Hi - been lurking for awhile and finally have a question. I just bought (cheap)an '82 300SD that has a hole in one piston. I bought it primarily to learn how to work on MB diesels so I won't mess up when I get a nice one. This car is running, albeit exuding a fair amount of uncombusted hydrocarbons. I am thinking of just replacing the one piston and seeing how it goes- has anyone out there done that without removing the engine? It runs and idles pretty good considering.

Naturally, the general consensus is that the size of the liner should be matched to the size of the new piston. But, what have you got to lose? If the cylinder walls are in good condition, and the damage was limited to the piston itself, take the chance and replace just the one piston.

I've not attempted to work on the internal engine components from underneath on the 617, but I believe that it would be possible. Other members will confirm this.

it is, i believe, possible to change only the #1 piston from below if indeed it is possible to do any at all. there may not be room to remove the piston with the crank in the block. it is not possible to remove the crank with the engine in the car.

do you know why the piston has a hole in it? if not be sure to find out before doing anything else.

if you can get the piston out, then get a scope to look at the cylinder before doing anything else. if it is deeply scored you will be wasting your time to put in a new piston.

the cheapest thing to do is prob to find a running engine and switch it out.

good luck

om w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Tom, why can't the piston come out the top? I'm presuming that he will remove the head and use a ridge reamer to eliminate the ridge at the top of the piston travel.

he didnt want to take the head off.

if he is taking it all apart considering the labor involved, it would be a shame to try to jury rig it. at that point i would look at everything and fix it right.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

you really dont need to remove the ridge to take a piston out

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have no worries.....President Obama swears "If you like your gun, you can keep it

Thats right if you plan on junking that piston. But if you plan on re using the piston you need to remove the ridge or run the risk of breaking/cracking ring lands. Something you might not find out about untill the piston is back in service.

if the ridge is bad enough. if you think about it, the ridge is the size of the piston and rings. as long as its not really deep it wont hurt anything. machine shops dont even recommend removing it if your not going oversize on the cylinder because of a risk of going too far.

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have no worries.....President Obama swears "If you like your gun, you can keep it

ahhhhh.... the piston has a hole in it. He won't be reusing it.

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"If anyone knows other lessons I need to learn, please tell me. I'm tired of learning them the hard way".
by JerryBro

The Glow Plug Wait: This waiting period is a moment of silence to pay honor to Rudolph Diesel. The longer you own your diesel the more honor you will give him". by SD Blue

My normal daily life; either SNAFUed- Situation Normal... All Fouled Up, or FUBARed- Fouled Up Beyond All Repair

62 UNIMOG Camper w/617 Turbo, 85 300SD daily driver- both powered by blended UCO fuels

I was planning on taking the head off, dropping the oil pan, disconnecting the piston/con rod at the crank and pushing the assembly out of the top, ream out the ridge if present, honing the bore and using another piston (used) to complete the job. I've done that before but on a '53 Ford flathead motor- any reason it wouldn't work here? Like I said, the car came pretty cheap.

as i said it is a huge amount of labor to tear apart and reassemble a benz diesel, so if it were me i would prob go thru it.

but you prob can get it running again by doing the one piston thing....the question is for how long? and what is your Time worth?

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

..When I can spare it. I'm looking to familiarize myself with the 5 cylinder Benz diesel motor over the course of the winter when I get some spare time, but frankly the car,though solid enough, is not in the kind of shape that would justify a full rebuild. Once I get my wife's 82 VW Rabbit diesel pickup out of the garage (master cylinder on order) I'll start on the SD. Now if I can find a decent manual...

You have to push them out through the top. I believe the first two pistons can be removed with only the lower oil pan removed. I have some spare 617 pistons if you need one. I'll let it go for a fraction of the new price.

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Jim

Bad injector/pre-combustion chamber spraying fuel directly on the piston making a hot spot?

Seen it happen before on other diesels (non-MB)

No $hit! Just an fyi for anyone else thinking on removing a piston for whatever reason