M20 intermediate shaft failure

[zaq123]

Then it definitely hasn’t been hot tanked as there was still paint and rust on the outside of the block.

Hot tanks aren't super hot too but the issue for the shaft bearing is the chemical solution which strips everything, from carbon to paint.

[Knoopa]

no, it's just a washer, spec says 120C is max temp. Hot tank removes paint etc. That machine wont mess up anything

Then it definitely hasn’t been hot tanked as there was still paint and rust on the outside of the block.

[zaq123]

So the machine shop that bored the block uses these kind of machines to wash engine blocks: https://www.laborex.com/en/cleaning-...-front-loader/. Does this process mess with the bearings or is it different?

no, it's just a washer, spec says 120C is max temp. Hot tank removes paint etc. That machine wont mess up anything

[Knoopa]

So the machine shop that bored the block uses these kind of machines to wash engine blocks: https://www.laborex.com/en/cleaning-...-front-loader/. Does this process mess with the bearings or is it different?

[digger]

i think the tendency is to think of these bearings as being soft like the babbit layer on a bearing shell and i don't think that is quite the case but aren't these more like aluminium from a hardness perspective? which hones ok obviously multi stage cleaning is required as for a honed cylinder.

The issue i see with honing is that most brake hones that will do this size are really cheap junky parts

[82eye]

I would be a little concerned about imbedding honing material in the soft bearing.

an ancient bmw mechanic advised us on how to install the first couple working with what we had. as far as i know everyone is still running, i talk to one of the owners occasionally, but the other car sold a long time ago.

edit: ironically the engine currently in my car does not have it replaced. couldn't source the bushing at the time of the build. would definitely have sprung for the ForcedFirebird bushing had i known it existed.

[82eye]

to me these things should be line bored concentric after install before minimally honing/reaming/burnishing.

i can easily see this. i wouldn't doubt that if there is a procedure written somewhere it would be this or close to it.

[zaq123]

the shafts were polished and diameters checked. a standard cam bearing installation tool installs the bearing in the block. they crush a bit when installing. a brake cylinder hone is carefully used to finish them, test fitting as you go.

it's not as bad as folk make it out to be, but you have to be careful and go slow.

edit: you can pre-check the bearings and hone them first in a lathe. have never needed to do this myself. they crush a little and change with installation anyway. putting them in a lathe first can take too much material. you will need to hone after.

I would be a little concerned about imbedding honing material in the soft bearing.

[digger]

the shafts were polished and diameters checked. a standard cam bearing installation tool installs the bearing in the block. they crush a bit when installing. a brake cylinder hone is carefully used to finish them, test fitting as you go.

it's not as bad as folk make it out to be, but you have to be careful and go slow.

edit: you can pre-check the bearings and hone them first in a lathe. have never needed to do this myself. they crush a little and change with installation anyway. putting them in a lathe first can take too much material. you will need to hone after.

The customer should always speak to their machine shop, to me these things should be line bored concentric after install before minimally honing/reaming/burnishing.

[82eye]

Either way whether the bearings were destroyed by hot tanking or it was a mismatch or maybe the bearings were already destroyed I guess we will never know. I mainly wanted to know if too much bearing clearance would have caused this because otherwise I wouldn’t know what else it could have been.

the hot tanking caused it.

the damage looks like heat/friction. if it was the original shaft and bearing it would have been fine on a rebuild if not tanked and left alone. most shops don't know about the bearing, or that it can be destroyed in the tank.

if you are assembling the engine most shops will tank them and let you deal with it.

[82eye]

Regarding IM shaft. Like I said, one can't just iblindly nstall IM from another used engine and call it good. Well I guess you can, in the similar fashion as some install main bearings on a crankshaft without measuring the clearance assuming BMW didn't just select crank bearings for that individual engine. Just there is a risk of creating similar post asking what happened.

New or some random used shaft - measure the clearance. If not within spec, ream or replace/ream new bearings and measure again. That what I would do. Using the original shaft to the block and the bearing looks good and wasn't damaged, there is a very good chance it will work OK as it id for xxx number of miles previously.

the shafts were polished and diameters checked. a standard cam bearing installation tool installs the bearing in the block. they crush a bit when installing. a brake cylinder hone is carefully used to finish them, test fitting as you go.

it's not as bad as folk make it out to be, but you have to be careful and go slow.

edit: you can pre-check the bearings and hone them first in a lathe. have never needed to do this myself. they crush a little and change with installation anyway. putting them in a lathe first can take too much material. you will need to hone after.

[Knoopa]

I'm not arguing the fact that the bearing will be ruined by hot tanking. It most definitely will , depending on the tank used of course. It looks like OP is not certain if it was even tanked in the first place and what tank was used if it was.

The block has been cleaned by the machine shop but my native language is not English so I’m not sure if the process they use is the same as hot tanking.

Either way whether the bearings were destroyed by hot tanking or it was a mismatch or maybe the bearings were already destroyed I guess we will never know. I mainly wanted to know if too much bearing clearance would have caused this because otherwise I wouldn’t know what else it could have been.

I will get a new shaft and new bearings and bring it to a machine shop that has experience with these blocks so hopefully this won’t happen again.

[zaq123]

i've seen them ruined by a hot tank here. i've also advised shops on them who have told me they have no idea about them. many shops here don't know how the m20 intermediate shaft is installed.




replaced a couple. bmw did not have a technician that sat honing each engine individually. new shafts are still available, and we've put at least one new shaft in before on a new bearing with no issue, and have installed a used shaft from a different engine with a new bearing over the same hot tank problem on another engine.

you are absolutely correct in the best practice always being keeping the original shaft with the original engine if possible. we've just never found it to be a problem.

I'm not arguing the fact that the bearing will be ruined by hot tanking. It most definitely will , depending on the tank used of course. It looks like OP is not certain if it was even tanked in the first place and what tank was used if it was.

Regarding IM shaft. Like I said, one can't just iblindly nstall IM from another used engine and call it good. Well I guess you can, in the similar fashion as some install main bearings on a crankshaft without measuring the clearance assuming BMW didn't just select crank bearings for that individual engine. Just there is a risk of creating similar post asking what happened.

New or some random used shaft - measure the clearance. If not within spec, ream or replace/ream new bearings and measure again. That what I would do. Using the original shaft to the block and the bearing looks good and wasn't damaged, there is a very good chance it will work OK as it id for xxx number of miles previously.

[zaq123]

blindly putting a IM shaft from one block into another seems like atleast a bit of a risk to me it should atleast be checked as a matter of course which isnt any more difficult than on rod or main

precisely.

[digger]

blindly putting a IM shaft from one block into another seems like atleast a bit of a risk to me it should atleast be checked as a matter of course which isnt any more difficult than on rod or main