Rod Bearing going bad
Thread Starter
Staging Lane
Joined: Mar 2007
Posts: 67
Likes: 0
From: Ocala, FL
Rod Bearing going bad My car has 113000 miles. Its a B4C. When i start it in the morning i get a tapping coming from the motor. It continues untill the car is warmed up. Once its warm it stops untill its next cold start. I took it to a mechanic. He said the i had a rod bearing going bad. He said i would need to be replacing the motor soon. He did a compression test and some other test and everything was to spec. How much am i looking at to have the bottom end rebuilt to stock specifications?
Or it could well be "piston slap". A search on this board might just save you a few grand. Check it out. There's more in our archieves that I could scratch the suface of. It boils down to having a larger piston-to-wall clearance on an aluminum block- which transfers more sound than a cast iron block. Once the motor is warm the clearances become smaller and the pistons don't rock in their bores.
How's your oil pressure looking?
Ben T.
How's your oil pressure looking?
Ben T.
Thread Starter
Staging Lane
Joined: Mar 2007
Posts: 67
Likes: 0
From: Ocala, FL
The mechanic said my oil pressure was to spec as well. I talked to a guy last night who builds race motors. He said the same thing that you said about the piston slap. Im just trying to make sure im not going to sling a rod before i go driving it again.
Thread Starter
Staging Lane
Joined: Mar 2007
Posts: 67
Likes: 0
From: Ocala, FL
Ive done some research on "piston slap" today. Sounds like thats my problem. My oil pressure is above 40. I think its 50 when it starts cold. Sometimes it will dip below 40 after ive been driving and i stop at a red light.
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Two rules of thumb. And dead nuts right too BTW.
1, if the noise goes away AFTER it warms up, it a piston noise.
2, if it STARTS makin noise AFTER it warms up, its a bearing clearance issue.
A bearing knock NEVER gets better with thinner oil!!
1, if the noise goes away AFTER it warms up, it a piston noise.
2, if it STARTS makin noise AFTER it warms up, its a bearing clearance issue.
A bearing knock NEVER gets better with thinner oil!!
Yeah X2 for not being a bearing problem. I just got finished replacing and rebuilding mine from a spun bearing. Definitely not fun, but still no need for a new engine. Good luck on your fix.
Banned
Joined: Dec 2004
Posts: 2,636
Likes: 2
A rod bearing would be...tap......tap.....tap (or knock or whatever). If you are hearing a "general chatter" then it is piston slap. If you want, when it is cold, crank it and begin pulling 1 plug wire at a time (ONLY! 1 off at a time...) and see which plug wire gets it to stop...if a certain plug wire stops it, then I would worry a tad.
+1 for slap!
+1 for slap!
Not to hijack, but my engine has about 1200 miles on it now. I babied it until about 800 miles. It has new rings & bearings. About 3 weeks ago my car threw a p0343 code (CMP high voltage). The tach gauge cut out intermittently (sp?). The day AFTER it threw that code I started noticed a knocking/tapping noise but only after the engine had warmed up and only when it was above 2,000RPMS. So after wasting $45 on a new sensor with no luck, i took the timing cover off last night to find loose cam sprocket bolts. put red loctite on them and torqued it back down, SES code is gone and my tach works fine now. The noise is still there after I fixed all of this but it's not as loud. Could it be lifters failing? The other day before I fixed anything, the noise wasn't there at ALL. Again, sorry to hijack, but this thread kinda goes along with my problem. thanks guys!
it is piston slap. mine sounded like a diesel truck. 160,000 miles on my B4C motor with no problems. your motor is just now at its peak.
also, usualy rod bearings are a really sharp and loud knock, and will show up once the car is warm. not at first start up
also, usualy rod bearings are a really sharp and loud knock, and will show up once the car is warm. not at first start up
Originally Posted by Cop Car
it is piston slap. mine sounded like a diesel truck. 160,000 miles on my B4C motor with no problems. your motor is just now at its peak.
also, usualy rod bearings are a really sharp and loud knock, and will show up once the car is warm. not at first start up
also, usualy rod bearings are a really sharp and loud knock, and will show up once the car is warm. not at first start up
If you're replying to my post above yours, the noise isn't there when it's cold. only once it's warm, like you said at the end of your post, hinting a rod problem.
If it were piston slap, wouldn't it have been there from the start? With my old block, I didn't have piston slap. This is a different block though. Guess I got an older block. The noise didn't start until after I starting going 90% WOT up to 6,000RPMS. I think I did this about 15 times in a 2 day period. My car is an M6, btw.
If it were a rod bearing, what are other signs?
My oil pressure has NEVER been lower than 35PSI+ at idle. My oil pressure is around 60PSI when I crank it up in the mornings after sitting all night. The weather around here is around 35-40 degrees in the morning. Once my engine is totally warmed up and the weather is warmer, my car sits about 1/8th of an inch to the left of the 40 mark on the O/P gauge.
Any other ideas or tests that I could perform? Thanks guys! If a mod would like to split this thread, that would be AWESOME!
