1986, #8 Bearing

redridge · 07-30-2011, 04:40 PM

I have much to learn about this engine... I am chasing down a leak and thinking worst case... see pics below. Thank you for the lesson...

1. Is the #8 bearing the same as the nose bearing?

2. Is the pulley seal for the #8 bearing?

3. What is the symptoms for a bad #8 bearing? Can it cause a crank pulley wobble? How can you check for a bad bearing?

4. Can the bad bearing cause an oil leak? such as this?

5. What is the direction to fix a bad #8 bearing... does the case need splitting to replace the bad bearing?

Flat6pac · 07-30-2011, 06:02 PM

First of all, you wont have a bad #8, you ll have a bad seal that needs replacing. #8 wont go bad because it is under complete oil and pressure. If you have a diffective #8m you ll be loosing the crank but not the bearing.
The case needs to be opened the seal the perimeter of the bearing which is an O ring.
#8 is the nose bearing.
The picture puts it in place in the half case.
Bruce

afterburn 549 · 07-31-2011, 01:40 AM

is that from just a 5 min run or is that leak all you have....does not look bad from here !

Eagledriver · 07-31-2011, 11:02 AM

There is a oil seal under the pulley that can be replaced without removing the engine. The leak looks very small to me. I'd just live with it until it gets too annoying to live with. It could be the o-ring, but it might just be the oil seal. You'll be able to tell once you remove the pulley.

-Andy

afterburn 549 · 07-31-2011, 01:09 PM

Ditto!

redridge · 07-31-2011, 06:01 PM

thanks guys... no, the oil leak is not that bad at all... Im just anal and hate oil leaks. I think the search has led me to this...

It looks easy enough for the O ring and the pulley seal is easy to replace.... Ill get around to it this winter. Again Thanks for the help!

PORSCHE CUSTOMERS of TOM AMON - Welcome to Mobile Works West!

afterburn 549 · 07-31-2011, 06:13 PM

Requires splitting the case halves......Not that EZ for me LOL

Walt Fricke · 08-03-2011, 07:17 PM

Heed afterburn's words well.

Best to replace the seal. You can do this with the motor in the car - prop up the engine, remove some sheet metal and the motor mount stuff, and you can remove the crank pulley. Then pry out the old seal and install a new one.

While there you can also look to see if the leak seems to be coming from either side (crank or case) side of the seal, or from the outside of the #8/nose bearing. If the later, then perhaps the O ring has, indeed, hardened and started to leak. But back to Afterburn's warning at that point.

Opening up the case requires an almost complete disassembly of the motor (you could leave the rods on the crank), which sensibly means you will be looking at replacing rings, bearings, other seals, maybe having the valves and seats touched up, and on it goes - a rebuild.

fredmeister · fredmeister's Garage

I just rebuilt my engine with brand new o-ring on this number 8 bearing and lubed it before glueing the case halves together. I am confident the o-ring did not get cut or damaged.
However, my engine is leaking with a fairly big drip every 30 seconds to a minute or so while idling from that area. Leaves a big puddle on the floor after a cool down in the garage before shutting it off.
I thought it might be a bad crank seal since I originally reused the #8 bearing and its seal since it was dry as a bone before the rebuild. SO I REPLACED THE CRANK SEAL THIS PAST WEEKEND AND PUT THE CAR BACK TOGETHER. FIRED IT UP AND IT STILL LEAKS FROM THAT AREA. I dont want to split the case to replace the oring since I find it hard ot believe it could be the cause.
QUESTION: HOW COMMON IS THAT ORING SEAL TO LEAK VERSUS THE CRANK SEAL ON FRESHLY REBUILT ENGINE? IT SEEMS THE ORING SHOULD SEAL MUCH BETTER THAN THE CRANKSEAL BY DESIGN.....TRUE OR FALSE?
IS THERE ANY TRICK I MISSED TO INSTALLING THE NEW CRANK SEAL SINCE I DID NOT USE SEALANT ON THE OUTSIDE DIAMTER INTO THE #8 MAIN BEARING AND ONLY LUBED THE INNER LIP SEAL WITH GREASE WHEN INSTALLING IT OOVER THE CRANKNOSE?

redridge · 08-09-2011, 12:54 PM

Fredmeister.... what is your plan on fixing your leak? If this area was dry before the rebuild, it may be possible that you pinched the O ring.... no?

fredmeister · fredmeister's Garage

Quote:

Originally Posted by redridge

Fredmeister.... what is your plan on fixing your leak? If this area was dry before the rebuild, it may be possible that you pinched the O ring.... no?

Nope was very careful here when joining case halves. I cannot think that the oring seal would leak like this since it gets crushed pretty well when the case goes together.
Now with the new crank seal installed it surprised me that its still leaking.
I just wanted some solutions since splitting the case again is a very bad prospect.

lindy 911 · lindy 911's Garage

It seems that it all depends on where you sourced your gasket set and whether or not you got the right size o-ring. I used a Reintz (sp) set and the through bolt o-rings leaked profusely and the #8 o-ring pukes oil in the upper right quadrant. You can tell that it's not the crank seal because it can be seen pumping from the crease between the case and the #8 bearing.

Recommended by a top level mechanic who frequents this site, I had a sleeve machined that goes around the outside of the #8 bearing and presses up against the case to cover the joint. I applied JB weld between the two pieces and stuck it together. It is better but it still leaks. I will be pulling the motor back out to fix this properly. I will never use Reintz gasket sets again and will source Writewood (sp) racing gasket sets from now on.

It's unfortunate that the o-rings in these sets are wrong. A lot of work for something a simple as an o-ring. Unfortunately, if you want it done right, you'll need to tear it back down. Most of the people in the know say to glue the o-ring in place if for nothing else the assurance that it will seal.

redridge · 08-09-2011, 05:41 PM

Fredmeister, Would the Tom Amon solution work for you in post #6, check out the link. It is a solution for keeping the case intact.

Walt Fricke · 08-09-2011, 08:44 PM

Fred - did you apply whatever case sealant you used around the outer lip of the #8, beyond the O ring but not sticking out of the case? On someone's advice I have always done that. A little sealant usually gets into the O ring groove, but that doesn't hurt anything.

I seem to recall that while all #8s are the same dimension up through somewhere - the 3.2s certainly - Porsche increased the thickness of the O ring at some point. The SC era? Anyway, one wanted the later dimensioned O ring.

I am doubtful that the O ring got pinched, but getting the #8 on and the dowel pin where it belongs is a bit of a rodeo. I guess having two people put the crank in would help. The other solutions suggested earlier are really clever, and well worth considering, band-aid or no.

Eagledriver · 08-09-2011, 10:31 PM

I had a 2.7 leak there after assembly. I now believe that the cause of the leaks there is the lubricant on the O-ring. The silicon grease gets into the case seam nxt to the o-ring and keeps the case sealant from sealing the seam there. I now install that o-ring dry and make sure the sealant gets all the way to the edge of the case there.

-Andy

930cabman · 08-10-2011, 11:21 AM

My 1975 911S had a bad leak behind the crank pulley, I just got it back together with the Tom Amon sleeve and a new seal, still leaks. Maybe not so bad but WTF.

Any ideas?

thanks in advance

lindy 911 · lindy 911's Garage

The #8 nose bearing is under pressure and if the oil is getting by the o-ring it will still have a lot of force once it gets to the outside. The "sleeve" must be installed perfectly and the surfaces SUPER clean or the JB weld will not seal the joint. There is also some question as to whether or not the JB weld will grow and shrink proportionately with the aluminum of the case and the #8 bearing.

I made my own sleeve that is a friction fit instead of set screws and had to be heated to install. Mine was exceptionally clean and I used plenty of JB weld but it still leaked. I have been told that a better "glue" is weather strip cement because of it's flexibility and durability. I'd be inclined to try that if it weren't for the fact that I want to pull the motor apart anyway for some crank and oil pump mods.

I think that if you applied vacuum to the case after it was blasted really well with break cleaner (carb cleaner will kill the o-ring) and then add the JB weld or weather strip cement, then the sleeve you could get it to stop all together. For me, it's a case split and I'm gluing the #8 o-ring in with Yama-bond this time around.

fredmeister · fredmeister's Garage

Quote:

Originally Posted by Walt Fricke

Fred - did you apply whatever case sealant you used around the outer lip of the #8, beyond the O ring but not sticking out of the case? On someone's advice I have always done that. A little sealant usually gets into the O ring groove, but that doesn't hurt anything.

I seem to recall that while all #8s are the same dimension up through somewhere - the 3.2s certainly - Porsche increased the thickness of the O ring at some point. The SC era? Anyway, one wanted the later dimensioned O ring.

I am doubtful that the O ring got pinched, but getting the #8 on and the dowel pin where it belongs is a bit of a rodeo. I guess having two people put the crank in would help. The other solutions suggested earlier are really clever, and well worth considering, band-aid or no.

I did apply sealant to that area outboard of the oring. I did lube the oring though with grease thinking that it would allow it to move and not tear during case halve assembly.
I used 2 man method to set the dowel pin and crank to the #8 journal so that went together fine also. There is no doubt it went together fine, just wondering if the sealant shuld have been applied more but my thinking is an oring should seal very well as long as it not torn. It is not a dynamic seal and as long as its sized correctly to the groove in the bearing it shouldnot leak.
Its funny that the seal was dry on the engine before I rebuilt it. Though the original engine had tons of sealant around the #8 bearing bore on the case halves. Both inboard and outboard of the oring.....I took this to be the work of a sloppy previous rebuilder. Maybe he was onto something with this case afterall.
My problem now is how to fix it without splitting the case.
So far a few people have commented that the additional sleeve and jb weld does not work 100%. My worry with this solution is how to get the sleeve back off the engine once its jb welded to the front case halves if you ever decide to split the case in the future.

afterburn 549 · 08-10-2011, 07:27 PM

Please read then destroy ...I have" herd" that if you super clean the area really well like with tons of brake cleaner..you can mix a batch of JB weld up and force it into the seem around the bearing and case halves (Not around the crank of course) that good results can be had...dont know anyone that did this.....is my nose growing?
Its a cheap alternitive ....

Walt Fricke · 08-10-2011, 09:29 PM

Fred

Maybe JB Weld is really that strong, and I may be fooling myself. But I don't think it would give you any trouble splitting the case. It is not a weld, and the case has a couple of places designed for good whacks with a rubber mallet to break the Loctite (or stronger) seals already in use.

Was it in this discussion or another that Henry Schmidt submitted a photo from his gallery of horrors, showing one of these seals all goobered around with some kind of external sealant. But Henry has figured out how to make things work right, so he can afford to lbe amused at how some of us struggle.

Me, I think the key is getting some case sealant right up to the parting line edge outboard of the O ring, so any oil which gets past it can't get any farther. Doing this means you will, on disassembly, find some sealant in the O ring groove. But I don't see that causing any trouble.

Fixing after the fact is another thing. My current motor, which I bought from a fellow racer, nas a persistent leak from near the flywheel seal. I had the wheel off, put in a new seal, still had a leak. What's more, the face of the seal was dry! So it wasn't leaking from the obvuous place - the seal lip, which can wear and so on.

I fabricated a little metal cup, and attached it below the opening in the tranny at the bottom of where they join. Thiught I'd catch this oil, and periodically drain it rather than wiping it off of the engine.

Didn't work, though I'm not sure just why. Might be because I was chasing another couple of small but irritating leaks. So it goes.