Knock thats not the Rod-Bearings???

[SHOwner]

After searching through the forum, I'm still a bit confused so any help would be fantastic. I just had the rod bearings replaced on my engine (140k) hoping to fix a spurratic knocking I was hearing. According to my (trustworthy) mechanic, the crankshaft looked perfect and all of the plasti-guage was within perfect tolerances. Unfortunately, the noise came back after about a half-hour light drive.

I was wondering if it was possible that the engine already chewed up a bearing (possibly some type of internal lubrication problem??) or if its likely that the cam tensioner is to blame? I had the "120k" tuneup done (with the exception of the valve-lash adjustments) recently and after spending a lot of money into the car I am worrying that the engine might be shot. I'm a little new to working with SHO's, but I loved 'em way before I owned one ... any opinions will be greatly appreciated. Also, I'll try and record the sound that the engine is making if that can help anyone help me. Thanks!

 

[Bizzy]

Maybe it would be a good idea to make an appointment with Fred. There are others in CT also that might be able to listen to it and help narrow down the problem.

First thing though is to pinpoint where the noise is coming from by listening to it. You can take a long screwdriver and place it on spots on the intake, cam covers, etc. to use as a listening device. I wish I could be more helpful, but with as little info as you've provided there's not much I can do. frown

 

[SHOwner]

Bizzy, thanks for the advice. I bought a mechanic's stethoscope today and I'm going to try and find out where the sound is coming from tomorrow. As far as the actual noise goes, you hear it when starting the car, and then usually around the 2000-4000rpm range. If I drive the car and hold the RPM's at around 2000, you seem to hear it the most. I'm mostly curious about whether or not anyone has ever had internal lubrication problems causing rapid destruction of a rod bearing (although none were ever 'spun).

Also, I'd love to have someone hear it but I'm a little nervous to drive it any long distance (like to neSHO for example). If I record the sound as an mp3 would that be helpful at all? Thanks again.

 

[Bizzy]

Sound clips are fantastic. If you can narrow down where the noise is coming from combined with a clip it would be awesome. Give it a shot, we're here to help.

There's bound to be someone in CT that could come to you to listen and hopefully narrow down what the problem is. Perhaps post a thread in the Open forum or Contacting forum to see if someone would help. I think you are wise for not driving it. thumb

 

[masho95]

SHOwner:
According to my (trustworthy) mechanic, the crankshaft looked perfect and all of the plasti-guage was within perfect tolerances. Unfortunately, the noise came back after about a half-hour light drive.

What were the condition of the bearings that were taken out? specifically the upper ones? Your mechanic visually looked at the crank? Any physical checking of it like running a fingernail across it feeling for scratches? I'm sorry to say it does sound like a rod bearing/crankshaft problem from the things you said. Especially that the noise went away after they were changed for 30 mins. If the crank is damaged it will just ruin the new bearings in a matter of time, from 1 mile to 3000 miles or whatever depending on how bad the crank is. Rod bearing problems usually start as a faint knocking in the rpm range you said you heard the noise and if continued to be drive the noise and damage will just get progressively worse. Definitely record the noise as that'll give us more to go on, but it may be difficult to capture the noise due to engine bay noise. BTW how loud does the "knocking" seem to be? If you are in the rpm range where it seems to be making the noise and you quickly floor it, does the noise seem to stop? Good luck narrowing it down.

 

[SHOwner]

masho95, I think you were right on the mark. After using a mechanic's stethoscope to listen to the engine, it seemed to still be coming from the oil pan. I took the car for a short drive (I didn't have a choice) and when I did the Check Engine light came on. I decided I may as well see what the dealership has to say, even though I usually would avoid dealerships, and they believe as well that the knock is a rod-related issue. According to them (and other posts I've read) the best thing to do is replace the engine. Sadly, I can't afford that so this will probably be one of my last posts (until maybe I can get another SHO).

I really do appreciate all of the replies though, and incase it will help anyone else out I'm going to at least try to record the sound the engine is making. Maybe it could help someone avoid throwing away as much money as I did headbang Thanks again!

 

[Electricat]

Here is a (messy) suggestion: drain the oil into a clean container, and also remove the oil filter and cut it open. Look for any traces of metal, flakes or dust or anything. If the engine actually ate up internal parts or bearings, there is often metal in the oil or filter. Don't throw in the towel yet, engines can do plenty of strange things that aren't catestrophic problems.

 

[SHOwner]

Electricat, I think I'll give that a try. I just bought an engine with about 60k miles on it that hopefully I will get soon , and once I can afford to switch it into my car I should be back in business. I am looking forward, however, to digging into the motor that I have now once the new one is in the car and seeing whats up. I figure I can at least learn something with it, and maybe find out more about what caused the rod knock (it has 140k on it, so this new engine should give me a little more piece of mind too). Thanks for the reply!