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Discussion Starter #1
164 000 Km on the clock and the shop told me that the Rings on the pistons are shot. They showed me, the smoke is only coming from the one exhaust pipe (right hand one). The car has a full service history. Are there any other guys that had to change rings on such Low Km readings. Does any one know what the cause could be?
 

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That's REALLY low..unless some foreign piece of material made it's way into the combustion chamber or a ring failed would be the only way I'd see that happening. Have they done a leak down test?

I'd sooner suspect a failed valve guide seal or valve guide.


Jonathan
 

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Aren't you the guy with the shops that are morons? The way you check rings is you do a compression check - you do NOT look at what comes out of the exhaust pipe. Great compression means the rings are fine even if the car is reducing the mosquito population. Now if compression is low add oil to the cylinders and try again. Even on bad rings the oil will help seal them. No improvement means the valves are the parts that are bad. But if you have good compression then it's the guides.
 

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A leak down test will circumvent all of the above...if you have low compression a leak down test is the next step, thus it's easiest just to start w/ the LD.

Jonathan
 

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i had smoke coming from one exhaust pipe, turned out to be the valve related.
 

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Discussion Starter #7
Car Finally 100%

After having my car at a couple of monkeys, I finally found an independent shop that specializes in older Benzes and know what they are doing. The did all the relevant tests and informed me that they suspect only the heads needs to be redone. The could not guarantee that the oil rings would be 100% but they said it is unlikely. So 2 weeks back they phoned me after removing the heads, they said the heads defiantly needs redoing and valves need to be replaced that would come to about R 10 000 (About 1,200 USD). I told them to go ahead. They phoned me up this afternoon saying that everything was put back and it was a success, no smoke and the car is running like a dream…. Now I just need to get it Valet cleaned (It has been standing for some time) Apart from 2 small dents that needs fixing and the Aircon that needs re- gassing the car is fine. I will keep you guys posted and post some nice pics as soon as she has been cleaned. I still don’t know why at 164 000 Kms the heads were shot??
 

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Car Finally 100%

After having my car at a couple of monkeys, I finally found an independent shop that specializes in older Benzes and know what they are doing. I will keep you guys posted and post some nice pics as soon as she has been cleaned. I still don’t know why at 164 000 Kms the heads were shot??
It's not exactly correct to say the heads were shot they just needed work. Shot mean they were cracked or beyond repair. Your main problem was worn valve guides, 100,000 miles is a bit early for bad valve guides but not out of reason. Valves worn beyond being able to be faced is early. You might check to see if the odometer was rolled back.
 

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Discussion Starter #9
It's not exactly correct to say the heads were shot they just needed work. Shot mean they were cracked or beyond repair. Your main problem was worn valve guides, 100,000 miles is a bit early for bad valve guides but not out of reason. Valves worn beyond being able to be faced is early. You might check to see if the odometer was rolled back.
Hallo NordRhein

Thank you for your reply!
Yes you are correct, that was not exactly the correct word to use (English not my first language). I have a good history on the car and I do not think that the odometer have been turned back. The Shop said it might be due to someone running the car on Unleaded Petrol at some stage.
 

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While on the subject of piston rings....

My odometer's at almost 298,000 kms. The cylinder head was removed, cleaned up (EGR, etc.), and thoroughly machined at a separate machinist, along with and new valve guides, seals, and intake valve. The cylinder head hasn't been reassembled yet, since I'm now awaiting new spark plug wires and various seals and gaskets, before the indy can reassemble the stuff back under the hood. (So a compression check wouldn't be possible now.) After machining the block, the machinist commented that the block was very blackened. The indy said he couldn't be 100% sure about whether all or several of the piston rings are rusted up, gummed up, or otherwise in bad shape.

My related questions are:

1) Is 298,000 kms. a good time, now that that other stuff's been renewed, to have the piston rings changed, and am I risking anything by now having the rings changed at this stage?

2) Is $200 a reasonable price for the piston ring set?

3) About the pic below (for illustrative purposes, not my own Benz's pic), the left-side's hole (bottom) is filled with a piston, and the right side's second-from-bottom filled, however the other spaces are filled in our V8s
. Why's that?

Cheers in advance,
RS
 

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What do you mean by machining the block? If it was bored then you have to change the rings and do other stuff too. If it was not bored then I'm not sure what you mean by machining. If the bores were not touched and the crosshatch pattern is still visible and there is no wear ridge where the top rings would reach at TDC then the rings are probably fine. At 435,000Km my block was still good but it always had oil in it.


After machining the block, the machinist commented that the block was very blackened. The indy said he couldn't be 100% sure about whether all or several of the piston rings are rusted up, gummed up, or otherwise in bad shape.

My related questions are:

1) Is 298,000 kms. a good time, now that that other stuff's been renewed, to have the piston rings changed, and am I risking anything by now having the rings changed at this stage?
 

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Hey Nord,

Excuse my wrong use of words -- I didn't mean block -- I meant the cylinder head "unit" (i.e. where the valve guides attach to, and where the EGR is) was machined. (Blackened colour.)

What do you mean by machining the block? If it was bored then you have to change the rings and do other stuff too. If it was not bored then I'm not sure what you mean by machining. If the bores were not touched and the crosshatch pattern is still visible and there is no wear ridge where the top rings would reach at TDC then the rings are probably fine. At 435,000Km my block was still good but it always had oil in it.


After machining the block, the machinist commented that the block was very blackened. The indy said he couldn't be 100% sure about whether all or several of the piston rings are rusted up, gummed up, or otherwise in bad shape.

My related questions are:

1) Is 298,000 kms. a good time, now that that other stuff's been renewed, to have the piston rings changed, and am I risking anything by now having the rings changed at this stage?
 

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I thought new piston rings wouldn't bed-in (spelling?) well with our cars.
The reason, I have a 500 engine that ran without oil for a very short while and I wouldn't mind resurrecting that engine as it had the heads done recently and the block is supposed to be heli-coiled.
Can anyone who has experience with new piston rings in a 116/7 engine eihter confitm or deny the theory.
 

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Hey folks,

Returning to this issue, could someone please answer Hankjay's question here ten days ago? Also, I'd really appreciate answers to my several questions, before his post -- as they say, knowledge is liberating. So please share your thoughts!

Cheers,
RS

I thought new piston rings wouldn't bed-in (spelling?) well with our cars.
The reason, I have a 500 engine that ran without oil for a very short while and I wouldn't mind resurrecting that engine as it had the heads done recently and the block is supposed to be heli-coiled.
Can anyone who has experience with new piston rings in a 116/7 engine eihter confitm or deny the theory.
 

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Hey folks,

Returning to this issue, could someone please answer Hankjay's question here ten days ago? Also, I'd really appreciate answers to my several questions, before his post -- as they say, knowledge is liberating. So please share your thoughts!

Cheers,
RS
My MB mechanic Jerry says the modern chrome moly rings are way too hard for our engines, and difficult to seat right. The cast iron rings are supposed to be the best to use.

There are other write ups, explaining why a rare / very special machine is needed to drill / increase the bores in the ALUSIL blocks, in order to bring the silicone back to the running surfaces of cyl. the bores for minimum wear. ALUSIL is an MB specific aluminum / silicone alloy.
 

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Thanks, Teutone, for the info from your mech.

So now I'm also asking others here, on our BB, who've experience in this area -- all knowledgeable viewpoints will help if you've personally changed 'em yourself, or got a mechanic to do it.

Update: myindy said that some of the rings may or may not need to be changed. He wasn't 100% sure. He wasn't particularly clear (from my viewpoint at least) about what he'll do to ascertain about this. And he certainly didn't talk about any difficult fit with new rings.

So, I ask once more, and I'd really appreciate replies on the following, some of which I asked about almost three weeks ago:

1) Now that all's off (cylinder heads, etc.) under my Benz's hood, how will he ascertain the state of the rings? (Please describe a litttle of the procedure.)

2) Given I'm now at 298,000 km., would it be risky not to have the piston rings changed? (Is it good preventive maintenance?)

3) What about the bore thing Teutone mentioned? Had that done in your case?

4) Reckon $200 is a reasonable price for the piston ring set? (From AutohausAz.)

5) About the pic I attached on page 1 of this post, why are two spots filled, and the others not?


Please help us out with more info -- cheers in advance...

//RS

PS. How many of you have actually had your Benz's rings changed? (And at what mileage?) And what was the condition of those rings? Were only the top rings (of the sets) shot, or were other rings also in must-replace condition?
 

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It's too bad you didn't do a compression test before the heads were pulled, but if this were my car I would rely on the fact that the Alusil small blocks are bulletproof, heads have their problems galore but if the block had oil in it they last forever. Therefore I would not do the rings. If you do, use MB rings - they are nickel plated. Cast iron rings or anything else is simply fools blabbering away. Also be prepared for an extended period of oil consumption because it can take a LOOONG while for rings to seat on worn crosshatching. Do consider new bearings, and again for my car I would throw a new oil pump/pump chain on. It doesn't really need it but it's a habit I have from 1969 Pontiacs.

298,000km is not so much actually. In the US where distances are greater we recommend people put new chains in every 100,000miles. So going by that you're only getting ready for your second chain

As for the holes filled in - (translation) I suspect you are seeing two pistons at close to top dead center. Other pistons are at varying places on the stroke. This allows cylinders to fire in a series rather than all at the same time.
 

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NordRhein,

Thanks for the detailed info. Just returning to this issue :).

A few qus, if you have time to answer them or anybody else, I'd be very appreciative:

1) Why do you suggest new bearings, too?

2) In terms of bearings, which ones -- connecting rod bearing set, or main bearings?

3) What's the effect of using the original bearings with the new piston rings? Any negatives/long term disbenefits/risks?

4) Should I chose standard or oversized?

5) How many hours labour at a typical indy's is this piston rings and bearings replacement process? (The indy mentioned something about two hours, but didn't include any assessment of bearings in that.)

6) Is honing done with that block in situ? If not, how, and where on that block exactly?

Cheers in advance,
//RS

It's too bad you didn't do a compression test before the heads were pulled, but if this were my car I would rely on the fact that the Alusil small blocks are bulletproof, heads have their problems galore but if the block had oil in it they last forever. Therefore I would not do the rings. If you do, use MB rings - they are nickel plated. Cast iron rings or anything else is simply fools blabbering away. Also be prepared for an extended period of oil consumption because it can take a LOOONG while for rings to seat on worn crosshatching. Do consider new bearings, and again for my car I would throw a new oil pump/pump chain on. It doesn't really need it but it's a habit I have from 1969 Pontiacs.

298,000km is not so much actually. In the US where distances are greater we recommend people put new chains in every 100,000miles. So going by that you're only getting ready for your second chain

As for the holes filled in - (translation) I suspect you are seeing two pistons at close to top dead center. Other pistons are at varying places on the stroke. This allows cylinders to fire in a series rather than all at the same time.
 

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