Tach Cable Seals and O-rings, was started as Any good rear main seal oil additives, that work?

[svwilbur]

THIS STARTED OUT ASKING ABOUT OIL ADDITIVES BUT ENDED UP RATHER QUICKLY BEING POSTS ABOUT THE DISTRIBUTOR CABLE SEAL AND ALL THE O-RINGS AND SEALS INSIDE OR ON THE DISTRIBUTOR PINION THAT DRIVES THE TACH CABLE


It appears that I have the clasic rear main oil seal leaking issue. it leaves a small puddle on my floor and coats the metal plate area infront of the bellhousing and back part of oil pan and drips off a nub seam under the front most part of the bell housing.

I have heard that some people that know how to replace rear main seals don't always even get it fixed the first time and have to pull the engine again to repair it again.

I don't want to go that route until the engine needs other work.

So I was wondering if any of these snake oil products actually help?:

Bar's Leaks Concentrated Rear Main Seal Repair
LUCAS ENGINE OIL STOP LEAK
Blue devil rear main sealer
ATP AT-205 Re-Seal Additive AT-205

I would be interested in any success or failures with these products.

this datsun is a U20 and was not used much the last 10 years or so. it was rebuilt at about 75k. has 107k now. I bought it 3 1/2 years ago. I have only put 4k on it. but the oil started to leak after driving it 500 miles or so. prior to that it sat about 10 years or so.

I drove it to the mt shasta get together this year and it leaked about 1/4 quart on the way. about 350 miles or so for the 6 bour drive.

it is not a big leak. some cars burn more than that. but it coats the area back there and leaves a small puddle on my garage floor.

I would like to try to slow it down. currently I use conventional oil, Kendal GT-1 20-50 oil with ZDDP zinc additive. I don't think it has any other additives for seals or leaking like some oils for older cars do.

[C.Costine]

I have never tried any of them, but on another forum that I visit frequently, the subject does come up frequently. The answer is always that they can work, and that they work by causing the rubber or neoprene of the seal to swell slightly, thus tightening the rubber against the surface that it rides against. However, since the roadster seal is a fiber "rope" seal, this type of additive is not going to be effective. Perhaps there are other types that would work by getting into the breach and grabbing onto the adjacent fibers, but it would seem that the spinning shift would pull them right away.

[Gregs672000]

Just be sure it's the rear main... Check the o-rings at the distributor pedestal for the tach cable. They are inside the pedestal as I recall and require minor disassembly to replace. In all my engine rebuilds I thought I had a leaking rear main, and it turned out to be these o-rings... The oil ends up traveling and dripping from the same spot. Unless the rear main is damaged, they really should not leak that much oil... A little if they are bad, but it seems to me there is just not that much room for oil to get past to drip ALOT of oil. At least, that's been my experience.

[fj20spl311]

I am with Greg.
The "sealing" on a U20 is two fold. There is a slinger built into the crank and the rope seal. There should not be a large leak unless something else is wrong.

[len62]

I also agree with Greg. I had a similar leak which pooled toward the rear of the block.
I changed the Tach o-rings as part of some cable maint. to resolve a waving tach ....after changing the o- rings, the oil leak disappeared.
There is a good description of the process on the Wiki, and I was able to get the o-rings from my local Nissan parts dept.
Hope you might as lucky.

[Linda]

Is there a rear "freeze" plug to the oil galley on a U20? If so could be rusted out.
Linda

[svwilbur]

ok that is a good idea on the distributor O rings. I will check out the wiki.

I did replace the distributor cable a while back. maybe 2 years ago or so. maybe about the same time I started seeing the leak. I remember seeing posts about a seal or O-ring for the cable but I do not remember ever seeing one on the cable. it was a new cable but the wierd thing is it had two boots for going through the firewall?

there is a little oil around the bottom of the distributor. maybe it blows off there and onto the bell housing end plate but it never drips down onto the floor from the distributor, it always drips from the bottom of the bell housing area.

maybe a good cleaning and a short run to check it again is in order?

I will check the wiki doc.


thanks everyone.

[dbrick]

The leaks I see the most are the distributor area or the oil passage at the back of the head, it runs down and back and looks like a rear main. Clean it all and recheck to be sure. If it's still a small leak, I'd tolerate the free rust preventative and park on cardboard.
If you're not sure, clean well and spray with spray foot powder. Any leaks leave a track in the powder residue. Cleans off easilly

If it is the rear main, here's food for thought, seems like a great logical fix, and a whole lot easier than pulling the engine.
From a muscle car site, but applies.
The Pontiac factory service bulletin detailed the following fix. I've done it a few times now and it works better than the other methods.

1) Pull the pan and remove the rear main cap only.

2) take a soft brass drift and bump the ends of the seal that remains in the block back up into the block about 3/16 of an inch. This will swell the seal in the block and make it seal tight again.

3) Remove the old seal from the cap and roll in the new seal. When you trim it, use a fresh razor blade and cut the seal about1/4" over long on each side. Use a fresh blade for each cut to make it nice and neat.

4) apply some RTV to each of the cut ends and the parting line. feed the ends into the spaces in the block and torque the cap down.

5) reassembly is reverse of disassembly.

[fj20spl311]

maybe a good cleaning and a short run to check it again is in order?

That's always a good idea, usually I skip the cleaning and go for a longer ride.

[svwilbur]

greg. is this the tech wiki page you were referring to:

http://www.311s.org/pmwiki-311/pmwiki.p ... achOilSeal

[svwilbur]

reading through the wiki doc I am not sure what the pinion housing nut is. is that what the distributor cable thumb nut screws onto?

here is a partial listing from the wiki:

"No loose parts should fall out. Unscrew the pinion housing nut and the pinion should stay in the distributor base with its shaft sticking out. On the pinion housing nut you removed, notice that there is an "o-ring" on the threads. This o-ring rarely leaks. Look inside the counterbored hole on the cable side of the pinion housing nut and you will see the small black oil seal at the very bottom. The flat side of the oil seal is facing towards you at the cable attachment end of the housing nut (the grooved side faces towards pinion shaft).

[Gregs672000]

reading through the wiki doc I am not sure what the pinion housing nut is. is that what the distributor cable thumb nut screws onto?

here is a partial listing from the wiki:

"No loose parts should fall out. Unscrew the pinion housing nut and the pinion should stay in the distributor base with its shaft sticking out. On the pinion housing nut you removed, notice that there is an "o-ring" on the threads. This o-ring rarely leaks. Look inside the counterbored hole on the cable side of the pinion housing nut and you will see the small black oil seal at the very bottom. The flat side of the oil seal is facing towards you at the cable attachment end of the housing nut (the grooved side faces towards pinion shaft).

Pretty sure, it takes a big wrench to remove the nut. Hope this is your problem! I tried for years to get the "tach cable" to stop leaking without really digging into what the problem was (o-ring). And as noted it is the bottom one that causes the problem.
I think there are two places where the cable goes through a panel, that is why there were two grommits.

[ed B]

How does one know what size O-rings to use?

[dbrick]

If you need a distributor base or tach drive, I have a bunch, just PM

[svwilbur]

I was searching around and found the original write up on changing out the seal for the distributor pinion housing / tachometer cable. it is a seal not an o-ring.

http://www.311s.org/phpBB3/viewtopic.ph ... p+to+themm

it also gives some dimensions. but it is a seal so don't try to use an o-ring.

nissan part numbers are listed as 32709-14600 which is really the speedometer seal. they are suppose to be the same seal.



but the online parts site. http://www.carpartsmanual.com/datsun/sp ... mounting#1
lists a different number and different price for what they call an ring-o with part number 22180-71200. maybe this is the outer o-ring not the seal we really want?

both part numbers are still available from online nissan parts sites for 1 to 6 dollars.

I will try to order some and replacd mine to treey to eliminate it as a possible source for the leak I have.