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Rod bearing questions

D

dmann

New member
Joined
Apr 22, 2015
Location
Sacramento CA
I am working on a 1995 940 w/b230. The odometer reads about 193K miles. I just recently purchased this vehicle. What I originally thought was probably piston slap I now believe is a rod knock.

The noise is not present when the car is started when cold. After a short drive, it becomes noticeable. I hear it at stoplights, sometimes I notice it when accelerating (slowly) and when decelerating. It's not the loudest sounding knock I've heard by any means, but I don't want it to get any worse.

I pulled the pan off to get a look at the bearings and check the clearances. Number 2 rod bearing showed the most wear on the upper shell, with some copper showing, about 10% of the upper surface showed some copper. The other bearing shells seem to be in pretty good shape if they actually have 193K miles on them.

I wiped the bearings and the crank journal off and then used plastigage on them. I get between 1.5 and 2.5 thousandths on all of them. I tried plastigage on each journal more than once, hoping to increase the chance of detecting any errors during measurement. They always seem to come out in that range. I tried a little experiment with rod number 1, I took some .001 thick foil and shimmed the bottom of the rod cap underneath the used bearing. I then tightened everything back up and measured again with plastigage, and it did tighten up. It measured about .001 total clearance. I don't honestly know how accurate the plastigage is, because when removing the rod caps I have to tap the bolt to break the cap away from the rod. I'm concerned that this could impart a load on the cap, and flatten out the plastigage even more and throw off my readings.

With the bearings and journal mostly dry of oil I can get a small clanking sound on all 4 of the rods - if I try forcefully rocking them back and forth pushing on the rod from the driver side towards the passenger side and then doing the opposite. It requires a concerted effort to make that noise however, and I can't push up or pull down on the rod and make the noise. This test was done with the original bearings in place, not the new ones.

I don't know what the oil pressure is, I don't have any gauge, though I may pick one up. I purchased a new set of bearings and new oil pump o-rings.

None of the bearings are blue or appear discolored from heat, even though I've put about 1500 miles on it since I started to suspect a rod bearing.

I'm wondering if perhaps I have low oil pressure. The oil pump screen looked ok to me, and I didn't notice anything in the bottom of the pan that looked bad. There was some carbon build up on the surfaces of the lower end; more than I'd like to see, but a lot less than some engines I've seen.

I thought about checking the mains, but I think I might as well pull the engine if I was going to do that, because they look difficult to get out in chassis.

I guess at this point the best thing I could do would be to put it back together and check the oil pressure.

Any other ideas?
 
dmann.....From what you just described about the appearance of the rod bearings and the clearance measurement obtained with plastigage, I would say that you don't need to do anything to the rod bearings. The specification for rod bearing clearance is .001"-.003". You are well within that tolerance.

As far as the Main Bearings go......It is possible, and not very hard to install new bearings on a engine that's still in the car.
We call it "rolling in" the bearings. You can take limber putty knife and turn the old upper bearing shell by tapping it on it's end.

It will only turn one way because of the locking "tang' on the bearing shell. Turn it far enough to be able to finish pulling it out from the other end. Installation of the new bearing shell is the reverse of this process, being careful not to damage the end of the new bearing....I would use a flat pointed hardwood punch to tap the new bearing back around the crankshaft.
Be sure to oil the face of the bearing before installing it.
 
Just did #3 main, it looks good and also measured out at below 2 thousandths. I took the oil pump apart, and it doesn't look horrible, but there is some wear. There was visual wear on the oil pump bottom plate, on the gears, and on the pressure relief piston. I haven't had one of these apart, so I'm not sure what is "normal" for 193K miles.

I'm going to put a melling m181 pump back in it, for piece of mind. I'll just save the volvo pump I pulled out as parts.

There is a fine black powder inside the block and it feels like sludge because it's oil soaked, but it is definitely a fine black powder. I believe it is carbon. I'm concerned that this will circulate back through the new pump. I believe this is probably from extended oil change intervals or low quality oil, maybe both.

I've sprayed the underside of the lower end to try and get as much of it out as I can...but it doesn't really seem to dissolve. I need to actually scrub it to get it off. Does anyone know of something that can break this stuff down and dissolve it? Something that won't ruin the engine or my skin? My only alternative is the change the oil frequently, but that isn't going to stop the pump itself from sucking up these particles and pushing them into the filter.


Here are some pictures of the pump:

Untitled by Dan Mann, on Flickr

Untitled by Dan Mann, on Flickr

Untitled by Dan Mann, on Flickr

This is what the main journals have looked like so far:

Untitled by Dan Mann, on Flickr

And here you can see the black sludge/powder stuff I mentioned, stuck on the inside walls of the block:

Untitled by Dan Mann, on Flickr

Dan
 
I wanted to update this thread for historical purposes. New rod bearings and new oil pump, no noise so far in about 70 miles.
 
It's not fun, but I can do it all in 4-6 hours or less. No coolant, no hoses, no taking the trans off it. Just hang the motor and get the cross member out of the way with the floor jack, leave the brake lines, tie the steering rack out of the way.

Some just lower the cross member down and drop the pump into the pan...I don't just because the oil transfer pipe is finicky to get seated nicely. YMMV.

You have to be under the car for many more hours with way more bolts and fluids to deal with to pull an engine, plus the heavy lifting to pull it.
 
I did change it on my back under the car. It's time consuming. I think if you are considering pulling the engine anyway, that's probably the best way to go because I think you can probably do a more thorough job. If I would have pulled mine out, I could have really cleaned the crud out of the engine much easier.

I think I ended up doing mine in a way that was pretty "back yard". I jacked up the engine (I was replacing the mounts anyway) and partially dropped the pan. I then needed to drop the pump before the pan could come further out. Upon reassembly I chose to modify the pan by making cuts into the windage area of the pan and bending the cut section up. This gave me enough room to bolt the oil pump to the block and then reinstall the pan.

If you have to remove the pan, you can definitely do it in the car. It's a bit of a pain, it's time consuming, and you'll most likely get oil droplets on yourself.

There probably aren't very many good reasons to pull the pan in the vehicle, but if you want to inspect the lower end or fix an oil pump tube seal it probably makes sense. I don't think my rod bearings were very bad to begin with, but they weren't too expensive and I already had the pan off, might as well do them :-)

I even bought Deckwar Tapered Shims (http://deckwartaperedshims.com/index.php) and trial fit them in a couple of rods, but they made the clearance too tight. This confirmed to me that my plastigauge was reading fairly accurately (I checked with and without the smallest sized shims) and that my factory sized replacement rod bearings were a good fit.

Deckwar are very nice people to work with.

I ended up pulling the head and getting a valve job, new water pump, timing belt, etc. Kind of spiraled out of control. I ended up doing the whole thing in the car, because I hadn't planned to do it all like this. Next time, I'm pulling it out.
 
Well 500 or so miles in and I started noticing the noise again. Less frequently and not as loud, but it may get worse. At this point I'm going to roll the dice and keep going until it becomes unreliable.

How many miles do you think it can go?

:)
 
Last edited:
Rod egged out of round?
How loud was/is it?
Definitely measure oil pressure!

What filter? Flow issue? gears worn in oil pump? Swap one rod? :lol:

I've had better luck with just used OE 1990+ "tall gear" oil pumps. I've seen them have excessive gear clearance, mostly on earlier shorter gear pumps?
 
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