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Discussion Starter #1
Hey guys,

I am planning on putting new rod bearings and rod bolts in within the next two weeks. I am wondering if anyone has done this themselves?

I have purchased new bearings and bolts and all associated gaskets. I have a few questions for those of you who have actually done this yourself.

1.Are all the bearings std size or did BMW use an array of sizes in a single engine?

The reason i ask is because there is a valid understanding that some bearings could be different sizes. I will be doing this in a day or two and do not want to be down for much longer so I do not want to get it ripped apart and find out that 7 bearings are std and one is .001 larger and be screwed with having to order bearings etc. I have a pretty money BMW parts dept and they said all engines are STD. from the factory. I bought all standard bearings so... any insight is greatly appreciated.

2. does anyone have the torque specs for both the upper and lower oil pan and rod bearings? Is there anything else to look at or check when I am in there I.E. oil pump, oil pump sensors, oil pick ups?

Again any insight is greatly appreciated

Ryan :M5launch:
 

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Discussion Starter #3
why? There is no damage to the rods at all. I am just swapping them before a potential issue as I tend to drive the car kind of hard :hihi:

It will be a direct swap for the bearings and bolts. The bolts screw into the caps and rod, they are not pressed fit or anything like that.

I have never heard of rods havig to be resized for bolts either... there is no coralation between the rods size and the bolts. the only pain usually is most rod bolts are pressed fit which requires the rod to be out of the engine.

Ryan :M5launch:

Don't the rods need to be sized after replacing the bolts ??
 

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Rod bearings absorb a greater load than crank bearings.
With that said, I have done many rod bearing changes on my previous muscle cars (70-Boss 302, Big Block Camaro's, 68-AMX, 66 Merc Cyclone GT) to keep the bottom end tight. I did this with out evidence of rod bearing problems strictly as preventative maintanence. The bearings were never worn down to the babit.
I have wondered if the same theory of preventative maintanence would apply to my BMW's. It would seem so.
Are you performing this change out with the motor in the car (from beneath) or with it out of the car?

Al. Wise
 

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Now let me preface this post by saying that I not an expert on this subject by any means-however, I did replace the rod bearings on my E30 M3 a couple of years ago, so I do have some experience in the matter that might help you a bit.

When originally built, all of the rod bearings should have been of the standard size. If they weren't, that would make me tend to think that there was flaw in the manufacturing process of those associated engine parts and different sized bearings were required to 'close the gap' so to speak.

The 'oversized' bearings that BMW offers are for those engines where some normal wear has occurred and once again, the oversize bearings are there to 'close the gap'. You are supposed to use special methods to measure this clearance once you are in there to determine what size replacement bearings.

Now with that being said, from what I have heard of thru the BMW community, as long as the original bearings 'seem' to be relatively fine, and the crankshaft journals are also smooth and free of defects, you should be able to install a fresh set of standard size bearings and be good to go. This is what I did on my '88 M3 with 144k original miles, and with more than 10k miles since the replacement everything has been perfectly fine. Your mileage may vary, but I think in most cases just putting in a new set of standard bearings is quite acceptable.

As far as torque values, I would probably buy the subscription to the BMW TIS website and download all of the documents that are relevant to this procedure. I know that the E30 M3 required brand new rod bolts, as they were of a stretch design-and when installed, they required two separate torque spec settings, and then a final spec using an angle torque gauge.

One thing I cannot stress enough while you are doing this procedure is to BE AS CLEAN AND ACCURATE AS POSSIBLE!! This was stressed to me over and over before I did the job on my M3, so I am passing the info along to you. Be very careful handling the bearings, make sure to completely clean the inside of the rod bearing cap surfaces, and use plenty of assembly lube when you are installing the bearings-and make sure the backside of the bearings are completely dry, being free of old oil and dirt.

Overall, its really not a bad job at all. The ***** part will be supporting the engine with a hoist and removing the entire front subframe to get access to everything...at least I would imagine you have to do this on the E39-you don't on the E30, but I did as I was replacing the front subframe and all suspension bits at the same time and it made access so much easier.

If you have any questions during the job I will try to help.
 

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Discussion Starter #6
Thanks for the response... I have built enough american engines, race and street as well as VW's to know the proper way to do this.

My queston about bearings has come from LSCMAN who is probably the most knowledgeable guy on this forum and many other forums on the internet. I have always been under the impression that the bearings were all std size, this isnt always the case. Nowadays it is more l\common for the to be the same but not a 100% rule. I am sure they are all std but just wondered if anyone had run into any problems while doing a bearing swap on the e39 m5.

I have never run into different size bearings on any vehicle or engine i have touched yet... I also have not looked for them, every engine i have built has been disassembled and sent to he machine shop to get the machining done or just new cranks and rods which were cut to spec's. So i am sure different bearings are in most vehicles and i truly hope i will have the same experience as you did with your e30.... I hope all the bearings are the std size and it should be an easy day! I was hoping someone on the forum would be able to give me all the specs so i didnt have to buy them.. i will if i need to but... hopefully someone will have the info for me.



Ryan :M5launch:


Now let me preface this post by saying that I not an expert on this subject by any means-however, I did replace the rod bearings on my E30 M3 a couple of years ago, so I do have some experience in the matter that might help you a bit.

When originally built, all of the rod bearings should have been of the standard size. If they weren't, that would make me tend to think that there was flaw in the manufacturing process of those associated engine parts and different sized bearings were required to 'close the gap' so to speak.

The 'oversized' bearings that BMW offers are for those engines where some normal wear has occurred and once again, the oversize bearings are there to 'close the gap'. You are supposed to use special methods to measure this clearance once you are in there to determine what size replacement bearings.

Now with that being said, from what I have heard of thru the BMW community, as long as the original bearings 'seem' to be relatively fine, and the crankshaft journals are also smooth and free of defects, you should be able to install a fresh set of standard size bearings and be good to go. This is what I did on my '88 M3 with 144k original miles, and with more than 10k miles since the replacement everything has been perfectly fine. Your mileage may vary, but I think in most cases just putting in a new set of standard bearings is quite acceptable.

As far as torque values, I would probably buy the subscription to the BMW TIS website and download all of the documents that are relevant to this procedure. I know that the E30 M3 required brand new rod bolts, as they were of a stretch design-and when installed, they required two separate torque spec settings, and then a final spec using an angle torque gauge.

One thing I cannot stress enough while you are doing this procedure is to BE AS CLEAN AND ACCURATE AS POSSIBLE!! This was stressed to me over and over before I did the job on my M3, so I am passing the info along to you. Be very careful handling the bearings, make sure to completely clean the inside of the rod bearing cap surfaces, and use plenty of assembly lube when you are installing the bearings-and make sure the backside of the bearings are completely dry, being free of old oil and dirt.

Overall, its really not a bad job at all. The ***** part will be supporting the engine with a hoist and removing the entire front subframe to get access to everything...at least I would imagine you have to do this on the E39-you don't on the E30, but I did as I was replacing the front subframe and all suspension bits at the same time and it made access so much easier.

If you have any questions during the job I will try to help.
 

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Thanks for the response... I have built enough american engines, race and street as well as VW's to know the proper way to do this.

My queston about bearings has come from LSCMAN who is probably the most knowledgeable guy on this forum and many other forums on the internet. I have always been under the impression that the bearings were all std size, this isnt always the case. Nowadays it is more l\common for the to be the same but not a 100% rule. I am sure they are all std but just wondered if anyone had run into any problems while doing a bearing swap on the e39 m5.

I have never run into different size bearings on any vehicle or engine i have touched yet... I also have not looked for them, every engine i have built has been disassembled and sent to he machine shop to get the machining done or just new cranks and rods which were cut to spec's. So i am sure different bearings are in most vehicles and i truly hope i will have the same experience as you did with your e30.... I hope all the bearings are the std size and it should be an easy day! I was hoping someone on the forum would be able to give me all the specs so i didnt have to buy them.. i will if i need to but... hopefully someone will have the info for me.



Ryan :M5launch:
Good for you Ryan! I am impressed with your mechanical ability...I am a reasonably competent home garage mechanic, but I wouldn't know where to start on this job. ( I am not yanking your chain, I am quite serious) Let us know how it works out, I am curious to see what your experience on this is. :cheers:

Brian
 

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I think only a few have had the bearings swapped out(maybe three at the most), you might try contacting them to see what the bearings were.
Most asian blocks will have the bearing selection stamped into the panrail, I've never seen that on a BMW.

does anyone have the torque specs for both the upper and lower oil pan and rod bearings?
Upper and lower pan bolts
M6(8.8) 10Nm (89 in-lb)
M6(10.8)12Nm (9 ft-lb)
M8(8.8) 22Nm(16 ft-lb)

Oil pump sprocket(tends to work loose on the V8s)
25Nm (18 ft-lb)

I know you mean rod bolt torque, but also find out what lube to use.
Most do use just oil(no synthetic oil) but some use a high pressure lube like CMD or antiseize.

I Invest in a couple cans of contact cleaner and those blue box towels(lent free) to wipe everything off, this really helps.

I'm still looking for the rodbolt torque in my books.
5 Nm
20 Nm
80 degrees
 

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I'ts been awhile for me as well (rebuilding RAT lower ends) but, I recall using plastigage to ensure the wear/bearing size was corrrect...
 

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Discussion Starter #10
Thanks but plasitgauge will not provide any useable info on a 75k mile engine. Plasticage is a decent tool for a common rebuild and only used to ensure the bearings are all within spec. I am not worried about the cranj journals or the rods inside dimeter at all. The engine runs fine with no noise and i just did a two daytrack event. Engine if fine. I will be installing the bearings for prevenitive maintenace, as long as I re-install the same bearings that are in the engine i will have no issues at all.

Thanks

Ryan
I'ts been awhile for me as well (rebuilding RAT lower ends) but, I recall using plastigage to ensure the wear/bearing size was corrrect...



I will keep you posted,

Ryan

Good for you Ryan! I am impressed with your mechanical ability...I am a reasonably competent home garage mechanic, but I wouldn't know where to start on this job. ( I am not yanking your chain, I am quite serious) Let us know how it works out, I am curious to see what your experience on this is. :cheers:

Brian




6spd, Thanks for the post. I will be trying to find a shop that has done the actually swapped out the bearings so i can see if they ran into any problems at all. i do not think i will but I am just trying to get some info before it turns into a huge project. Thanks for getting the info for me, I wonder what oil to use. I know i will put some assembly lube on the bearings and most likley conventional oil on the bolts. I am also curious if there is a rod bolt stretch measurment or just a tighten loosesn tighten loosen final torque like an APR rod bolt. Great call on the rags and cleaner....
Thanks

Ryan

I think only a few have had the bearings swapped out(maybe three at the most), you might try contacting them to see what the bearings were.
Most asian blocks will have the bearing selection stamped into the panrail, I've never seen that on a BMW.



Upper and lower pan bolts
M6(8.8) 10Nm (89 in-lb)
M6(10.8)12Nm (9 ft-lb)
M8(8.8) 22Nm(16 ft-lb)

Oil pump sprocket(tends to work loose on the V8s)
25Nm (18 ft-lb)

I know you mean rod bolt torque, but also find out what lube to use.
Most do use just oil(no synthetic oil) but some use a high pressure lube like CMD or antiseize.

I Invest in a couple cans of contact cleaner and those blue box towels(lent free) to wipe everything off, this really helps.

I'm still looking for the rodbolt torque in my books.
5 Nm
20 Nm
80 degrees
 

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Subscribed :)

Dave
 

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i had asked my parts guy about bearings at one time, he said bmw has some color code dots on the bearing cap to denote any variance, so it is possible to have different bearings in a given engine, and you generally won't know until you pull the pan.
 

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Discussion Starter #14
thanks

ryan

i had asked my parts guy about bearings at one time, he said bmw has some color code dots on the bearing cap to denote any variance, so it is possible to have different bearings in a given engine, and you generally won't know until you pull the pan.
 

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I wonder what oil to use. I know i will put some assembly lube on the bearings and most likley conventional oil on the bolts.
Mineral oil(Castrol,Kendall, Valvoline, etc) will work fine, the synthetic oils allow a low breakaway at the bolt head. The less under head friction also stretches the bolt longer then normal raising the chances of rodbolt failure.
Since this engine isn't going to sit long after the bearing replacement I would just put a film of your current oil on the bearings. All the journals are filled with oil, it doesn't need to prime itself much. If your really worried you can keep the sparkplugs out and spin the engine before firing it(no load on the bearings).

I am also curious if there is a rod bolt stretch measurment or just a tighten loosesn tighten loosen final torque like an APR rod bolt.
You lost me there, but the factory bolt is torqued twice(snugged at 5Nm then pulled to 20Nm) then angle torqued to 80 degrees for proper stretch.
That will give the threads of the bolt its engineered stretch and clamping force.
Normally ARP bolts are measured before(free length) and after torqued for the proper stretch using a micrometer. If you ever do that, I really suggest finding a digital 1"-2" double ball end, it makes it alot easier.
 

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I would check out this post

There is good information on what you are trying to do.
 

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i had asked my parts guy about bearings at one time, he said bmw has some color code dots on the bearing cap to denote any variance, so it is possible to have different bearings in a given engine, and you generally won't know until you pull the pan.
This sounds entirely possible. OEM's occasionally use color-coded pistons and bearings in tiny fractional sizes to achieve optimal clearances on the assembly line. Ford and GM have been doing it for the last 30 years in everything from Pinto to Camaro & it may be more common on modern, tight clearance motors. This may be done in hand-built sports car motors like S62. I am not clear whether color-coded bearings would have std stamped markings, perhaps so. One can only hope the paint does not wash off.

This is one argument for plastigage. You can't ever be 100% sure what the OEM factory folks did or what special fitment bearings they had at their disposal. A really anal person "could" reuse the old rod bolts, retorqued to spec with new bearings for a plastigage check. If the clearances are acceptable, you remove the plastigage and torque to spec again using the fresh bolts. This basically ensures optimal results.

This plastigage check would add some hours to the job and it also adds more risk of nicking the crank journals from all the rework. It takes a lot of care to prevent crank damage and working clean....avoiding contaminants.
 

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+1 on the plastigage with the old bolts first(just to the 20Nm).
A cheap insurance that they are the right selection of bearings.
 
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