Replace #1 piston on 617 with engine in car? - PeachParts Mercedes-Benz Forum

jkubica · #1 06-27-2010, 12:31 PM

Greetings.
In the case of a 617 engine with turbo - with suspected broken piston ring or damaged piston in the number one cylinder, Is it possible to change the piston with the engine still in the car - removing the lower oil pan and cylinder head?
Thanks,
Joseph

t walgamuth · #2 06-27-2010, 01:23 PM

Yes, but if it has a broken ring I would suspect the rest of the engine might be on its last legs too unless it is a head problem. Before pulling the head i would blow into the cylinder and see which side it is leaking from....intake, exhaust or into oil pan. That way you can isolate whether it is valves or ring sealing problem.

leathermang · #3 06-27-2010, 05:54 PM

Quote:

Originally Posted by t walgamuth

Yes, but if it has a broken ring I would suspect the rest of the engine might be on its last legs too unless it is a head problem.

Well, on most engines that would certainly be true..
but the MB engine's number one piston and bore are a different size from the others.... and I suspect many a time that people did not see that in the FSM ( or were not using it ) to rebuild the engine...
There are LOTS of reports of bad things happening to the number one cylinder and not the others in the same engine.
I think it is because of cooling problems....
If you take the head off to do this replacement... be sure to check out the different head gaskets which were offered at different times since changes in the holes on heads and head gaskets almost always involved trying to improve the cooling.
The FSM has many warnings which you never see in the forums... so getting a paper copy of the FSM would be a high priority on my list before doing anything to the engine...

Alastair · #4 06-27-2010, 06:14 PM

Yes, the number 1 pot piston is removabe without taking whole engine out...

There is a different running-clearance for number 1, just slightly more clearance than others, so I'm guessing they expected it to run just a tad hotter than the others, and compensated by increasing clearance--Aluminium of pistons expands more than the iron of the block in which it runs...

Its the same for N/A engines too....

t walgamuth · #5 06-27-2010, 06:34 PM

Quote:

Originally Posted by leathermang

Well, on most engines that would certainly be true..
but the MB engine's number one piston and bore are a different size from the others.... and I suspect many a time that people did not see that in the FSM ( or were not using it ) to rebuild the engine...
There are LOTS of reports of bad things happening to the number one cylinder and not the others in the same engine.
I think it is because of cooling problems....
If you take the head off to do this replacement... be sure to check out the different head gaskets which were offered at different times since changes in the holes on heads and head gaskets almost always involved trying to improve the cooling.
The FSM has many warnings which you never see in the forums... so getting a paper copy of the FSM would be a high priority on my list before doing anything to the engine...

So you think there is a good chance the rest of the motor is just fine?

leathermang · #6 06-27-2010, 09:22 PM

I think it is possible for just the number one bore and piston to have problems and the rest of the engine be fine... further investigation... like compression and leak down tests would be needed... but since the option is there for putting in a new sleeve and piston and starting fresh... if nothing indicates the rest is bad would be worth a shot given that number one is " special "....case...
If it were a different piston and bore I would not feel the same way....

jkubica · #7 06-27-2010, 11:29 PM

Quote:

Originally Posted by leathermang

I think it is possible for just the number one bore and piston to have problems and the rest of the engine be fine... further investigation... like compression and leak down tests would be needed... but since the option is there for putting in a new sleeve and piston and starting fresh... if nothing indicates the rest is bad would be worth a shot given that number one is " special "....case...
If it were a different piston and bore I would not feel the same way....

Hi

Thanks All

Very interesting that the number one piston is differant from the others

Can the number one piston be bought separately? If the cylinder bore looks good - can just the new piston be installed?

This is the situation:

The engine has lots of power, idles smoothly, good oil pressure, temp stays at steady 85C., runs quiet at speed with no exhaust smoke even under full throttle The tea kettle test sh0ws light dancing of the 0il fill cap

Cold compression is 300psi on number one and 350 -360 psi on the last four.

Hot compression is 390psi on number one and 450psi on the last four.

At idle there is a clacking sound (nailing perhaps) at number one that goes away above 1000 rpm. When injectors are switched, the clacking sound stays at number one. Loosening the number one injector line stops the clacking at idle.

When the number one injector is removed and the engine spun fast with the starter -some engine oil can be seen blowing out the injector hole.

The same test with the number three injector removed shows no engine oil escaping.

I'm assuming that the clacking sound and escaping engine oil is from a broken piston ring - or damaged piston and/or bore.

What conclusions should be drawn? Any & All?

Regards,
Joseph

leathermang · #8 06-27-2010, 11:34 PM

I would not go to the trouble of taking it that far down... and putting in a piston without putting in a new sleeve.... the tolerances are very close...
For the record..
you are supposed to measure the piston which is going into that new sleeve and hone the sleeve to fit it...
A piston and sleeve can be bought one at a time...
The sleeve can be pulled from and then installed in the block with the engine in the car....

leathermang · #9 06-27-2010, 11:47 PM

Where do you think I got that information ?

Diesel911 · #10 06-27-2010, 11:54 PM

When Piston Rings Break they often score the Cylinder and installing new rings and a new Piston will not cure that.

Even if the Cylinder is not scored if it is out of round the new Piston Rings are not goint to seal well.

But, you will not know until you take a look and do some measuring.

leathermang · #11 06-28-2010, 07:40 AM

Exactly true....all good reasons to pull the sleeve and put in new one if there is any problems in that bore... along with the new piston honed to fit that sleeve.
I do not know what jt20 is referring to.. perhaps that joker instinct...as most of you know I have paper manuals and have read them. Others have talked about building the puller for the sleeve and using it.. several threads about that... not that it is easy to get the top setting correct in terms of height above the block surface... but that can be done with patience and a file... thread exists on that too... but that is much easier than pulling the entire engine out of the car..

vstech · #12 06-28-2010, 10:27 AM

wow... in car liner honing, and deck height adjustment with a file...
uh, not for me. I like funding my machine shop's mortgage...

leathermang · #13 06-28-2010, 11:15 AM

Some people can not afford the new higher cost of their mechanic's children's college education....
It is not the optimum way... but with patience perfectly doable...
Lots of clean rags changed out regularly, oil rinses, measure measure measure, go slow...

layback40 · #14 06-28-2010, 12:14 PM

X2 jt20,
The best that can be expected would be to remove the head & sump, Inspect the bores, Make a decision about how to proceed. If rings only, then maybe pull the piston out & re ring.
If the bores are bad, remove the block from the car & proceed with sleeve replacement. You are unlikely to be able to just hone the bore when replacing a sleeve. it will need boring to insure its true.
I have done a sleeve/piston replacement on a GM 2 stroke without pulling the motor, thats a completely different situation though as no boring/honing is required.
If you only need rings for 1 piston, there is a single set on fleabay at the moment.
I would be doing all 5 if I had gone that far as well as rod bearing shells.

leathermang · #15 06-28-2010, 01:24 PM

That is nice that the two of you agree with each other...

Have YOU checked the FSM concerning this issue ?

Have you seen the specs for the puller given in there?

Are you aware this is a pull from the top type of sleeve ?