[428RA4]

REAR MAIN SEAL LEAK

Well after all my efforts and replacing entire major car systems, I think I'm having a real main seal leak that is caused by vibration that increases at higher RPM's at freeway speeds. I have a brand new Ram Air V motor along with a brand new Richmond 5 speed trans. Rearend is fresh as well. The only parts that remain in question are the harmonic balancer and the drive shaft, but both are new. The balancer is an original NOS GM part and the drive shaft is supposingly balanced.

Does anyone recommend anything else to look at? Im lost for words and am about to go ape on the engine builder.

The engine has been internally balanced = crank, rods and pistons.

Balancer and drive shaft is in question, but again, any ideas on what else could cause this?

thanks

mike

[Ron H]

Are you showing an oil leak after driving at higher speeds rather than just cruising or idling around? Or is it leaking when the engine is running no matter what rpm or speed?

[428RA4]

Breaking the motor in without driving it - the motor has no leak. When I drive it at high speeds, it leaks. Driving it period it leaks.

[drevil1]

neutral balanced flywheel ?

[428RA4]

I hope so, I purchased all the internal parts from Butler Performance.

[goquick]

Draw a chalk line on the damper (balancer), then take it up to where it vibrates. Slow down and get home. If the outter part has moved, it is junk. If the damper is still in the same place as marked (and the movement can be as little as .030") check it for any signs of the bonding seperating. Next, check your flexplate/flywheel for any cracks, especially up close to the center at the crank flange. I am thinking that after all these years the Damper's bonding has deteriorated and it's about to let go. Just because it's NOS does not mean it's good !!!! Age is still the enemy on it.

[Ron H]

Functioning PCV?

[428RA4]

Thanks for the advice goquick. I will give that a try.

[428RA4]

Yes Ron, The PVC is working.

[goquick]

Keep us updated. I will be out of town for the next week, so i may not get to check in.

[rod cole]

This is all grabbing at straws. There is no way balance will cause a leak and you in good conscience could drive the car. It is all about crankcase pressure and good sealing techniques. Look closer at the pan seals and there is dye you can buy to trace oil leaks. Personally I would clean it well then hold rpms to cruising rpm while watching it from underneath well supported. Rod

[68gtoMN]

Location of leak and description of vibration have me leaning toward an out-of-balance Driveshaft. Check your u-joints. You can put a run-out gauge on this easily. Is there vibration while stationary? If not, go for a drive on a level road, get to rpm where vibration happens in 1st and note speed. Then depress clutch and coast. Do you still feel the vibration? If so, notice if vibration lessens as speed lessens. Try the same in 2nd and so on up to the same speed. If you have the vibration as the same speed, I'll bet driveshaft over engine balance any day...

[Half-Inch Stud]

NOT suspecting the Front Balancer.
I suspect the Flywheel, or Power-imBalance (dead CYL under load or RPM).

As for the oil leak. STOP! do a compression test on all 8 CYLs, write-it-down and report back. Rather high Positive crankcase pressure is needed to cause a BAD rear seal to leak out of the rear flange. I suspect the Oil Pan seal shifted to cause a gaping gap between the oil-pan & Rear Cap. Use the Cork band wetted with RTV there & watch where is tries to go during oil pan bolt torquing.

[HWYSTR455]

Aside from the leak, there's some things here that raise a flag with me. First, you need to make SURE about the balance, and the other items, such as the flywheel and balancer. Period. An OE balancer is not zero-balanced out of the box, and you would KNOW if it was balanced or not (look at the bill if nothing else, but it should have weights/drilled holes). For the most part though, OE replacement balancers are junk, and you should really get an aftermarket one.

Flywheels you can order zero-balanced, but they should still be checked, and usually are when balancing a rotating assembly. There again, you shold be able to tell by looking at the bill/invoice and part number, check and see if it's zero-balanced, and if the rotating assembly was balanced (internal or external).

Driveshaft. Is it a factory one that was in the car before? Did it vibrate before? Driveshafts fail, just as u-joints do, and yokes wear. As inexpensive as a driveshaft is, why not replace it? For the piece of mind if nothing else? How much did you spend on the engine? Can you swing another $250 for new shaft, yokes, joints, and balance?

Now, the leak, sometimes it may LOOK like it's the rear main when it's actually something else. Check the filter housing, they sometimes spray under load when hot. Check the filter. I've seen where the rubber ring stuck to the housing after a filter change and the next filter was screwed right on top of it. Look at the distributor area and see if it's puddled up around there, it can trickle down the bellhousing and look like a rear main leak. It can leak on the pan rail too. Wipe it all down, go around the block, and check again until you're sure where it's coming from. If it's the rear main, check your PCV setup, etc.

.

[Ron H]

If the valley pan is leaking it will also run down the back and look like the rear main or pan.

I think you have excess crankcase pressure and it's pushing out when at higher rpms.

Ditto on buying an aftermarket balancer.

[ho428]

My balancer came apart during a race weekend, didn't know it at the time that's what it was, the trans pilot bearing came out as well, not sure which came apart first though.
By the end of Saturdays races the rear main was leaking from the vibration, but the vibration was pretty severe.


If everything already mentioned checks out though the next thing to check is the bellhousing alignment.
Also check the clutch assembly. Vibrations can be tough to pin down.

If everything external checks out there's only one place left to go. Don't want to toast a V engine.
V block or just the top end?

[Tim Corcoran]

As previously stated the leak may not be associated with the oil leak. What kind of seal did you use on the oil pan where it goes around the rear main bearing cap? If you used a rubber seal you may be leaking there and when it leaks there it it very hard to tell if it coming from the back of the pan or the rear main seal. In either case it would require you to pull the engine to repair. I never use the rubber seal on the back of the pan. SD performance sells a special made wide cork seal ($5.00) that is used in lieu of the rubber seal, that seal is the best you can get and mine never leak when I use the SD cork seal. Also it may be remote but if the crank was cracked that would cause a vibration. To rule out the driveshaft, the driveshaft would only cause a vibration while driving and would not be related to engine RPM, so if it does not have the vibration when you rev it in neutral then that would cause me to suspect the driveline.

Tim C

[428RA4]

Thanks for all the advice. Let me try and clarify some things.

I just got the drive shaft out and repaired. Threw it back in the car and the condition and leak is still there. The front joint was bad even though the drive shaft only had about a 1000 miles on a rebuild. The joint was out 10K and the limit of play is 2k. The shaft was also out of balance a bit and was brought back into specs.

Unfortunately, the vibration is still there. It's hard to pin down if the vibration is coming from the engine, drive line or rear end. I have tried to rev the engine in neutral and still cant quite verify if it's the engine or not.

The car has NEW everything and this is no bull. The rotating assembly = Kellogg crank, Ross pistons and H beam rods were all neutral balanced by Butler. The General Motors balancer made in Mexico is also GM = but who knows whats up with that. If I rev the engine, it looks true and not wibble wabbling around. The car also has a brand new Richmond 5 speed manual trans. The flywheel and clutch should be neutral balanced, but am uncertain if Butler did the internal balance with the fly wheel parts. They did not do the assembly. The oil pan gasket is a cork gasket but the rear portion is rubber as all Pontiac's are. The rear main seal is a BOP Vitton seal.

Oil filter housing is solid.

It for sure is leaking from the back end of the engine inside of the clutch bell housing. Yes, I had the bell housing check on the block with the trans bolted up to verify alignment. I think the play was 2 or 3 thousands which I believe is way within in spec.

The oil pressure gauge is pegged at 80 PSI when driving the car and the pump was also supplied by Butler. As far as the PVC system, the car is running the original 303 Ram Air V carb that has the extra PVC pipe running off the side of the carb base with new hose and pvc valve. Not sure how this can cause a leak, but that is the info.

As far as what the engine is, it is a NOS 428 SR block 4-bolt main motor. It would be the correct block for a Ram Air VI motor configuration. NOS heads, and intake to boot.

Any more thoughts on where to go from here besides blowing the car apart again?

damn...

[Ron H]

It may be that the pressure control valve (PCV) is not keeping up with the crankcase pressure that the engine has when running at higher RPM.

What kind of oil are you running?

Best to do a compression test as HIS suggested.

[Probird]

Originally Posted by Ron H

If the valley pan is leaking it will also run down the back and look like the rear main or pan.

I think you have excess crankcase pressure and it's pushing out when at higher rpms.

Ditto on buying an aftermarket balancer.

I agree with Ron here. Excess crankcase pressure that the PCV cannot vent fast enough forcing the oil out of any place it can find.

Not all Pontiacs used the rubber rear seal. A lot of the gasket kits have both the rubber and cork seal. I always use the cork seal, the rubber ones usually leak.