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Old 03-30-2022, 01:03 PM
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Default Common Leak Points?

Frustratingly I am still fighting a fairly substantial oil leak at the back of the engine after resealing the top end last year.

After 2-3 days there will be a puddle of oil about the size of a Folgers can directly below the rear of the engine at the crank housing.

While I was having some transmission work done last year I had the techs check to see if the rear main was leaking. I was advised that it was dry. However, oil pools on to the starter and flows to the bottom of the crank housing, between the block and torque converter where it drips.

I've tried a fluorescent oil dye, but have not been able to verify where the oil is coming from visually. The top of the block around the distributor housing is dry to the touch, so I know I'm not weeping oil out of the distributor housing or from the back of the valley pan.

I do have a known oil leak at the fuel pump block-off. I believe I need to seal the threads on that. I've not been able to see that leak flowing rearward to the back of the engine however.

At this point I'm looking for any ideas, but I think I'm going to end up having to deal with it for this driving season, then yank the engine in the fall for a complete refresh if I can't find the source of this thing.

Thanks in advance!

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Old 03-30-2022, 01:27 PM
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cam plug? oil galley plug?

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Old 03-30-2022, 01:32 PM
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My moneys on the rear pan seal, or the rear main seal

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Old 03-30-2022, 02:00 PM
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Did you feel the back of the heads for oil? I had a valve cover leaking on the back of the drivers side. It coated the starter with oil and the rear of the pan.

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Old 03-30-2022, 02:09 PM
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I will check there this evening. I'm running Butler's fabbed valve covers with Edelbrock's steel core reusable gaskets. Those are new as of a year ago.

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Old 03-30-2022, 03:42 PM
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If oil is pooling onto the armature section of the starter, or if the top of the stater solenoid is getting wet I would have to conclude that it’s not a leak source from within the bell housing.
I would say it’s a valve cover leak from at the rear of that drivers side head.

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Old 03-30-2022, 04:26 PM
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what year oil pan? if its the older ones with the 3 holes in the rear U section they are known to leak there due to the rubber U seal, it can roll or get squished out of place & cause a leak that will look like a rear main leak. inspect that area real good after wiping it dry with a good solvent or brake cleaner. it could be leaking anywhere in the U area & where the ends meet the side rail gaskets.

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Old 03-30-2022, 04:31 PM
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Smoke it, you can even make your own smoker pretty cheap. All good shops will smoke the rebuilds so they don't get come backs. Not new or high tech engineering here, but WILL find your leak.

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Old 03-30-2022, 04:58 PM
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Quote:
Originally Posted by 78w72 View Post
what year oil pan? if its the older ones with the 3 holes in the rear U section they are known to leak there due to the rubber U seal, it can roll or get squished out of place & cause a leak that will look like a rear main leak. inspect that area real good after wiping it dry with a good solvent or brake cleaner. it could be leaking anywhere in the U area & where the ends meet the side rail gaskets.
The engine is a 73 455. Pan appears to be a factory pan.

Are you talking about what's pictured here?

This is precisely where my drip is coming from.

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Old 03-30-2022, 05:06 PM
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Quote:
Originally Posted by 25stevem View Post
If oil is pooling onto the armature section of the starter, or if the top of the stater solenoid is getting wet I would have to conclude that it’s not a leak source from within the bell housing.
I would say it’s a valve cover leak from at the rear of that drivers side head.
Quote:
Originally Posted by Formulabruce View Post
Smoke it, you can even make your own smoker pretty cheap. All good shops will smoke the rebuilds so they don't get come backs. Not new or high tech engineering here, but WILL find your leak.
Quote:
Originally Posted by Gary H View Post
My moneys on the rear pan seal, or the rear main seal
Thanks for the suggestions. Looking like rear pan seal based off of 78w72's post. I just put my hand on the back of the head as well and it's a bit moist. Nothing that would be causing the oil slick that I currently get, but definitely what is coating my starter.

I'm wondering if I can clean that area of the rear pan up and RTV it. Anyone have success with sealing that up with the engine in the car?

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Old 03-30-2022, 05:24 PM
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Try an aerosol can of Right Stuff. Clean the area in the gap with brake clean and compressed air, then fill with right stuff. I have done a few hack jobs similar to this and it might just get you by until the next time you have the pan off.

Sent from my SM-G965U using Tapatalk

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Old 03-30-2022, 05:25 PM
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Yes I have done such on a neighbor’s Buick, but with the conveter backed off and the flex plate off for good access.
A sprayed down that whole area with carb cleaner and also right into the pan to main cap gap , let that all evaporate off for 2 hours and then layed on blue gasket maker and packed it in.

Then let that all set up for 2 full days due to no motor heat.
Last step was touching up the paint due to the carb cleaner removing it.

Just to reiterate, the key here is good access and total oil film removal!

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Old 03-30-2022, 05:26 PM
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Originally Posted by leeklm View Post
Try an aerosol can of Right Stuff. Clean the area in the gap with brake clean and compressed air, then fill with right stuff. I have done a few hack jobs similar to this and it might just get you by until the next time you have the pan off.

Sent from my SM-G965U using Tapatalk
Thanks for the advice. The engine is due for a refresh at minimum. If I can make it through the summer and early fall, I'd be able to pull the engine and have it gone through over the winter.

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Old 03-30-2022, 05:26 PM
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Quote:
Originally Posted by JLMounce View Post
The engine is a 73 455. Pan appears to be a factory pan.

Are you talking about what's pictured here?
This is precisely where my drip is coming from.
yes, thats the 3 hole pan.. very easy to roll the thin bead in the rubber seal & even if it doesnt roll or move its a weak seal. what rear main seal do you have, if its the BOP & your engine builder is familiar with installing them & knows to check the crank surface, chances are its not the source of the leak.

i just went through this with a milodon 7qt pan that uses that same seal, didnt leak quite as bad as yours but i thought it was a rear main. after replacing the the pan gasket & rear main (BOP) it still leaked, after talking with a couple pontiac guys, the fix was to use the 1/4" thick cork gasket in place of the rubber U seal with a good gasket sealer/RTV. been 6+ years on a 500+hp stroker motor & its still dry.

i'd start there if you confirm no other source up higher that could cause that big of a puddle. sounds like you verified it was coming directly from that area, after wiping it dry & running for a few minutes then let sit overnight, you should be able to see fresh oil, if its dry above that U seal its not from higher up on the block. also be sure you have the metal load spreaders for the corner pan bolts. another gasket option is the one piece BOP that gets great reviews.

good luck finding the leak, i hated dealing with mine for a couple weaks... i pulled the engine each time to replace the pan gasket, but when its that fresh of an install, it came out quick & easy.

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Old 03-30-2022, 05:30 PM
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Quote:
Originally Posted by 25stevem View Post
Yes I have done such on a neighbor’s Buick, but with the conveter backed off and the flex plate off for good access.
A sprayed down that whole area with carb cleaner and also right into the pan to main cap gap , let that all evaporate off for 2 hours and then layed on blue gasket maker and packed it in.

Then let that all set up for 2 full days due to no motor heat.
Last step was touching up the paint due to the carb cleaner removing it.

Just to reiterate, the key here is good access and total oil film removal!
Excellent suggestions as well, thanks.

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  #16  
Old 03-30-2022, 05:37 PM
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Your oil pan does not seem to follow the rear main cap at 2:00 and 10:00 very well.
A thick cork gasket sometimes does a much better job.

Tom V.

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Old 03-30-2022, 05:47 PM
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Quote:
Originally Posted by 78w72 View Post
yes, thats the 3 hole pan.. very easy to roll the thin bead in the rubber seal & even if it doesnt roll or move its a weak seal. what rear main seal do you have, if its the BOP & your engine builder is familiar with installing them & knows to check the crank surface, chances are its not the source of the leak.

i just went through this with a milodon 7qt pan that uses that same seal, didnt leak quite as bad as yours but i thought it was a rear main. after replacing the the pan gasket & rear main (BOP) it still leaked, after talking with a couple pontiac guys, the fix was to use the 1/4" thick cork gasket in place of the rubber U seal with a good gasket sealer/RTV. been 6+ years on a 500+hp stroker motor & its still dry.

i'd start there if you confirm no other source up higher that could cause that big of a puddle. sounds like you verified it was coming directly from that area, after wiping it dry & running for a few minutes then let sit overnight, you should be able to see fresh oil, if its dry above that U seal its not from higher up on the block. also be sure you have the metal load spreaders for the corner pan bolts. another gasket option is the one piece BOP that gets great reviews.

good luck finding the leak, i hated dealing with mine for a couple weaks... i pulled the engine each time to replace the pan gasket, but when its that fresh of an install, it came out quick & easy.
This engine was in the car when I purchased it in 98. The previous owner had it built and I received no records on it. All I know for sure is what I've put into it or seen with my own eyes. Speed Pro slugs, stock rods, N crank. I did the top end and roller cam a couple years back. It's always had a few leaks here and there, but really started leaking 2 years ago.

Quote:
Originally Posted by Tom Vaught View Post
Your oil pan does not seem to follow the rear main cap at 2:00 and 10:00 very well.
A thick cork gasket sometimes does a much better job.

Tom V.
I should have clarified, that's not my engine. Just a pic I found on the net of the oil pan for reference.

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Old 03-30-2022, 06:58 PM
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Quote:
Originally Posted by Tom Vaught View Post
Your oil pan does not seem to follow the rear main cap at 2:00 and 10:00 very well.
A thick cork gasket sometimes does a much better job.

Tom V.
That's a pic of an IAII block and aftermarket pan. You need to use an extra piece of flat gasket in the 2:00-10:00 area over the cork gasket because of the 1/8" raised pan rails.

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Old 04-01-2022, 09:08 AM
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Quote:
Originally Posted by JLMounce View Post
I will check there this evening. I'm running Butler's fabbed valve covers with Edelbrock's steel core reusable gaskets. Those are new as of a year ago.
Sounds like you have tracked this down to the back of the oil pan. But just for whatever its worth:

I had these fabbed valve covers on both of my E-Headed cars with the thin, steel reinforced Viton VC gaskets. They look fantastic. But, at least on my cars, the bolts that drop through the holes in the valve covers were just barely bottoming out in the holes in the heads before getting a decent compression on that Viton gasket. It all ‘felt’ snug - but they leaked like crazy - especially at the rear of the head by the firewall. My starter was coated with oil. I ended up using a band saw to carefully lop the last 1-1/2 threads off the bolts then cleaned them with a die. That gave me just enough clearance to compress the Viton gaskets. All was good after that.

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Old 04-01-2022, 09:50 AM
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General post concerning Pontiac oil leaks. Little background. I was in charge of repairing ALL the oil leaks at my Pontiac dealership when I worked there. actually all leaks period including water leaks and wind noise. The #1 Pontiac oil leak is the rear main seal. (at least it was when rope seals were all I worked with). #2 was the rear of the oil pan #3 was valve covers. Both the oil pan and valve covers had the same problem. Thin, crappy sheet metal parts and not enough fasteners, and spaced too far apart. #4 was the valley cover. (again, huge thin, cheap piece of sheet metal, 2 fasteners, #5 Timing case to block and front pan. I replaced 13 rear main seals in Pontiac V-8's in one week at the dealer. Took 2-2.5 hours in the car once you had all your proper wood blocks for each body style. Moving on: Oil plugs, freeze plugs, cam plugs, casting porosity, pretty rare leak sources. Occasional fuel pump pad and oil filter pad leaks.
My best fix methods and procedures/products. Rear main seal: Rope: the "Best" brand seal, packed hard into the groove and cut with a NEW razor only, Dot of RTV on seal ends. Rubber seal: BOP 2 piece or 1 piece seal following their instructions and lube the lip. MUST have a second person to install the 1 piece seal. Rear of pan: cork seal if cap has a groove, I do not use the 3 or 5 tab rubber seal. That is a leak source. If cork, a light film of RTV on pan side of the cork and small blob in corners. If no cork, thick bead of RTV only. Valve covers: I do not use any type of rubber gaskets. Cork only, glued to cover lightly with a tack agent, like high tack or weather strip adhesive, nothing on cylinder head side. Do not over tighten. Valley cover: Preferred method Cork gasket. I test fit cover first, no gasket, adjust with shot filled hammer as needed to get consistent gap. Then lightly tack cork to cover with high tack or weatherstrip adhesive. Then I apply a light film of RTV to the cork, cylinder head side and install. I put a small amount of RTV around the bolt heads at the top where they contact the valley cover. Timing case to block: I use the paper gasket and aviation form a gasket liquid on the paper gaskets for timing case, water pump and thermostat housing, very thin coat. If case is badly eroded, sometimes use a small amount of RTV to fill. Use a small blob of RTV at front corners. I hope all this makes sense and helps.

I love Pontiacs, but they are very difficult engines to seal, because of a number of compromises in the design. The #1 fault is too much space between fasteners IMO. Then when over tightened, it just makes a bad situation worse. Much like owning a Harley, I guess, we have to live with a little drip sometimes. I have mentioned using a smoke machine to find a specific leak point is by far the best way to pinpoint a leak. IMO, much better than dye. Good luck with your repair and I hope this long post has a few ideas some can use. STAY DRY!

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