Lost a Ring! - PeachParts Mercedes-Benz Forum

McRoth · #1 05-18-2004, 10:11 AM

Well, I was driving to work the other day after doing a valve adjustment 2 days before & it was running really well when I hear a weird sound & all of a sudden I loose a lot of power! It still drove OK until I had to push in the clutch & it died. I was able to pull off to the side & it finally started again after it cooled down some & I made it to work & back home, which I probably shouldn't have, looking back on it now. Anyhow, I thought maybe a valve nut came loose so I pulled off the valve cover again & checked them & they were fine, but I noticed that one spot in the rotation the engine turned over WAY too easy. I did a compression test last night & here's the numbers: #1 340, #2 390, #3 0, #4 440. awfully big spread, not counting #3.
Anyhow, I'm thinking that the easiest, cheapest & quickest way to get her back on the road is to get a running engine to transplant for now & get the old one overhauled at my leisure. Anyone within a day or so of Cleveland, OH have a 123 240D engine available?

Thanks!

#2 05-18-2004, 10:26 AM

just my opinion here but I don't think you "lost" a ring ... Go back under the cam cover and look a little closer at the valve train on the dead cylinder. I think you'll find your problem there. You'll have compression with even the worst set of rings .. heck, you'll have some compression with no rings at all.

boneheaddoctor · #3 05-18-2004, 10:33 AM

Quote:

Originally posted by Fritz Yoda
just my opinion here but I don't think you "lost" a ring ... Go back under the cam cover and look a little closer at the valve train on the dead cylinder. I think you'll find your problem there. You'll have compression with even the worst set of rings .. heck, you'll have some compression with no rings at all.

I agree, you don't have a rattle or anything? , I am thinking a hung alve but that will cause piston contact and worse.

McRoth · #4 05-18-2004, 10:52 AM

Hmm, I'll have to check on that. By lost a ring, I figured it just broke & a piece came out or something like that & all the compression was leaking past it. If it is a stuck valve or something like that it'd probably be much easier than the ring. I'll open it up again tonight & check the valve train better on that cylinder.

Thanks!

McRoth · #5 05-18-2004, 10:55 AM

Oh, I forgot, no there's no rattle or anything. I suppose if it is a hung valve that still requires the head to come off & get repaired. I'll have to call around & see what that will run. first things first though is to check out the valve train.

Thanks again.

boneheaddoctor · #6 05-18-2004, 11:09 AM

Quote:

Originally posted by McRoth
Oh, I forgot, no there's no rattle or anything. I suppose if it is a hung valve that still requires the head to come off & get repaired. I'll have to call around & see what that will run. first things first though is to check out the valve train.

Thanks again.

no rattle is a good sign, that means no valve head broken off and banging around. You may want to try retaking that compression again on that cylinder , just in case you got something wrong taking it first time. Low is one thing ZERO is something else altogether.

P.E.Haiges · #7 05-18-2004, 11:10 AM

McRoth,

I had a old 190D engine that ran OK, but was it just time for an overhaul. When disassempled, all 4 top compression rings were found to be broken. The rings were still in the pistons, just broken. Unless the pistons are severly damaged, the rings do not come out of them.

Maybe that's why they put 3 compression rings in the engine????

I agree that your problem is with the valves, not the rings. Possibly one of the valves cracked and a chip came out of the valve. That would explain why the problem occurred so quickly and would give you zero compression. What did the weird sound like?

P E H

McRoth · #8 05-18-2004, 11:17 AM

I can't remember exactly what the sound sounded like, I think it was like a dull crack, though.
I'm kinda glad it's not the rings then, that's good at least.
There was enough compression to make the release come out on the compression tester, but not enough to register on the gauge, so there was at least a slight amount of compression. I made sure the adapter was in there nice & tight & I rechecked it twice after I got no real reading, so I'm pretty sure it was true.
Guess I really need to get a shop manual now so I can do everything right! Anyone know where I can get one reasonably? I'll keep an eye on eBay too.

Thanks!

#9 05-18-2004, 11:26 AM

I don't think that you need a shop manual at this point, you just need to remove the valve cover and closely examine while the ol' noggin is in gear.

You'll find it.

Good luck,

P.E.Haiges · #10 05-18-2004, 07:36 PM

McRoth,

Using an air hose with an air nozzle on the end blow air into the cylinder that has no compression. Then have someone listen at the end of exhaust pipe for hissing air. If you don't hear any, take the air cleaner out and listen for hissing air there.

This will tell if you have a leaking valve and which one it is.

P E H

boneheaddoctor · #11 05-18-2004, 10:53 PM

Quote:

Originally posted by P.E.Haiges
McRoth,

Using an air hose with an air nozzle on the end blow air into the cylinder that has no compression. Then have someone listen at the end of exhaust pipe for hissing air. If you don't hear any, take the air cleaner out and listen for hissing air there.

This will tell if you have a leaking valve and which one it is.

P E H

yes, a very good and quick test. air has to go quite quick out someplace since comression is zero.

you will need to crank it around where you can visually confirn both valves are closed.

P.E.Haiges · #12 05-18-2004, 11:11 PM

Quote:

[i]

you will need to crank it around where you can visually confirn both valves are closed. [/B]

Opps, I forgot to tell him that.

McRoth,

You will need the valve cover off to ascertain that both valves on the no compression cylinder are closed.

P E H

boneheaddoctor · #13 05-19-2004, 12:34 PM

Quote:

Originally posted by P.E.Haiges
Opps, I forgot to tell him that.

McRoth,

You will need the valve cover off to ascertain that both valves on the no compression cylinder are closed.

P E H

As simple and comom sense like that may seem when you are seriously frustrated it could be an easy one to forget.

McRoth · #14 05-19-2004, 12:40 PM

Don't worry guys, I am a novice with taking the engine apart, but I did realize that I would need to make sure the valves were closed!

I haven't had a chance to do it yet, hopefully tonight or tomorrow night. I'll post what I find.

Thanks for everyone's help!

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