nose 8 bearing o-ring leak

[mtelliott]

Originally posted by Henry Schmidt
Loctite 574 is a Form-in-Place Anaerobic » Flange Sealant . Fast curing, medium strength compound specially formulated to cure through large gaps. It is not a gasket sealant.

__________________

What is meant by large gaps. Are we talking microns?

[Henry Schmidt]

Loctite 574 is rated at 300 to 1200 psi at .25mm after curing. Full strength curing time 6 to 7 hours @ 22 degrees C.
This rating is for steel.
When applied to aluminum, 574 seems to rate @ 75% of these values.
Does this mean 75% of the gap? I'm not certain but it looks like with a .25mm gap on aluminum the tensile strength is 75%.
The tensile strength is also lowered by heat as follows.
0-50 C 100%
50 -100 C 65%
100-150 C 25%
Aging @120 C has no effect.
@150 C strength is around 80%
These are tested at 5000 hours

[AndreasLanghoff]

Hi to all listeners, it is very nice to see so much interest in this topic.

Finally we dismantled the engine and from the attached fotos the cause for the nose 8 bearing leak is obvious:

The o-ring (this is the 4.5mmx51) is too big for the groove and was squeezed out in between the case halfes.
Some part of the o-ring was even torn out and pushed into the o-ring oil-return channel. Some part of this channel was also obstructed by Curil-Dirko Silicon sealant, although that had been used sparingly.

The pictures speak of themselves, but here some advice for the future. We will reassemble the engine the next days so then I can tell you weather the below described procedure works.

1. Use the original o-ring. For the Mag cases this is the 4mmx50 o-ring. One word here to performance products: I used the 4.5mm o-ring only because in their catalog the use of the bigger o-ring is suggested to improve sealing. I do not agree and their advice is a bad advice (see catalog 53A summer 2003 page 143)


2. Put the o-ring into the nose 8 bearing

3. Put some Curil-Dirko or similar sealant (listen to Henry's advice here) sparingly on the nose 8 bearing. Keep clear of the oil return groove and be careful not to fill the oil pressure hole full of sealant.


I will tell the results soon.

For completeless, here are the measurements of the case bore.

These are within the 0.004inch max. tolerance as given by Henry.
The italian rebuilder has practically the same limit (0.08 - 0.1mm) for the maximum allowed unroundness of the bores.

crankshaft: Freshly polished, all bearing 56.97 , round

bore bearing new tolerance: 62.00-62.02
max. alllowed tolerance given according to Henry and ital. rebuilder 0.1 mm


measured
bore bearing 1 (flywheel) 61.98 - 62.00 -62.05
2 62.00 - 62.03
3 62.00 - 62.04
4 62.00 - 62.05
5 62.00 - 62.03
6 62.00 - 62.03
7 62.01 round
8 62.00- 62.03
part outside o-ring
(was that sqeezed?)
on bearing 8 62.05 -62.1

We did not measure cyl. spigot plane tilt, no need for this.

If mag cases are so often out of specs as reported by Wayne and Henry, where do they come from? HAve those cases been used for racing or was these 2.7s with thermal reactors.


Have a nice evening

Andreas

[AndreasLanghoff]

Actually the leaking occured only on the upper side of the nose 8 bearing - case halfes joint. The picture insteas shows a detail of the o-ring on the lower side only. It didn't leak from the lower side.

The upper side shows in a very similar way a sqeezed o-ring between the case halves. It was sqeezed less nicely, and that made it leak!

[Eagledriver]

I had this exact same problem. Lucky for me I discovered it before I finished putting the engine together. I think this is responsible for many of the leaks we read about on this forum.

-Andy

[garibaldi]

I think I found you r problem- the italian rebuilder. Those-a damn italians only do a coup of tingsa good, make-a shoes, and make-a food, da rest...........eh!

If you really want to get the case right, mag or aluminum. you take the halves, set them up straight, and clip both halves entirely at the parting line. Then you go back through and align hone the main housings straight and round and to the standard size, no need for o.s bearings, then you hone the layshaft housing back to size and straight and round, and then rebore the seal housings back to size. Now not only are the mains round and lined up, but the entire "seasoned" case is flat and has the original intended surface area around its entirety. Which means that you are not bending the case when you torque up the fasteners to get the halves to come together. Less sealant, no leaks, no crazy bearings, and a crank that spins so sweet, but.... more time, more specail tooling to do, and more costs.

[Henry Schmidt]

Nice, but how much? How long? and finaly why send it to NJ when you can have your case remanufactured right here at SUPERTEC.
The point is that many machine shops perform this process, but it is pricey, it takes some time and many if not most cases don't need this costly, time consuming process.

[rick-l]

Originally posted by Henry Schmidt
Nice, but how much? How long? and finaly why send it to NJ when you can have your case remanufactured right here at SUPERTEC.

hey.... NJ IS closer to Cremona, Italy <--- joke

[garibaldi]

If you find .015 out of round in the front bearing housing, how much do you think the rest of the case moves by? ALign boring only the mains does nothing but bore the mains larger, the rest of the case is still twisted up. Now you have an expensive set of oversize bearings, and a case that still isnt sitting flat against itlself.

All I am saying is that to do it 100%, the entire mating surfaces should be milled flat, this allows more control, and a better end result.

And yes, it takes more time, and costs more, but guess what, its done.

I agree with what you say, what you do fixes the line bore, what I do fixes the entire case, main housings and all.

[Wayne 962]

The method that Christian uses on the cases is what I advocate in the book.

Speaking of which, I do not recommend using the larger o-ring in the book. I recommend using the proper one for your size throw-out bearing.

-Wayne

[Fishcop]

Is there agreement on using a sealant in conjunction with the o-ring or dry like the factory?

[Henry Schmidt]

I guess the question is "where do you stop"? Do you just buy everything new ? Do we blindly do every machine process we can ? We all agree that we can spend all the money we can find rebuilding these engine. My question is " where do we stop? What is good enough ?" I assume that the reason most of us are asking these questions, doing our own work and making ourselves crazy with "what if "questions, is that we want to repair these engines as close to perfect as possible without taking out a second on the homestead. In most cases, the case when torqued will retain most of it's original shape. Have I sen some that don't ? Of corse I have. That's why you bolt the case together before align boring. For those of us who've tried, quite often if you don't align bore the mains will get tight. That is not because the case is twisted, it is because the mains are not round. Bolt the case together, align bore it, buy the bearings and your good to go. When it needs another overhaul perhaps a new case is in order. Now if we're talking high performance, all this cost saving nonsense is out. But if you're looking to rebuild your fairly stock street engine, be careful not to overdue. This is not rocket science and these are just cars.

[garibaldi]

Align boring twisted cases does not solve the problem, it only helps the crank turn. It doesn't unload the case from stresses, milling a seasoned case, that has setled out over time, and then align honing it back to standard size takes care of all of aspects of the case in that regard, including a crank that spins freely when installed. New cases are quite expensive. We are addicted to excellence, this is the way we do it. It just depends on how thorough you want to be when doing an engine.

[Henry Schmidt]

Originally posted by garibaldi
We are addicted to excellence, this is the way we do it. It just depends on how thorough you want to be when doing an engine.

Removing the studs, decking the case, honing the intermediate bearings and align bore back to std. all good when necassary. We just did this prosedure on a 2 liter aluminum cased race engine. Just an expensive exersise when not necassary. That's why we bolt it together and measure it.
As for doing a thorough job: we do a thorough enough job to offer all our customers a 2 year unlimited mile warranty, in writing. What's yours?

[AndreasLanghoff]

Quite a big discussions going on between many perfectionists there.
My point is simply that I don't want to spend as much as buying a new 2.7RS engine directly form Porsche (is at least 25000 Euro).
All main bearings are less then 0.004inch out of round, which is acceptable by machine shop standards.

The crank turns smoothly and the case has NOT leaked before opening, taking all these points together there is no point in align honing.

There are two other points that I would like to address:
1. In all machining there is some risk: Things can go wrong and in the worst case 2 case halves have to be thrown away.

2. Allthough I apreciate the very good advice from this forum I can also imagine that there is some financial interest involved. By proposing over-precise tolerances and by porposing to change as many components of the engine as possible I understand that the professional who has to stand up for what he says does risk less because for shure more new components in an engine translate to less items that cause trouble in redone engines. At the same time everyone is happy, the parts seller, the machine workshop...
Only the final customer would be happier if he could spend a little less and at the same time have a very reliable engine. ( Here we are talking about a STOCK 2.7RS engine)
This is where the engine rebuilders experience comes in and it is the rebuilder who can propose a well balanced (financially and work/precision) solution to the customer. This is why rebuilders exist, otherwise a customer would just buy from Porsche.
I am sure that in the long run every rebuilders attempt to find this correct balanced solution for the customers is very appreciated by the customers and will bring him many content customers in the long run.
In our case we were unlucky because the otherwise correct rebuild was cancelled by using the suggestion from the performance products part supplier (the 4.5mm o-ring)

[Wayne 962]

Squaring the case back to true is a technique pioneered by Ray at Competition Engineering (now owned by Walt). As far as I know, it is the right way of doing things, and the only real way that you can be assured that you'll have a quality, leak-free engine. These engines, particularly the magnesium cases, are very unforgiving. If you don't true up the case, you will indeed have oil leaks later on. If the case measures in-spec, then great - no machine work necessary. However, if it's out of spec, and this fact is ignored, then you are significantly increasing your risk of having an oil leak.

I wrote the book with this in mind. The techniques and tips given in the book are what someone needs to follow in order to build a solid, strong, leak-free engine. You can cut corners, but you will pay for it in oil leaks later on.

Originally posted by Henry Schmidt
As for doing a thorough job: we do a thorough enough job to offer all our customers a 2 year unlimited mile warranty, in writing. What's yours?

Okay, I'll bite. Does this warranty cover oil leaks?

-Wayne

[Porsche_monkey]

Okay, I'll bite. Does this warranty cover oil leaks?

-Wayne

Probably not, because he's still in business.

[wm711]

A couple uears ago one of my best friends bought a 2.7 RS spec from Henry. We installed the engine, and a small leak developed, rear main I think it was. I live in a different city than my friend, he didnt notice the leak until he got home and the car sat. He said the leak was about quarter size after the car sat for a couple days. He told Henry about it, no big deal, I told him not to worry to much about it. The engine was a work of art, and FAST, it was in a 69S. Both of us were very happy with the engine. Henry insisted we take the car to a shop we both knew that knew 911 engines, and the leak was repaired. Henry paid for it all. Stand up guy!

[Henry Schmidt]

Originally posted by Wayne at Pelican Parts

Okay, I'll bite. Does this warranty cover oil leaks?

-Wayne

We take a great deal of pride in our work. We love these engines. 911 air-cooled engines is all we do. We like what we do. If something we do is not up to our standards ( st*t happens) we want to fit it. It's a matter of pride for us. If one of our engine leaks, it's embarrassing, so we want it fixed. No matter how much it cost.
Perhaps that's why we're still in business ?
Here's a copy of the SUPERTEC engine warranty.
Supertec Performance

Porsche Engine Warranty
.

TWO YEAR, UNLIMITED MILE PARTS AND LABOR
1. Normal use [no racing, no abuse, damage by over rev not covered ]
2. Damaged caused by lack of oil not covered.
3. No towing or labor cost associated with any repair not completed by Supertec Performance is expressly excluded
4. In-house (all repairs must be performed at Supertec Performance unless written authorization is received prior to repair.) shipping costs are owners responsibility
5. Call or fax for authorization and shipping instructions [numbers below]
6. Porsches leak oil, so minor oil leaks are excluded. Major oil leaks covered.
(Minor leaks defined as moisture not dripping, if it drips it's covered)
7. Piston ring damage due to poor fuel excluded
8. Normal ware items not covered
9. Clutch defects covered 2 years, wear covered for 2 year or 15,000 miles (which ever comes first)
10. Electrical parts carry manufacturers warranty
11. Over boost damage not covered [ turbo only].

[Porsche_monkey]

Seems pretty fair to me.

Beats the typical 'Exclusive Maple Warranty' ie once you go past the maple tree at the end of our driveway your warranty is over.