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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: thrival on May 20, 2007, 08:18:40 pm
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Hi, I love my 85 chevy C-20 truck, rust-bucket that it is. A few weeks
ago the oil light went on, I checked the dip-stick to find it dry! Since
then, after changing filter and adding a few quarts, have noticed there
are stains on the ground at the back of the motor which I take to be a
leaky rear seal (checked valve covers and intake manifold, seems to be
coming from somewhere lower.)
Anyway, my question concerns the rear seal. Is it single or two piece?
Must I remove the entire tranny/bell-housing or can I get away just
dropping the oil pan? Again this is an 85, V6 4.3L motor. Thanks.
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Take a look at the flexplate... see if it is counterweighted.
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Of course this is going to sound ignorant, but what is the flexplate?
If I recall, that's part of the clutch assembly. I haven't taken off
the bell-housing and tranny and hope I don't have to. Anyway would
counter-weights on the flexplate have to do with rear seals, and why
would their presence or absence indicate whether I have a one or two-
piece seal on my motor? Thanks.
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a flexplate is on automatic trannys. YOu must have a manual trans.
If it is an 85, i think you have a two piece. Is the oil dipstick on drivers's side under the master cylinder? i think they went to one piece in 86.
Changing the rear main is not that difficult. I would drain the oil atleast a few hours before dropping the pan due to drops of oil conitnuously dropping on you from the crankshaft once the pan is off.
You will have to remove the rear main cap and the bottom half should be in the cap itself, the tricky part is removing the top half which is inside the block...you will have to push it on one side and with pliers, pull it out the other side....very carefully as to not touch a metal tool onto the crank shaft or you will have a scratch on the crank and you will always be dripping oil.
Same thing putting the new one back in....coat it with oil and do not touch the crank with a metal tool. it should just slide in place with your fingers pushing in on it....do not push it flush with the bottom of the block...kind of off-center it so one side is a little lower than the block surface. Then when putting the bottom half in the bearing cap, pull one side up a little. Remember, coat the seal with oil or it will burn when first starting the engine up. The "V" gap on the seal must face the front of the engine.
Ensure you torque the bearing caps correctly. If you have four bolt mains, the outer is a little different torque specs than the center. I forget what the specs are, but chiltons manual will set you straight.
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when u go to put it back together it will be alot easier with the oil pan gasket if you put fishiing string throught the wholes when u put it up because other wise it wil slide around and be a PITA
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SgtDel: Thank you very much for the specifics. Yes mine is a manual shift, the dip-stick
is on the LEFT side, standing in and facing the front of the vehicle with the hood up.
The local dealer also said the seal is two-piece ($38.00-- yikes!) ...but I just wanted to
be sure with you guys. Very much a pain to start work and discover otherwise, since I'll
probably be doing it on the street.
75 C20-- How do you mean I should use the string? I guess I'm not quite clear what you
mean.
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The best way to prevent your oil pan from leaking and the gaskets from becoming misaligned when reinstalling the oil pan is to clean the block surfaces, rear cap (especially where the tabs of the rear seal sit) and the timing cover. Use 3M weatherstripping adhesive (yellow) and glue the end seals into place. Run a small bead of the adhesive on the rail gaskets and install them with bolts lightly and allow the adhesive to dry and the gaskets will be held in place. Take some RTV (use "the right stuff" in the easy cheese can - I don't use anything else anymore) and place a thin bead across the two rubber seal and over the corners where the seals and gaskets intersect. Install all the bolts then tighten them criss cross and torque to specs. Wipe any excess RTV for a neater appearance and your pan will never leak.
As far as the rear main seal is concerned when you install it, misalign the seal with the cap slightly and you will not have that seepage problem either.
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VileZ: Thanks for those suggestions!
One last question (well, actually two.) Assuming my '85 V6 DOES have a two-piece
seal, might we assume it's the same as the V8 "mouse-motor" that the V6 is just a
shortened version of? (Same main-bearings, etc.) Point being, isn't $38.00 just a
bit high for a piece of rubber? Would the V8 seal be cheaper (i.e. more common
motor.) Does anyone know a supplier who might be cheaper than my local dealer?
Also trying to fix the problem before posting, I added some rubber swelling agent,
supposed to restore leaky seals. Well it didn't work. But my concern is that it's in
the oil now, and even letting it all drain out, concerned that any residues on upper
surfaces could cause the new seal to swell before it's fully installed.
Well I like to talk a thing to death before going to work, to be certain I don't miss
anything. Thanks again.
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I would get the part that is designed for your specific motor. It is a lot of workto replace this thing and I would not take any chances.
Dont worry this thing to death, just do it. If you have a lot of miles on your engine, you may consider replacing the oil pump too, since you have to remove it to get to your mains.
If you want to see if the seal number is the same V8 vs. V6, just go to autozone.com or advanceauto website or something to plug in the different engines and see if it is the same part number.
I concur about the oil pan gasket....it is tricky sometimes lining up the holes and then trying to put the bolts through, all while laying on your back. I used the fishing string in the past. Just tie fishing line around four bolt holes to hold your gasket onto the pan. Then, once bolted in place, i like to take a knife and cut the line out. Then put those last four bolts in place where the line was. I use a one piece gasket, so i dont have to worry about the end rubber pieces.
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Haven't you guys heard of gasket glue by Emersons?
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3M yellow snot (weather stripping adhesive) is the best gasket adhesive I've ever used. It dries fast, it's cheap and a tube lasts a long time.
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SgtDel:
You mention using a one-piece gasket and yet that's not what the parts store wants to sell
me for my model/year ('85) which is two pieces of cork with rubber pieces (total of 4.) Are you
saying that later model/year one-piece gaskets will fit my oil pan? Note I looked up the part#
for one-piece gasket and found: GMC 10220906 GASKET. 4.3 GM 97-98 available at:
http://cgi.ebay.com/ebaymotors/NEW-GM-OIL-PAN-GASKET-
FITS-4-3L-ENGINES_W0QQitemZ250116035069QQcmdZViewItem
...and
http://www.southeast-service.com/parts/parts.php
I guess I just want to be sure it will fit since it was obviously made for different year vehicles.
Thanks in advance, --thrival
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http://cgi.ebay.com/ebaymotors/SBC-CHEVY-Reusable-Oil-Pan-Gasket-305-350-383-400_W0QQcmdZViewItemQQcategoryZ33669QQihZ020QQitemZ300114375418QQrdZ1QQsspagenameZWDVW
One piece gaskets are awesome. I have one on my 79, should be same as 85
http://cgi.ebay.com/ebaymotors/SBC-CHEVY-Reusable-Oil-Pan-Gasket-305-350-383-400_W0QQcmdZViewItemQQcategoryZ33669QQihZ020QQitemZ300114375418QQrdZ1QQsspagenameZWDVW (http://cgi.ebay.com/ebaymotors/SBC-CHEVY-Reusable-Oil-Pan-Gasket-305-350-383-400_W0QQcmdZViewItemQQcategoryZ33669QQihZ020QQitemZ300114375418QQrdZ1QQsspagenameZWDVW)
http://cgi.ebay.com/ebaymotors/Fel-Pro-1-Piece-Oil-Pan-Gasket-sb-sbc-Chevy-350-383-400_W0QQcmdZViewItemQQcategoryZ33669QQihZ008QQitemZ180114399796QQrdZ1QQsspagenameZWD1V (http://cgi.ebay.com/ebaymotors/Fel-Pro-1-Piece-Oil-Pan-Gasket-sb-sbc-Chevy-350-383-400_W0QQcmdZViewItemQQcategoryZ33669QQihZ008QQitemZ180114399796QQrdZ1QQsspagenameZWD1V)
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OK, that's great, but again mine is a 4.3L V6. Are you saying
the lower block / oil pan / holes are the same? Parts store
says mine has the two-piece rear main seal. Thanks!
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The 350 and 4.3L are not the same oil pan gasket but the rear main seal should be the same. However it isn't listed any cheaper for the 5.7L and it's not a dealer item. In fact I believe Fel pro makes a double lip seal and an offset lip seal if the crank is scored and you think it might not seal well.
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I just looked it up on autozone.com $8.99
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VileZambonie:
Thanks for clearing things up about the gasket; so now I know
NOT to order a one-piece gasket from ebay because the one
mentioned will NOT FIT the 4.3L motor / oil pan (wish there
was one that did, though.) Also the tip about the double and
offset lip seal is good to know. Autozone has quite a selection f
or my model/year and I didn't know which to pick; now you
explained why.
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Dear SgtDel / VileZambonie
OK the ebay seller said if I've the two-piece rear seal, the one piece gasket
SHOULD fit the 4.3L (but maybe he doesn't really know) and yet you say they
are different / not a dealer item. So I guess I want to be 100% sure if it will
or won't fit. Do either of you know for certain? Sorry to be such a pain about it.
I'd like to go with a one-piece oil pan gasket, no goop, if that's possible.
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The 4.3L is a V6 the 5.7L is a V8 so the pan is going to be longer on the V8. Use the method I described and you'll see there is no problem putting on the standard oil pan gasket. Just glue all the seals correctly in place. Run a small bead of the right stuff across the end seals over lapping onto the side rail gaskets. Install ALL the bolts and then tighten them criss cross to specs and you'll have no leaks.
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OK, Thank you again! You guys are great!
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Gents:
Has been a while, back again to report my progress (or lack thereof.)
Have had my oil pan off more times than I care to tell, after changing the
rear seal, and still leaks at the dip there, between the pan and bell housing.
Yes, I'm sure the seal lip is pointed in the right direction, installed it slightly
offset and joined the ends with silicone.
Used the 3M weatherstrip adhesive (great stuff) on all bolt holes and none
of them leak. I did NOT use any adhesive where the rubber pan seal joins
the flanges, maybe that was my mistake, but I didn't want to make it too
difficult to remove just in case I needed to do it again! Two questions tho:
Even IF the rear main seal leaks, shouldn't the oil pan contain it?
What IS the recommended torque? Somewhere I read 12 ft.lbs. while my
book says 80 to 165 ft.lbs(!) My experience is that the higher torques
totally destroy cork gaskets so they leak. This time I only tightened as
snug with one hand, and leak-tight all but the place mentioned. I know I
need to do it again, but I hope it's the last time.
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DO NOT put any sealant on the rear main seal. Just lubricate it well. in the corners of the rear main bearing cap you can put a teeny weeny itty bitty dab. Torque the rear main bearing cap to 80 lb-ft (on 4 bolt mains the outters are 70). If you do use a little dab of rtv under the cap use a pocket screwdriver to completely scrape out any excess. Install the oil pump and driveshaft. You should upgrade to a steel sleeve shaft. Torque it to 65 lb-ft. No gasket or sealant there either. Using the yellow snot glue the pan rail gaskets into place and use a few bolts to hold them there while the adhesive dries. Glue in the end seals making sure the tangs are fully seated and they are installed properly. Put RTV (the right stuff is the best) across the rubber end seals overlapping onto the pan gaskets. Install the pan and all of the bolts just to get them started. Once ALL the bolts are in start snugging them down with your 1/4" drive ratchet so you don't overtighten them. Torque the 1/4-20 bolts to 80 lb-INCH (not lb ft) and tighten the 5/16 bolts to 165 lb-INCH. Double check all your bolts again and wipe off any excess RTV. IT won't leak this time especially now that you're a pro at it :P
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Dear VileZ:
Thanks for clarifying what you have.
Q: So are you suggesting a person, by possibly using too much RTV on the seal itself,
could prevent the bearing cap from seating properly, thereby the seal leaking? I don't
THINK I made a mistake here, and DID torque the bolts to the rates you said.
More likely, my omitting RTV across the rubber end seals is the cause of leak. Wouldn't a leaky
rear seal still be captured/covered by the pan itself? (Engineers could have made things easy.)
Reason I ask is really don't want to remove the bearing cap and do the seal over, if I can just
remove the pan again, apply goop to the pan end seals and bolts, call it done. Thanks again.
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Don't use RTV on the rear main seal.
The rear main seal is designed to prevent leakage around the rear of the crankshaft. It's not insed the oil pan. If oil leaks past the seal it will exit rearward of the crankshaft and end up running down the back of the engine.
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My pan is off (again) as I write this, 3M adhesive drying in the summer sun.
I noticed the leak was coming from the rubber oil pan end-seal next to the
bell-housing, specifically leaking THROUGH the weatherstripping adhesive. This
time I built up several layers and allowed to dry a goodly while before bringing
the parts together. The tube says oil-resistant but what was inside the pan last
time does peel away pretty easy. I'll let it dry overnight before adding the oil
back in.
I noticed the rear rubber oil pan end seals DO join ahead of the rear seal, so
technically (at least in the '85 V6), a leaky rear engine (crank) seal shouldn't
even be noticed; it SHOULD dump into the oil pan. At least I can see now that
changing the engine/crank rear seal a third time won't be necessary and probably
wouldn't help much.
I think it's the leaky rubber oil pan end seal that lets it escape. I'll use the
"Right Stuff" over the cork tangs and rubber seal per your suggestion. I didn't
know a sealer was needed there and probably (another reason) why it leaked
on that end.
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UPDATE:
I checked my work today after driving about 10 miles, end results being, still leaks;
not a lot but as much as ever (half a shot to a shotglass ful per night.)
I still can't see exactly where the leak is between the pan and bell housing but assume
the oil is pushing through the 3M adhesive holding oil pan rubber end seals in place. The
rear one is obscured by the clutch shroud but the front one is wet. (Note I did use a
generous bead of "The Right Stuff" over the cork tabs and rubber end seal surfaces this
time so presume that's not the problem. Therefore to solve my problem is I believe I must
find an adhesive/sealant that adheres strongly to metal AND the silicone end seals. Oil
"resistance" means nothing, it must be oil IMPERVIOUS.
I've been on this forum too long, asking for help on this one issue, and yet I still need it.
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the rear main seal does NOT leak into the oil pan if it leaks. It leaks behind the crankshaft and down around the back of the engine. If you are sure your oil pan seals are seated correctly and flush and you installed everything correctly torqued to specs yet it still leaks then get a new oil pan.
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I am no 4.3 expert, but I agree with Vile on this one. Rear main seal will leak on the exterior of an engine. I would look at that rear main again. Did you coat it with oil before sliding it in place and bolting the cap back on? If you don't it will burn from friction on first start up and leak. Did you put the "V" facing front of engine? Hopefully you didn't touch the new seal with anything metalic, like a screwdriver to push it up. The slightest nick will cause you to invest in an oil company.
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SgtDel & VileZ:
Thank you for getting back to me.
It's always possible I made a mistake replacing the rear main crank seal, but I don't think
I did; (changed it twice.) Anyway the rear seal is under the rear main bearing cap, which is
under the oil pump, which is all confined inside the oil pan. The oil pan / end seals enclose
everything. So even if the rear engine seal were leaking, it must leak past / through the oil
pan end seal to be visible. It would have to leak through / between the end seal and the 3M
adhesive and / or "Right Stuff" goop. I'm not sure a new oil pan would help because i don't
understand how the original could fail. I didn't hit anything. It just started leaking out of the
blue. I think I need to find a sealant to attach the end seals that's absolutely impervious to
oil and won't let it out. The 3M adhesive is good for attachment purposes but it's not impervious.
I can't speak for the "Right Stuff" material but I'll know how easily it peels away when I remove
the pan again (like the 8th or 9th time.)
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The crankshaft sticks out of the engine block. The rear main seal's job is to keep oil inside the crankcase. If it leaks past the seal it will exit right where the crankshaft exits the engine block. If it is your rear main seal leaking after you replaced it then make sure you don't have excessive crankcase pressure. Are you sure it isn't leaking from somewhere else up above? Like the intake manifold or oil pressure sender and just running down the back of the engine? Is it wet above the oil pan area?
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Hi VZ;
Missed your message, haven't checked this board for a while.
As a matter of fact I do have oil dripping off the starter bolts,
and the support rods holding the tranny up. Most is dripping off the
pan near the rear seal / bell housing but maybe because that's the
lowest point on the engine. If I feel up near the dip at the front of
the oil pan, it's wet, and the puddle on the cement is at the rear of
the pan.
I can't really see or tell where it's coming from, just too hard to see
up there. I redid the intake manifold early this spring and the silicone
seems to be holding. The valve covers seem tight, no leaks or wet
spots around them. Could the head have separated? Cracked block? How does
a person find an oil leak???
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Lay the pan upside down on a truly flat surface and see if there are any dimples at the bolt holes. Fix those as needed. Now, did you apply sealant to the rubber strips that fit into the timing cover and rear main cap? If so, did you remove all of the old rap first and rinse/scrub the surfaces with acetone or prep-all? Check the back of the intake manifold for oil as well as the back of the valve covers. If you happen to have a one piece rear main seal on you engine, then you may want to consider a rear main seal sleeve.
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Definately check the back of you intake. If the leak started after you installed the intake, this would be the logical source.
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pick up some oil dye tracer and pour it in the engine. You can get a small UV light for a couple bucks or one of those ones that Napa sells with the pen. You can't miss it that way.
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Actually the leak started BEFORE I did the manifold which WAS loose
but seemed to've fixed it. Then started leaking at the bell-housing
(seems to be running down inside the gravel-shield front of the bell-housing)
which is why I thought it might be the rear seal; but have since
determined that the rear seal is inside of and behind the oil pan seals.
Changed the rear seal twice, don't think that's it.
The last attempt I used blue silicone as a sealer and allowed to dry 24
hours before driving, by the advice of a local mechanic. The end seals are
wet so I need to do something else.
I've tried a lot of things to date for sealers. The 3M weatherstriping is
a good adhesive but leaks when exposed to hot oil. This next time I might
just crazy glue the end rubbers down and fill the gap inside and out with
the Right-Stuff. Cork gaskets are NOT the problem, a little of the Right-Stuff
on bolts prevents leaks there.
UV blue dye; that's a great idea, I'll try it! thanks!