[craigs69]

After a nearly complete restoration on my 69 convertible this winter, I was re-installing my engine and transmission today and noticed a real bad oil leak when I tipped the rear of the engine down to clear the transmission under the body. It looks like it may be coming from the oil pan gasket at the rear main cap. I have read many of the posts on this forum concerning oil leaks from the rear main seal and the pan gasket and I would think that oil wouldn't be leaking from the rear main seal if the engine isn't running. I purchased the car a year ago and the engine was supposed to be rebuilt with about 2,500 miles on it. It did look like a fresh motor, but I have always had a small oil leak from the rear of the engine. It was hard to tell how bad it leaked because I had a really bad transmission fluid leak also. I can see that I have the rubber 5 tab pan gasket, so my money is on that being the issue. Any thoughts?

[Garage Goat]

Before you installed the pan did you check it for warpage?

[craigs69]

I didn't remove the pan. The motor was supposed to be fresh, so I only detailed the engine while it was out. I didn't notice the leak when I took it out because I didn't remove the engine and transmission together, so I didn't have to tip it as far back to get it out of the car.

[goat2789]

my engine also leaked oil while installing the engine. It was a very steep angle. The engine does not leak at all now.

[craigs69]

Goat2789,
How bad was yours leaking at that steep angle? Mine was a steady drip that made a 12" puddle on the floor in about 20 minutes.

[goat2789]

Mine leaked about the same, i never saw it drip but noticed the puddle after the engine was in. i think it came from the back of engine but i could not see where from. I use royal purple oil and synchromesh fluid in trans and the oil i saw looked purple.

[lust4speed]

One of the tests many of us do before dropping the engine in the car is to point the rear of the engine as far down as we can while it is on the cherry picker, and let it set overnight. A properly sealed engine won't have any spots on the floor the next morning.

Both the rear main and the rear of the pan seal are never exposed to any direct pressure source, so it shouldn't matter whether the engine is running or not. There is a shot of oil being spewed from the rear bearing, but the oil slinger built into the crank between the bearing and seal should deflect the oil away from the seal. If there is a buildup of crankcase pressure when the engine is running, then this would provide some push to the oil spray to more easily exit the rear of the engine.

Now might be the best time to figure out where the oil is coming from. The 1/2" or so space between the main seal and the pan seal will either be wet or dry before the engine is fired again. If that area has oil on it, then the rear main isn't doing its job; and if that area is dry, then look to the pan seal. And if both areas look dry, then the leak might be from the valve covers not sealing well and allowing the oil to travel down the back of the engine.

[craigs69]

Well, I got home from work tonight and lifted and tipped the motor with my cherry picker and the oil is definitely coming from the rear main seal. Now the million dollar question is do I have to remove the crankshaft to change the seal or can it be done with the crank in?

[old66tiger]

Best practice is to remove the crank. What seal are you using?

[grivera]

Originally Posted by craigs69

Well, I got home from work tonight and lifted and tipped the motor with my cherry picker and the oil is definitely coming from the rear main seal. Now the million dollar question is do I have to remove the crankshaft to change the seal or can it be done with the crank in?

If it's a 400, and you use a BOP Viton seal (3"), you don't have to remove the crank.

[old66tiger]

With all respect, I disagree with the seal replacement without removing the crank for the viton unit. For one, you need to fill the anti-rotation holes with silicone otherwise it will leak. Second, these seals seem to work best with a micro bead of sealer spread along the back bone of the seal to make up for any inconsistencies in the seal and the groove.

[ck67goat]

Common problem for these to leak unless you read up on tricks to install correctly. If you are not sure, would recommend getting help from someone local that knows Pontiacs intimately. Possibly somewhere there is already a post on this forum if you do a search.

[61-63]

The factory shop books say to run a bead of sealer between the rear main cap and the block before installing that cap. If that is not done oil can and will weep from between the cap and block and you will have a small leak even if the rear main seal and pan gasket are installed correctly. Unfortunately the only way to run that bead if it hasn't been done is by removing the oil pan and rear main bearing cap.

[tom s]

I agree with Mick,we always to the overnight tilt deal on a engine now before it goes in a car,even before it goes on the dyno.Tom

[lust4speed]

With the rods still attached, the crank will come up off the block just a little less than an inch -- and I would consider this a tough installation process for either the standard rope seal or the graphite rope seal. I attempted the shortcut of not pulling the crank, but it's just too hard to see if the rope is properly positioned in the bottom of groove before setting the crank back down. Plus if the crank comes down on its own while you are positioning the seal, it would sure smash your fingers. I figured I had done the hard work and didn't want to do it again, so I removed the crank and did the job correctly.

If I'm not doing a complete tear down and only replacing the seal, I remove each rod cap and both bearing shells from the rod and put the set into separately marked bags. I then push the rods/pistons down into the bores so they are free of the crank. All that's left is to remove the main caps and lift out the crank completely.

I would start with pulling #5 cap and see what the rope looks like in the cap portion. This might shed some light on what went wrong. Also take a good look at the seal in the block after the crank is out. If rear main is leaking before the engine is run, I'd say that the problem is probably the parting line where the seal halves come together.

[grivera]

Originally Posted by old66tiger

With all respect, I disagree with the seal replacement without removing the crank for the viton unit. For one, you need to fill the anti-rotation holes with silicone otherwise it will leak. Second, these seals seem to work best with a micro bead of sealer spread along the back bone of the seal to make up for any inconsistencies in the seal and the groove.

My response was based on the instructions that come with the seal and only apply to 400 blocks. The anti-rotation holes, per BOP's instructions need filled on 455's because the seal doesn't always cover the width of the groove in 455 blocks.

[HWYSTR455]

This is all assuming that it is actually the rear main seal that's the issue. Obviously, the poster should check the pan gasket first.

.

[Tim Corcoran]

Wow Craig, this is sounding like a real hassel that you weren't expecting. If it's the rear main seal I believe the best thing to do is remove the crank as instructed above. I believe your chances of changing that seal without removing the crank and it not leaking are slim. Good luck. You have two choices of seals, the viton seal from BOP or the new graphite rope seal from Best Gasket Company. Under no circumstance should you use the factory replacement rope seal as it will leak.

[craigs69]

Tim,
Yes, this is a real hassle. This whole car has been a hassle. This was one of those "restored" Ebay cars that everyone should avoid. I knew the risks of buying a car that way, but the price seemed reasonable enough to take the gamble. Well, the seller did a fine job of making it look pretty, but the man was a hack at best. Everything was listed as "new, new, new" on the car. As I found out, "new" doesn't necessarily mean that it is a new product, just newly installed on the car. I admit that I am very picky when it comes to workmanship, however spray foam should never be used as body filler and bailing wire makes for a poor throttle cable clip. I am well over $10K bringing this car up to the condition that I thought it was in when I bought it. He sent photos of the car before the "restoration" and images of receipts that obviously were not for the car as they did not come along with it as promised. I really thought I was buying a decent car, but ended up with a major project.

[craigs69]

Well, after much deliberation and many hours of research on this forum, I decided to give Wade a call at BOP Engineering and explain to him my situation. I told him that I wanted zero leaks, but I also didn't want to pull the crankshaft out of the engine. He was confident that I can install his seal with the crank in and get the results I'm looking for. I also ordered the one piece pan gasket since the majority of the posts on this forum are favorable for it. Since the motor is already out and I can do the overnight tip test on it before I re-install it, I figured I didn't have much to lose by giving the seal a shot. I have the measuring equipment to check the seal diameter as well as concentricity to the bearing bore, so I can verify that before assembly. I hope to have the car ready to fire up in about 5 weeks, so I will be keeping my fingers crossed when I turn the key.