Author Topic: successful M42 rebuilds (Read 6571 times)

doitover · « **on:** August 13, 2012, 03:44:42 PM »

I'd never spend the money for a MM rebuild, but I'd really like to have an M42 that didn't leak oil on my driveway. I've replaced the front seal, timing case, profile gasket, and valve cover gaskets. Either I'm incompetent (likely) or I've missed something. In my case I've had a mechanic suggest that with the DA supercharger, I might have too much blowby and that's forcing oil out through whatever path it can find. Sound probable?

Any success stories out there for having a basic, leak free rebuild done on an M42? Who did it, how was it done?

bmwman91 · « **Reply #1 on:** August 13, 2012, 04:27:58 PM »

I was able to get rid of most leaks by coating the various gaskets with Permatex Ultra Black RTV. Just a thin coating spread onto either the gaskets, or the two mating surfaces.

A lot of times the rear main seal poops out. That caused a lot of oil leakage into the bell housing and all over the driveway.

How many miles are on your engine? If the piston rings are worn, then you might be having blow-by issues. It is more likely that it is just form having positive pressure in the intake / PCV system. All that pressure inside the timing case & crank case will push a lot of oil out.

doitover · « **Reply #2 on:** August 13, 2012, 05:19:30 PM »

No idea how many miles are on the engine but it had leaks from the front seal and valve cover, and probably the profile gasket. when I bought the car. Now the origin of the leaking isn't that clear, somewhere from the front. I know I'm burning some oil, I can smell it in the exhaust, but it isn't a lot. I don't have a working odometer but I think probably 1qt every 600 miles or so.

DesktopDave · « **Reply #3 on:** August 13, 2012, 06:25:37 PM »

Most likely it's that oil housing o-ring & paper gasket on the driver's side. Mine leaks there as well, but not nearly as badly as yours does (yet).

wazzu70 · « **Reply #4 on:** August 13, 2012, 06:46:23 PM »

To really seal stuff up you need the anaerobic sealent which cures with the absence of air. Also most people lay a fat bead of RTV and then clamp the parts together. Dont do this. Tighten lightly by hand, let the RTV cure, then clamp it down. Big difference results wise!

I have a build thread on here with lots of pictures of my rebuild. It didn't cost much at all. More of a refresh than rebuild, but a full rebuild wouldnt cost much more. Just some machine time for perfect decking and bore/hone.

bmwman91 · « **Reply #5 on:** August 13, 2012, 08:16:24 PM »

Quote from: DesktopDave;114607

Most likely it's that oil housing o-ring & paper gasket on the driver's side. Mine leaks there as well, but not nearly as badly as yours does (yet).

+1

This was also a source of leaks for me. The front of the motor was disgusting!

doitover · « **Reply #6 on:** August 13, 2012, 08:32:51 PM »

wazzu70, bookmarked your thread here and on e30tech. Thanks!

wazzu70 · « **Reply #7 on:** August 14, 2012, 01:34:14 AM »

If you have any questions about the engine stuff, just ask. Always willing to help someone who wants to learn!

doitover · « **Reply #8 on:** August 14, 2012, 06:54:16 AM »

Quote from: bmwman91;114613

+1

This was also a source of leaks for me. The front of the motor was disgusting!

I wish that were the case for mine but I had the SC pulley bracket off a couple of weeks ago and it was clean as could be around the filter.

doitover · « **Reply #9 on:** August 14, 2012, 06:56:59 AM »

I really need to get started on this, if anyone knows of a rebuildable M42 near Raleigh NC, please let me know.

Quote from: wazzu70;114627

If you have any questions about the engine stuff, just ask. Always willing to help someone who wants to learn!

keflaman · « **Reply #10 on:** August 14, 2012, 07:48:35 AM »

Not exactly in your backyard, but...

http://onslow.craigslist.org/pts/3204451859.html

http://asheville.craigslist.org/pts/3073796019.html

Batman · « **Reply #11 on:** August 28, 2012, 09:30:30 PM »

I'm rebuilding my spare m42, but putting a 325i clutch system in it and possibly getting a new chip? Any suggestions? Ideas?
-Batman

rufiox426 · « **Reply #12 on:** September 29, 2012, 10:49:03 PM »

For anyone that has done this, what was the total costs for all parts? Pistons,rings, connecting rods, gaskets etc...? I have access to a machine shop at my school so that wont be a problem and will be doing all installation myself, just wanna know the cost of parts.

wazzu70 · « **Reply #13 on:** September 30, 2012, 03:19:46 PM »

Assuming nothing is way out of spec, upper and lower gasket set, main and rod bearings, rings, tensioner and oil relief valve update parts are the main ones.

I didnt really track my cost. For an engine rebuild though, it was dirt cheap if you can do the work.

Rokkuman · « **Reply #14 on:** December 03, 2012, 09:36:17 PM »

For Any one who has rebuild their engine what Sealant was used for this P/n 11141734422
did anyone install this dry? mine is made of metal not paper.