Rear main seal backing out??: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Dec. 5, 2011 7:06 a.m. E_AT_me New Reader

this isn't on a racecar, but all cars have rear mains.. my winter beater i picked up, (2001 Kia Sportage) stop laughing... anyways, like i said, my winter beater i picked up was leaking from the rear main. no biggie. 16 hours later and new rear main installed. it had literally pushed the main seal out against the flex plate. i installed the new one correctly resealing the plate also. it's like a 2.0 miata engine. it's a mazda FE3 engine built in korea. just giving you an idea. anyways, i started it and it ran and didn't leak. hurray. then i drove it around about 5 miles and it's leaking the exact same as it was. i'm assuming rear main has backed out again.. before i pull it apart this time i would like suggestions as to WHY it's backing out? PCV valve "rattles" so i assume it is fine. maybe a clog or pinch in the pcv hose?

pic of seal i pulled out:

1119111718 by fragile_this_side_up_retro_club, on Flickr

old vs. replacment:

1120110731 by fragile_this_side_up_retro_club, on Flickr
Dec. 5, 2011 7:41 a.m. mike Reader

I've had a similar problem, and it was definitely pressure in the crankcase pushing the seal out.
Dec. 5, 2011 8:02 a.m. Don49 Reader

Did you check for end play on the crankshaft? It's possible the crank is pushing the seal out.
Dec. 5, 2011 8:05 a.m. E_AT_me New Reader

i will need to check end play. was thinking about that and hoping not. the truck does have 170k on it. i really don't want to pickup a new engine. :( not quite the cheap winter beater i thought it was..
Dec. 5, 2011 8:59 a.m. 44Dwarf Dork

Is the PCV valve in the valve cover or off the block? Sometime the passages in the head get so choked up with goo theres not enough room for the oil to run back and the blow by to make it up to the valve. Try pushing seal back in (slip two pry bars in from underneath) the running with dip stick not pushed down if this "fix" works then you know you've got a problem. I'd pull the seal clean and loctite it in then cut a sheet metal Keeper tab. Think a large bow tie with hole in center to pass over crank and a ring to go over the seal now on the wing end fold the tips down and bolt in to the oil pan rail. Look at the back side of the block and see if theres any thing to can drill and tap to hold the top side (pipe plugs in oil galleys can be replaced with hex head type instead of allen head type most OEM use drill and tap part of the hex for a 10/32 screw ect)
Dec. 5, 2011 9:09 a.m. E_AT_me New Reader

44Dwarf, thanks for the quick tip. i never even thought to just try to use a pry-bar to push back in. i guess a leak-down test is in order also. the PCV valve is in the valve cover. i guess i'll be pulling that back off and cleaning out that as well. this poor little piece of junk led a terribly maintenance-deprived life before i picked it up for a measily sum of $1200... i'd like to keep the entire project under $2500, which is do-able if i don't have to replace the engine..

and using loctite on the seal? really? i read on a neon board this am, as it seems neons have the same issue, to use red loctite around the outside of the seal to the block area. interesting..
Dec. 5, 2011 10:08 a.m. Streetwiseguy Dork

PCv is blocked, or its freezing up in the cold and pressurising the crankcase.
Dec. 5, 2011 9:55 p.m. NewEdgePerf New Reader

I went through a similar situation with a Dodge 2.2. Service manual called for Green Loctite to be applied to the seal where it was pressed into a seal retainer plate. It also stressed that the Loctite be given sufficient time to "dry or set" before operating the engine.

I hope this helps.

Tony D
Dec. 5, 2011 10:38 p.m. Curmudgeon SuperDork

I think you have too much crankcase pressure too, you need to fix this root cause to keep the problem from returning. Along with checking the PCV, make sure the vapor separator in the valve cover is not clogged with goo. Old carbureted Escorts were famous for that and they'd blow the valve cover gasket out at highway speed.

FWIW, MGB engines have a big retainer designed to hold the rear seal in the rear engine plate similar to what 44 dwarf describes and GM designed a retainer for the 'helix' (torque converter) seal on a bunch of different automatic transmission because on a long highway trip the front pump housing would expand enough for the front seal to blow out. So the mfgs. have run into this as well.
Dec. 6, 2011 2:31 a.m. novaderrik Dork

i just fixed a rear main on a 92 GMC with a 350 that did the same thing.. the truck overheated due to a blown heater hose shortly before ti happened.. my thinking is that the heat cooked the seal that had 170,000 miles on it and it just pushed out..
Dec. 6, 2011 4:40 a.m. E_AT_me New Reader

i'll be able to poke the truck with a stick on saturday. thanks for all the suggestions as i was kind of stumped, and majorly bummed, about it. at least it's parked at a spec miata garage. fun stuff to look at while i'm working on it. :D