Tachometer drive connector leak

[66andBlue]

The connector for the tachometer (RPM) drive cable to the engine block has developed a leak.
The leak does not occur around the connector piece but through it and I suspect that the radial seal ring (#27) is bad.
This seal is still available but I am wondering how the old one can be removed. 
I have an old defect connector and tried to get it out. I could scrape out the rubber portion but it appears that the there is a metal ring associated with it that needs to be removed too. 
Anybody out there who has done this and knows how?
I'd appreciate all the help.

[J. Huber]

Hi Alfred, my experience went like this:

I too developed a leak at the connection maybe 4-5 years ago. On the advice of counsel (this site), I first checked the play of the tach gear bushing. There was a bit but not really alarm-worthy. I then ordered just the seal (#27) from Ray Paul. I had a challenge getting the old one out... resorted to using a drill bit and sort of side-slicing the seal from inside it. This went ok except I slipped just enough to make a teeny gouge in the brass? housing. I went forward anyway and pressed the new seal in. Simple. After reassemble, the leak was cured .... for about a year, I think. Then it reappeared. Wondering if it was the glitch I made? I simply bit the bullet and replaced the entire thrust bushing (about 75 bucks then). It has the seal inside. Dropped it in, tightened things up and problem was officially resolved.

One note: my thrust bushing went in easily but I believe Bob (Hands Aus) had trouble getting his either in or out? Not sure.  A couple searches on tach thrust may shed light on this -- and my story.

[Naj ✝︎]

Hi, Alfred,

From what I remember, I had to grind down one side of the seal sleeve with a dermel until I could fold it over with a screw driver and pull it out with pliers.

Not as easy as it sounds!

naj

[George Des]

I encountered this same problem many years ago--1978 to be exact. The leak allowed oil to ride up the tach cable and exit from the connector on the tach itself. I had oil on the driver's floor as a result. I tried to change out the seal itself but ran into the very same problem you guys have had. Tried using a drill press and ended up destroying the cap, so in the end I ordered the complete cap assembly that included the seal. Hvae not had a problem since

George Desiderio

[jacovdw]

Same here.

Took the cap to a local engineering shop and they removed the seal and refitted the new one I supplied while I waited. What they did was to carefully drill the old seal out in a drill press. Some minor damage to the cap was inevitable, but the new seal was pressed in place after applying some locktite sealer.

This was back in 2005 and so far it has not leaked at all.

[66andBlue]

Thank you all!
I'll go ahead and try to be a dentist for a day and let you know later how it worked.
But first I need to get the new part.

[jacovdw]

Alfred,

Just something interesting I noted from the part number for the little oil seal you quoted earlier (A007 997 73 46).

That specific seal is actually used on an automatic transmission (722.1xx and 722.20x series).

The seal specified in the EPC for use in the tachometer drive for the pagoda has been superseded to A115 274 00 60 (which is NLA as far as I know).
However, when you do a search on the EPC for A007 997 73 46, this number comes up as an "optional with A115 274 00 60" description.

Just a bit of useless information...  

[66andBlue]

Hi Jaco,
the original p/n was 120 261 0080 for the M127 and M129 engines which indeed became 115 274 00 60 for a M130 engine as you wrote. This was replaced by 011 997 64 47 which then morphed into the generic seal part number.  But it is the same part for all engines.
When I ordered it from Dave Gallon he came up with the transmission part and the history of these part numbers.
The good news is that it costs less than $4 whereas the complete connector is now $150+!  

[hands_aus]

Hey James,
The thrust piece gave me problems until I realised that it must be aligned perfectly for it to go in.
One of the major issues was visibility as I have big hands I couldn't see very well and it was a feel job.

[Benz Dr.]

Part numbers change all the time and yet some very old parts still have the same original numbers. Having an up to date EPC helps sort this maze out.

 Relative to being able to find the right part is comprehensive diagnosis. What's causing oil to migrate out of this area in the first place? The seal on my car is as hard as rock yet it doesn't leak a drop. Why would one engine leak, and another not leak at all, given that both seals are hard?

[66andBlue]

... Why would one engine leak, and another not leak at all, given that both seals are hard? ..

Because, Doctor,  you are feeding different amounts of little blue pills to some and not others. 

Seriously, why would you NOT expect oil to emerge when the radial seal is compromised?
After all the vertical tachdrive gear is connected to the horizontal gear and the oil pump and all are part of the engine lubrication system. 

[Benz Dr.]

There really isn't any oil pressure in that area which would force oil out of the seal. Oil runs into the cavity which surrounds the helical drive gears and then drains out into the front chain case.
Must be something else, eh?  But what could it be?

[66andBlue]

No oil pressure there? Now I am really stumped   
How then does the bushing/thrust piece get the oil it needs?
http://www.sl113.org/forums/uploaded/ja17/200362923756_Removal%20of%20bushing.jpg

[Benz Dr.]

Through the main oil galley.
 It also sends oil to the IP through the small line that runs from the block to the side of the pump. Oil pours out through the bushing for the distributor drive gear and most of it will drain back into the chain case. Some of that oil simply runs over to the gear set and down the shaft where it lubes the shaft that drives the oil pump. All of this is barrier lubrication similar to what you would find on a rocker arm or valve stem.

So, why will oil come out of that seal? 

[66andBlue]

So, why will oil come out of that seal? 

Ask BP, they'll have the answer. 

[Benz Dr.]

Well...... the major difference is, you only have six liters until it's empty. They had 6 billion spill out ( or something like that )  and it's still not empty.

The similarity is no one seems to have the answer. Yet......

[Benz Dr.]

( drum roll please )

 The short answer is:

 Plugged crankcase ventilation system.
 Sometimes the line going to the air control valve will freeze up in really cold weather and that will really make oil shoot out of the tach drive fitting.

[66andBlue]

... Sometimes the line going to the air control valve will freeze up in really cold weather and that will really make oil shoot out of the tach drive fitting.

And I thought I was driving around San Diego Bay all this time but I guess it must be freezing Prudhoe Bay! 
Sorry Dan, but I don't get it.  It appears the hotter the engine gets the more oil seeps out although I make sure the coolant temperature never gets close to the red range.

[Benz Dr.]

Blow by gasses can do strange things. On a diesel I can stall the engine just by plugging the crank case vent on top of the valve cover. A really good engine will keep running but a worn one will stop quickly.
Excessive pressure can force oil to seep out anywhere. The tach drive is one of those places. I mentioned freeze up because that's a common problem on some cars. This is why they changed the tube to plastic because the earlier ones would rust inside from all of the moisture due to condensation. I've seen them pretty much plugged solid with carbon and rust or sometimes ice in the winter. This would only happen after a short drive where all of the moisture wasn't purged out and then the car was left sitting for a while in freezing temps. All of these freeze up problems need just the right conditions to occur.

In your case, it seems that once your oil gets hot there's a lot of blow by or something causing oil to purge out of the tach drive area. This is not normal at all. It is however, one place where oil can easily come out if the right conditions are met.

Try plugging the vent on top of the valve cover to see if the engine stalls. If it stays running there isn't too much blow by. Only a fresh engine will next to no blow by. If you see oil starting to shoot out of the tach drive that's a good indication that you have some sort of obsruction either in the vent tube or inside of the engine around the drive gears.
This oil is supposed to drain back into the chain case through a hole in the casting but it could be blocked.

Just some ideas. It may be none of these things but I've seen this before so it's worth a look.

[66andBlue]

Thanks Dan.
I'll do the vent plugging test and check how the engine responds.