Video: 97 m3 engine knock/rattle

[m3f_hardtosee]

It's not called a small block lol that would be in reference to small block v8's. What you're thinking of is Short block which means just the bottom end with rotating assembly or long block which is the whole motor (not including accessories).



Now that's cleared up, yes you are better off buying a decent motor to swap in. Look for one with lower mileage with maintenance history so you don't have to open it up. Just swap your accessories onto it and drop it in. The time you buy a new crank, rods and gaskets you'll be around a grand. Then add in machine work and you're close to the money for a lower mileage motor. Unless you plan on full on building your motor then it isn't worth it to try and save it. You can sell what you have to offset the costs

Thanks, meant short block.



Unless the engine I purchase has known maintenance history and/or recent head gasket done, I'll be doing all new gaskets and seals on the replacement engine.



I liked the ideal of building up a short block, my mechanic and I are both willing to tackle it and feel it would be a worthwhile experience. Long blocks are much more common though, so will probably end up going that route.



Thoughts for the existing engine are to rebuild it after the M is back on the road, and put it in an e30.

[m3f_matty.]

OP how did the bearing get spun? Was this preceded by long high g turns, high rpms , misshift, etc..?

[m3f_hardtosee]

OP how did the bearing get spun? Was this preceded by long high g turns, high rpms , misshift, etc..?

That is the mystery.



I've never lost oil pressure, or seen the oil light go on. No misshifts.



In the last couple years, the car has seen it's most frequent service running 15 mile highway trips to and from work, 5-6 times a week. I regularly have the car running in the 4000-4500RPM range for sustained periods of time on the highway.



The off ramp of the exit on the way to work is a full 180 degree bend of a several hundred foot radius that I take at 60-70mph often. I'm wondering if doing this for years could have contributed?



As expected with these engines, I did burn oil.. usually about a quart every 1500 miles. Only once or twice have I found it near the "fill" mark (1 quart low?) before filling it back up.



It has never seen track time or autocross during my ownership... I drive the car hard when it's safe to do so, and I do my fair share of drifting when it's snowing out.. but nothing I would expect to cause this.



Any more thoughts from anyone on whether to pull crank and cyl #1 piston and rebuild vs buying a replacement engine?



Also, thoughts on whether the oil pump could have failed, and how I could test the oil pump prior to putting it back into this or another engine?

[m3f_camdinans3]

when my z3m spun the bearing it wasn't even worth trying to rebuild it. i just bought another low mileage one. i knew the crank and rod it self were going to be ruined.

[m3f_matty.]

What kind of oil and how long of change intervals were you using?



I guess you could gamble on pulling the crank (leaving the rods and pistons in the cylinders), micro polish crank, upsize bearing on cyl #1, new standard size bearings everywhere else. That would cost how much, nothing more than bearings, crank machining, oil pan gasket? Possibly head gasket if you have to pull top end to remove cyl#1 rod if damaged? That might be worth a try, more or less comes down to time on that one..

[m3f_hardtosee]

What kind of oil and how long of change intervals were you using?


I guess you could gamble on pulling the crank (leaving the rods and pistons in the cylinders), micro polish crank, upsize bearing on cyl #1, new standard size bearings everywhere else. That would cost how much, nothing more than bearings, crank machining, oil pan gasket? Possibly head gasket if you have to pull top end to remove cyl#1 rod if damaged? That might be worth a try, more or less comes down to time on that one..

I used liqui-moly when I had the foresight to order it before doing my oil change, otherwise castrol synthetic. Every 5k miles.


Not sure if you saw the picture, but it looks like the rod has a nice big divot taken out of it.. I doubt it's part of the casting.


Looking at a couple engines now, one from a forum member. Most likely will go that route.

[m3f_matty.]

I see. Sounds like you maintained it and didn't abuse it. Bummer.

[m3f_hardtosee]

Replacement heart obtained - '97 auto convertible part out. 120k miles.



Engine very clean, leak down test passed with flying colors: egligible pressure loss observed at 120psi. Got an x-brace for $50 too.



Front end is off, current engine ready to be removed as soon as we find a catch can for the refrigerant.

[m3f_hardtosee]

Also had this little gem hiding away in the garage..


http://drive.google.com/uc?export=vi...1ZTaXdrampCeDQ

[m3f_hardtosee]

Compromised engine is out! New engine on stand ready to get cleaned up/prepped for the swap. The replacement engine is unbelievably clean and came with almost all the accessories.


Also went on a nice little shopping spree.. front end refresh/upgrades:


koni yellows and OEM springs

OEM strut mounts

x-brace

new ball joints for control arms (meyle)

OEM FCABs

OEM sway bushings

OEM transmission mounts (thoughts on Rogue, or E21? could still go that direction..)

driveshaft CSB

Guibo


Can't wait to get it back on the road.. eta two weeks. Pictures of build coming soon.


http://drive.google.com/uc?export=vi...UY3Zkp0R011XzA

[m3f_matty.]

Tranny mounts but no motor mounts?



If you don't mind drilling out the tranny mount holes to fit the larger diameter studs of the e21 mounts, then get those. When I checked the price of the e21 mounts had gone up and were almost the same as the Rogue mounts (which do not require drilling) so I went w those. Gone are the days of the super cheap bmw parts. I've used rogue FCAB's, RSM's, and black RTAB's. Quality was good and performed great. None added harmful NVH, install was easier than OE rubber, so I'm a bit of a fan of their (bushings) stuff.

[m3f_hardtosee]

Tranny mounts but no motor mounts?



If you don't mind drilling out the tranny mount holes to fit the larger diameter studs of the e21 mounts, then get those. When I checked the price of the e21 mounts had gone up and were almost the same as the Rogue mounts (which do not require drilling) so I went w those. Gone are the days of the super cheap bmw parts. I've used rogue FCAB's, RSM's, and black RTAB's. Quality was good and performed great. None added harmful NVH, install was easier than OE rubber, so I'm a bit of a fan of their (bushings) stuff.

Hey, thanks for the feedback.



Motor mounts were replaced with OEM parts <12 months ago.



I'm tempted to go with the rogue transmission mounts; for now, I'll stick with OEM and can always swap in Rogue as needed, they're an easy job.



Rear end refresh will come later this spring, will definitely consider the rogue parts. Rogue FCABs also look worth it, but they're not in the budget right now.

[m3f_matty.]

True. The fcabs are a little on the pricey side but you can save some if you provide your own lollipops and press them yourself. Don't forget to budget for an alignment after said bushings are replaced.