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EFV-8 Club Forum / 1940 Ford Discussion / rear main oil leak

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Posted By Discussion Topic: rear main oil leak -- page: 1 2     missouriron 01-25-2022 @ 5:23 AM reply profile send p.m. Member Posts: 27 Joined: Jun 2011 I recently purchased a 1940 Deluxe. I noticed a larger than expected puddle of oil under the rear of the engine. I waited until it stopped dripping, then drove it 5 miles and place an eight inch pan under the oil pan. It filled the bottom of the pan before the drip stopped. I pulled the engine and tranny to see where the oil was coming from. After removing the pan and checking for a path of oil, I find nothing so far. I also noticed the rear main has no rope seal like my 1951, It only has an oil slinger. Can someone give me some advice? Where else do I look? How do I solve this problem. I don't want to put everything back together and find I still have the problem. Thanks Ron Ron 37RAGTOPMAN 01-25-2022 @ 9:03 AM reply profile send p.m. Senior Posts: 1941 Joined: Oct 2009 hi rear main oil leak Seems like you have a major oil leak how much oil in the engine,? maybe over full ! WHAT is the oil pressure ? if it is low it might be worn bearing, alowing the oil to seep out the rear main I would remove the rear main cap and plastice guage how much clearance you have, also check the if there is any dirt in the cap restricting the oil flow, or anywhere also was there any clogged breathers, causing inside pressure in the engine, pushing the oil out the rear main, also check your oil pressure switch for leaking, on back of engine on the LS. and the oil pump drive gears, there is a cover behind the flywheel, maybe the gasket is bad,? LET'S HEAR HOW YOU MADE OUT, !!!! Hope this helps 37Ragtopman, Maine, This message was edited by 37RAGTOPMAN on 1-25-22 @ 1:50 PM carcrazy 01-25-2022 @ 1:36 PM reply profile send p.m. Senior Posts: 1587 Joined: Oct 2009 There are several things that will cause an oil leak past the rear main bearing on an early Ford V-8 engine: 1. Too much oil in the engine - over 5 quarts 2. Too much oil pressure - over 50 PSI 3. Too much clearance in the rear main bearing - specified clearance is .000 to .003 inch 4. Too much crankshaft end play - specified is .002 to .006 inch 5. Oil of too thin a viscosity - less than SAE 30 weight 6. Car parked on hill with front facing up 7. Use of high pressure/high volume oil pump - If the engine has been rebuilt and a high volume/80 PSI pump has been installed, remove it and replace it with an original 50 PSI pump On a 1940 Ford V-8 there is no proper rear seal, only an oil slinger and a labyrinth sealing system to redirect the oil thrown off back down into the oil pan. This message was edited by carcrazy on 1-25-22 @ 1:39 PM 37RAGTOPMAN 01-26-2022 @ 5:54 AM reply profile send p.m. Senior Posts: 1941 Joined: Oct 2009 rear main oil leak I have a 80 lb pump in my 21 stud engine, left the pressure relief valve inplace, NOT leaking, any more then it ever did. not enough to be concerened, It is FORD., I think if you have worn bearing. the higher pressure pump would cause more leaking past the worn rear main bearing, this is possible 2 cents 37Ragtopman ,Maine TomO 01-26-2022 @ 8:19 AM reply profile send p.m. Senior Posts: 7243 Joined: Oct 2009 The slinger system works OK in most situations. There should be a pipe in the rear main bearing cap to direct excess oil into the pan. I use a non-hardening sealer like Permatex to seal around the outside of the 2 pot metal pieces that the slinger rides in. I have never found that the weight of the oil used had any effect on oil leakage. Are you sure that it is engine oil and not a mixture of engine and transmission oil? The main shaft oil seal could be contributing to the problem. Tom missouriron 01-26-2022 @ 4:15 PM reply profile send p.m. Member Posts: 27 Joined: Jun 2011 I will plastiguage the main bearing and let you know what happens with that. The oil gauge is bad but no evidence of leaking. Just turning on the key let the gauge peg to the maximum. This happens without the engine running. I will have to get the engine disconnected from the engine stand before I can get the clutch and flywheel disassembled. Will let you know after I get that done. Ron Plastiguage shows main bearing clearance being .002 with 100lbs torque. Seems to be within tolerance. I have removed the pot metal "horseshoe?" from the block. It appears to be wider than standard. It measures .318 in at the widest part. Another on my parts shelf measures .268 in. Is that enough difference to allow oil clinging to the slinger to let oil get past the block and into the oil pan that houses the flywheel and clutch? Any advice is appreciated Ron This message was edited by missouriron on 1-27-22 @ 7:49 AM missouriron 01-26-2022 @ 4:41 PM reply profile send p.m. Member Posts: 27 Joined: Jun 2011 TomO, there is a weap pipe in the main bearing cap. Where is the pressure relief located? I was unaware of such a thing. Ron Ron TomO 01-27-2022 @ 8:26 AM reply profile send p.m. Senior Posts: 7243 Joined: Oct 2009 The "horseshoe" should have a sharp V shape groove. I don't have one available to measure the width. Did you look for a P/N on the part? Most of the slinger type had the P/N 78-6335 cast into the part. The rope types had the P/N 91A-6335 cast into them also, but there were some aftermarket ones made that did not have the P/N cast into them. The block has a pressure relief valve at the front of the oil galley under the intake manifold. If you have the short body oil pump, it also has a pressure relief valve on the side. The short body pump is an 80# pump. You oil pressure dash unit appears to working, but the wire going to the sending unit is either grounded or the sending unit is shorted. If you have an aftermarket sending unit it could be the cause. Look for a good used King-Seeley sending unit or a NOS one. Match the sending unit to the oil pump pressure, 50# sending unit with 50# pump and 80#sending unit with an 80# pump. Tom missouriron 01-28-2022 @ 11:55 AM reply profile send p.m. Member Posts: 27 Joined: Jun 2011 The part number seems to be correct for my engine. The attached photos show that 2 "horseshoes" are different. The wider one has one side plain with no gussets. While the other has gussets on both sides. I included a photo of the oil pump. It reaches to the bottom of the pan with its attached pickup screen. I assume that it is a 50# pump? Ron Ron TomO 01-28-2022 @ 3:06 PM reply profile send p.m. Senior Posts: 7243 Joined: Oct 2009 The oil pump is a 50# pump. If you think that the narrower piece will control the oil better, use it. Every source of a rear engine leak that I know of has been mentioned, did you see any signs of the front seal leaking and the oil traveling back or the drain plug leaking and traveling back to the cotter key? Tom

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