Rear main distress

TinCup

TinCup

Well-known member
Well it took me almost 2 years to organize a rebuild of the coupe. My local club guys all pitched in helped me replace clutch, pressure plate, lightened flywheel along with new valves and seats. We set the rods and mains with plasti-gauge and the babbits all looked in great shape. Nothing to make me think I was going to have this issue.

Well this morning was it's first big outing since what I have called my motor refresh. I had taken a number of 5-7 mile trips and the car is running great. A little oil out of the rear main but not anything to get worried about. Well I drove 18 miles to our destination only to have one of my buddies remark how much I was leaking out the the main. I looked down and had never seen that much oil before. A circle about the size of a frisbee marked my spot. Checked the oil and it was about a half a quart. Made the return trip and after parking noticed the same large puddle. Waited a few minutes and checked the oil and almost a full quart low.

I am going to wait a few days before I get back into it but I am very disappointed with my results. 1 step forward 3 steps back.
 
Be sure the rear main oil drain pipe is in place and sticking below the oil level in the pan. Mine dropped out and I was really leaking.
 
Make sure the rear main was plastigauged to a thousandth to 1 and 1/2 thousandths, and the shims pressed in as close to the crank as possible. A nd of course the tube has to be full length, and open.
 
Several people have reported that repop oil filler caps can be shoved down far enough on the filler tube to seal the opening, causing pressure to build up and force oil out the rear main.

Doesn't seem likely that you would lose the main bearing in 18 miles. Seems more likely to be something simple like the filler cap or the drain tube coming loose.

Joe
 
there are many causes of this problem and not all from the rear main. it could be the cam shaft gasket or the valve cover. This treatise by Rich Falluca is an excellent checklist to follow on your next journey into the engine. I know its a pain to do it over, but we've all had to do this at some point in the hobby, usually on our first restoration. its all part of owning an A

http://antiqueenginerebuilding.com/REARMAINLEAK.html
 
ntqlvr said:
Make sure the rear main was plastigauged to a thousandth to 1 and 1/2 thousandths, and the shims pressed in as close to the crank as possible. A nd of course the tube has to be full length, and open.
Click to expand...

Exactly what we did which is what makes this even more frustrating.
 
What did your thrust measure? If it is over .012 it will cause a noticeably oil leak getting progressively worse as the thrust gets larger.
 
Check the tube and make sure it is not screwed in too far. It will block oil return to the pan and force it out the rear main.
 
Chasing engine leaks...frustrating!

pat in Santa Cruz said:
there are many causes of this problem and not all from the rear main. it could be the cam shaft gasket or the valve cover. This treatise by Rich Falluca is an excellent checklist to follow on your next journey into the engine. I know its a pain to do it over, but we've all had to do this at some point in the hobby, usually on our first restoration. its all part of owning an A

http://antiqueenginerebuilding.com/REARMAINLEAK.html
Click to expand...


It only takes one missed detail when putting it all back together and you have a leak. Pull up the info that Pat suggests from Rich @ Antique Engine Rebuilding. He pretty much covers the entire subject.
Given that you have as much oil showing as you describe after turning the engine off, it suggests that the oil is coming from the back of the camshaft or through the rear main. (I know...I'm stating the obvious.) You can pretty much eliminate a leak at the cork gasket or oil traveling along the pan rail as that type of leak will not produce as much oil as you describe after the engine is turned off. Did you remove the galley plug in the rear main cap and clean the passage from the rear of the cap to the oil drain tube? Blockage at the rear main cap drain or missing sealant at the rear of the camshaft would be my first look if I was chasing the leak.

Good Day!
Dave in MN
 
Since my last weeks trip I have retraced my step and found the answer to my problem. At some point in it's life someone had placed steel wool in the oil filler cap. I removed it and made a 64 mile round trip today including a parade and when I parked the car back in the garage I had a quarter size drop and that was it.
Too much pressure pushing oil out the rear main. Dave thanks for link it helped me track this down.

What a relief!
 
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