oil leak rear main
 

Hi,
I'm french, and live in Brittany, West of France.
Please excuse me for my english. I can read it easily but it's more difficult for me to speak it or write it ;
I'm a 1928 Model A phaeton owner. it is a family car my father bought 30 years ago in Uruguay.
The engine has been rebuild there at this time. the car had not driven for 20 years and I restart it.


It has a real leak at the rear. I mean a leak, not just a drop. And it is worst just after engine is stopped. I read several threards on this forum.
Oil level is ok, just above L
Oil filler tube is ok and new. I even tried to run the engine without cap.
Rear cork seal of the oil pan is properly sealed
I pulled the 3 bolt of the inspection cover and had a look while engine was running : oil seems to come from the rear main.
I dropped the oil pan. Drain tube seems to be ok.
I attach 3 pictures.

Can someone tell me if there is something wrong or excessive play visible on these pictures.
Thanks !

P { margin-bottom: 0.21cm }

Re: oil leak rear main
 

Welcome to Fordbarn Eric. It is nice you are here!!


So I will first confess that I don't work in Metric measurements however I used a calculator and it showed that .21CM converts to 0.080". If the bearing to journal pin clearance is truly eighty-thousandths of an inch, it is no wonder you have a massive oil leak! If you meant 0.021CM, that is about 0.001 which is a little tight. In looking at your pictures, it does not appear there are shiny places in the bearing surface indicating you have that tight of clearance.

One other thing you must check is the crankshaft thrust clearance. This is how much you can move the crankshaft forward and backwards in the engine block. Much more than 0.008" will also cause an oil leak like you describe.

Re: oil leak rear main
 

The rear crankshaft journal looks like it has some deep scratches. I am afraid that you may need an overhaul and perhaps a new crankshaft. Get a local mechanic to look at it. I am sorry to have bad news.

Re: oil leak rear main
 

thank you for your answer. I did not write the last words of my first post with the 0,21 cm. I don't known why it is written there. Maybe because I copied the words from another software or came with the pictures

Re: oil leak rear main
 

Good Day eric...Your rear main bearing should have a clearance of 0.015 to perhaps 0.025 so oil can support the bearing. If more, the rear main will leak. You can use Plastigsage to check the clearance...you should have some shims between the block and the bearing cap that are used to adjust the clearance. If you have too much clearance and no shims...then the engine is in need of a rebuilding...if no shims and the clearance really is 0.001 then you could/can use some very thin shims to open it up a bit. Good luck. Ernie in Arizona

Re: oil leak rear main
 

Ernie ... possible typo ? :D

Quote: " 0.015 to perhaps 0.025 "

don't you mean 0.0015 to perhaps 0.0025 ?

Re: oil leak rear main
 

I think Ernie means 0.0015 inch to 0.0025 inch clearance. However, with the score marks (scratches) on the crankshaft journal, you will not be able to maintain a proper clearance in the bearing. You need to regrind the crankshaft or get a new one.

Re: oil leak rear main
 

Ernie,

The length of the drain tube matters ... if too short crankcase pressure will blow oil out rear main. Tube is about (Correction pipe is 4 inches long end to end with a bend at lower end).

Click link to see photo of drain tube.
https://modelastore.com/index.php?ro...scription=true

1. Also remove the "freeze plug' near the drain tube and check for debris or Babbitt in the horizontal hole in the main cap.

Is babbitt blocking inside of drain tube?

2. Also check the opposite end of this horizontal hole to be sure that it is not blocked on opposite end of main cap.

3. Some times the drain tube is screwed into cap too far and that will block oil coming out of cap into the drain tube.

There are two sizes of drain tubes 5/16ths inch and 3/8ths inch.

Re: oil leak rear main
 

Before doing anything major to your engine, blow air through the rear main bearing drain to be sure that it is not clogged or restricted. The drain pipe on the bearing cap should have a 0.38" diameter, and it should not have a check valve in it.



Avant de faire quelque chose d'important sur votre moteur, soufflez de l'air à travers le drain du palier principal arrière pour s'assurer qu'il n'est pas obstrué ou restreint. Le tuyau de vidange sur le chapeau de palier doit avoir un diamètre de 0.38" et ne doit pas contenir de clapet anti-retour.

Re: oil leak rear main
 

RE; "1. Also remove the "freeze plug' near the drain tube and check for debris or Babbitt in the horizontal hole in the main cap" Snyders sells replacement plugs.

https://www.snydersantiqueauto.com/P...shaft-camshaft

Re: oil leak rear main
 

Those marks on the crank shaft look like stains from old oil
setting a long time , just clean and set the rear main at 1 to 1/1/2 thousands
and put it back together also do the rods the same.
Dennis

Re: oil leak rear main
 

Thanks everybody for yours words, I really appreciate.


I do think that the marks on the crank are only stains of oil illuminated by the camera flash.
I now attach a picture of the drain tube before I opened the rear main.
What I understand in Benson's words is that my drain tube may be too short and not bended enough.


Ernie, I have shims but I took picture without.


My first question was to know if the rear main thrust (first pictures) is correct or need to be changed.


Merci encore !
P { margin-bottom: 0.21cm }

Re: oil leak rear main
 

1. Total length of tube is 4 inches ( I measured one) and has a bend as shown in the link I posted in post #8 above. The tube has to be long enough to be below the level of the oil in pan to stop back pressure from blowing oil out the rear main.

2. I enlarged the last photo and maybe it is just the photo but it looks like drain tube is partially plugged. The bend looks good.

Re: oil leak rear main
 

Eric, If those are stains and not scratches in the journal, then I take back my words. Clean the journal and take another photo for me.

One trick that people have done is to remove a leaf from one shim pack on one side, put the bearing back together with proper torque and see if you can turn the engine over with the hand crank. If you can, then remove a leaf from the shim pack on the other side and re assemble the bearing with proper torque. Repeat this, going from side to side until you cannot turn the engine over with the hand crank then put the last removed shim leaf back in. That will provide you with about the right clearance.

Most people use the Platigauge, Part Number A-6304 at Snyders.

The shim packs are made up by many thin leafs of shims that are usually about 0.001 inch thick. You can measure one with a micrometer. If it is 0.001 inch thick you will decrease the bearing clearance by 0.0005 inch if you take one out of one side.

You can measure the fore and aft crankshaft clearance with a dial indicator and forcing the crank to the front then rear with a leaver.

Re: oil leak rear main
 

Eric, my name is Henk, I am from Holland. Today I finished solving exactly the same problem. My engine was rebuilt 30 years ago and I never ran it. Today no leaking rear main anymore ! Even when shutting off the engine, it doesn’t leak anymore.
Reasons were:
1. Blocked oil return channel; a clot of well meant locktite sealant ...
2. Felt had been pushed into the channel where the oil baffle runs ...
3. End play was 0,1 mm. which is at the very limits of factory tolerances ...

Do check the oil return channel properly !

Best regards

Re: oil leak rear main
 

I took another photo with total length of the tube. As you can see, the total length is 7 cm, what is less than 3 inches.
Do you think the problem could be caused by a too short tube ?


Thanks again

Re: oil leak rear main
 

Could be. As Benson said, the end has to live in the oil at the bottom of the pan so that pressure in the crankcase does not blow up the tube. But also check your clearances. Adjusting the bearings is a maintenance task and needs to be done more often than 30 years.

Re: oil leak rear main
 

1. Yes the tube being 1.25 inch too short is a likely reason for rear main leak.

2. Then if oil in pan is 1 quart low that makes the OIL level another one inch lower.

3. The bend in end of tube is to clear the oil pan so bend is important.

You not want the tube to break off because the oil pan pushes the drain pipe sideways.

The bend should point forward.

Re: oil leak rear main
 

Note:

I would buy the correct tube instead of making one. The "tapered pipe threads" on tube MUST line up so that bend points forward.

Re: oil leak rear main
 

Another thing I have seen.

If any welding is done on the main cap remember that too much heat will melt the Babbitt in the cap!

No brazing or gas welder only tack the tube with an electric welder. :cool: