Engine Knock

[wncsho]

1991 - MTX - 75k miles

I have a serious clacking sound coming from the passenger side of my motor.

After reading numerous posts and guides, I was convinced it is crank cancer. So I tore into it and found that indeed, there was a problem. I had replaced the CPS about 20k ago, and did not torque the dampener bolt . When I got to it, it wasn't even finger tight. Sure enough, I found the timing gear to be worn and allowing 3-5 degrees of slop.

I replaced the timing gear, front seal, timing belt, DIS (it was damaged due to contact with the (engine (shock) balancer?), and the 2 outer belts.

It wouldn't start originally, but today it fired right up. But.......clack, clack, clack....

I used a mechanics stethescope and found the the noise seems to be coming from inside the motor. This noise is LOUD. It can be heard from 30' away or even further. There is no miss, or rough idle present.

Any ideas or direction would be appreciated!!

1991 - MTX - 75k miles

 

[revhardSHO]

Im guessing a rod bearing knock if its internal. 75K is a little low but ive heard of a few around that milage. Make sure its coming from the bottom - run the car as little as possible to find out. Drop the oil pan and pull a rod cap to see how the bearings look. That crank cancer issue may be partly to blame.

 

[wncsho]

Thanks for the info. If it is major internal trouble, are there rebuild parts available? Or is this going to become a parts car?

 

[yamahaSHO]

If it is a rod knock and your crank is not damaged, you can replace the bearings.

 

[sdpatt]

See how in this topic. The six sets of Clevite CB1435P connecting rod bearings cost only $45 at NAPA. The Fel-Pro OS30636R oil pan gasket set is only $17 at AutoZone. The oil pickup tube gasket can be cheaply cut from bulk, oil-resistant gasket material.

 

[revhardSHO]

you'll be lucky if you didnt damage the crank. If you hear the knock chances are the crank is done. Drain the oil and look for obvious signs ... metal shavings, chunks, etc. If the crank is bad you can get it reground and oversized bearings can be used, but i havent heard many good results from that method. Easiest thing to do IMO if your bottom end is shot is to buy a used 3.0L on ebay, they sell from $300 up depending on milage and condition.

good luck

 

[stevetatro]

BAH!

I've seen quite a few that weren't caught until they were knocking around, and have yet to see any crank journal damage.

In each case, replace the bearings, bolt it up, and go!

I know this is not always the case, but there's a very good chance the crank is okay.

 

[Bizzy]

mine had a spinning bearing on piston #2 from the flywheel. I replaced the bearings with standard sized ones and sealed her back up. that was 7k miles ago. I hear some clacking on cold startup, and I try and take it a little easier on the car, but a 3.2 will be going in over the winter so if the $60 in parts for the rod bearings carrys me 10k total till the car is put to bed for the winter than it was all good.

my bearing spinning did damage to the rod and rod cap, virtually left the crank unscathed. Unless you drive on a knocking bearing for a long time and it beats the ***** outta the bearing chances are your crank will be fine. The crank is hardened, as are the rods, when the bearing gets so pulverized that it almost no longer exists then I'd be wary of crank damage. My bearing came out about the correct thickness for what I saw happening, but I saw TheNoachSHO's bearing from one he spun and it was hammered to tinfoil thickness.

 

[shobikes]

wncsho - check your PM's!

 

[wncsho]

Ok, pulled the oil pan today. Found some slivers, almost copper in color. I ran a magnet through the sludge and found some real fine slivers, and the above mentioned paper thin slivers (half a dozen or so). No major chunks. I'm going to pull the rod caps and have a look. If the crank is bad, I may part the car . I haven't made up my mind yet.

Looking at the crank, what are the "obvious" things to look for. Sorry, I'm not that mechanically inclined.

If I decide to do a bearing change, should I order them online? Or can I trust the locals at NAPA/AZ - etc...

Again, thanks for ALL the help you guys provide here. thumb

 

[shobikes]

For someone "not mechanically inclined," you sure got deep up into your motor awful fast! wink

For starters, you can trust NAPA - they'll have mine in tomorrow, and we've got a Clevite warehouse in Charlotte.

As far as the crank, you would be looking for any obvious scoring or hammer marks caused by the wiped or spun bearing - anything you can feel with a fingernail or bare fingertip is "BAD."

Another thing you can do is get some plastigauge when you get your bearings and make sure your journals haven't gone undersize - to use this, you must assemble & disassemble each rod big end with the plastigauge between the bearing and the journal. Spec is .0009-.0022, with a "max wear limit" of .003. The clearance measurement is determined by the width of the crushed plastigauge.

You should be able to get all the rod ends apart from beneath, but you'll have to spin the engine a tad to get them all - the easiest way we came up with to do this is put the car in 4th, and simultaneously turn both front wheels forward (or hold one and spin the other). It takes less than 1/4 turn to spin the crank enough.

I'll be thinking good thoughts your way. Good luck!

 

[midospike]

Well.. do the bearings is not the hard. I did mine last week and everything when fine until 20 miles later... knock knock.. shit. Well i do have a v1 charger on it so i am guessing i have too much boost or bad oil pump. I found a engine for 250 to 500. I am getting a build engine next week for my toy... unless someone wants to buy the car before i get it. good luck..

 

[wncsho]

Bingo....Found one spun bearing, and another that had some flakes peeling off. I am concerned about the condition of the crank. The surface has a rough feel to it. Its not bad, but is noticable compared to the rest. I've ordered new bearings, I will see what the plastigauge tells me. I will probably go ahead with the replacement and hope it lasts!!!!

I plan to replace the 02 sonsors while here (they have never been replaced). is there any thing else I should do while this deep?

Again, THANKS for the help and input!!

 

[stevetatro]

Yeah, you might as well put the bearings in and hope for the best.

What are your other options? Remove the crank from the engine, spend the money to have it precision ground, and then find the right oversized bearing to work with it? Right.

Or you could just trash that engine now and drop in a new (used) one. Without even giving the one you have another chance to live!

Sounds like you're doing the right thing to me!

 

[jelloslug]

If you need any help drop me a line, I sure SHObikes or myself can help you out.

 

[AutoSHO]

wncsho:
The surface has a rough feel to it. Its not bad, but is noticable compared to the rest.

That is very bad. I sincerely doubt the new bearings will last at all, before that one spins again. Sounds like its time for a new crankshaft.

 

[Off Road SHO]

AutoSHO:

wncsho:
The surface has a rough feel to it. Its not bad, but is noticable compared to the rest.

That is very bad. I sincerely doubt the new bearings will last at all, before that one spins again. Sounds like its time for a new crankshaft.

Not just yet. That rough feel is probably bearing slough off. It's what happens when a soft bearing is spun around a hard journal. The only way to damage the crank is with a hard rod, soft bearings are not going to do it.

Go to an auto supply and ask for crocus cloth, 2-8 1/2 by 11 sheets. Cut strips the width of the rod journal, 11" long. Clean off any loose stuff from the journal with a rag soaked in mineral spirits (paint thinner).

Dip the strip of crocus in the mineral spirits, really soak it, the more fluid the better.

Pass one end of the soaked strip around the rod journal with the grit side towards the journal. Now slowly and softly pull the cloth back and forth. No need to put a lot of pressure on the journal, let the grit do the work.

Rinse off the cloth with fresh mineral oil whenever the grit surface becomes clogged with bearing particles. If you can't rinse it off, toss it and get another piece.

This is a very messy process when working under the car so be well protected with goggles and old clothes.

After you are done you will have to clean out the oil hole of ALL grit and bearing material. This is best done with mineral spirits through a small tube stuck up into the oil hole in the crank journal. A gear oil hand pump adapted with a smaller hose works great for this.

After you put the new bearings in, I would reccommend running it for no more that 2 minutes and then I would change oil and filter. Run it then for another hour and change the oil again. Hope this helps.

Tom

 

[wncsho]

I've gone to far to turn back now!! (And its only money....right? wink )

Thanks thumb for the advice about the crocus cloth. I wondered if there was anything I could do other than pull the crank. Should I run the cloth over the rod/rod cap as well?

Both sides of the bearing were still in place, they are about 30% to 50% worn, but they were there, and intact.

Oh well, I'm gonna do it...and hold my breath...and pray....and cross my fingers...

Parts won't be here till Friday afternoon, I work Saturday, so it will be a few days before we here the SUCCESS!! story.

Thanks again for the support.

David

 

[Off Road SHO]

David,

Yes you can use the crocus cloth to clean up any residue. Steel wool size 1 or finer also works well for the rods but don't use it on the crank. Too difficult to get the broken off steel wool fibers cleaned off of internal things.

Good luck

Tom

 

[wncsho]

One more thing. Where can I find the torque specs for the re-assembly? shrug