The Ford Barn

History · 08-18-2022, 05:22 PM

Finally got the A tagged and took it for a spin “UP” the parkway. It was a pretty good climb but was able to pull it in 3rd gear. I then came back down and took back roads to my home. I have a concrete drive and immediately noticed a pretty big spot as soon as I got out of the car. I have a leak at the castle nut above the oil stick, not even sure yet what that nut is for. Leak at the front of tube on the other side of the engine and the rear main is leaking pretty bad. I know there was thread just a few days ago bout a rear main leak and I looked but couldn’t find it. My question is,, what all is involved in changing that seal and the nut and tube?? I have the Les Andrews books and will read up tonight but hoping some of you know maybe an easier way or what I need to look out for.

Thanks for any help you can give!!

Chuck Sea/Tac · 08-18-2022, 06:07 PM

The castle nut is a main bearing fastener. It can’t be tightened without the pan off. Sometimes oil will creep up the bolt and weep out of the nut. There are several different “seals” people use to stop the wicking. The oil filler/crankcase breather tube is a press fit.
The rear main is a whole nother ball game. You can take the three bolts out that hold the inspection plate on, at the rear of the pan and get a better look at just where the oil is coming from. Have someone step on the clutch while you watch the front crank pulley to see if it moves forward. There should only be a few thousands movement on the rear bearing thrust surface. I’ve seen some that move well over an eighth inch, which pretty much guarantees an oil leak back there. It’s possible your oil return tube is the problem, so time to start the elimination process.

History · 08-18-2022, 07:58 PM

Is the “oil return tube” the one close to the valve cover? That’s the tube that is leaking at the front round part with a bolt in it. Do I need the engine running and have some step on clutch or can it be done with it off? Thank you

nkaminar · 08-19-2022, 06:58 AM

The tube that returns the oil from the valve cover just needs a new gasket with a light coating of gasket cement. As chuck said, the castle nut is for the center main bearing and to stop it leaking use a thin O ring or some good gasket cement, but you have to get to the other end of the bolt located inside the engine. The pan needs to come off to fix the rear main leak. You can move the crankshaft back and forth with a lever to check the thrust bearing. The engine does not need to be running.

For me, it is easier to remove the engine from the car and put it on an engine stand to work on it. That way I am able to check everything and be assured that I won't have any problems once it is back in the car. However, I know that a lot of people are reluctant to take this on because of various reasons.

One option is to get one of those metal pans for your garage that will catch the oil, fix the gasket at the oil drain tube for the valve cover, and drive the car.

History · 08-19-2022, 07:13 AM

Thanks for the explanation and suggestions. I guess they ran the crank cap bolts up and out to stiffen the entire assembly? This old engine makes a lot of noise, not sure if piston slap, worn bearings, timing gear or what. I have a supposedly rebuilt B engine that might be a better choice than what I have, at least until I could rebuild the A engine. Is there literature on installing a B engine as I know there are a few differences?

CWPASADENA · 08-19-2022, 10:45 PM

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I would strongly suggest you install the B engine. It is a better engine with bigger bearings.

Unless you have to have toe original A engine, definitely consider the B engine.

My opinion,

Chirs W.

Synchro909 · 08-19-2022, 11:12 PM

Quote:

Originally Posted by CWPASADENA

I would strongly suggest you install the B engine. It is a better engine with bigger bearings.

Unless you have to have toe original A engine, definitely consider the B engine.

My opinion,

Chirs W.

But have the block crack tested first.

old31 · 08-20-2022, 09:17 AM

Also, doesn't the Model B have an extra 10HP?

Will N · 08-20-2022, 09:23 AM

Just to be picky, there is no rear main seal on a Model A. The oil working past the bearing surface rearward hits a slinger ring, and the centrifugal force throws the oil into a channel in the bearing cap where it drains back through the tube into the pan.

History · 08-20-2022, 09:25 AM

I know there are differences, the engine I have is a BB and supposedly rebuilt. It’s a 33 I believe with a balanced crank. I’ll start another thread on what’s involved to switch from A to B engines and the differences as I do t know the answers. Thanks everyone for the help, suggestions and opinions!!

History · 08-20-2022, 09:26 AM

Quote:

Originally Posted by Will N

Just to be picky, there is no rear main seal on a Model A. The oil working past the bearing surface rearward hits a slinger ring, and the centrifugal force throws the oil into a channel in the bearing cap where it drains back through the tube into the pan.

It’s missing the pan on mine and hitting the asphalt. 😉

mcgarrett · 08-20-2022, 07:51 PM

Be extra careful before you swap in a Model B engine. My experience has made me cautious since they are notorious for cracking in and around valve pockets - sometimes repairable, sometimes not. Good ones can be found, but even the so-called Diamond Blocks can have issues. Have the block magnafluxed and pressure tested before you drop too much money on one. They are not necessarily a slam dunk.

rotorwrench · 08-21-2022, 09:59 AM

There is also a tube attached to the rear main cap that is a drain for the oil slinger cavity. The tube has to be there and protrude far enough down so as to be below the oil level in the pan. This keeps crank case pressure from exiting through the drain and pushing oil out the back. There is also a gasket at the rear of the cam that is held in place by the flywheel housing. This gasket can deteriorate and allow oil to leak from the rear cam bore area.

The tubes sometimes fall out or are removed for some reason.

Ivan in southeast va. · 08-22-2022, 03:43 PM

Quote:

Originally Posted by History

Is the “oil return tube” the one close to the valve cover? That’s the tube that is leaking at the front round part with a bolt in it. Do I need the engine running and have some step on clutch or can it be done with it off? Thank you

My oil return tube had a weld crack and was leaking pretty bad. A new return tube fixed the problem.

History · 08-22-2022, 03:50 PM

Quote:

Originally Posted by Ivan in southeast va.

My oil return tube had a weld crack and was leaking pretty bad. A new return tube fixed the problem.

Hopefully that’s all I need. Thanks

08-18-2022, 05:22 PM	#1
History Senior Member Join Date: Oct 2017 Location: NC Mountains Posts: 689	Rear Main seal and other leaks Finally got the A tagged and took it for a spin “UP” the parkway. It was a pretty good climb but was able to pull it in 3rd gear. I then came back down and took back roads to my home. I have a concrete drive and immediately noticed a pretty big spot as soon as I got out of the car. I have a leak at the castle nut above the oil stick, not even sure yet what that nut is for. Leak at the front of tube on the other side of the engine and the rear main is leaking pretty bad. I know there was thread just a few days ago bout a rear main leak and I looked but couldn’t find it. My question is,, what all is involved in changing that seal and the nut and tube?? I have the Les Andrews books and will read up tonight but hoping some of you know maybe an easier way or what I need to look out for. Thanks for any help you can give!!

08-18-2022, 06:07 PM	#2
Chuck Sea/Tac Senior Member Join Date: May 2010 Location: Between Seattle & Tacoma Posts: 2,354	Re: Rear Main seal and other leaks The castle nut is a main bearing fastener. It can’t be tightened without the pan off. Sometimes oil will creep up the bolt and weep out of the nut. There are several different “seals” people use to stop the wicking. The oil filler/crankcase breather tube is a press fit. The rear main is a whole nother ball game. You can take the three bolts out that hold the inspection plate on, at the rear of the pan and get a better look at just where the oil is coming from. Have someone step on the clutch while you watch the front crank pulley to see if it moves forward. There should only be a few thousands movement on the rear bearing thrust surface. I’ve seen some that move well over an eighth inch, which pretty much guarantees an oil leak back there. It’s possible your oil return tube is the problem, so time to start the elimination process.

08-18-2022, 07:58 PM	#3
History Senior Member Join Date: Oct 2017 Location: NC Mountains Posts: 689	Re: Rear Main seal and other leaks Is the “oil return tube” the one close to the valve cover? That’s the tube that is leaking at the front round part with a bolt in it. Do I need the engine running and have some step on clutch or can it be done with it off? Thank you

08-19-2022, 06:58 AM	#4
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,898	Re: Rear Main seal and other leaks The tube that returns the oil from the valve cover just needs a new gasket with a light coating of gasket cement. As chuck said, the castle nut is for the center main bearing and to stop it leaking use a thin O ring or some good gasket cement, but you have to get to the other end of the bolt located inside the engine. The pan needs to come off to fix the rear main leak. You can move the crankshaft back and forth with a lever to check the thrust bearing. The engine does not need to be running. For me, it is easier to remove the engine from the car and put it on an engine stand to work on it. That way I am able to check everything and be assured that I won't have any problems once it is back in the car. However, I know that a lot of people are reluctant to take this on because of various reasons. One option is to get one of those metal pans for your garage that will catch the oil, fix the gasket at the oil drain tube for the valve cover, and drive the car. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. Last edited by nkaminar; 08-19-2022 at 07:04 AM.

08-19-2022, 07:13 AM	#5
History Senior Member Join Date: Oct 2017 Location: NC Mountains Posts: 689	Re: Rear Main seal and other leaks Thanks for the explanation and suggestions. I guess they ran the crank cap bolts up and out to stiffen the entire assembly? This old engine makes a lot of noise, not sure if piston slap, worn bearings, timing gear or what. I have a supposedly rebuilt B engine that might be a better choice than what I have, at least until I could rebuild the A engine. Is there literature on installing a B engine as I know there are a few differences?

08-19-2022, 10:45 PM	#6
CWPASADENA Senior Member Join Date: May 2010 Location: PASADENA, CA Posts: 1,882	Re: Rear Main seal and other leaks Sponsored Links (Register now to hide all advertisements) I would strongly suggest you install the B engine. It is a better engine with bigger bearings. Unless you have to have toe original A engine, definitely consider the B engine. My opinion, Chirs W.

08-20-2022, 09:17 AM	#8
old31 Senior Member Join Date: Jan 2016 Posts: 2,093	Re: Rear Main seal and other leaks Also, doesn't the Model B have an extra 10HP?

08-20-2022, 09:23 AM	#9
Will N Senior Member Join Date: Jul 2010 Location: Pennsylvania Posts: 1,101	Re: Rear Main seal and other leaks Just to be picky, there is no rear main seal on a Model A. The oil working past the bearing surface rearward hits a slinger ring, and the centrifugal force throws the oil into a channel in the bearing cap where it drains back through the tube into the pan.

08-20-2022, 09:25 AM	#10
History Senior Member Join Date: Oct 2017 Location: NC Mountains Posts: 689	Re: Rear Main seal and other leaks I know there are differences, the engine I have is a BB and supposedly rebuilt. It’s a 33 I believe with a balanced crank. I’ll start another thread on what’s involved to switch from A to B engines and the differences as I do t know the answers. Thanks everyone for the help, suggestions and opinions!!

08-20-2022, 07:51 PM	#12
mcgarrett Senior Member Join Date: Dec 2013 Location: Waxahachie, Texas Posts: 949	Re: Rear Main seal and other leaks Be extra careful before you swap in a Model B engine. My experience has made me cautious since they are notorious for cracking in and around valve pockets - sometimes repairable, sometimes not. Good ones can be found, but even the so-called Diamond Blocks can have issues. Have the block magnafluxed and pressure tested before you drop too much money on one. They are not necessarily a slam dunk.

08-21-2022, 09:59 AM	#13
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,422	Re: Rear Main seal and other leaks There is also a tube attached to the rear main cap that is a drain for the oil slinger cavity. The tube has to be there and protrude far enough down so as to be below the oil level in the pan. This keeps crank case pressure from exiting through the drain and pushing oil out the back. There is also a gasket at the rear of the cam that is held in place by the flywheel housing. This gasket can deteriorate and allow oil to leak from the rear cam bore area. The tubes sometimes fall out or are removed for some reason.