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Rear main seal leak :(

7K views 11 replies 8 participants last post by  champaign777 
#1 ·
Been tracing an oil leak for awhile :( the leak seems to be found between engine and transmission bellhousing. The oil filter gasket has been replace about a year ago and since then hasnt been leaking from there. Oil pan gasket replace under a month ago. Valve cover gasket seems to look dry from behind engine and all areas. My only choice would be rear main seal. Anyone have a DIY info on the rear main seal thanx. By the way i have a 2002 BMW 530i with 178k


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#3 ·
The rear passenger-side corner of the valve cover gasket can leak down the edge of the engine right along the seam between the block and the trans bell housing and end up dripping right at the bottom, resulting in what would look like a rear main seal leak.

Be very sure that you have a RMS leak before you get into it, because (re-) fixing the VCG is a whole lot easier and cheaper. I'd take the top cover off and look at the inner bolts of the VC to make sure they aren't leaking anything.
 
#4 ·
Stretch yourself out and place your hand on the back of the engine block below the valve cover gasket between the block and the firewall. Please do this on a cool engine. More than likely your hand will come back with some oil on it verifying your valve cover gasket is leaking. I just replaced mine on my 2002 530i that has 73,000 miles. The gasket was bad. I'd bet one year of Aaron Rodger's salary that your valve cover gasket is bad also, especially with the miles you have.
 
#6 ·
No leaks were found on the VCG or OFG nor the oil pan gasket. My last thought would be is the rear main seal :( at this point the leak isnt that bad yet but i well consider doing the rear main seal when the leak gets worst. Is there a link where i can find a diy or a step by step on what is involve.


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#7 ·
Check your crankcase vacuum. High crankcase pressure can push oil past seals. With engine idling, remove dipstick, put clear tubing 5/8 or 3/4" dia from Home Depot over dipstick tube, put other end of tube in a glass of water. Measure how high water is drawn up into tubing. Measure from surface of water in glass to water level in tubing. Should be 4-6".
 
#10 ·
Check your crankcase vacuum.
High crankcase pressure can push oil past seals.
With engine idling, remove dipstick, put clear tubing 5/8 or 3/4" dia from Home Depot over dipstick tube, put other end of tube in a glass of water.
Measure how high water is drawn up into tubing.
Measure from surface of water in glass to water level in tubing.
Should be 4-6".
+1...!
Homemade Manometer...!
:D
Typically, a bad CCV will cause reverse pressure towards the crankcase, and blow the oil filter housing gasket, valve cover gasket, oil pan gasket, and rear main seal.
Ask me how I know...
:(
 
#8 ·
For minor leak, a trick is to place a small piece of cardboard about 2 feet x 2 feet on the garage floor.
Place a few small rocks to keep the cardboard from flying around.
This way your garage floor is not stained.

RMS is never fun because the trans has to be dropped.
Don't ever use "Stop Leak" snake oil!
 
#9 ·
I was in the same boat tracing a leak for years with no luck. I replaced so many of the noted things including my rear main seal and still drips in the driveway. Finally When my timing guides shattered and i fixed those i chose to buy a new timing chain cover and boom zero leaks. Just another item to check on your list:thumbup: Good luck!
 
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