M127 engine vibration - recommended options

[franjo_66]

The original M127 engine in my 230SL runs great except for a noticeable vibration.
Engine has great compression, does not consume oil, no smoke and oil pressure is fine. Importantly no knocking sounds whatsoever from the bottom end

Last year I had the bolt on my crankshaft damper fail, and I replaced both the damper and bolt.
Residual effect is that there is a noticeable vibration. Additionally, I also had to replace the torque converter when the original one developed a split.
I think from memory that I have read it is recommended that the crankshaft & flywheel be rebalanced under these circumstances (since it is calibrated as a single unit).
Can anyone confirm this?

Given that the engine is fine in all other aspects, from experience, what would be the best way to tackle this?
Can I simply attempt to repair & balance the crankshaft unit together with new bearings, etc ?

Or am I up for a rebuild?
Is it worthwile trying to address just the crankshaft or do I need to take her apart to assess.

[ja17]

You have two basic components here, the front engine crankshaft counter-balance and the vibration dampner, which is fitted to the front of the counter-balance. Make sure that the front crankshaft counter-balance has been installed correctly. It can be forced on 180 degrees off causing a sever vibration.  The vibration dampner is basically in-balance itself and the crankshaft counter-balance is "counter-balanced" against the off-set mass of the crankshaft.  When the front assembly comes loose, often times the end of the crankshaft is damaged. If this is the case your front counterweight might be wobbling around and causing the vibration. The problem should not be the converter.
The crankshaft assemblies are balanced as an assembled unit on the 230 engines, since all the components are "counter-balanced" to each other forming a complete balanced assembly. A good automotive machine shop or Speed shop can keep the components identical by matching the new component against the old one prior to assembly.
I would double check to make sure your installation is correct and the new parts are secure first. If you have a damaged crankshaft end there is no simple permanent fix.

[franjo_66]

Thanks for the reply Joe

Double-checked the installation and it was all installed correctly.

We can see that the front assembly is loose and it definitely wobbles around so looks like the crankshaft end is damaged
I would suspect that this requires welding/repairs to the crankshaft before rebalancing etc

[ja17]

Hello franjo,

Do you have the early BBB? Go to section 03-10/3.  "Refastening of Loose Counterweights on Crankshaft of Models 190c to 250SL. This factory procedure involves installing  new oversize pins, and a different crankshaft bolt with three spring washers to solve the dilemma. It even has some part numbers. Maybe someone could scan the information to you if you do not have the BBB?
In the mean time, I would stop running the engine to prevent further damage.

[andyburns]

Hi Joe,

I also need to tighten up this assembly when I have recovered.  I cant find the information in my manual about this but remember the 3 big cupped washers.  Can you tell me what the orientation of these should be.  I am guessing one sprung/cupped back toward the engine, the forward most one cupped to the front of the engine but then what do you do with the one in the middle.  Guess it doesn't matter.

Also what is the best way to lock up the engine to crank down on the big front bolt.  Any idea of the torque setting on this. 

Certainly reading this thread I now want to get this spot on as well and ensure everything is bolted in and cant move.

Any advice would be fantastic.

[66andBlue]

... Maybe someone could scan the information to you if you do not have the BBB?  ..

Here you go:

[franjo_66]

Hi Joe

I did install the upgraded bolt and pins (bought from the classic centre), along with a new vibration damper (but did not balance the whole assembly)

However, I still get the vibration and my pagaoda mechanic has noticed that the front damper is wobbling so I suspect that damage has been already done to the front end of the crankshaft

Given that a/c has never been fitted to the engine, and that the original damper came loose, I have that awful feeling that I am in for crankshaft repairs
But, I will get them to triplecheck the installation of upgraded bolt & pins.

[franjo_66]

Well it doesn't look good
Crankshaft is definitely damaged.

We rechecked the installation, all done correctly but you can see the damper wobbling around

The workshop recommends that the engine be rebuilt

I suggested that given everything else is in great order, can't we simply repair/replace the crank along with new bearings, etc.
Their suggestion is that pistons, etc have to be taken out an there is no point in putting in a new bottom end and reassembling the other old components

Any thoughts from you guys on this? Should I bite the bullet and do the whole engine?

For the other aussies, who had you used in Melbourne/Sydney/etc to do your engines?
Or do I send mine o/s to Metric or similar

Lots to think about

[stickandrudderman]

Well, a good engine shop should be able to measure everything to determine whether the cylinders/pistons are good to go or not.
There are a couple of things to consider:
1. Pistons are not easy to get and are very expensive.
2. Have a number of checks done before disassembly; compressions, leak down and most importantly, manifold vacuum. If these are all good then you might not want to bother but:
3. A large part of the cost of an engine overhaul is the labour and you might want to consider the risks of having to pay that labour again in a few years time if you don't do it now. The labour difference between the two jobs done now is maybe 2 hours max.

[franjo_66]

Good point Stick

I am leaning towards getting the motor rebuilt as I don't want to revisit this again in a few years
However will need to check with other aussies as to recommended engine builders as I got a quote of $18k !

May be more cost effective to ship it over to Metric (or others) as that price floored me

[ja17]

220 and 230 Sedans of the era used the same crankshafts.  At this point you might consider drilling and adding two more pins (total of four). Shim the surfaces, locktite everything up and bolt it down. You might get lucky and delay the inevitable for a few years. *Note, this is not a recommended factory repair. 

[franjo_66]

Joe, thanks for the suggestion 

May give me some extra time to save those pennies....gonna need a lot of them

[rutger kohler]

Hi, can we get some accurate reading on how much slack there is between the two components in 0.000" and whether the gap is concentric around the crankshaft?  It would be useful to deal with actual figures before recommending a fix.  The repair shop should be able to give you these figures. Would also be useful to see how much of the gap is on the crankshaft (male) and how much on the female diameter.

[Garry]

Franjo,

Have sent you a message re several decent engine builders in Melbourne, but be ready for high numbers, even the pistons cost 2-300 each  and if you get into the head then it is really costly.

Good luck

Garry

[ja17]

I would also drill the new holes a little shallow so the new pins stick out about 3/32" .  In this way  when you tighten down the big crank bolt the pins will jamb down tight and expand a bit taking-up any slop and tightening the assembly.  Don,t forget the locktite. (stud and bearing mount). If you can space three appropriate thickness  shim strips around the crank nose before you install the counterbalance that will help also.  Even feeler gauges could work, let them hang out the front as you install the counter balance and trim them off when installed.

[franjo_66]

Joe - thanks so much for the advice & suggested temporary fix

Garry - thanks mate, I got your message and will be in touch to get input from your guys on the engine rebuild

Regards
Franjo