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EFV-8 Club Forum / 1940 Ford Discussion / 59AB engine oil leak on 40 Ford Coup

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Posted By Discussion Topic: 59AB engine oil leak on 40 Ford Coup -- page: 1 2     TomO 08-17-2021 @ 7:35 AM reply profile send p.m. Senior Posts: 7250 Joined: Oct 2009 Carcrazy, I think that you have the viscosity change of oil backward. The 15-40 oil has the viscosity of 15 weight oil when the 15 weight is cold and the viscosity of 40 weight when the 40 weight oil would be hot. The 30 weight oil will thin out at operating temperatures and have a lower viscosity than the 15w-40 oil at operating temperatures. Oil viscosity does not seem to be a contributing factor in leaks. A 5W-20 oil seems to leak just as fast as a 20w-50 oil. Dick, I would follow Alan's advice about the compression check. If the engine sat for a number of years, it is possible that the rings could be stuck and not controlling the oil consumption. I seriously doubt that you are leaking a quart every 600 miles. My Lincoln drips oil from the drain plug and the oil consumption is about 0.5 quarts in 2,000 miles. There are 45,000 miles on the car and engine. ( I wish that I could find a fix for it, but new drain plug gaskets do not seem to have an effect on it. It is too hard for me to crawl under to see the source of the leak and I have had to leave it up to others to diagnose the leak source) To replace the rear seal, you will have to drop the pan, and I have found it easier to pull the engine to get all of the seals on the pan and crankshaft seated correctly. If you do replace the seal, use a modern replacement for the rope seal. They seem to seal better. Tom JayChicago 08-17-2021 @ 7:55 AM reply profile send p.m. Member Posts: 480 Joined: Jan 2016 “The base weight oil for a 15-40 weight oil is SAE 15. The straight SAE 30 oil will not leak from the engine as readily as will a multi-grade. “ But we are talking here about leakage past the rear main seal. I thought that seal will only be seeing oil and leaking while engine is running, while oil is warm. Shouldn’t see any oil when engine is sitting, when oil is cold. Am I wrong about that? 37RAGTOPMAN 08-17-2021 @ 12:59 PM reply profile send p.m. Senior Posts: 1958 Joined: Oct 2009 hi I would check the oil breather, it might be clogged and causing pressure in the crankcase causing the oil leak also do a leak down test and a compression test, do the compression test dry and wet, see if the compression rises, check for blow by, take the oil breather pipe off and see if it puffs,out fumes let hear how you made out, my 2 cents 37Ragtopman also check your OIL PRESSURE SWITCH on the back of engine for oil drips, seen it before This message was edited by 37RAGTOPMAN on 8-17-21 @ 3:44 PM carcrazy 08-17-2021 @ 3:05 PM reply profile send p.m. Senior Posts: 1651 Joined: Oct 2009 Dick, Do you know if the original oil pump was replaced with a later, higher pressure/higher volume pump when the engine was overhauled? If so, this could be causing an oil leak past the rear main bearing oil seal. missouriron 11-09-2021 @ 4:33 PM reply profile send p.m. Member Posts: 27 Joined: Jun 2011 I'm having the same experience with my 40 4dr. It was restored 12 years ago and parked. I run the engine 7 to 8 minutes and was able to loosen the valves so that the engine doesn't snap, krackle and pop any more. But I collect a little over 2 ounces of 30 weight. It doesn't drip, it pours. I was hoping that you would get some info about replacing the seal without pulling the engine. Ron TomO 11-10-2021 @ 5:05 PM reply profile send p.m. Senior Posts: 7250 Joined: Oct 2009 Ron, Ford used 2 different styles of rear main seals. The most common on a 1940 engine would be the "slinger type". This is a thin disc that rotates with the crankshaft. It fits in a potmetal piece V groove and deflects the oil that come from the rear main bearing back into the oil pan. This type of seal is not replaceable. It works very well when the rear main bearing does not have excessive clearance, the original 50# oil pump is still in the car and the pipe on the rear main bearing cap is in place. On steep hills, some oil will leak past the slinger into the clutch housing. That is why the cotter pin is there. The other type of rear main seal used is the rope type seal. These work very well until they dry out and become hard. This type can handle the 80# oil pump better than the slinger seal. This seal can be replaced. The normal way to replace this type of seal is to remove and clean the pot metal pieces that hold the seal, replace the pot metal parts back in the block and then replace the seal. I have never done this without disassembling the engine, but there are people who claim to have replaced the upper seal by using a piece of wire to remove the old seal and pull in a new seal. The reason that I have never tried to replace the rope type seal in the car on a 37-48 Ford is that dropping the oil pan is a bigger hassle to me than pulling the engine. To pull the oil pan, you must unbolt the wishbone at the ball joint, brace it to give you clearance for the oil pan, remove the engine side pans, remove the exhaust cross over pipe, jack up the engine and support it so you can get at the front bolts on the pan and have enough clearance to get the oil pan clear of the front cross member. Then you have turn the engine over to find the sweet spot where the front crankshaft counter weight will allow enough clearance to slide the pan back to clear the front cross member. When you reinstall the pan, you must be careful to not disturb the cork oil pan seal on the rear main. It is much easier to do this on an engine stand or with the engine laying on the floor top down, than lying on your back fighting the counterweights, wish bone and frame while you are trying to line up the bolt holes. I hope that I have been able to help you make a decision on which way to go to fix your oil leak. If you need more help, or a better explanation, I suggest that you start a new topic devoted to your circumstances. The people on this Forum will help you any way that they can. Tom

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