rod bearings?

[ckinart]

hi... a bit of a story... last nite, i performed the decarboning procedure on my '94 MTX as explained on shotimes.com (inject a bottle of carb cleaner, and let it sit for a bit... i've read the various opinions on doing this, and decided to give it a shot)... anyway, the last portion of this operation involves a few miles of "aggressive" driving to clean things out... after doing this, i was listening closely to the engine, and noticed a slight knock that could only be heard with my ear next to the driver's side wheel. i could not hear anything unusual from the top side or the passenger side wheel. i'm pretty sure the knock is once per revolution, and is proportional to engine speed. needless to say after this stint of aggressive driving, the engine was running relatively hot. so this morning, i started it up and couldn't hear it at all... i drove it rather daintily to work, and had a listen again, and still can't hear it...

from the reading i've done on shoforum.com and other sites, i think this sounds like rod bearings, but i wondered if anybody could give me any more info... by the symptoms i have described, i would think that this is probably a developing problem, but not a terminal illness that requires immediate attention, but i dunno... i know it's hard to diagnose sounds via a web posting, but i thought it would be worth a shot...

sorry for the long post, and thanx for any input...

oh, and by the way, i very rarely drive my SHO as aggressively as i did last nite...

<small>[ June 21, 2002, 10:36 AM: Message edited by: ckinart ]</small>

 

[srfdude]

As you say, diagnosing via web is difficult at best. However, any knocking sound should be investigated ASAP; all it will do is get worse, taking the crank with the bearings. As easily as the bearings are changed (relatively speaking) I would suggest dropping the pan and having a look. It seems the bearing failure rate starts to increase when you get much over 100K miles.
Mike

 

[slickn56]

After I drive my car for a while or real aggresively I get the same kind of sound next to the driver side wheel. The sound I have sounds like a ticking and increases with revs. My problem is the throw out bearing in the transmission. `And well after a while it is going to destroy the clutch and make it hard to get into gears. If the noise comes back see if it will go away by pressing the clutch in. If it does then you know it is transmission related.

Nick
89 Sho

 

[stevetatro]

I don't think that's where the sound of worn rod bearings would be heard the most. I'd guess something in the clutch or tranny.

You're correct, it's hard to diagnose over the web frown

 

[sdpatt]

There has been some discussion regarding the rod bearings and there failure and replacement, but I have not seen much about the crankshaft main bearings. How many of failures have occurred and what does a worn crank bearing sound like? I think that removal of the crankshaft would be a much harder job than to access the lower rod bearings.

 

[ckinart]

well, you guys are great... i had a bit of an "aggressive" trip home from work today, and i could hear the slight "knocking" sound from the driver side wheel area when i got home... but once the clutch was pushed in, it went away... so i guess the TOB is the likely culprit... that is fantastic news as far as i'm concerned... i was planning on putting a clutch in it anyway, so that's alot less trouble than tearing out the bottom end of the motor...

thanx a million guys...

 

[BeatDaSHO]

yeah. i got the same problem. i just turn up the music louder.....lol

Greg

 

[pete c]

scott,

Unfortunately, I know what a bad main bearing sounds like. Way back when, I rebuilt the engine in my '79 supra, because of a bad rod bearing. I got everything back together, started the car and it ran flawlessly for maybe 30 seconds. Then it stalled. It restarted, stalled again, but shuddered a little as it stalled. It seemed as if some invisible force was braking the engine, kinda like letting out the clutch with the e-brake on. Then it wouldn't crank over. I figured the battery might be dead. A friend and I pushed the car down the street, I jumped in, slid it into second and popoped the clutch. It dragged the rear tires to a halt. The motor was froze. So, for me, the sound of a bad main bearing is an old supra skidding to a halt as if the e-brake was locked up.

The next time I rebuilt it, I did NOT block the main bearing journals by putting the bearing in backwards, and I'm fairly certain that I never will make that screw up again.

When I brought that crank back to the machine shop with a main bearing welded to it I felt like a serious *****.

BTW, I have been searching for info on bearing replacement and haven't found much concerning suppliers and whether or not I should buy bearings identical to the old ones. Since the crank is not being machined can I use the same size bearing? I will plasti-guage it anyhow.

<small>[ July 01, 2002, 02:11 PM: Message edited by: pete c ]</small>

 

[srfdude]

NAPA On-line has Clevite 777 bearings available for quick delivery, @$7.50 ea. pair. At least for the MTX; not sure if they are different for the ATX.
Mike