Crankshaft bolt question

[Hybrid775]

I have a spare M50 sitting in my garage and i'm trying to loosen the crankshaft bolt. Unfortunately, this engine did not come with the flywheel, so i cannot lock it into place.

How would you guys go about this?...would placing wood in block to wedge the crankshaft work?

And do the lightweight flywheels have the options to allow the lock pin to work? thanks.

[flyfishvt]

All flywheels will have a hole for the locking pin. Actually I should edit that. The dual mass flywheel doesn't have an actual hole it has a kind of tab or slot in the rear section of it. The locking pin doesn't really go all the way through. The last time I checked the torque spec on that crank bolt was well in excess of 200ft/lbs. I can't think of anyway to lock the engine (other than installing a flywheel) that will keep it in place and allow you to get that sucker off. If its torqued on with 200+ you can bet you'll need close to 300 to get it off.

hehehe...I have a spare dual mass wheel I'll sell cheap.

[TheDurk]

There's an old farmer's trick you can try. Take off two of the plugs and fill the cylinder with 3/8" rope or whatever you have around that fits. Pick two cylinders where the pistons are low in the cylinder at the same time. Leave the rope hanging out the plug hole, and just pull the rope to remove when done.

I haven't tried this on a car, let alone a BMW, but it works on tractors.

[Boland01]

If the oil pan is off the car you might be able to secure a 2x4 in the crank to keep it from rotating. Certainly not ideal though. If you do you'll have to find a way to secure the engine so it doesn't move.
When we just did ours it was still in the engine and we pinned the fly wheel. I had a 3/4" breaker bar with an extension and I was lifting the car off one jackstand before the bolt finally broke loose. On the M52's I believe the torque spec is 244 ft/lbs. It took a good hour and alot more force than that to break it free. It's not a fun job unless you get lucky.

[flyfishvt]

LOL a 2.4 on the crank? why not just drag it through the mud?

I like the rope trick. sounds a bit less Draconian

[motion]

Use the crank holding tool #112150 which is made for the task. Just my .02

[TylerBoland]

Use the crank holding tool #112150 which is made for the task. Just my .02

This is the best method, though I just jammed a crowbar between the harmonic balancer and the A/C bracket, then I slipped a 4ft cheater bar over my 3/4 breaker bar. The motor was still in the car while I was doing this and it actually started to lift the left side of the car up before the bolt broke loose.

[dano670]

I would drive and visit some indepent mechanic shops and see if anyone would agree to use an impact on one and then take the engine down there. I had to use a 3/4 drive socket with a floor jack pole that weighed 20 pounds to remove with using the locking pin method. It was an M42 engine that I did this on.

[motoden]

Lock the flywheel and get a good quality impact on the crank and it comes off fine

[dano670]

Maybe post in the Nevada forum and see if anyone has a flywheel and bolts so you can lock this thing down. I think I used a 5/16" punch instead of the pin.

[luminmiller]

When I tore down a m50b25 block it was delivered on a pallet and my neighbor and I attached it to a engine stand laying on its side.

We placed the engine gently on a towel on the ground
We attached the engine stand laying on its side
Stuck a 2X4 in-between the crank and block (Iron Block with oil pan off)
I stood with one foot on the engine and the other on the engine stand while my friend used a 2foot breaker bar to remove the Hercules crank bolt.
The same day we removed the crank bolt from a m52b25 with the same method, but it seemed much easier.


Use the crank holding tool #112150 which is made for the task. Just my .02 +1 if you can get one ( with BMW's having the right tools make things easy.)

[paniolo]

I would drive and visit some indepent mechanic shops and see if anyone would agree to use an impact on one and then take the engine down there. I had to use a 3/4 drive socket with a floor jack pole that weighed 20 pounds to remove with using the locking pin method. It was an M42 engine that I did this on.

Still going to need to lock the crank or it will just spin. If the shop doesn't have the proper locking tool they will probably just fill the cyl. with rope like suggested above. ;)

[Eric93se]

Still going to need to lock the crank or it will just spin. If the shop doesn't have the proper locking tool they will probably just fill the cyl. with rope like suggested above. ;)

REALLY? even with an impact gun? Never heard of such a thing.

[cjsdad1]

Do you have either flywheel bolts or bolts that will thread in where the fly wheel goes?

If so screw one in at 12:00 and one at 6:00 and use a crow bar between the bolts. Then loosen the crank bolt. It might take more than one person to hold the crowbar and loosen the crank bolt....

[Hybrid775]

Finally broke it loose with the help of stock flywheel and one other person standing on the short block, and a long cheater bar.

[ross1]

There's an old farmer's trick you can try. Take off two of the plugs and fill the cylinder with 3/8" rope or whatever you have around that fits. Pick two cylinders where the pistons are low in the cylinder at the same time. Leave the rope hanging out the plug hole, and just pull the rope to remove when done.

I haven't tried this on a car, let alone a BMW, but it works on tractors.

This method has always worked for me UNTIL I met the BMW crank nut. I had so much rope in the cylinder I was afraid of bending a valve as I was starting with the piston way down. Perhaps something bigger and denser than the cotton rope I tried. Filling two cylinders never occured to this rocket scientist:(.
My trick of using the starter motor can't be applied here so a wood block in the crankcase if a flywheel can't be fitted. Perhaps a couple of longer bolts in the crank hub with a bar across them will hold it.
I wouldn't want to be doing this on an engine stand.

[Joshh]

Good luck.

I had to bring my motor to a mechanic shop and their 180psi or so (was higher than 120 I know that) air system couldn't get the bolt off even with their strongest impact wrench.
We had to have two 4 foot breaker bars (opposing, one drilled through the pulley) and the mechanic had to jump up and down on his till it finally broke free.

[Boland01]

To add to Ross1's post if you would stuff rope in two or more cylinder heads make sure they come to TDC at the same time. If not only one would be holding the crank. You could go with cylinder #1 and # 6 for example.

It's a job best done while the engine is still in the car and then it's not easy.

[luminmiller]

Today I worked with a couple guys from a local Dutch forum that showed me a good trick for the crank bolt. Using an Angle Grinder we cut the head off of the crank bolt just above the washer then the bolt can be removed with two fingers!. We did 4 engines in 10 minutes and were able to not damage the washer and only replace the crank bolt with oe for a couple bucks. (The washer is also pretty cheap if damaged...so no worries):

http://i115.photobucket.com/albums/n317/Luminmiller/Screenshot2012-07-23at120632PM.png

When the head of the bolt is removed all the torque is released:redspot