the comparison to see if your compression problem is the rings.

When you compare the increased pressure from the oil in the "good "cylinders, to their dry reading that gives you your baseline. Then the percentages are done just like a gas engine.

I could be wrong, but I've only diagnosed about 50 or 60 worn out sets of rings/ wall damage over the years this way. I never once figured it was upper end to later find bad rings or scratched cylinder.
 
I would do an oil sample to see if there is something like a flat cam, pushrods installed backwards, etc. I hoped you had kept up on UOA's like you were doing in the past... It may prove to you that K&N is or is not a bad idea.

In light of my 1992 project here (link) a UOA could tell you if you had an oil failure. In that case it was gasoline in the diesel that washed down the rings and related or not ate the timing sprocket keyway and key. The oil failed (of course) and left sludge in the pan that used to be rings.

UOA is just another tool you need to take one of now before the heads come off and contaminate the oil. This is a tool for questionable problems like I am going through on my 2003 5.9 Cummins. We are 75% sure it's the garbage head. But, could be broken rings or a tappet issue still. Inspect the oil filter and then if no damage is found cut it open. Warning cutting a filter open makes warranty claims 100% harder with filter companies.

With the FOD debris the turbo has seen during the last engine I am concerned it finally caught up with you.

What is your confidence on the compression test?

IMO with head studs it is easier to pull the engine if heads have to come off.
 
Last edited:
WarWagon said:
What is your confidence on the compression test?
Click to expand...

I'm reasonably confident. I went back and checked the low cylinder on each side and got the same reading +/- 25 PSI.

On the K&N, I know they are typically panned on most forums due to a bogus “test” run years ago. I don't want to get into that here, but I have experience going back some 30 years and run them with great confidence.

It will probably be a few weeks, but I'll get back to the Suburban and see what is up. Regardless of what I find, if we decide to keep it I'm seriously considering going back with a 350 gas engine.

I have a set of new head gaskets. I bought a gasket set a while back, they were military surplus. They are unused, but probably 10+ years old. What do you think of using them or should I buy a new set of gaskets?
 
I've used 20 year old head gaskets on a flat fender jeep gas 4 cylinder engine with no problems. Oldest on a diesel (ford 7.3) I've ever ran was about a 5 year old set, no problem there.
 
I would say figure out what is wrong with the engine and then plan from there. It's either not getting air or leaking air. Sadly I just don't see anything but major causing that.

Really curious as to how many miles you got out of it?

A 350 would be a gutless wonder, vs. the diesel torque, you will notice and hate unless it's a hot rod build. But that's coming from the hot rod 6.5 2500 burb to a 2002 Yukon 5.3L.

My personal K&N experience of dusting engines... Ruining idle air control motors by coating them with dust so the engines won't stay running due to lack of airflow from dirt caked idle air passages... Don't need a test to know there is better out there starting with a flame arrestor and improving from there. I hope it's (dusting the engine) not the cause of your issues.
 
If you go with a 350 TBI engine(swirl port heads), I don't think you would be that disapppointed in the bottom end torque if you run a converter that will utilize it. The 350 swirl port heads make great torque, but run out of power around 4500 RPM's. I would stick with the diesel and find out what is going on with it. Try and take the time and pressurize the cylinders with air before you yank the heads off, this will tel lyou real quick if you have leakdown, and where.
 
A dirty K&N will filter fine, clean ones let the dust in, think of a sand filter.
 
Finally got around to taking the engine out. Didn't see anything that looked that bad. I'll take the heads in and have them checked to be sure. A few pictures:








 
You must log in or register to reply here.
Back
Top