He probably bent a valve doing timing.
Mercedes Diesel Misfire After HG Replacement
- Thread starter JHZR2
- Start date
I don’t know the firing order/crank throws on this to be able to say, if cylinder 1 is TDC then cylinder 6 is TDC. I’ve tried reading through web-based manuals for the engine, but I’m not finding that information.
A Decent borescope would be able to see TDC, however.
When I had a MB diesel, the OM 617 in my 240D, I had the big, paper, factory service manual. It was wonderful. While the information is available on the web, being able to look through the manual was a huge help in figuring things out with that engine.
Any chance you have the FSM for the OM 603?
When I am down at my shop, let me see if my old WIS still has your chassis and the OM 603. If so, I can print out every single procure and detail on servicing this engine. Can you PM me your VIN?
A Decent borescope would be able to see TDC, however.
When I had a MB diesel, the OM 617 in my 240D, I had the big, paper, factory service manual. It was wonderful. While the information is available on the web, being able to look through the manual was a huge help in figuring things out with that engine.
Any chance you have the FSM for the OM 603?
When I am down at my shop, let me see if my old WIS still has your chassis and the OM 603. If so, I can print out every single procure and detail on servicing this engine. Can you PM me your VIN?
JHZR2
Staff member
Could be
If it was off by a bit I guess it could have happened. And would create a big challenge especially if a piston is cracked. Let’s hope it is not!!!!!!
Thank you! Firing order is a standard inline 6, with 1-5-3-6-2-4
I believe as a result, when I manually turn the engine and put the harmonic balancer marks on 0|T, both #1 and 6 are at top. When the cam mark is aligned, cyl 1 is in the valve closed position, when it’s 180 off with the balancer at 0, then 6 is valves closed.
I have the stack of paper FSM for the w123. I have access to electronic versions of most all W126/OM603 FSM, as well as the OM603.97 annex. I don’t know how the WIS differs so that would be interesting/helpful, if it differs from the old Startek interface.
I’ll send VIN sepcor.
Is it the 603 or the 606 that 0 was not really zero when going by the crank pulley? I don't remember which one but it was one of those that is about 3 degrees off at 0. Like I said an articulating boroscope is your friend with this, you can look up at the valves at TDC.
My WIS has service info for your chassis and the OM603.
JHZR2
Staff member
I’m pretty sure the 603 is 0 at 0. FSM says the chain wears 2 degrees in the first 20k miles, so maybe that was a mod to prevent that???
I’ll look into it…
I know water under the bridge however why be proactive on thing like head gaskets on rarely used car?
JHZR2
Staff member
Because there was oil seeping into the coolant. Not good. This specific model engine is known for bent rods that are attributed to breaches in HG.
JHZR2
Staff member
Ok major finding right now.
I have a leak and it’s not in the head.
First I swapped injectors as was noted by some folks. No change. No I didn’t drive it, but it’s not like idling on a new injector changed much.
I set the engine to TDC, cyl 1 cam lobes down.
I set up a leak down tester via the compression tester unit I had. It was a HF Maddox unit.
Regulator pressure was 80 in my shop. The car is outside, so I ran two hoses. I saw 72 in and 64 out.
No bubbles in the coolant, but I could hear the flow. I could hear it loud with the oil filler cap off but wasn’t getting much out the dipstick tube.
I then pulled the breather hose. That was it.
When I clogged that breather hose with my finger, oil popped out through the dipstick (which was removed).
So, it sure seems to me like the leakage is in the head. I hear it through the oil fill cap, and it’s coming mostly out the breather which is integrated into the valve cover.
I have a leak and it’s not in the head.
First I swapped injectors as was noted by some folks. No change. No I didn’t drive it, but it’s not like idling on a new injector changed much.
I set the engine to TDC, cyl 1 cam lobes down.
I set up a leak down tester via the compression tester unit I had. It was a HF Maddox unit.
Regulator pressure was 80 in my shop. The car is outside, so I ran two hoses. I saw 72 in and 64 out.
No bubbles in the coolant, but I could hear the flow. I could hear it loud with the oil filler cap off but wasn’t getting much out the dipstick tube.
I then pulled the breather hose. That was it.
When I clogged that breather hose with my finger, oil popped out through the dipstick (which was removed).
So, it sure seems to me like the leakage is in the head. I hear it through the oil fill cap, and it’s coming mostly out the breather which is integrated into the valve cover.
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Worth running the headbolts with a torque wrench?
I think the head has to come off anyhow, it sounds like a bad HG and something went sideways--barring a scored cylinder wall that is. Which isn't out of the question, if the head was off.
Can the oil pan drop down so you can pull #6 rod and piston out? Would hate to go that far, but if after pulling the head doesn't show something, then what is the next path to take?
I think the head has to come off anyhow, it sounds like a bad HG and something went sideways--barring a scored cylinder wall that is. Which isn't out of the question, if the head was off.
Can the oil pan drop down so you can pull #6 rod and piston out? Would hate to go that far, but if after pulling the head doesn't show something, then what is the next path to take?
With head off you could visually inspect piston height which would be an indicator of a bent rod.
JHZR2
Staff member
That was supposedly done.
There was no sign of bent rods before. Only the very slightest oil to coolant leak. Nothing else. Certainly not this.
But this engine specifically is known for bending rods…
Those results to me indicate leakage past the piston. I don’t see how it could leak just out of the head unless it had a large crack that extended from the combustion chamber straight to the valve springs. I haven’t seen a head crack like that.
Nothing out of the intake or exhaust ?
Nothing out of the intake or exhaust ?
It seems the primary problem is TMM/TMC. Too much money and too many cars. Forgotten and abandoned for 5 years and if the mechanic hadn't gotten sick for another 5 years it would have been abandoned for a decade. Sell it to someone who has the time and interest, along with any other surplus cars, and focus on kids/family, then on work which sounds extreme, and when the right phase of life appears get more toys.
JHZR2
Staff member
There is a lot of theory on the bent rod situation with the 3.5L OM603. The 3.0L version didn’t bend rods.
I tend to agree. Particularly since the bores were coated with lithium grease, it seems plausible that it gummed up the rings. If it held dirt or grit it’s a bigger deal.
It wasn’t immediately noticable. I guess it could still be there, but it wasn’t as straightforward to hear/feel compared to the breather.
Maybe TMC, but I had misplaced confidence. Sure, I’ve had another child since, lots of stuff going on. But if low use cars sit in my garage or theirs, it doesn’t make a whole huge difference.
Right now getting it diagnosed is what I’m looking to do. Whether I sell it or buy another or anything else is of no consequence. Low mileage older cars don’t tend to get a ton of miles piled on. They tend to sit. A lot. That’s why I wasn’t overly concerned.
Yes, we all have to justify our choices, especially to ourselves. But 5 years is not low use. It is no use and waste.
JHZR2
Staff member
I don’t know what you think you’re doing…
It’s neither helpful or salient.
I let some of my cars sit. My 1982 300cd sat in my garage for many years when my first child was born. So what? I think it was seven years. Fired up immediately. AC still worked. No harm, no foul. I manage tires and rubber items.
I thought this was going to get fixed. I was on no schedule. I was wrong, it didn’t get fixed properly.
Should I have pulled it way earlier? Yup.
But as of now I’m not interested in your assessment of how I manage my collection of cars. If you have info to support diagnosis, aid appreciate it. Otherwise your comments are not necessary. I’m acutely aware of the issues associated with the car sitting and me not being proactive enough to get it back.
JHZR2
Staff member
Ok, so I’m in the midst of more diagnosis.
First based upon @Astro14 recommendation to add some oil, I added some SAE 30 HPL EC. I figured it would be a good cleaner and lubricant.
I turned the engine by hand, then did a “wet” leak down and compression.
I guess one could argue I might not have added enough, or whatnot. But I can always redo these things quickly if needed.
Leak down definitely improved, but not a lot.
Compression went from 120 warm to hot, to 150 cold.
Then I went for kicks and turned the engine so cylinder #1 was TDC closed valves.
There was next to no leak, cold.
I pulled the glow plug and am prepping to pull the prechamber…
First based upon @Astro14 recommendation to add some oil, I added some SAE 30 HPL EC. I figured it would be a good cleaner and lubricant.
I turned the engine by hand, then did a “wet” leak down and compression.
I guess one could argue I might not have added enough, or whatnot. But I can always redo these things quickly if needed.
Leak down definitely improved, but not a lot.
Compression went from 120 warm to hot, to 150 cold.
Then I went for kicks and turned the engine so cylinder #1 was TDC closed valves.
There was next to no leak, cold.
I pulled the glow plug and am prepping to pull the prechamber…
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