Rod bearing change questions..

[boat]

Getting ready to check the rod bearings in the 93 MTX in my sig. This would be my first solo flight. Had some help the first time, I did them.

While the previous owner owned it, it developed a very notable clacking with no oil light flickering or coming on. The guys he worked with diagnosed it as having bad main bearings, just by sticking a stethoscope to the motor, not pulling anything to look at it. I have been told by someone else that knows these engines well, that clacking (rod knock?) is NOT main bearings, more likely rod bearings.

So, I have it ready to check the rod bearings tomorrow, everything is off, except the girdle, splash guard, and pickup tube. If everything looks good, new bearings will go in. If anything is found bad, like a spun bearing, or what ever else bad I may find, this car will get a 3.2 already on the engine stand.

Which rod bearings are typically known to fail first? 1-6, Top or bottom? What am I looking for on the crank, prior to putting in new bearings?

 

[NotSoSlowSHO]

Unless you had a serious knock, I wouldnt expect to find much more than worn bearings.

If thats the case, just replace them and go on your way.

If you do have bearings that are severely worn or worn, replacing them without machining the crank journals and running undersized bearings is simply postponing the inevitable.

 

[Irish Pride]

I've never done rod bearings, but from what i've heard and read i think the #5 bearing is the one to check first. I believe its the first one to fail due to oil starvation.

 

[Off Road SHO]

It doesn't matter which one is the worst one, you're going to do them all anyway. The top inserts always get the worst punishment since they convert the power stroke of the piston to rotation of the crank to accelerate a 3,000 lb car. The bottom inserts only get really pounded when you lift and the pistons are trying to slow down the rotating masses.

If there is any scoring on a rod journal deep enough to catch a fingernail dragged crossways, it's time for a new crank.

Mains hardly ever wear out on these engines.

Tom

 

[jimtash]

A spun bearing is very noisy at low RPMs and goes away once the engine is revved.

Curious to know how they could diagnose a clacking noise to be bearing related in a solid lifter engine that makes all sorts of noises naturally.

 

[rubydist]

in my experience, a spun bearing on these engines rattles like heck at any speed....

 

[jimtash]

When my car suffered it, it made a loud knocking at idle with the oil light on. As soon as the RPMs went up, the noise would go away and the oil light would go off as well. The bearing in that engine didn't "spin" but got twisted sideways out of the saddle from oil starvation so that might be different from a bearing completely coming loose. Nasty and something I'd rather not experience again.

 

[JRA2000TL]

I've also heard about the #5 being the worst. I've done bearings twice now and some were noticeably worse than others; but overall, none of mine were really bad. Like they said, if the crank isn't scored, that's the most important relief. Put new ones in and be done with it. Make sure to go through the proper 2 step torquing sequence when installing the caps. I'm a really louzy mechanic and I managed to not screw mine up. 7-8k on the 95 after a bearing swap, and about 3-4k on the 89 after that swap.

 

[boat]

Got the bearings out...

Here they are. None of them were spun or worn through. It looks like all the rod journals on the crank are nice and smooth, no scoring of any kind. I pulled them all first (trying to find the culprit to the knocking,never found it), kept them in order as I pulled them out, so all the caps/nuts go back on the same rod. Thinking I probably won't plasti-gauge any of them, being that the journals look as good as they do.

While I am glad that none were spun, I am a little confused as to what caused the clacking. Would anyone have anything on this?

All bearings showing copper.

Cross-hatching still looks pretty good.

A little concerned here, looks like oil seepage down the cylinder wall from above the piston. Not sure if that is what that is or a burn or stain of burnt oil.

 

[kevinspann]

Looks all good to me

 

[rubydist]

on the crank journals, run your fingernail across them (front to back) and make sure you do not feel any ridges. they need to feel smooth to your fingernail.

on the cross-hatching - you can see in your photos how far down the rings move when the piston is down - what the cross-hatching looks like above that point is what you care about.

on the oil leaking down (?) past the one piston - it is likely that the ring gap in the bottom oil control ring happens to be located there. if that is the case, nothing to worry about. if not, there is a good chance that at least one of the rings is stuck (very common on these engines) in which case it would be a good idea to pull the heads, pull the pistons, and soak them in parts cleaner solvent to loosen them before you put it all back together.

on the clacking noise - these engines have lots of other things moving that can sound a lot like a rod knock, including loose timing belt and loose timing chains. another reason to at least pull the valve covers off to see what it looks like under there.

 

[NotSoSlowSHO]

I bit into the copper, but it all looks good to me. Fresh bearings and on your way.

Most people misdiagnose top end noises as rod bearings. Cam chains and tensioners are terrible at transferring noise all kinds of places...

 

[jayro]

on the clacking noise - these engines have lots of other things moving that can sound a lot like a rod knock, including loose timing belt and loose timing chains. another reason to at least pull the valve covers off to see what it looks like under there.

x2. You may have already looked at it, but have you checked the timing belt/marks etc. I bet the clacking is something in the valve train making noise. That would also account for the lack of power and the starting issue.

 

[jimtash]

x2. You may have already looked at it, but have you checked the timing belt/marks etc. I bet the clacking is something in the valve train making noise. That would also account for the lack of power and the starting issue.

Si. And along with that clacking noise which might end up being the chain tensioners or the chains themselves, you're looking at performance issues as well. Especially if cam timing is slightly off on the rear exhaust cam.

 

[boat]

On the crank journals, with my fingernail, they all seemed to be smooth with no ridges, I will confirm this prior to putting in new bearings.

Okay, makes sense.

Okay.

I never thought about the timing belt. If that is off (alignment wise, teeth) that could be a reason for the no start, couldn't it?
As soon as I get the bottom buttoned up, I will be doing the top and front 60k's. There is oil in 4-5 of the 6 plug wells, and oil is leaking from just about every other orifice possible, much over due for some new gaskets. I have all
the parts, may as well.

on the crank journals, run your fingernail across them (front to back) and make sure you do not feel any ridges. they need to feel smooth to your fingernail.

on the cross-hatching - you can see in your photos how far down the rings move when the piston is down - what the cross-hatching looks like above that point is what you care about.

on the oil leaking down (?) past the one piston - it is likely that the ring gap in the bottom oil control ring happens to be located there. if that is the case, nothing to worry about. if not, there is a good chance that at least one of the rings is stuck (very common on these engines) in which case it would be a good idea to pull the heads, pull the pistons, and soak them in parts cleaner solvent to loosen them before you put it all back together.

on the clacking noise - these engines have lots of other things moving that can sound a lot like a rod knock, including loose timing belt and loose timing chains. another reason to at least pull the valve covers off to see what it looks like under there.

I was not going to dig into the front of the motor until I knew what the condition was of the rod bearings, as I believe that my no spark is coming from a bad crank sensor, as I have swapped everything else but the PCM and CCRM. I didn't want to do a front 60k and find out the crank was trashed.

I think something that may have attributed to being down on power was the Accel coil pack. There were 2 ports that were melted enough the plug wires wouldn't stay in them, and the ends of those plug wires were severely corroded. Already changed out the coil pack and plug wires. We shall see what comes of the top and front 60k's.

x2. You may have already looked at it, but have you checked the timing belt/marks etc. I bet the clacking is something in the valve train making noise. That would also account for the lack of power and the starting issue.

 

[SuperHO]

A clacking noise...down on power...hard start...pull your crank pulley off and check for crank cancer. Typically when a timing tensioner is bad, it'll rattle at double time. Ask me how I know.....

 

[boat]

I didn't think of that either.

Thanks, Tim, I'll check for that before I go another step. If this is the case, I'm not wasting anymore money or time on this motor.

EDIT:
Its not even a hard start, its not starting at all. I do have fuel, verified this already, no spark.

My understanding of crank cancer, is that the key/keyway on the crank being ruined by not torquing down the crank bolt properly. Then it wallers out the crank pulley and timing belt sprocket, then you have problems with the timing belt jumping teeth and the car loosing timing. Bubba has had this car for about 15k hard driven miles, I would think that if the crank bolt was loose, it would have shown itself a long time ago. The previous owner never did any engine work on it, it was all suspension work. He had it for about 10k miles. I wouldn't think it would take 25k miles for it to show itself. By the looks of the everything underneath the motor, it is sooo oily, dirty and rusty (bolts wise) under there, that my suspicion, is that motor has had next to no maintenance done to it, in at least the bottom end or front of the motor. By that account, I think it could be a far reach of being crank cancer. I would think crank cancer is more from operator error than anything else.

Is there any other way it can happen???

Like I said, if this is the case, thankfully I already have another motor. I have to spend some $$ to assemble it, that I was trying to avoid for now. If I have to, I will.

A clacking noise...down on power...hard start...pull your crank pulley off and check for crank cancer. Typically when a timing tensioner is bad, it'll rattle at double time. Ask me how I know.....

 

[rubydist]

I think anyone with an Accel coil on one of these cars should be using it for a boat anchor rather than a spark generator.

you need to pull valve covers anyway to replace all those bad seals, so you can carefully inspect the timing chains and tensioners while you have that open.

and, btw, a 3.2 is noticeably more fun....

 

[SHOtimer]

I think anyone with an Accel coil on one of these cars should be using it for a boat anchor rather than a spark generator.

This.

Doug