What the hell, The car has 2800 miles on it since I put it all together, New engine,tranny rear end exhaust. you name it and it is brand new. I spent 5 months putting this car together and now this. i have check all upper seals in the back of the motor, clean and dry, checked pcv and the same. Now the thing I am really pissed about is that i ordered the short block assembled with the rear main seal in it. So why the hell is this happening? Anyone ever have this happen with a new motor? I have babied the car, No high rpms yet. I have really only driven it to denver and back a couple of weekends to help break in the car. i changed the oil at 500 miles and was going to change it at 3000 as well and then normal changes. I am sporting a 347 with scat crank, rods, and keith black pistons, The rest of the motor is trick flow.
Brand new 347 has rear main leak!!
- Thread starter Spook302
- Start date
BK_CAULEY
it's built for speed not longevity, woman
where did you get the short block from? if it was a cheap company they probably had cheap workers assembling it and they probably just beat the seal in with a mallet and galled it all up. hell it might not even be set in all the way. if it was a reputable engine builder let them know and they will more than likely work with you on fixing it.
I got the short block from a company called Bullet racing engines from the trough the shop i used to work at. I have installed a couple of 383 strokers and a big block ford stroker as well from this company and not had any problems. The motor has a year warranty but it would really suck to pull it all back apart.
cenok is family
15 Year Member
302RollinHard
New Member
IMO romping on an engine won't cause a rear main leak. It is either improper installation or excess crankcase pressure.
I am running a brand new pcv valve along with breathers on both valve covers. what I have seen on some of my other mustangs is that positive crank pressure like that would also push my dipstick tube out. i am looking at a new bbk x pipe to mate with my long tubes and a new flowmaster cat back that is sitting in my living room. i guess i will pull the tranny and clutch and the rest and see what is going on. it sucks it is 95 degrees outside and there will be no room in the garage for quite some time.
my cars never leaked.... and it was the original one with 80K on it. Now i hope the new one holds up with the new engine ha. Now i'm scared!
maxine-70
20+ Year Stangneter 
its a nuisance but not that big of a deal. ford one piece rear main was a brilliant idea, far better than the old 2 piece rope-type seal. you just have to pull the trans to get to it. once youre there, pop it out, put the new on in it (OIL/GREASE THE LIP FIRST!), and put the trans back in.
likely it wasnt oiled when they put it in and it burned the sealing lip up.
likely it wasnt oiled when they put it in and it burned the sealing lip up.
daddystang
New Member
- Aug 13, 2006
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I do not think it is your rear main seal at all. It's probably the bolt's that connect the flywheel to the crank. You have to put sealant on the bolts or they are GUARANTEED to leak oil on the back just like a rear main seal leak. Don't know if you sealed them with RTV or not, but reading this brought back horrible memories of installing my new engine and trans, having oil leak down the front of the trans, and thinking it was the oil pan gasket or rear main seal. After pulling the engine, and trans twice my wife found online a small blurb that said you MUST seal those bolts. We then used RTV black sealant, put it all back in, and presto no more leak after a year. I hope this helps you out.
Good luck to you......
Good luck to you......
BK_CAULEY
it's built for speed not longevity, woman
yep. thats what you get when you buy engines from cut rate companies with under paid workers. (no one take that personally)
ShortThrow50
Member
I had my engine and trans out of the car and replaced bassically everything. Also put a teflon rms in. I did this while sitting on a nice comfy chair with engine dangling in front of my face. Guess what? after 200 miles, my rms is leaking. I just laughed it off and said oh well. Its a mustang. ***** it. lol
I didn't read this whole thread so this may have been mentioned already.
My brand new DART motor leaked shortly after startup. Drove me insane and I KNEW it was a rear main leak.
To make a long story short... the intake was leaking. There is a small space between end of the heads and the deck surface that has to be sealed when you put the lower intake on. It's on the back of the block (dpends on the heads you're using). Of course, the block is black and it ran down the bellhousing and had ALL of the indication of being a rear main. Even dripped right down the rear main seal surface on it's way to the pavement.
At any rate: Check for ANY unfilled spaces between your lower intake, the heads, and the deck surface.
My brand new DART motor leaked shortly after startup. Drove me insane and I KNEW it was a rear main leak.
To make a long story short... the intake was leaking. There is a small space between end of the heads and the deck surface that has to be sealed when you put the lower intake on. It's on the back of the block (dpends on the heads you're using). Of course, the block is black and it ran down the bellhousing and had ALL of the indication of being a rear main. Even dripped right down the rear main seal surface on it's way to the pavement.
At any rate: Check for ANY unfilled spaces between your lower intake, the heads, and the deck surface.
daddystang
New Member
- Aug 13, 2006
- 185
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The intake leaking is a possibility. Rub your hand back there and check for oil. If there isn't any, I feel relatively certain that it is your flywheel to crank bolts. Just in case you don't know (I didn't), the bolt holes on the back of the crank go straight through into the motor. Just a heads up to anyone doing an engine, or flywheel swap. Save yourself a ton of headaches, and use sealant on those bolts. Again, thanks to my wife we found that little bit of highly important info (thanks honey). That ought to be worth a few points.
Good luck bud....
Good luck bud....
maxine-70
20+ Year Stangneter
the flywheel bolts going into an oil source is true, another of fords genious ideas. but since you have to pull the trans out to reseal them, put a new rear main in it while youre there just to be sure
I checked the intake manifold and every single thing that it could be hoping i didnt have to pull the tranny out of my car. This is my 8th fox body. I made sure that spots like the corners of the intake were sealed good. And I used thread sealer on my flywheels bolts just like I do with the head bolts. This just pisses me off so much. I triple checked everything when I put this car together and now this. I bet if I would have installed that myself this wouldnt be happening. I have had 125,000 miles stangs with the stock rms holding just fine. This motor has 2800 miles on it.
So I just got down to the rear main seal. It doesn't look very straight at all. So the machining guys are dumbasses. You know I checked everything inside the short block before I put the rest of it together,but I never checked the rms. Well they are paying me 500 for the labor, and refunded the seal I buy. Does anyone have the teflon rms seal part number from autozone. Ill be picking it up here in an hour or so. They are just down the street from me. oh and I guess I should have put an energy suspension tranny mount in as well. i put a brand new stock one I had lying around,and energy on the motor. Well the mount was in two pieces and one of my U joint isnt to happy either.
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