Is it normal for thru bolt o-rings to get mangled?

[914/6]

Look at Henery's pics, the direction of through bolts.. Is correct ....
Previous poster is incorrect.. The un chamfered side is for the threaded end of bolt..

[stownsen914]

Originally Posted by 914/6

The un chamfered side is for the threaded end of bolt..

Thanks, I was wondering. What is different about orings on the threaded end of the through bolts that they don’t need a chamfer?

[914/6]

Yes ,, never had a problem... The old blue soft ones where delicate.

[stownsen914]

I removed the one through bolt where the washer spun probably a full turn. I expected the oring to be mangled, but it wasn't. Perhaps the Dow 55 paste saved it.

I reassembled, making sure that there wasn't any oil on the washer at the nut end (aside from a light smear of Dow 55 in the beveled oring recess, and oiled the underhead of the nut. No spinning washer this time.

[draw]

Henry, if you don't mind me asking, do you see a problem with removing a nut to see if the o-ring is okay? One through bolt at a time, of course...

I closed my case recently and a few of the washers turned during the torquing process. I even had an assistant holding the washers with pliers and they still moved. The o-rings were lubed with DOW 55, but I'm paranoid...

[Neil Harvey]

I received call to day from a gentleman in Canada regarding what we do when installing the case through bolts. Since this question came up we have had several asking the same question. My answer was, plenty of lube as It has been stated and go carefully. We have never had to clamp the washers or anything odd.

I got thinking about this and decided to help. The 964/993 use a stepped washer and the O ring is fitted down inside the case counterbore. This would work on the 911 but only on the hex head end of the through bolt. I think the O ring sits over the threaded portion of the through bolt on the nut end. I think so.



So we will make up 2 stepped washers, different ID bores to fit each end of the through bolt with two different O rings. The case will get counterbored so the O ring will sit in the counterbore, seal around the contact surfaces of the through bolt and case with nothing touching the stepped part of the washer other than maybe 0.004" at most.

The case will require the through bolt holes to be counterbored. It will need a standard size 2 flute end mill with the nose ground down to the stock through bolt hole diameter uses as a guide. Not sure the cost of the end mill but it will not be a lot. This could be done at home on a drill press, carefully. Have no idea of the kit price yet, but it will come with directions, Washers, O Rings, grease and an end mill if this will be done at home.

Hopefully this may give confidence that the Case Through will not be a cause of a leak.

We use this system on our through bolts.



sy

[Coultl]

Are the red o-rings from Porsche viton? I already have them on hand from a Porsche gasket kit and it would be great to use them!

[proporsche]

Originally Posted by Neil Harvey

I received call to day from a gentleman in Canada regarding what we do when installing the case through bolts. Since this question came up we have had several asking the same question. My answer was, plenty of lube as It has been stated and go carefully. We have never had to clamp the washers or anything odd.

I got thinking about this and decided to help. The 964/993 use a stepped washer and the O ring is fitted down inside the case counterbore. This would work on the 911 but only on the hex head end of the through bolt. I think the O ring sits over the threaded portion of the through bolt on the nut end. I think so.



So we will make up 2 stepped washers, different ID bores to fit each end of the through bolt with two different O rings. The case will get counterbored so the O ring will sit in the counterbore, seal around the contact surfaces of the through bolt and case with nothing touching the stepped part of the washer other than maybe 0.004" at most.

The case will require the through bolt holes to be counterbored. It will need a standard size 2 flute end mill with the nose ground down to the stock through bolt hole diameter uses as a guide. Not sure the cost of the end mill but it will not be a lot. This could be done at home on a drill press, carefully. Have no idea of the kit price yet, but it will come with directions, Washers, O Rings, grease and an end mill if this will be done at home.

Hopefully this may give confidence that the Case Through will not be a cause of a leak.

We use this system on our through bolts.



sy

looks fantastic....
Ivan

[stownsen914]

That looks like an elegant solution! Thanks Neil for these innovations.

[Neil Harvey]

Originally Posted by stownsen914

That looks like an elegant solution! Thanks Neil for these innovations.

For years never had an issue but if this makes it easier and less stressful we will have these. Anytime you remove the chance of leaks or failures, it has to be a good thing.

There is added machining to be done to the case that will add time and cost to your rebuild.

I guess its a trade off, cost verses the cost of a leak.