Author Topic: Thrust Bearing Replacment Require Machining? (Read 4060 times)

RotCowboy · « **on:** July 06, 2019, 02:06:39 PM »

So I have the upper pan off of my 1991 M42 E30 as part of a timing case refresh and I was planning on replacing the half a thrust bearing with the other half. I have been reading and searching the forum and the web for a couple of hours and cannot find a definitive answer to whether I can just replace the missing thrust bearing on the cap (or even roll in the other half too) or if the cap will require me to send it off for machining?

Can anyone answer if I can just buy the BMW Main Bearing Set (Standard) - Glyco H 023/5 STD and plop it in without machining? These are the only replacements listed so I wouldn't think they would require anything extra, but Metric Mechanic has a service listed "required on the 360� Main Bearings: Labor for machining Main Bearing Cap Lock Tang groove" which makes it sound like there is more to it.

Thanks.

DesktopDave · « **Reply #1 on:** August 05, 2019, 09:31:47 PM »

Sorry it's been a month, missed your post. Short answer...I just don't know. I was pretty sure it was posted somewhere on here, but I had no luck finding it here nor at 318ti.org.

If MM said it was required, I'm inclined to believe them.

colin86325 · « **Reply #2 on:** August 30, 2019, 11:18:50 AM »

Yes, machining is required for the cap. It's been a while since I had it done but it is necessary.

keflaman · « **Reply #3 on:** September 01, 2019, 09:48:57 AM »

A great question and something I had to investigate before I (someday

) begin the refresh on my motor.

Open the link to view a picture of stock M20/M2 crankshaft bearings: https://www.bimmerworld.com/core/media/media.nl/id.193550/c.3750282/.f?h=29242e374b2c4be79bdc

- Starting with the left column are the lower bearing shells. Notice the short groove on the RH side of the bearings?

- In the middle column are the upper bearing shells and notice they have a complete groove in them?

- The right hand column are the thrust (aka "guide") bearings; the upper bearing has an oiling groove, whereas the bottom bearing does not.

Now refer to page 10: https://metricmechanic.com/wp-content/uploads/2016/07/M42-Engine-Booklet.pdf

- In order to achieve a 360� oiling groove, Metric Mechanic uses TWO upper thrust bearings which requires machining a lock tang groove in the main bearing cap. Quoted directly from MM's engine book:

"Using a milling
machine and
custom keyway
cutter .140� wide,
we machine in
the new lock tang
groove to accept
the 360� oiling
main bearings."

Since I intend to install ONLY the LOWER thrust bearing on my M42, I believe it will require machining only THAT main bearing cap.

Note: MM charges $25 for the service according to the list price at the lower right under "Block Parts" on page 7. https://metricmechanic.com/wp-content/uploads/2018/05/Price-Pages-3_4_18.pdf

RotCowboy · « **Reply #4 on:** October 08, 2019, 09:24:21 PM »

So I just rolled in a full new thrust bearing on my 1991 E30 vert. I was worried about it needing to be machined or not being a direct replacement. I wrote to Pelican parts and they advised that it is drop in stock replacement requiring no modification.

The new full thrust bearing fit into the stock caps perfectly. However it was much more difficult to roll in than what YouTube videos make it out to be.

After I rolled out the old bearing the crank moved slightly forward towards the front of the car. This meant that the space for the shoulder of the bearing (thrust surface) was too small on front side. I had to push and tap on the main crank bolt to get the crank back in position to allow the thrust bearing edges to fit. Once this was lined up it rolled in easy.

I wish I had known this though, I got stuck on this for hours.

Author Topic: Thrust Bearing Replacment Require Machining? (Read 4060 times)

RotCowboy

Thrust Bearing Replacment Require Machining?

DesktopDave

Re: Thrust Bearing Replacment Require Machining?

colin86325

Re: Thrust Bearing Replacment Require Machining?

keflaman

Re: Thrust Bearing Replacment Require Machining?

RotCowboy

Re: Thrust Bearing Replacment Require Machining?