1985 Corvette

I've got oil coming out of the bellhousing again, so it's time to take the transmission out again and see what is going on this time. A little backstory: got the 383 with a fresh rear main seal in it, I didn't even think to worry about it. Hooked everything up and did a break in run of the motor and I had generous amounts of oil coming out of the bellhousing. Yanked the trans back out, popped the new seal out and put....the second new seal in. I then ran the motor for a good 15 minutes at idle, with revs, and elevated throttle. No leaks.

Buttoned everything back up, ran the car around several times with 1/2 throttle to 3/4 throttle jabs and everytime the car was parked, it was dry as a bone underneath. I even checked with a mirror everytime and drop light to see thankfully the seal housing was dry as can be. I recently went out for a drive about 10 miles of cruising, nothing major other than getting on it a little here and there. Got to the house and something told me to check underneath the car. Sadly, I had oil all over the back of the pan and dripping out of the bellhousing.

So, I'm doing this one more time and if it doesn't get done this time, I'm saying bye bye to the 383 and thinking of going LS. I'm making this post to get some input on ALL areas to look at while I'm in there for the last time. Here are some additional areas I want to go over:

1) When I was in there the first time replacing the seal, I noticed one of the oil galley plugs was also leaking. Looks like these plugs are stainless. I have done a little research and have found some people have trouble with stainless oil galley plugs leaking. I have a spare iron block that I'm thinking of pirating the factory plugs out of to replace these stainless pieces. What is the best method to seal these? The plug leaking had thread tape on it when I took it out.

2) The crank was turned down, so a speedy sleeve was put on the crank end to help restore thickness. Are there one piece seals that are thicker than factory? Is it worth trying to remove the speedy sleeve and let the seal sit flush against the turned down crank?

Ultimately, it's my fault for going with a used crank that needed some machine work but it's one expensive lesson to have learned. Maybe someone better at stopping leaks will make it happen and end up with a sweet motor if I can't this time around.

bjankuski

Are you sure oil is not leaking from the oil pan at the rear of the block? Do you have a breather and PCV valve?

RWDsmoke

I pulled a transmission once only to find the seal dry and it was the back of the valve cover leaking. I also have learned that tapping the seal in with a hammer and block of wood is a crap shoot. I made a tool to press them in and never had another seal leak.

cadmaniac

I feel your pain...Just put in a fresh 421. Tons of power and torque...Almost too much...Thought it was a perfect install, all is great. Then....parked, after driving it a few miles from a distance I see a little wet spot under the car, just enough to make your heart sink.

Dammit!!!!! rear main seal or something. I'm discouraged, and havent even looked at it.

Sorry your having problems. It's discouraging.

Churchkey

If the oil seal has a spring around the inner circumference pack the void with chassis grease to keep the spring in place while tapping the seal in.

1985 Corvette

Already been back there with a droplight hoping the China wall was dribbling oil but no luck. It's a little trickle from the 6 O'Clock position on the seal housing inside the bellhousing.

Yeah, it shouldn't be rocket science but I'm missing something. Sorry you're having problems as well but you're right, it sucks the passion out of you to wrench when you see oil coming out of the bellhousing. It doesn't sound like a big deal tearing everything out to get to the rear of the block but when you spend more time doing that than driving it stops being fun.


With a drop light and mirror it looks like it's just a small trickle at the 6 O'clock position on the housing. The first seal replacement I did, I noticed oil running down the passenger side of the seal housing. Maybe it's just the rear of the pan....that would be nice. The breathers are El Cheapos from Autozone. I think they're the Spectre brand they sell. I have about 4 feet of emission hose on each one which runs down the frame and dumps out under the car. I have read PCV problems can cause a leak but I don't think these are the problem.




Thanks for the tip on packing in the grease. If it's the seal again, I'll do it. The seal I placed in got a generous coating of grease but I didn't pack it around the spring.


For what it's worth, the first seal leaking oil was probably on me: I'm running a Nappa Gold big filter and a 5qt Canton pan. After 5 quarts of oil between priming the filter and the rest in the pan, the dipstick only showed 3/4 to full. I ended up adding about 6.5 quarts total to get it to the full mark so it may have been a case of too much oil blowing past the seal. However, I kept it to 6 quarts the next change after the break in oil was drained out and it was fine for a while until recently. Willing myself to start tearing everything out this weekend.

mtwoolford

well I don't know, but let me relate something learned from another motor made by those guys "Found On the Road Dead", yeah they know who they are.....

Anyway, tor the front crank seal, the drill was to (first) install the front crank seal into the timing chain cover and then install the assembled seal/timing chain cover as a unit, the idea being that the seal itself would center itself and the timing chain cover on the crank. Unusual thought I, but that 460 hasn't leaked a drop of oil.

Now, let me ask you, was your block line honed or line bored? In that case the seal assembly is no longer centered over the crank, or even if it wasn't bored / honed, there is no guarantee that the seal and the seal housing were ever properly centered over the crank....

so. take the seal housing off the back of the block...remember to use a new gasket...reassemble it with a new seal and don't trust any alignment pins in the block to locate the housing/seal assembly. Let the seal itself locate the assembly in relation to the crankshaft and block and tighten it down in that position, even if it seems slightly askew in relation to the mounting bolts (enlarge the bolt holes in the seal housing if necessary; ditto for any alignment dowels).

I'll bet that this will eliminate any leaks, at least from the rear seal.

eguyett1985

I would pick up some uv dye for the oil and a black light; I've found that to be really helpful finding the source of oil leaks on many of my customers cars over the years. On my own 408 I fought a rear main seal leak at first due to a standard size rear main seal being installed when the block was line honed and should have had an oversize seal (fel-pro 2909) then I put it back together only to find it was still leaking although not as much. The uv dye helped me determine one of the rear pipe plugs was seeping and so was the cam plug. I removed all the pipe plugs, carefully cleaned the threads and used ARP thread sealer on the threads and snugged them up. I also cleaned the recess around the cam plug with acetone and ran a bead of Permatex right stuff around the plug which did the trick. For the most part now everything is good; after about 500 miles I only have a very slight trace of seepage at the rear of the pan if I look really close but not enough to drip which I don't mind considering it's a 2-piece seal block with a HV oil pump and 60 psi of pressure at hi rpms.

1985 Corvette

I don't recall which method was used on this block. That's always an option dropping the pan and re-position the housing but I hate going through that trouble. I can see going through all that trouble and still having a leak only it's in a different spot on the new seal. Then I've got to buy a new oil pan gasket and make sure I don't goof sealing up the pan. I'd rather sell the motor than spend more $$$ for a new leak. Sorry, I'm a little salty about it all still.






I have heard a lot about the UV dye and it's an option but now I'm wondering: what if I tried a "leak stop" additive? I saw some by Lucas Oil Products and Blue Devil today at the parts store. Wondering if I try one of those first before going nuts on tearing everything out. The lucas bottle said it may take 2 days of driving time to stop the leak and this leak from what I can see seems to occupy a 1/4 inch spot at the at 6 O'clock side of the seal.

What do you guys think about a Lucas or Blue Devil seal stopper additive? If it won't damage anything, I'll give one of them a shot before making parts fly off the car.

A Peter C4

Blue Devil has very good reveiws.Locktite has very good thread sealant for plugs and pipe connections.Blue Devil will not harm anything check thier website,good read.

mtwoolford

so I probably missed this, but I was thinking you have a block with a one piece rear seal...if your block has a two piece rear, well ignore my previous post

Kevova

If block was aligned bored it's possible rear seal housing doesn't fit correctly. I would install seal in housing, then on crank look at how bolt holes align on block. You may need to elongate holes a little so seal is centered. The seal that came will "Band-Aid" sleeve is designed for it. I believe there is supposed to be loc-tite to hold and seal sleeve to crank.

1985 Corvette

If I'm back there I can give that a try but does that involve dropping the whole pan to give the housing bolts enough clearance to remove it?

1985 Corvette

Alright, I went and picked up the Felpro kit to redo the seal housing gaskets and the one piece seal. Talk to me a little more about tweaking the seal housing: am I just opening up the bolt holes a little to allow some slop in the housing so I can "center" the seal around the crank? Both sides of all the gaskets get a nice smearing of sealant right? I picked up The Right Stuff black sealant for this job. I didn't grab the oil pan gasket but I'll make a trip out tomorrow for it if I absolutely must have it.

Lazy Tom

Be sure the crankshaft is clean and free of burrs that can cut into the seal.

Pack the seal with grease.

My friend has an LS on the stand he got for 100 bucks.

1985 Corvette

Hey guys, is there a way to remove the seal housing without having to drop the entire pan? I'll pick up a new felpro gasket just in case but was curious.

Lazy Tom

Mine leaked like a sieve, especially when I ran it hard.
I replaced what appeared to be a leaky valve cover which after further examination was dry beneath the cover.
The oil was blowing out of the dipstick hole.
Apparently the crankcase pressure caused this.
The crankcase was pressurized by a clogged PCV. It was packed solid.
The PCV was clogged because the EGR was stuck and was baking the intake manifold.
I replaced the PCV and plated the EGR.
It quit leaking oil.
Injecting hot exhaust gases into the intake is counter intuitive.

Interestingly to me anyway the oil blew out of the valve cover vent and made its way into the electrical conduit that leads to the coil and ignition module where it dripped and must have caught on fire and burned the pigtail.

So, check your PCV.

1985 Corvette

Hey guys, it's been a while. I still haven't gotten around to replacing this seal yet but I forgot your post, Tom. I've got some El Cheapo Spectre breathers on the valve covers with vapor hoses running underneath the car to dump the fumes. Maybe these aren't working like they should and it's making enough pressure to push oil past the seal. Strangley, the oil is leaking from the 6 O'clock spot on the seal housing, wheres it used to leak from the 9 O'clock spot, where there was a hairline gap.

What are some great reliable breathers to use? The original leak happened even when the car idled and was cold. The new leak doesn't happen with idling, only when the engine is under load and warmed up. It drips out in one 1/4'' area (which drives me batshit insane) and pools in the bellhousing and when I use the brakes, the pool of oil dribbles out of the bellhousing where I brake. If this just turned out to be a case of bad crankcase ventilation, I'd be beyond happy.

I just can't make sense of a replacement that is bone dry for a few miles and then starts leaking in a different spot again.

Edit: I also have a Melling high volume oil pump. I wonder if that's the problem.

QCVette

I don't know what is causing yours to leak.

I had a problem with a new crate motor a few years ago. It was nice and dry for a couple of months then a lot of oil out of the bell housing. When I pulled the seal, the spring inside of the seal had come apart so there was no tension at all. I don't know what brand of seal, but the spring had one end that was slightly smaller and simply pushed into the other end. It didn't hold. I replaced it with an Fel Pro seal and no more problems.

If you take out the seal you might check to see if it is the same problem. I would also try Churchkey's suggestions since I am now cautious about the seal.

I also have an LT1 that just started leaking and I haven't found the leak yet, but I suspect I will be pulling the transmission and need a rear main seal too. It is leaking a lot of oil.

Good luck.

1985 Corvette

The first new seal was a Felpro. The second was also a Felpro. The third one sitting on the work bench is also a Felpro. I dont' think it's the seals that are the problem. After a little more research, I think I'm going to run PCV valves to the appropriate locations on the manifold and throttle body. I did notice the oil looked like it has soot in it and it has a fuel vapor-like smell. Apparently, this can happen without a proper pvc setup. Probably not enough to just have the vapors dump out hoses. This might cure the leak if I'm lucky.

The pistons have Total Seal rings on them. Can't remember the exact part number but I've read blow by on Total Seal brand rings can cause decent crankcase pressure. Guess this is worth a try before attempting to replace the seal.