how to tell if your engine bearings are bad

[cyclist01]

What is the best way to tell if your engine bearings are going bad?

[Tom D]

oil analysis. sure fire way.

[epmedia]

Yup - inspect that oil. You can do a self test by looking for silver or gold colored "sparkles" in the engine oil, in the sunlight. A few sparkles is not too bad, but you should hook up an actual oil press guage to verify press if concerned.

[Beemer Tech]

the best way to tell for sure is to pull the motor down inspect the bearings lol. if not just listen to the motor, you can hear a bad bearing, if its a rod bearing you can locate the bad bearing be disconnecting the spark leads one by one, knocking on start up before the oil light goes out isnt a good sign. oil pressure is another good test but there are other reasons for low oil pressure. Panning for gold in the oil again indicates a problem but might not be a bearing.

[pommeree]

Polaris Laboratories used to do free 1st time sample tests.
They'll run the analysis and give you an interpretation.
Really cool stuff.
http://www.polarislabs1.com/how-to-get-started.php

[Beemer Tech]

you guys are serious bout the oil analysis, i have never heard of this before as a diagnosis of bearing failure. But if it works that is good. Saying that normally the bearing failures i see are so bad the bearing has spun and you can do the spark plug trick, then pull the sump off and there is about a 1mm or more clearance in the bearing. you can jst push on the rod with you finger and see the movement.

[DHoang]

I had to repair a bad bearing on my other motor. I could hear the knocking. All I did was drop the oil pan, felt each rod for play until I found the culprit, unbolted the rod from the crank, and installed a new bearing. I torqued down the rod cap and put the oil pan back on, and ran it w/ no more rod knocking probs for several more yrs until I put in a fresh motor. Surprised me that I could replace a bad rod bearing within a couple hrs tops w/ just hand tools.

[Tom D]

the oil analysis does more than comfirm bearing failure.

his question was "pending bearing failure" meaning that it hasn't failed yet. that's where oil analysis comes in.

a plain sleeve bearing is made from multiple layers of different materials. the analysis tells what bearing material is in the oil and thus the condition of the bearings.

[Beemer Tech]

righty oh tomy, i get what your saying. why would you care though? if its not broke dont fix it. where did he say "pending" exactly??

[Tom D]

why would you care though?

because inquiring minds what to know!

seriously, say you have a large investment in a race motor ($50k+-). you wouldn't just wait till it blows up. maybe your running full systhetic oil and want to take advantage of extended drain schedule. analysis would tell you when it's time to dump it or even to just change the fillter.

here are some of the "wear metals" in a car engine that end up in the oil.

Iron (Fe) Cylinder Liners, Rings, Gears, Crankshaft, Camshaft, Valve Train, Oil Pump Gear

Chrome (Cr) Rings, Liners, Exhaust Valves, Shaft Plating

Aluminum (Al) Pistons, Thrust Bearings, Turbo Bearings, Main Bearings

Nickel (Ni) Valve Plating, Steel Alloy from Crankshaft, Camshaft

Copper (Cu) Lube Coolers, Main and Rod Bearings, Bushings, Turbo Bearings

Lead (Pb) Main and Rod Bearings,

Tin (Sn) Piston Flashing, Bearing Overlay, Bronze Alloy, Babbit Metal

Silver (Ag) Wrist Pin Bushings

oh yeah, and he asked "What is the best way to tell if your engine bearings are going bad?" pending was my word.

[cyclist01]

What I am trying to do is rule out a rattling sound that I am getting

[Beemer Tech]

Fair play, Im jst trying to get my head round it thats all, yeah I can understand now what they would be looking for in the oil. Its just interesting that being around race cars, being a qualified mechanic and building engines for close on ten years ive never heard of this process, maybe its jst not that popular in Australia. How expensive is the test?

Everyone i know that races seriously does strip downs on a track hours basis not on what they find in the oil, not saying it wouldn't be a bad idea. BTW im a semester into a science degree doing a double major in Chemistry and Physics, so they chem lesion wasn't really necessary.

Sorry if you took my enquirys the wrong way or dont share my opinion, i don't mean to rub ppl the wrong way.

Good luck finding the rattle mate, i hope the fix isnt something too expensive.

[cyclist01]

Beemer tech,
No offense taken

[epmedia]

Fair play, Im jst trying to get my head round it thats all, yeah I can understand now what they would be looking for in the oil. Its just interesting that being around race cars, being a qualified mechanic and building engines for close on ten years ive never heard of this process, maybe its jst not that popular in Australia. How expensive is the test?

Everyone i know that races seriously does strip downs on a track hours basis not on what they find in the oil, not saying it wouldn't be a bad idea. BTW im a semester into a science degree doing a double major in Chemistry and Physics, so they chem lesion wasn't really necessary.

Sorry if you took my enquirys the wrong way or dont share my opinion, i don't mean to rub ppl the wrong way.

Good luck finding the rattle mate, i hope the fix isnt something too expensive.

I hear you. Who spends mucho dinero to have oil analyized? not me
Techs already know when crap is ready to hit the fan. The other scenarios relate to VERY expensive equipment, ie: 60k ship propulsion auxiliarys, or as Tom mentioned - race engines. I use to test lube on a daily basis for sediment and water - not something to ignore on a piece of equipment that keeps a battle ship in motion. A free first test, pommeree? - thats super

[Trackrocket]

I've read that some of you have just dropped the oil pan and replaced rod bearings.
Where is a good source for rod bearings and is there a good link to pics/procedure?
I can build a pretty mean motor but think my E21 has a knocking rod bearing...I'd like to sell it and would sleep better if I could make the car "sound" for the next owner.

[e21Terry]

Is the noise at start up, after warm up, or all the time?

[Trackrocket]

At start up, I know the noise. :grr:

If you're driving it, under load you can hear a muffled knock.

Not too bad at this point, so figure it can be resolved by changing them out. Not trying to "mask" anything, so if I get it apart and the crank has seen better days...well... :

[e21Terry]

The reason I asked, I had one that the spring behind the piston in the timing chain tensioner collapsed (wore clean thru one of the coils) and the resulting slack in the timing chain ate the cam gear, the metal flakes from the cam gear ate the oil pump. It started taking longer than normal for the oil pressure idiot light to go out and and then got to where it would knock a bit until it built pressure. Fortunately, the oil filter took care of the shrapnel before it got to the bearings. New oil pump, timing chain, & cam gears and all was well again. A peek under the valve cover will tell. edit Damn honey, took out the cam too, gotta buy a new one!

[77 320i]

large fleets that have millions of dollars invested in equipment have elaborate maintenance organizations that routinely utilize fluid sampling...if you have are running large industrial applications like turbines, jet engines trains, or those engines in long distance marine applications are heavily dependent on fluid monitoring as a means to achieving the highest possible ROI...fluid sampling is an important monitoring method used to determine a piece of equipment's overall health/age in the same way a doctor analyzes human blood to determine organ failure/fatigue...my father once bought a used caterpillar D8 from a large firm and the oil sampling tests for YEARS were included in that sale...as has been suggested the various metals found in the fluid samples..the parts per million found in the fluids indicate the percentages of 'risk' based on failure/fatigue...that internal wear when tracked over time...prevents costs...

in your situation...if you are like me and you don't have a fancy mechanics stethoscope...cut a piece of garden hose that is about 36'' long...put one end against the engine block where the number 1 rod would be as you'd line up the hose with the spark plug and with the other end of the hose up to your ear listen to each rod and see if you can hear the knock better...it might help if you have someone help you with revving the engine...sounds foolish i know...but...trust me...it works.

[Tom D]

if the noise (knock) is at startup, then i'm going to agree with terry in that it could be the timing chain tensioner.

i once touched a M10's bearing due to oil pump cavitation. the bearing didn't actually spin but it was rocking. the rod knock was under throttle at approx. 3000-3500 rpms. by adding STP and walking it very gingerly through the danger zone, i was able to drive it for several hundreds of miles without further damage.

in the end, i turned the rod journals .25mm over and resized that rod's big end. drove the motor for another 50K.

rod bearings are easy to do in place, unlike mains, but main bearings don't usually fail. when i bought the E30M3 i enjoyed the sound of it at 7K rpms so much that i decided to change the rod bearings as a preventative measure. here is a photo of the S14. the M10 would be similar.

[Trackrocket]

I'm quite certain this is rod knock...and the other thing I'm pretty certain of is that I probably won't have any severe damage. The sound is prevalent on startup and you can hear it under load.

I'll verify the chain tensioner, as yes, that would be a good catch, vice doing rod bearings...but my best guess is that it's the latter.

Where do you guys source rod bearings? IS there a good source and a certain brand to use? Anything to look out for?

[Layne]

I used kobelschmidt bearings from Autohauz AZ.

Personally I wouldn't count on much success with just changing the bearing. At least mic the crankshaft and plastigauge the bearing clearance. If that checks out it will be fine.

[Bimmerknut]

As most know, I found a spun rod bearing along with a bad pump. End result? I'm building another engine. I would never rest easy knowing whether the rest of the bearings were okay or not, much less the condition of the crank. And if I gotta go that deep into it, I might as well go the full distance. But then I love tinkering on my bimmer. <3

[pommeree]

Polaris Laboratories used to do free 1st time sample tests.
They'll run the analysis and give you an interpretation.
Really cool stuff.
http://www.polarislabs1.com/how-to-get-started.php

I'm not seeing the "free first sample" offer anymore, but a crystal ball that can see everything going on inside your engine for $22.13 still seems like a whole hell of a lot easier than rebuilding your bottom end on a hunch.

http://www.polarislabs.biz/store/tes...fm?page=single

[e21Terry]

One other way to determine a bad rod bearing - find a long straight road, run at redline, when there's a loud bang and the engine dies get out and look under the hood. The rod that's sticking out of the side of the block was the one that was bad.