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MG MGB GT V8 Factory Originals Technical - Rear Main/Oil Pan Leak
|I have been running my Rover 3.5 conversion for about a month now and I have noticed an oil leak right at the back of the oil pan. It is hard to tell if it is the rear main rope seal or the oil pan itself. The oil is running down the face of the tranny/flywheel plate and the flywheel is oil free on the engine side. The original oil pan seal I used didn't fit quite right, if I lined up all the holes on the side and front of the oil pan the back 4 holes weren't quite lined up. Inspecting the gasket I could see on the back of the gasket where it looked as if it had been leaking. So I have replaced it but the same problem occurred (I suspect I have sold a Buick 215 oil pan gaskets), this time I siliconed both sides of the gasket but I could see where the corners of the gasket split because of the bad fit. I think there should have been enough silicone to seal any leaks but it is again leaking. I can see the oil leaking down the front face of the tranny plate. After replacing the gasket there were no leaks for a period of time and then it started to leak again. It got worse at higher RPM. I guess my question is 'how do I tell for sure if the oil pan gasket of the rear seal is leaking|
I can't suggest how to tell where your leak originates, but there is a difference between Rover & Buick pan gaskets. The spacing of the holes at the rear corners is different.
|If the oil is up on the tranny/flywheel plate, that'd suggest it isn't the sump, no? |
BTW, modern Rover practice is to do away with the paper gasket and just use Permatex. In fact the only Rover V8 that came with the paper gasket was the 3.5. I feel for you either way as I just re-did the sump a while ago and when you just have block-hugger headers, etc. as I do and the sump is right on top of the steering rack, just about everything needs to be taken apart first, yuck.
Unfortunately your P6B engine doesnt exactly have state of the art oil seals. Too late now but when you had the engine down for overhaul you could/should have modified it to accept lip seals at both ends of the crankshaft.
The oil leak is most likely from the rope seal although the sump/oil pan gasket has to be suspect from your description.
It got worse at higher RPM Im suspicious of the breathing, are you sure there is not excessive crankcase pressure? This oil leak and the valve stem/guide seal problem that you have could have a common cause. Air needs to get in to the crankcase and fumes need to escape, usually air will enter the rear of one valve cover and vent from the front of the opposite cover through a flame trap to down stream of the air filter. The P6B probably had a vented oil filler cap for the air inlet.
Remove the oil filler cap and run the engine, do you get pressure or suction?
|It was a little hard to tell if there was suction or not. I removed the oil filler cap and I thought I felt a little suction, then several seconds later I saw oil vapors rising out of the oil filler hole. Since then I have removed and flushed out the flame traps and blown air easily through them. I have replaced the oil pan gasket and the leak seems to have stopped but that has only been at @1500RPM. |
I have 2 flame traps, one on each rocker cover (5/8 pipe dia) and then there is of course the small (pipe) outlet at the back of the engine which is a direct line to the lifter gallery, that hose I have taken to the recycle canister.
Another side note, after replacing the oil pan gasket the first time the leak got worse, so although I didn't fix it, I at least affected it, this is why I feel it is the oil pan gasket. I have purchased a couple of gaskets now and noticed that the gaskets don't line up for the back 2 corner bolt holes? This time I siliconed the gasket to the pan and place some weigh on it until it cured and then cut out the gasket which covered the back 2 bolt holes, placing silicon around these holes I then bolted the oil pan back on.
I have now run the car for a bit, the leak is still there. I had the rear end blocked up about 2' in the air and the front as low as the wheels will let it in the assumption that if it was the rear seal then it wouldn't leak jacked up like that, it still leaked. I still am not really sure it is the rear main. I am now going to cut a new oil pan gasket (one that will fit properly in the back corners) and hope that it will cure the problem.
I chased a similar leak for over a year in my 1963 buick skylark, it turned out to be a convination of 3 problems 1st. the cam plug in the back and top of the block somehow had come loose, 2nd. the valley gasket did not have the rubber seal underneat it and the clamp also was missing, 3rd the rope seal itself was bad, i had replaced those three items plus a new pcv valve, the oil filler cap whith a clean breader, etc
i still have a leak but not as before now it is only the size of a dime over night, before it was the size of a small lake after a short drive. I also have a leak comming from somewhere under the distributor.I hope i helped some.
|I have cut my own gasket and the oil pan is silconed in place. |
For those pf you interested, this time when the pan was off I replaced the rope seal with a neopream one. Actually a very easy job. It just slid in. The old rope seal didn't even have any oil on it, so the oil is definitely not get past it then, or now.
I have noticed upon start up that my oil pressure goes right up to 100, so I will replace the spring in the oil pump and then start it up. I will be keeping my fingers crossed.
|Romney and all|
I have now replaced the oil pan gasket for the forth time. This time I used a straight edge and a hammer to get the oil pan edges straight from side to side and end to end, I have replaced the rear main with a noepream gasket, siliconed it as suggested, the flame traps have been tested and breath nicely, the oil pump pressure relief spring has been replaced with a lower one and the leak is still there. I am now wonder if Romney is right about perhaps the rear cam seal leaking? I suppose the only way to tell is to pull the engine. Any thoughts on this before I do it. Is there any where else it could be leaking from? Is there any place else it could be leaking from behind the flywheel?
|Bruce, when i pulled my engine out (last summer) it was because i wanted to replace thet rope seal, iy was the only way i knew how, but, once the engine was out i replaced all seals. I should tell you that the engine had a fresh rebuild, and in order to get the cam plug out some stupid idiot had pry it off with an screw driver damaging the bore of the surface where the plug seals, therefore the big oil leak. The way i fixed this was using cold weld filling all the screw driver damage and setting a new plug before the weld had a chance to harden, this way sealing it for good. By the way you can get this plug at NAPA for 0.84 cents, dont pay D and D fabrications price of $ 4.50 + shipping. Beside the cam plug there isn't anything else back there where the oil could be leaking except the rear main seal and you already had replaced that.|
I assume you are not using a modern oil, prob unlikely as still running in.
I replaced my sump flange gasket recently in an attempt to fix a very similar sounding leak. No luck! So now I need to replace my rear main seal (it's a Rover P6 - with the rope seal). You say you managed to replace yours with the engine in the car?
How do you do this? I thought you had to take the crank out?
|I took off the rear main bearing and slid in the new neoprene seal. It was that easy. I did have to push in the top seal a little firmly but it went it surprisingly easily. I bought the seal from D & D and the instructions said to use a thin coast of silicone.|
I currently using 30w but previously was using 20-50
I pulled the engine yesterday and the cam plug is slightly cocked and there was a pool of oil on it so I will replace it, I sure hope that is the problem.
|Bruce, you work fast. when you replace the plug use permatex to seal it, this is great stuff is used in aviation, the dimention of this plug is 1 51/64" and you should be able to read it normaly, imagine a bowl of soup if you will, the surface in contact with tha table goes toward the cam, the cavity where the soup is, goes towads you.|
I hope this cures it, I hate leaks.
I have just "sussed" a simular leak on my engine, it turned out that my leak was coming from the crank case breather, did not start to leak untill about 1500rpm, it was weeping from the interferance fit where it fits in the block and was running down making me think it was the sump [oil pan] gasket. I needed one of those small angled mirrors to find it.
Hope this helps, Graham.
I too noticed that and I have used locktite on it. It appears that the cause of my oil leak is the rear cam seal. Upon removing the tranny I notice a small pool of oil on the seal and could actually trace the path of the oil. The seal was cocked. I am not sure if it was installed cocked or if the cam pushed it out. The obvious answer is to replace the seal and not drive it in as far so the can can't contact it.
Thanks for the info. Probably would have had the engine back in but today is a Canadian holiday, will have to try the local parts people tomorrow and see if I can get one. Do you know if the Buick one would fit a Rover 3.5?
|Hi Bruce, yes the pug is the same, as I said the dimention is 1 inch 51/64th. and it is stamped in the dished part of it, NAPA will have it, but, it will be steel not Alumininum i don't have the part number. just ask for a cam plug for a 215 v8 Buick special '61 to '63. for some reason they only list the specials and not the Skylark. if you can't find it let me know I will get the part number. |
|Finally found a new can plug in the small town where I live and got it installed. Lifter the engine on a severe angle to get it into the engine bay and oil started to pour out. Cut back the excess oil pan gasket and saw oil leaking from the oil pan gasket. Although all this work has probably not been in vain, I had to think that for a moment. Banged the bolt holes back into position and placed a new gasket. Tomorrow will smear the gasket - block part of the gasket with silicon and let set for a awhile and re-install. Hope it works.|
|Well the engine is back in and I started it up, it ran about 18 min with only a couple of drips of oil (I pulled the engine and replaced the rear cam seal in my Rover 3.5). After I shut it down I then looked under the car and there is a small lake, upon starting the car up again it is leaking 1 drop every second. The oil pan seems tight and the leak is now running down the back of the tranny plate which covers the flywheel, thinking that the new cam seal is ok (pit in as per Grahams instructions) and the pan is now ok. All that is left is the rear main bearing which I replaced with a neoprene one from D & D. I was told it wouldn't be easy to do in the car but I pulled the rear main bearing, pulled out the rope seal and the new neoprene one fitted in no problem. Siliconed it up as recommended and bolted it back up to specs. |
My thought now is that there is a problem with the rear main? I might be able to get the Buick one here in the small town where I live. Will it fit? Is there an over size one I can get?
The weather here is gorgeous but there she sits, leaking too much oil to drive her. Any input would be greatly appreciated.
|Well I have fixed the leak, finally. Apparently I probably didn't need to replace the rear main or the cam plug at all. But once I had replaced the oil pan so many times and no luck I replaced the rear main. That didn't work so replaced the cam plug and that still didn't work. The long and sort of it was that I had placed the bottom rear main seal in backward. DHHHH. Live and learn.|
Thanks all for all your help.
This thread was discussed between 20/06/2001 and 05/07/2001
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