need to remove 617 crankshaft, best procedure? - Page 2 - PeachParts Mercedes-Benz Forum

97 SL320 · #16 01-31-2014, 05:44 PM

A few things, an out of balance FW _won't_ cause a rear seal leak unless the rear bearing has beaten out so badly the crank is flopping around. If it was out of balance that far you would have known it long ago.

You could get the FW balance checked and decide if it is out enough to warrant pulling the motor apart. ( RE: if the FW is very close to zero balance pulling the crank won't do much. )

If you do pull the crank, remove the engine. Working upside down is difficult.

Given it is a 5 cyl, you need to pull _all_ pistons and rods otherwise you are guessing on the weights of the others. ( An inline 4 cyl can be balanced without knowing weights. )
And, the rods need to come out the top.

JB3 · #17 01-31-2014, 06:09 PM

Quote:

Originally Posted by Stretch

That's exactly my concern - just look at the underside =>

It is curved - no piston ring compressor is going to work - you will probably break piston rings trying to do it that way.

I could have sworn I read a thread on here where a guy installed a single 616 piston from underneath without removing the head. Ive been looking for it, but thats where I even got the idea that it might be possible.

It was one of those uninformative on specifics threads though

JB3 · #18 01-31-2014, 06:13 PM

Quote:

Originally Posted by 97 SL320

A few things, an out of balance FW _won't_ cause a rear seal leak unless the rear bearing has beaten out so badly the crank is flopping around. If it was out of balance that far you would have known it long ago.

Could have just been its time then, but it wasn't leaking, and is now definitely leaking. The vibrations couldn't have cracked a 30 year old rope seal? I am assuming the shuddering vibrations have something to do with the seal starting to leak, but it could just be a factor of age I guess

Quote:

You could get the FW balance checked and decide if it is out enough to warrant pulling the motor apart. ( RE: if the FW is very close to zero balance pulling the crank won't do much. )

If you do pull the crank, remove the engine. Working upside down is difficult.

Given it is a 5 cyl, you need to pull _all_ pistons and rods otherwise you are guessing on the weights of the others. ( An inline 4 cyl can be balanced without knowing weights. )
And, the rods need to come out the top.

on the piston weights, why wouldn't they all be within the same tolerance? One wouldn't be an example of the other 4?

ROLLGUY · #19 01-31-2014, 08:12 PM

Having done a rope seal replacement with the crank installed, I will give my opinion as to what you should do. I agree with 97SL320 that you should get the FW balanced and installed before deciding to pull the motor apart. The way I would proceed if I had the same problem is this:
1) get FW match balanced and see if that fixes the problem.
2) Just for peace of mind, you could pull the pan and check the main bearings with the engine in the van. If they prove to be bad, proceed to #3. If not, replace the rope seal with engine in the van. It will be fairly easy with all 5 rods and pistons still connected. The only challenge would be keeping the chain taught so it does not get out of time. I would suggest connecting one end of a spring to the chain, and the other end to a part of the body above the cam gear.
3) If you decide to balance the crank out of the engine, and/or need to replace main bearings, I would suggest removing the engine and pulling the crank with the engine on a stand. You will thank me (or whoever suggested it) later. The job is so much easier with gravity not working against you. Besides, installing a crank in an engine that is above you is risky at best. It is also much easier to seal the upper pan with the block on a stand.
You asked about removing the upper pan before removing the oil pump, and yes you can. In fact, removing the oil pump with the upper pan in place is nearly impossible (tried it once, didn't happen). The bottom line is, lets hope that the bearings are fine, and just a match balancing of the FW will fix it other than replacing the seal.......Rich

JB3 · #20 02-01-2014, 06:01 AM

Quote:

Originally Posted by ROLLGUY

Having done a rope seal replacement with the crank installed, I will give my opinion as to what you should do. I agree with 97SL320 that you should get the FW balanced and installed before deciding to pull the motor apart. The way I would proceed if I had the same problem is this:
1) get FW match balanced and see if that fixes the problem.
2) Just for peace of mind, you could pull the pan and check the main bearings with the engine in the van. If they prove to be bad, proceed to #3. If not, replace the rope seal with engine in the van. It will be fairly easy with all 5 rods and pistons still connected. The only challenge would be keeping the chain taught so it does not get out of time. I would suggest connecting one end of a spring to the chain, and the other end to a part of the body above the cam gear.
3) If you decide to balance the crank out of the engine, and/or need to replace main bearings, I would suggest removing the engine and pulling the crank with the engine on a stand. You will thank me (or whoever suggested it) later. The job is so much easier with gravity not working against you. Besides, installing a crank in an engine that is above you is risky at best. It is also much easier to seal the upper pan with the block on a stand.
You asked about removing the upper pan before removing the oil pump, and yes you can. In fact, removing the oil pump with the upper pan in place is nearly impossible (tried it once, didn't happen). The bottom line is, lets hope that the bearings are fine, and just a match balancing of the FW will fix it other than replacing the seal.......Rich

My reasoning for a complete removal of the crank, is let's say I go to the trouble of match balancing the two flywheels. I still have to guess what was the correct position of the original flywheel. I have found no marks on the crank itself, and unfortunately, its entirely possible the mark is gone from the pilot bearing adapter spinning when it was jammed to the splines.

Plus with the rope seal, even if I go as far as replacing it via your procedure with a hanging crank in the van, I've come so close to removing the whole crank anyway doing that, that I might as well take the whole thing out and drop it off for balancing with the flywheel. The machinist was saying that it just makes sense to know exactly, especially with 12 positions.

He can jig up the crank, and even if I was just trying to rematch the original flywheel, he can find its exact position. His comments were there's only one exact postion, but there might be a whole host of approximate positions that are close to how it was, but not exactly right. Let's say I find one of those that's livable, it will be very hard for me to determine exact from approximate, with potential longevity issues over time.
Id just hate to go to all that trouble to do the rope seal, have things match balanced, the play a guessing game as to position of how that match balance is supposed to fit.

There is a guy over on 4btswaps who tells me he's made this exact mistake and had to do the same thing with the crank, but at least he says it produced results.

If I have to drop the subframe and pull the motor eventually, so be it.

By biggest current question though related to what was said about the piston weignts, is why do I have to pull all 5 to determine their weight? wouldn't one be representative enough?

Stretch · #21 02-01-2014, 07:52 AM

Quote:

Originally Posted by 97 SL320

A few things, an out of balance FW _won't_ cause a rear seal leak unless the rear bearing has beaten out so badly the crank is flopping around. If it was out of balance that far you would have known it long ago.

...

If the seal was a bit old and crusty I could imagine it might not take kindly to excessive flexing - movement - in either an axial or longitudinal direction. Imagining JB3's description of the front to back wobble on the new flywheel makes me shiver!

When I had the machining done on my OM617 way back when I was informed by the machinist / engine builder to pay particular attention to that rope seal. His story was - poorly fitted seals create too much friction - creates too much heat - kills the back (two?) bearing shells. True story or not - it made me think more than twice about getting that rope seal in the correct position.

May be JB3 will post up some pictures of his rope seal when he gets that far? The one I removed was almost brittle - well kind of mummified (for a bit of oil impregnated rope)!

Stretch · #22 02-01-2014, 07:57 AM

Quote:

Originally Posted by JB3

...
By biggest current question though related to what was said about the piston weignts, is why do I have to pull all 5 to determine their weight? wouldn't one be representative enough?

I don't understand that either - it is a bit of a gamble to assume that the five pistons are in spec - i.e. within 5 grams of each other but it isn't too too a big of one is it? (It isn't like Getrag made the engines!!!!)

I'd even be tempted to say each piston is 900 grams to 1kg or so - go for the heaviest likelihood and see what the machinist says about that. I would come clean and say it is a guess and explain you don't really want to remove the head...

97 SL320 · #23 02-01-2014, 09:56 AM

In order for the crank to bounce around in the bearing enough to damage the seal, main bearing clearance needs to be say 0.040" + where normal running clearance is in the 0.002" range.

The rope seal is, well rope mixed with graphite and such so there really isn't anything to crack, though it does get compressed and wears out. Think of it as packing in a faucet stem. How is your crankcase venting? If blocked, this is one of the first places oil will be pushed out.

On this engine, do the flywheel bolts extend into oil or are they blind holes? ( Some engines can leak from flywheel bolts if they don't have sealer applied to the threads. )

As for measuring one piston / rod and using that as a balance weight. You are going to all the trouble to take things apart for balance but are using a single sample or 5 choices. Who knows how close the others are in weight.

I say to check FW balance by it's self to see how far it is out from zero. If it is near zero already, you vibration lies elsewhere.

Simpler=Better · #24 02-01-2014, 11:01 AM

Be careful, this is how you wind up with aftermarket rods, ARP hardware, a girdle, head work, and then a 10mm pump that can use it.

funola · #25 02-01-2014, 11:09 AM

I thought everything was going well on your project and this is a major bummer. Very sorry to hear this. How bad is the rear main oil leak? FYI, that engine was never totally dry. It may leave a drop or two of engine oil parked overnight and never leaves a puddle idling.

Let me get my facts straight:

1. You removed the stock fly wheel without marking it and replaced it with an aluminum flywheel that is lighter in weight.

2. Neither the stock or the aluminum fly wheel is neutrally balanced as indicated by your videos.

I think the stock (not neutrally balanced) flywheel was mounted on the crank in one exact position to balance the crank/rod/pistons that are also not neutrally balanced.

The suggestion to match balance the two flywheels wouldn't help since you did not mark the stock flywheel upon removal. Even if you did mark the stock flywheel, will the matched balanced aluminum fly wheel work since it is lighter in weight and the mass distribution is different than the stock fly wheel?

It seems like the only solution is to balance the aluminum flywheel to the rotating parts of the engine. Isn't there a way to do that without pulling the rotating parts off the engine? That is a lot of work! There must be some portable equipment that is available to do the balancing dynamically. Wireless sensors (accelerometer) that is glued onto the flywheel while running the engine which tells you exactly how much material to add or remove and where.

There's a place called Connecticut Driveshaft that do mostly truck work . I have never used their service and do not know exactly what they do and what kind of equipment they use. It may be useful to give them a call and describe your situation and see what they have to say.

JB3 · #26 02-01-2014, 04:12 PM

Quote:

Originally Posted by Stretch

I don't understand that either - it is a bit of a gamble to assume that the five pistons are in spec - i.e. within 5 grams of each other but it isn't too too a big of one is it? (It isn't like Getrag made the engines!!!!)

I'd even be tempted to say each piston is 900 grams to 1kg or so - go for the heaviest likelihood and see what the machinist says about that. I would come clean and say it is a guess and explain you don't really want to remove the head...

Im still confused as to why one wouldn't represent them all, or at least be a very slight gamble.

I definitely have to pull one, the machinist flat out said he wouldn't do the job without a piston to be weighed by him, and I can't say that I blame him honestly.

Stretch · #27 02-01-2014, 04:24 PM

Quote:

Originally Posted by JB3

Im still confused as to why one wouldn't represent them all, or at least be a very slight gamble.

I definitely have to pull one, the machinist flat out said he wouldn't do the job without a piston to be weighed by him, and I can't say that I blame him honestly.

Well that's head off as well then to get it back in safely.

I'd remove the engine and put it on an engine stand. (For the record the kicking of broom sticks under the car approach was never my favourite)

I've recently arsed about with my M102 on the floor and it is less than ideal. Engine stand - careful re-alignment of the upper oil pan - proper job.

I think Simpler=Better is right about the direction this project is taking.

Also if he is insisting on one piston you may as well give him the five weights

JB3 · #28 02-01-2014, 04:28 PM

Quote:

Originally Posted by 97 SL320

In order for the crank to bounce around in the bearing enough to damage the seal, main bearing clearance needs to be say 0.040" + where normal running clearance is in the 0.002" range.

Im not saying the crank appears to be doing that, BUT, the seal is suddenly leaking a lot more (it may have been wet before). I connect the balance issue and the crank seal because it was fine day one, and day 3 was leaking a lot, but they may not be connected. Its certainly possible

Quote:

The rope seal is, well rope mixed with graphite and such so there really isn't anything to crack, though it does get compressed and wears out. Think of it as packing in a faucet stem. How is your crankcase venting? If blocked, this is one of the first places oil will be pushed out.

during the test runs, I ran it without even a line on the valve cover vent, just venting to atmosphere. No blockage

Quote:

On this engine, do the flywheel bolts extend into oil or are they blind holes? ( Some engines can leak from flywheel bolts if they don't have sealer applied to the threads. )

the bolts are attached to an external flange of the crank, outside of the oil pan

Quote:

As for measuring one piston / rod and using that as a balance weight. You are going to all the trouble to take things apart for balance but are using a single sample or 5 choices. Who knows how close the others are in weight.

Thats the crux of my question though. how much plus and minus can there possibly be? and IF (and thats a big if

) a piston can actually be installed from underneath (doubtful, but would be curious to give it a go as an experiement before pulling the whole motor and head), taking one out to deliver to the machinist vs all, and avoiding removing the head makes a huge difference between a full engine rebuild, and an ornerous specific repair.

The FSM seems to indicate that the 617 pistons are all within an acceptable tolerance as part of design, and this motor has over 300k of smooth running on it, right up until I bolted the new flywheel to it without match balancing.

I feel like making the assumption that all 5 pistons are within an acceptable tolerance of each other weight wise, and only removing one for the machinist seems a reasonable risk, BUT, im basing that on just feeling its logical, not any experience with 617 piston weights. Have you encountered some that are really off in weight from each other?

Partially the machinist is saying it doesn't matter enough to bring all of them, but he also admitted that sometimes there are specific circumstances that would merit a special process, so really I have to decide if he gets all or one.

Quote:

I say to check FW balance by it's self to see how far it is out from zero. If it is near zero already, you vibration lies elsewhere.

ive done a super crude spin test on my own, but I did show it to the machinist, and he agreed that it was a biased balance based on the video. He didn't see any reason to add cost by testing the stock flywheel, not if I intended to bring him the crank anyway

Stretch · #29 02-01-2014, 04:32 PM

My guess =>

840 grams with piston rings fitted

{Wrist pin will probably be about an additional 200 grams}

JB3 · #30 02-01-2014, 04:33 PM

Quote:

Originally Posted by funola

I thought everything was going well on your project and this is a major bummer. Very sorry to hear this. How bad is the rear main oil leak? FYI, that engine was never totally dry. It may leave a drop or two of engine oil parked overnight and never leaves a puddle idling.

Let me get my facts straight:

1. You removed the stock fly wheel without marking it and replaced it with an aluminum flywheel that is lighter in weight.

Correct, apart from the aluminum flywheel is so massive in comparison, that its actually considerably heavier, about 30 lbs not counting the pressure plate

Quote:

2. Neither the stock or the aluminum fly wheel is neutrally balanced as indicated by your videos.

not by the crude test ive done, though I don't have a professional test result. The aluminum is considerably closer to neutral though, maybe even within an acceptable tolerance

Quote:

I think the stock (not neutrally balanced) flywheel was mounted on the crank in one exact position to balance the crank/rod/pistons that are also not neutrally balanced.

The suggestion to match balance the two flywheels wouldn't help since you did not mark the stock flywheel upon removal. Even if you did mark the stock flywheel, will the matched balanced aluminum fly wheel work since it is lighter in weight and the mass distribution is different than the stock fly wheel?

I think it should, its heavier than a cast iron automatic flywheel (as mentioned above), and additionally there are numerous duplicates running around in other vehicles without this problem

Quote:

It seems like the only solution is to balance the aluminum flywheel to the rotating parts of the engine. Isn't there a way to do that without pulling the rotating parts off the engine? That is a lot of work! There must be some portable equipment that is available to do the balancing dynamically. Wireless sensors (accelerometer) that is glued onto the flywheel while running the engine which tells you exactly how much material to add or remove and where.

There's a place called Connecticut Driveshaft that do mostly truck work . I have never used their service and do not know exactly what they do and what kind of equipment they use. It may be useful to give them a call and describe your situation and see what they have to say.

This was mentioned by someone else as well, it might be worth checking out definitely