Rear oil leak and knock

[newshirt]

I got some sobering advice from a knowledgable Model A club member, but want to hear what the experts on fordbarn had to say...

I have a very bad rear oil leak from the bell housing cotter pin hole. It has slowly gotten worse over the last six months. It leaves long trails of oil when I drive, and 12" puddles when I stop. Plus, I have what sounds like "knocking on hollow wood" when the engine is cold. This "soft knocking" sort of goes away as the engine warms up. But there's always a tick sound as the engine idles.

My friend says the "soft wood knocking" is likely a bearing problem and related to the leak, although he has not actually heard it firsthand.

I'm afraid to pull the bearing caps because the babbet might fall apart in my hands.

Any thoughts? Thanks in advance, guys!!!

[John S]

Originally Posted by newshirt

.

I'm afraid to pull the bearing caps because the babbet might fall apart in my hands.

Any thoughts? Thanks in advance, guys!!!

I hate to put it this way, but if you don't fix the problem soon the crankshaft or a rod could remove itself from the block while you are driving. In other words, the internal parts could become external.
The longer you put off a proper repair the more damage is done and the cost of repair will just go higher IMHO.

[pat in Santa Cruz]

My Guess is that the wooden sound is piston slap. Main bearings are a dull knock from the floorboards when under a heavy load. Rod knocks are sharp, unless its only a couple of thousanths beyond the 1.5, then it is a cluck type knock at the crankcase line at very slow idle when hot ( thin oil). I still think its time to pull the pan and inspect everything armed with some information regarding what you are looking for. Try shorting out the spark plugs to see if it affects the knock, that will give you a direction to look for the knock. Get some plastigage or try the foil method and check all bearings. Oil leaks can arise from a loose center main too. In fact the center main is the one taking the most beating, until it fails then the others come into play, which could be what is going on now causing the increased leak. Waiting will only incur more damage. Nipping it in the bud is the cheapest way. always.

Your leak could be any number of things, see this link.:

http://www.antiqueenginerebuilding.c...RMAINLEAK.html

[newshirt]

A few more things to add:
1. A plastic storage bag sealed around the oil filler tube does not inflate. It flutters.
2. Driving without the oil filler cap does not help the leak.

[Tom Endy]

At the very least it would be prudent to drop the pan and take a look at things. You are likely to find a pile of babbitt in the pan under the rear main.

At the recent MARC meet in San Diego a fellow came into the maintenance tent with the same description of a problem such as yours. He had driven the car from somewhere in the east. Around Arizona it started knocking and losing oil. When the pan was removed there was a pile of babbitt in it under the rear main.

Tom Endy

[Brian T]

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Hello Newshirt,
Not sure why I took this pic as I have seen this many times in my life in the auto service repair, this is from the engine that Tom refers to, so if you see this after removing the pan then you may need not look further, just remove the engine for repair.

[newshirt]

Anything bad here? Or can't you tell until the bearing caps are pulled? (Sorry to be so stupid.)

There's a fair amount of fine metalic dust, but no pile like the previous posts described. Is this too much?

BTW, I don't see a drain tube. Can anyone post a pic showing what it looks like? Or point it out on mine?

[Tom Wesenberg]

You see that hole in the low spot on the rear bearing? That's where the pipe should be. That oil doesn't look good to me. If that drain pan was clean before the drain, then it sure looks like a lot of little pieces of babbit. At this point, it would be wise to remove the rear bearing cap and see how the babbit looks.

[John S]

The brownish color of that oil makes me think it has water or anti-freeze mixed with it.

[pat in Santa Cruz]

no oil pipe, a common cause of rear main leaks. But, I also see babbit chunks in the oil. The rear main thrust looks good on the cap, but I cannot see the top bearing. Is there a place in the pan, like the center of the dipper tray, where there is an accumulation of chunks? Take those chunks out of the oil, wash them off and see if they're metal. If so, you will have to remove the crankshaft to inspect all the mains. Tom Endy's suggestion that its time to pull the engine is appropriate. Its easier to tear it down on a stand than lying under it.

[newshirt]

Originally Posted by pat in Santa Cruz

Is there a place in the pan, like the center of the dipper tray, where there is an accumulation of chunks?

There was no accumulation. The tray at the top of the pan was completely clean, but the oil in the shallow cups was twice as thick as normal. This stuff came from the sludge under the tray, at the bottom of the pan. These ten slivers are the only ones I could find, but I'm sure there are plenty more I missed.

These biggest "chunks" are still micro-thin slivers, a fraction the thickness of aluminum foil. Very thin, like gold flake. All the rest is very, very fine dust. But there is a lot of it.

There were much larger chunks of black stuff, which is was not metal. I crushed them up with my fingers.

But I do understand the need to check the bearings.

[700rpm]

Please keep us posted. We all learn from what others learn.

[Tom Endy]

Attached photo of a rear main bearing cap with the oil pipe.

If you fish around in the bottom of the pan you may find the one missing from your cap.

Tom Endy

[bogdonj]

Originally Posted by 700rpm

Please keep us posted. We all learn from what others learn.

agreed.. let us know the outcome

[d.j. moordigian]

From the San Diego meet, I think the people were from Ohio. I wondered , as they
were changing the engine out, if it was number matching to the dead player?

[pat in Santa Cruz]

well, it does not sound as bad as it looked. Nevertheless, there is some metal in there. It could just be an accumulation from wear in, but with the knocking, I would be suspicious until I found something that explained it. As far as you have gone, it will not hurt to check the bearings. A poor babbitt job has a tendency to crack and fall apart, especially if the clearance is allowed to become too great and pounding begins. The missing oil pipe is probably your leak, but there must be a source for those shreds of metal, and checking the bearings seems warranted. As I said, the center main is the weak link in a Model A. Checking it for condition and clearance can't hurt other than take your time, tho' it is bit of a pain. The rear main is easy to remove, and also suffers frequently. Might as well check the front too as long as you're under there. Keep track of how many shims are in each bearing and which side they come from. If you don't want to pull the engine, its entirely possible to do the job lying under the car. Jack it up on stands so you have room to move, get a nice pad to lie on and take your time. After a few days, there is not so much dripping oil. Take a rag and dry off the drops before they hit your face and eyes. You can even nap under there. Rods wear more quickly and are easy to adjust. Might as well check it all so you can drive it without worry for many miles to come.

Originally Posted by newshirt

There was no accumulation. The tray at the top of the pan was completely clean, but the oil in the shallow cups was twice as thick as normal. This stuff came from the sludge under the tray, at the bottom of the pan. These ten slivers are the only ones I could find, but I'm sure there are plenty more I missed.

These biggest "chunks" are still micro-thin slivers, a fraction the thickness of aluminum foil. Very thin, like gold flake. All the rest is very, very fine dust. But there is a lot of it.

There were much larger chunks of black stuff, which is was not metal. I crushed them up with my fingers.

But I do understand the need to check the bearings.

[newshirt]

Originally Posted by pat in Santa Cruz

well, it does not sound as bad as it looked. Nevertheless, there is some metal in there...

Dan, up at Bert's, said the exact same thing after listening to my description. But then he took me over to a bunch of bearings and showed me the cracked ones. He said, if you take those caps off and they fall apart, then stop right there because you need the engine repaired. So there's a risk in removing the bearing caps.

I'm not financially ready for that risk.

He also showed me a bunch of rod bearings where the sides of the babbitt had flaked off. In the old days, they babbitted the rod bearings for side thrust but then learned that it wasn't necessary.

So, I guess I'm going to have to do this... but not until I check the leak status after adding the drain tube.

[pat in Santa Cruz]

I don't think you understand. Removing the bearing caps does not break the babbitt or increase the risk of doing so. if the babbitt is so bad it will fall apart when you take the caps off, the engine is already toast. You risk breaking the crankshaft and/or ruining the block with a broken rod by running it with shattered or loose bearings. If the bearings have excess clearance but are intact, driving it that way increases the odds of cracking the babbitt into pieces. If the babbitt is good, all you risk is your time to adjust the bearings and the possibility of screwing it up with human error.

[Ed in Maine]

This situation is very similar to a Town Sedan I had years ago. The soft knock would happen on start up and last for several minutes until the oil was well distributed and then the noise would stop and the engine sounded wonderful. When at 40 mph it sounded like it could run forever. Many folks told me it was piston slap. I drove that car over 8000 miles over a period of twenty years.

My car also had an oil leak. Your missing oil tube is the problem. On my car, the engine builder crimped the end of the tube and then dropped a ball bearing down the tube before the tube was threaded on to the rear main bearing. This restricted the draining capability in an attempt to flood the rear main bearing with oil. All this did was make a big mess on my garage floor!

Rebuilding an engine these days is a lot of money. I would be tempted to drop the pan, inspect, clean the pan and install a drain tube and see how it goes. Stay close to home for awhile until your confidence level is up and then go for it! Good luck, Ed

[Tom Wesenberg]

"In the old days, they babbitted the rod bearings for side thrust but then learned that it wasn't necessary."

What would contol the side play if they didn't have babbit on the sides of the rods? Without the side babbit that would leave a lot of distance for the rod to float back and forth.