JHZR2
Staff member
I have talked about my two almost identical 1991 MB 350SD cars for a while. The first one I bought, low mileage, nice car:
The engine used in these cars is known for bent rods. They also tend to damage head gaskets due to being a larger bore (3.5L) than the original design of the engine family (3.0L), and being a mixed metal engine with iron block, aluminum head.
Years ago, like 2018-2019, I noticed a little bit of diesel oil in the coolant. I knew that to be proactive I needed to get the HG done. I had a mechanic I had used 15 years earlier, very knowledgeable, that I trusted, so I took the car to him.
He did the job, there was some issue that turned out being a leaking oil line. He did the job again. Then there was a misfire. I didn’t follow up proactively. The car was at the shop, locked there behind a gate, and I had kids, activities, work, more cars, new hobbies, etc.
Fast forward to Friday… I get a call. Was really hoping it would be notice that the car was done… nope. He has to retire for health reasons. Needs me to pick up the car… still misfiring.
Ugh.
So I consulted a bit with @Trav and today was the day… in 100 degree heat, to go get it. I knew the battery was flat, so I got a new EP Napa battery. Installed it, had my wife crank it while I held the stop lever to shut off fuel. It built oil pressure. So then we glowed it and cranked it. Fired right up. But with a worse misfire than I had imagined.
In that video, it’s idling slow, then I had my wife take it up to 750, then 1000. It smoothed out a bit but not great.
Idle shows low.
Oil was about a quart low, and it took about a half gallon of water. But otherwise, it ran, idled, and I could drive it. Despite sitting a while and having yellowjackets under the hood…
The belt is squeaky, brakes had some rust, but otherwise it was ok. Original R-12 system still has charge and the compressor came right on.
The mechanic told me it was compression. I thought it sounded like injectors or fuel. But he said a cylinder was low. He had done a lot. He always talked about doing timing chains as a maintenance item in higher mileage diesels. I don’t know that it needed it, but he put one on. Changed the oil pan as the old one had a small crack from the PO, had the head redone with new guides and seals.
But it misfires. When I gave it to him it ran perfectly, I just saw the oil. Now it doesn’t work.
I did drive it, for better or worse, about ten miles from the shop to my garage.
I looked at the fuel cap and filller. Yikes. I’ve seen this sort of thing on these MB cars but never this bad. I can add a racor to filter. I’ve done that before…
Lesson learned. I should have cared much more and been much more proactive. I should have taken the car back years ago.
But now I have a car that has some real high points despite this, but that I have to figure out. And I have three kids, a lot of work in a job with rapidly increasing responsibilities, and no time. But I’m not sure that well qualified folks exist. My mechanic said part of his issue has been the inability to find good help.
I don’t know that I have much recourse. What am I going to do, sue for the proceeds of his shop sale? Take some tools? One of the old cars he has out front? So im not really interested in discussing that side of it much. It’s just the way ahead. Repair or junk it.
Since I gave him the car, I’ve also learned a ton and taken on increasingly complex jobs on these engines. I’m not really set up or inclined to pull an engine, but I think I could pull a head if need be.
So this is the start of that story…
I wanted to get to the bottom of what was misfiring. He said low compression but I didn’t want to believe it. He thought it was cylinder #2. I wanted to see just how bad it was.
Well it’s not #2, but it is bad…
I checked them hot today, and got the following:
Cyl 1: 370
Cyl 2: 350
Cyl 3: 370
Cyl 4: 400
Cyl 5: 370
Cyl 6: 120
I had the car parked outside and a thunder storm rolled through, and it was getting late, so I didn’t do a leak down. I think that cylinder 1&6 are both at TDC at the same time. So I’m hoping that I can easily get the engine there, and then do a leak down test. I should have at least checked for blowby when the engine was hot and running. It had zero when I gave it to the shop.
The mechanic indicated that he used white lithium in the bores when the head was off to protect from corrosion. I don’t know if that’s part of the issue?
What o know is that I found this on the #6 injector:
I have no idea if this would be white lithium or something else.
So far I don’t see oil in the coolant, not that it has been driven much at all. The cooling system holds temperature very consistently in 100 degree weather.
At hot restart, twice it almost sounded like there was a brief pause or halt partway through cranking. Not sure if this means something is possibly leaking through into the cylinder.
My wife drove behind me and said there was no smoke, soot, etc. However, she was standing there when one time I was cranking it and it did that ”pause”. She said there was a bit of black and white smoke just during that.
So that’s what I know. I’m fearing the worst. Hoping for the best.
Hoping that anyone has any thoughts about diagnosis, the injectors, etc, and can start to take part in resolving this. I’d like the car to be operational once again…
Thoughts? Suggestions? Ideas?
The engine used in these cars is known for bent rods. They also tend to damage head gaskets due to being a larger bore (3.5L) than the original design of the engine family (3.0L), and being a mixed metal engine with iron block, aluminum head.
Years ago, like 2018-2019, I noticed a little bit of diesel oil in the coolant. I knew that to be proactive I needed to get the HG done. I had a mechanic I had used 15 years earlier, very knowledgeable, that I trusted, so I took the car to him.
He did the job, there was some issue that turned out being a leaking oil line. He did the job again. Then there was a misfire. I didn’t follow up proactively. The car was at the shop, locked there behind a gate, and I had kids, activities, work, more cars, new hobbies, etc.
Fast forward to Friday… I get a call. Was really hoping it would be notice that the car was done… nope. He has to retire for health reasons. Needs me to pick up the car… still misfiring.
Ugh.
So I consulted a bit with @Trav and today was the day… in 100 degree heat, to go get it. I knew the battery was flat, so I got a new EP Napa battery. Installed it, had my wife crank it while I held the stop lever to shut off fuel. It built oil pressure. So then we glowed it and cranked it. Fired right up. But with a worse misfire than I had imagined.
In that video, it’s idling slow, then I had my wife take it up to 750, then 1000. It smoothed out a bit but not great.
Idle shows low.
Oil was about a quart low, and it took about a half gallon of water. But otherwise, it ran, idled, and I could drive it. Despite sitting a while and having yellowjackets under the hood…
The belt is squeaky, brakes had some rust, but otherwise it was ok. Original R-12 system still has charge and the compressor came right on.
The mechanic told me it was compression. I thought it sounded like injectors or fuel. But he said a cylinder was low. He had done a lot. He always talked about doing timing chains as a maintenance item in higher mileage diesels. I don’t know that it needed it, but he put one on. Changed the oil pan as the old one had a small crack from the PO, had the head redone with new guides and seals.
But it misfires. When I gave it to him it ran perfectly, I just saw the oil. Now it doesn’t work.
I did drive it, for better or worse, about ten miles from the shop to my garage.
I looked at the fuel cap and filller. Yikes. I’ve seen this sort of thing on these MB cars but never this bad. I can add a racor to filter. I’ve done that before…
Lesson learned. I should have cared much more and been much more proactive. I should have taken the car back years ago.
But now I have a car that has some real high points despite this, but that I have to figure out. And I have three kids, a lot of work in a job with rapidly increasing responsibilities, and no time. But I’m not sure that well qualified folks exist. My mechanic said part of his issue has been the inability to find good help.
I don’t know that I have much recourse. What am I going to do, sue for the proceeds of his shop sale? Take some tools? One of the old cars he has out front? So im not really interested in discussing that side of it much. It’s just the way ahead. Repair or junk it.
Since I gave him the car, I’ve also learned a ton and taken on increasingly complex jobs on these engines. I’m not really set up or inclined to pull an engine, but I think I could pull a head if need be.
So this is the start of that story…
I wanted to get to the bottom of what was misfiring. He said low compression but I didn’t want to believe it. He thought it was cylinder #2. I wanted to see just how bad it was.
Well it’s not #2, but it is bad…
I checked them hot today, and got the following:
Cyl 1: 370
Cyl 2: 350
Cyl 3: 370
Cyl 4: 400
Cyl 5: 370
Cyl 6: 120
I had the car parked outside and a thunder storm rolled through, and it was getting late, so I didn’t do a leak down. I think that cylinder 1&6 are both at TDC at the same time. So I’m hoping that I can easily get the engine there, and then do a leak down test. I should have at least checked for blowby when the engine was hot and running. It had zero when I gave it to the shop.
The mechanic indicated that he used white lithium in the bores when the head was off to protect from corrosion. I don’t know if that’s part of the issue?
What o know is that I found this on the #6 injector:
I have no idea if this would be white lithium or something else.
So far I don’t see oil in the coolant, not that it has been driven much at all. The cooling system holds temperature very consistently in 100 degree weather.
At hot restart, twice it almost sounded like there was a brief pause or halt partway through cranking. Not sure if this means something is possibly leaking through into the cylinder.
My wife drove behind me and said there was no smoke, soot, etc. However, she was standing there when one time I was cranking it and it did that ”pause”. She said there was a bit of black and white smoke just during that.
So that’s what I know. I’m fearing the worst. Hoping for the best.
Hoping that anyone has any thoughts about diagnosis, the injectors, etc, and can start to take part in resolving this. I’d like the car to be operational once again…
Thoughts? Suggestions? Ideas?
