OM605/6 piston advice - Page 2 - PeachParts Mercedes-Benz Forum

spock505 · #16 03-30-2009, 07:08 AM

Thanks for all the replies, will answer in order.

Please see comments posted with photo, the marking is very light but looks worse against the black carbon background.

This will polish out now the piston is out.

Quote:

Originally Posted by JonL

I don't like the looks of the center of the piston crown where the prechamber gets close... it looks like it is eroded or even worse that the piston has hit the prechamber. Maybe it's just the picture.

spock505 · #17 03-30-2009, 07:18 AM

Quote:

Originally Posted by compress ignite

Please be Very,Very Careful not to remove Too Much Material...
Only the Carbon!
OP is correct,You can "Bust" the ring "Lands" if the carbon ridge is left in place
when removing pistons upwards...(Then you are Screwed).

The piston wasn't forced out as most of the carbon removed with kitchen scourer, I think oil scraper may have already been broken.

On the next four pots I will use one of the following recommendations below to remove all of the build up to allow them to slide out freely.

Your "Crosshatching" on the Cylinder Walls is still evident visually.'Can you "Feel"
it with a fingernail?If so, I'd be tempted to do nothing else than remove the
carbon ridge at the top of the Cylinders (and IF the ring Lands are O.K.),and install new rings and fire her back up!

I am a bit confused here when you say 'ring lands' are ok, are you referring to the slots which the rings sit inside on the piston itself?

If so there is no damage at all as the rings are fully compressed and stuck completely inside the grove protecting it so to speak, this is why there was little or no resistance getting them out.

There was nothing protruding to catch onto the remaining carbon.

spock505 · #18 03-30-2009, 07:25 AM

Hi bud, posted this in response to CI's post

Quote:

Originally Posted by babymog

I would be concerned about the ring lands / spacing if the piston was forced out across a ridge. Measure them before installing new rings.

"I am a bit confused here when you say 'ring lands' are ok, are you referring to the slots which the rings sit inside on the piston itself?

If so there is no damage at all as the rings are fully compressed and stuck completely inside the grove protecting it so to speak, this is why there was little or no resistance getting them out.

There was nothing protruding to catch onto the remaining carbon."

I am also very curious why the ring grooves are so impacted with
carbon/crap.

Are we talking about something different as you cant see the ring grooves with the rings still in - please see my response to CI asking for clarification on this, I know sometimes being from different sides of the pond we use alternative names for things?

Will you be so kind as to enlightnen me/us on what besides burning SVO might have led to this problem (possibilities such as extended idling, oil additives with Teflon/PTFE, past engine problems et al)?

Nothing burnt apart from svo and only when engine above 65c using a twin tank system with two heat exchangers. No wvo or cold starts on veg, very little idling although the car has been infrequently used for about three years.

spock505 · #19 03-30-2009, 07:28 AM

Quote:

Originally Posted by babymog

If you don't have a ridge-reamer, I would try using a die-grinder or Roloc with a fiber disk, the disk harness > cast iron. I have such a tool, can't remember the name.

Dremmel would probably work with the same fiber/abrasive disk but with anything harder than the cylinder liner it would be extremely difficult to control it and avoid damaging the liner.

It's all about the hardness of the abrasive, they make them for so many types of materials, and the right one is magic.

Ok, I'll check back here with my proposed tool heads to use and you can let me know if on or not.

spock505 · #20 03-30-2009, 07:30 AM

Quote:

Originally Posted by babymog

Yes, oven cleaner is a bad idea IMO, most say on the can to avoid ALUMINUM as it is extremely corrosive to alkali metals.

They can be boiled in a solvent tank, your friendly neighborhood machine shop should be able to provide this service at a reasonable price and leave them looking like new. Same deal with the cylinder head.

Brill, thanks - i do have a friendly machine shop, thats a great idea - heads ok as its new (reconditioned)

Will the solvent tank free the rings?

spock505 · #21 03-30-2009, 08:49 AM

Quote:

Originally Posted by ForcedInduction

Great pictures. Can you take some of the cylinder head and camshafts?

Here we go, threw in a couple of the car as well in case your not familiar with this model (not sure if it was a US import)

car pic t/f)

Alastair · #22 03-30-2009, 09:57 AM

Just a a bit of background, as I have been talking to Spock on this over a few weeks....

The engine was actually running fine....

But a glow-plug or two had issues and needed renewal. One or two, --cant remember-- Snapped off in the head, and attempts at removal damaged the casting...

Head came off, and was replaced with a 'reconditioned' part. The engine was 'open' for some time, which I guess gave carbon/crap/veggy/moisture/ whatever time to set like cement on the rings...

The rest as they say is 'history'....

bobodaclown · #23 03-30-2009, 10:36 AM

WOW!!! Good reason not to run WVO (Waste Vegetable Oil) or any Vegetable Oil straight.
Process it and get out the glycerin.
I'd be concern about oven cleaner etching the aluminum. Bores look good (the crosshatching is still there). How about soaking in some type of solvent (BioDiesel) to see if that will loosen the crud on the rings and such.

Great pictures.

pimpernell · #24 03-30-2009, 10:45 AM

Quote:

Originally Posted by spock505

Brill, thanks - i do have a friendly machine shop, thats a great idea - heads ok as its new (reconditioned)

Will the solvent tank free the rings?

To kill two birds with one stone, you might want the shop to check out the pistons regarding the ring groves themselves, along with any related damage to the piston skirts. There are special tools that can be used to clean out and dress up the groves. Even though they appear to be ok to the naked eye, you are dealing with tight tolerances, and you would hate to go through all the labor and have the same problem occur. Good luck

Alastair · #25 03-30-2009, 11:53 AM

Quote:

Originally Posted by bobodaclown

WOW!!! Good reason not to run WVO (Waste Vegetable Oil) or any Vegetable Oil straight.
Process it and get out the glycerin.
I'd be concern about oven cleaner etching the aluminum. Bores look good (the crosshatching is still there). How about soaking in some type of solvent (BioDiesel) to see if that will loosen the crud on the rings and such.

Great pictures.

Nah, Not necessarily the veggy.....

Ive seen exactly the same happen with a petrol/gasser engine that was 'open' for a while....

Personally I reckon that Moisture was the main culprit. The engine was open during the peak of Winter here with moist air everywhere.....

OPnly needs a spot, and over time with capillary attraction will conduct itself round the rings, Rusting does the rest....

spock505 · #26 03-30-2009, 12:12 PM

Here's what she looks like in one piece

bobodaclown · #27 03-30-2009, 02:00 PM

sweet looking ride.

compress ignite · #28 03-30-2009, 03:39 PM

Beautiful Automobile!
No,We were never "Gifted" with the Twin cam OM605 engine.
(Only in our dreams)

The "Lands" are the Ridges in Pistons that separate the Grooves the Rings ride in.
(Also the UpStanding portion of the piston separating the Grooves themselves)
With a substantial carbon buildup at the top of the Cylinder...Pushing the piston
upwards...will BreakOff the UpStanding portion of the "Lands"
BEFORE the Rings are subjected to Breakage Pressure Tolerances.

Thanks, JONL
I've EDITED and corrected my misnomer.

JonL · #29 03-30-2009, 03:45 PM

Quote:

Originally Posted by compress ignite

Beautiful Automobile!
No,We were never "Gifted" with the Twin cam OM605 engine.
(Only in our dreams)

The "Lands" are the grooves cut into the pistons that the Rings ride in.
(Also the UpStanding portion of the piston separating the "Lands" themselves)
With a substantial carbon buildup at the top of the Cylinder...Pushing the piston
upwards...will BreakOff the UpStanding portion of the "Lands" Separators
BEFORE the Rings are subjected to Breakage Pressure Tolerances.

I've always referred to the parts of the piston adjacent to the grooves as the lands, while the groove is... well, the groove is just the groove.

spock505 · #30 03-30-2009, 04:10 PM

Thanks for the feedback, I really like the car which is so original.

I am always sceptical when I buy a car with such low mileage and the seller puts it down to lack of use but this does look to be the case.

That said it comes with a few problems such as the glow plugs never being removed or at least two of them leading (eventually) to this.

CI, that's what I thought but not 100%

I have a local Bio Diesel supplier up the road so will pop by tomorrow and get 20 litres to soak the pistons to see if that helps.

Several folk have mentioned coca cola as being a good solvent fo carbon, any views on this (thinking of the copper penny here)

Dremel tools for removing carbon lip; picked out the brass wire brush as being soft but abrasive enough to remove the carbon - have also ordered a pack of very fine wet and dry paper.

I am going to take my time to get this right so if the soaking doesnt work off to the machine shop, my only concern here was after thinking about the solvent is that it may damage the small end bearing?