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#1776254 - 05/27/09 04:25 PM A sad day: rear main engine seal leak
Seffywuff Offline

Registered: 04/14/08
Posts: 53
Loc: Oklahoma City
I decided to get under my car today and try to find out where my oil leaking was coming from. I only go through about half a quart per oil change, so I was never very concerned. I'm pretty sure it's the rear main seal. It's coming form a small gap from where I believe the engine and transmission meet. It's right above a metal bar who's function I am unaware of, but which goes from left to right across the vehicle, as does the slot where the oil is coming from.

I hear you have to either pull the engine or transmission to get at the rear main, so I think it'd probably be best just to let it leak until I get the transmission rebuilt. It lasted 135 thousand miles, so I guess it's not too bad, though, I don't know exactly how long it's been leaking. Should I bother with any of those seal repair additives, or just let it go?

Thanks for reading.
1987 Grand Marquis 2 door, 110k

Stock 1989 LTD Crown Victoria. 125 thousand miles and counting. - Sold.

#1776278 - 05/27/09 04:42 PM Re: A sad day: rear main engine seal leak [Re: Seffywuff]
JeffBoudah Offline


Registered: 06/05/03
Posts: 9427
Loc: Holland,MI
Check the rear intake manifold lower gasket. This has a tendency to blow out over the years, making it look suspiciously like a rear main leak. Run your hand back along as if you were attempting to change out the PCV valve, and see if the back of the block is covered in oil above the rear main.

1979 LTD 2-Door, 64k miles - Restomod W.I.P.
1979 LTD Wagon, 120k miles - Ratrod W.I.P.
2005 Honda CR-V, 102k miles AWD 5-speed - Daily Driver

#1776348 - 05/27/09 06:05 PM Re: A sad day: rear main engine seal leak [Re: JeffBoudah]
mrltd Offline
Over the Hill

Registered: 01/09/03
Posts: 1359
Loc: MD/OH
more than likely a large part of it is the valve covers and/or intake manifold. Oil leaks are also made worse by non functioning PCV systems. The usual culprit with the PCV is the screen underneath it. (lots of posts on the PCV screen)
Original Member #4 of CVN
15.02@90mph in a 4500lb wagon!!!
1989 Country Squire LX
1990 Country Squire LX
2004 Grand Marquis GS

#1776386 - 05/27/09 07:52 PM Re: A sad day: rear main engine seal leak [Re: mrltd]
TheBlunderbuss Offline
Over the Hill

Registered: 02/24/06
Posts: 1506
Recap the other possibilities: Upper intake manifold gaskets, valve cover gaskets, PCV valve/seating area, or oil pan gasket. Fear not!

Quick rundown of the screen: Often called a "crankcase breather filter," this will run you from $3-7 and could be had at Autozone.
Extraction is easy. It involves a wood screw of at least 6" so you can grip it. You don't need much thread on it. $1 at hardware stores.
One thread is really all you need to screw into the mesh, and the whole thing should slide out.
Install the new one by pushing it in with the PCV grommet.
02/88 LTD Crown Victoria - 860 miles (hehe)
Don't forget that Throttle valve cable clip update!

#1777563 - 05/28/09 10:23 PM Re: A sad day: rear main engine seal leak [Re: TheBlunderbuss]
Unforgiven Offline

Over the Hill

Registered: 01/29/02
Posts: 2128
Loc: West Tennessee
If it is the back of the intake its really not hard at all to fix... As long as you have the tool to disconnect the fuel line... I had mine done in my driveway in an afternoon on my 87.
Former owner of: 1989 LTD Crown Victoria p73, 1989 LTD Crown Victoria p72, 1987 LTD Crown Victoria p72, 1997 Crown Victoria p71

Current ride: 2002 Eddie Bauer Expedition

#1778080 - 05/29/09 01:21 PM Re: A sad day: rear main engine seal leak [Re: Unforgiven]
Dave58 Offline

Registered: 09/08/08
Posts: 37
Loc: Colorado, USA
My '87 CV with 5.0L had the same rear of engine drip. I replaced the valve cover gaskets and now it is perfectly dry.

#1784964 - 06/07/09 10:08 PM Re: A sad day: rear main engine seal leak [Re: Dave58]
BillB Offline

Registered: 10/11/06
Posts: 157
Loc: Revere MA
I agree with others--may not be a big problem.
my 87CV had similar oil leak.
Left side valve cover bolts were so loose did not need a ratchet to tighten--theres one bolt way in back cant see it but its there waiting to be tightened along with the other 4 or 5.

and check the right side vlv. cover too--for both L and R covers, at least two of these bolts are hard to see
87F CV P73
91 Merc GM

#1785247 - 06/08/09 10:34 AM Re: A sad day: rear main engine seal leak [Re: BillB]
Jeff2 Offline
Over the Hill

Registered: 08/11/08
Posts: 4980
Loc: Cincinnati, Ohio
My biggest oil leak turned out to be my oil pressure switch. The switch was cheap, but I had to buy a big socket to replace it and the socket cost more than the switch!
1991 Crown Victoria LX (sold) - Had something like 160k miles on the original 302W and AOD trans. The odometer gears broke at a bit over 100k miles, so miles were calculated by gallons of gas times prior average MPG.

#1787826 - 06/11/09 11:13 AM Re: A sad day: rear main engine seal leak [Re: Jeff2]
88grandmarq Offline

4R70W rebuilder

Registered: 07/10/02
Posts: 6183
Loc: North Georgia
80% of the time engine oil leaks are caused by a clogged PCV screen.

take some engine cleaner, apply it and pressure wash everything as best you can. then replace the PCV valve, grommet and screen.
If your leak continues, you can at least get a better idea where its coming from.

NOT very common for rear main seals to leak on these motors, more likly the valve covers or intake manifold gasket.
2003 Lincoln Town Car Signature - 3.27 RAR, dual exhaust and J-mod - SOLD 09/2011
89 Crown Victoria LX- HPP Box - SOLD 09/2010
88 Grand Marquis LS - The original - Totaled 5/2006

I rebuild AOD/AODE/4R70W/4R75E Transmissions, check out my Facebook page for my latest project;


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