Okay, I got a 70 Cutlass S Holiday Coupe with a 350 that I am in the process of replacing the oil pan gasket. I am at the point where I have the old oil pan gasket removed (PITA, BTW) and I figured I should replace the the rear main seal (preventive maint) before I button everything up. Because I do not want to do this again any time soon. Especially doing everything from my back, not having a engine hoist, etc.

So, I read the Chassis service manual. Clear as mud, since I have never done this before. But I think I have the basics.

1. Remove bearing main cap to access the upper seal.
2. Pound the upper seal into the groove from each side
3. Measure the amount of seal needed on each side then add 1/16" to the measurement
4. Cut off seal needed from lower seal to make up difference on both sides of upper seal groove
5. Add RTV to seal ends, then pack seals on both sides and cut flush
6. Install lower seal with seal installer tool, hammer into groove
7. Cut seal flush

What special tools do I need to buy? Do I need the special seal installer tool? What lubricants can I use? Do I use RTV to seal the ends of the upper seal?

Sorry for all the questions, but I am a little over my head and don't want to make this worse.

 

Those directions seem to me to be for an engine that has the crank removed? The upper seal is behind the crank and is most likely a rope seal. Are you replacing this with a neoprene seal? If so you may be able to remove the original seal and install with the crank in place. There are tools for installing an original rope seal without removing the crank but results are usually less than desired.

 

So with the crankshaft in place, am I able to remove the old rope seal? The way the manual read it inferred to leave the old seal in place and just pack it tighter and backfill with additional seal segments.

I will use neoprene seal if I can get it installed without removing the crank. I am trying to figure out what I need before I go to the parts store tomorrow...

 

You did say you wanted to replace the seal...... The upper seal part can be removed with difficulty with the crank still in. There is a kit with some special aka mickey mouse tools in it. I am not sure of the part numbers you need for the neoprene seal. The BB Olds seal commonly used is a Ford seal.

 

Yes, I am trying to install the seal with the crank still in.

 

Sometimes its better to let "sleeping dogs lie" and if there are no signs of a rear main seal leaking leave it alone. You may open a can of worms.

 

I have an oil leak and thought it was the oil pan gasket. But to be sure I want to take care of the rear main seal while I have everything apart...

 

I did a upper rear main in a Buick with the crank in it once and I will NEVER do that again. I've never heard of anyone packing it in then backfilling it, might work. I think I'm with the maniac on this one, let the dogs lie. You can always just change the lower main seal thats easy enough, it seems thats where the crank usually leaks anyway.

 

I might do just the lower seal. I am having a hard time getting the main cap off though. Not sure how much "persuasion" to give it. Just the 2 bolts hold it on, right?

Disregard, I got it off. Flat hammer a few taps alternating on both sides and she came off.

The lower seal did not come out with the main cap. One end was attached to the upper seal, while the other end was dangling. So, can I just replace the lower seal with a new rope seal and call it good? Or should I attempt to push out the upper seal? How can you tell if an upper seal is bad by looking at it?

If you need pics let me know...

 

I'll just keep updating progress until someone chimes in.

Cleaned up the main cap and bearing cap insert. I found that the edges of the grooves of the bearing cap insert are rough. I was able to remove the "finish" with my fingernail. Should I replace this???

The upper seal looks tight in its groove with no oil saturation or fraying. Can I assume this is good to go or is it really one of those things that you won't know unless you take the crankshaft off or remove the seal?

The bearing had brown discoloration rings that corresponded with the width of the grooves in the bearing cap insert is this a sign of friction, overheating, etc? Or is this normal? The bearing was smooth, the discoloration was the only thing I saw.

The top of the main cap has two reliefs cuts on both sides (factory). Someone filled these full of RTV. Is this correct? The best I can tell from the manual is the only thing that gets coated lightly with RTV is the machined surface adjacent the seal on both sides.

Finally, I read I can polish up the oil passage on the main cap for better flow. Anyone have any insight?

This all new to me, so it is unnerving and awesome all at the same time. Any rate, as my Grandpa used to say, "God hates a coward." So I will continue figuring out this Cutlass until I either have it running tip top or the best looking lawn ornament on the block.

 

I hope you have a torque wrench to re torque the Main Bolts at least??

 

There shouldn't be rtv on your main caps. Sounds like it's asking for trouble.
I used a Ford 292 motor rubber rear main seal, and off set it a little bit. The crank was removed though.

 

The more I think about it, it was probably Permatex #2 that was on the machined surface and the grooves (which I still don't know if gasket sealer is supposed to be there).

Can I assume they don't make anything other than a rope seal for a SBO? Is that why you used a rubber seal for a Ford 292?

 

The ford 292 2 piece neoprene seal is the way to go since crank will remain in place. The Fel Pro number should be B/S 6141 You need to remove the upper rope seal.

 

Sounds good. I am hesitant on removing the upper seal with the crank in. But if that's what needs to be done, I will hopefully have no problem getting the old one out and putting the new neoprene one in.

Is it even possible to stagger the seals with the crank in? I would imagine there would be alignment issues with the lower seal when putting main cap in place?

 

"If it ain't broke, don't fix it" is sound advice. However, it appears you are way beyond that point?

There should be no sealer in the groove(s). The tool I have seen is a wire mesh net loop type of thing. You push on it to open the net. Then it is slipped over the end of the upper seal. When you pull on the tool the net tightens around the seal, and permits you to pull it out.

That is the easy part! -

The same tool is used, theoretically, to install the new seal. However, there is little-to-no working room to feed the tool through the upper groove. One might be better off with string/nylon line or something long and thin?

Feed it through the groove. Attach one end to the seal. (I would be inclined to coat the seal with STP to enable it to go into the groove far easier.) Start the seal in the groove by hand. Hand feed it in as far as you can. Pull, slowly, on the device while pushing on the other end.

Take care to prevent pulling the seal too much, too far. The drawing showing the staggering of the seal ends, in an earlier message is a good example of how you want to end up with the 2 halves of the seal.

Having done all that, there is no guarantee that the new seal will work any better than the old.

Good luck!

 

Thanks for the advice. Hopefully, I will have good news to report tonight after I get after it again.

 

It is possible to stagger (a little) the neoprene seal with crank in. Make sure seal is facing the right way as both sides are not the same. A picture diagram may come with new seal and put dab of permatex on each end.

 

Well it is done. It did not go as expected or at least as easy as I thought it was going to be based on responses and people I talked to.

The old upper rope seal did not want to cooperate. It did not want to be pulled out or pushed out. I used wire to no avail. I suppose if I had that special tool it might have went better. When I did get a needle nose on it, it pulled chunks off of the seal but not enough to pull it around at all.

So, basically I reverted back to the Chassis manual instructions and packed the old seal in place. Added more rope seal to make up the difference (added sealant to both ends).

Used a new rubber lower seal (Napa did not have the neoprene in stock). Used sealant on machined surfaces of main cap. Oiled the cap bolts, reassembled and torqued to specs.

Only time will tell if it will work. I have to install a new oil pump, water pump, replace cracked fuel line, etc. So, it will be awhile before I can start the motor (mainly waiting on parts to get here).

But hopefully it did the trick. Thanks to those who responded.

d1

 

It kinda sounds like you might not have had a Rear seal leak in the first place but now that you've done what you were only capable of doing Half of the job you may have a leak like you've never had before. I personally have never heard of anybody finishing the job the way you explain you have and expect it not to leak.
After you installed and torqued the Main Cap you should remove the Main Cap and use Plasti-Gauge to check your clearances by re-installing the Main Cap, torquing it to specs,removing it again and measuring your clearances of the Plasti-Gauge. Plasti-Gauge and its specs can be obtained at most engine rebuilding shops. With what you have done I would repeat these steps first before I tried to restart this engine and confirm your clearances meet specs.

 

Defiant 1, so I just read this old post and I'm dying to know... How did it turn out???

 

It worked well. No issues or leaks.

d1