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Posted by: cuddyk Jan 12 2017, 09:26 PM

Hi Guys,

I have new pushrod tubes and viton o-rings ready to install as my quest to keep kitty litter out of my garage continues...

The bores are super clean and look like they'd make a good seal...but when I serviced the tubes last year, they did leak a bit. That was using new viton, but the old tubes. The new tubes definitely seem to "seat" the rubber better.

What are your thoughts about using yamabond (or some other flexible sealant)? Is there any downside? I assume it would only go around the seals on the case side, right?

Thanks!

Posted by: mark04usa Jan 13 2017, 12:13 AM

IMHO, push rod tube seals should be installed with a coat of engine oil but no sealant. Sealant was not used there by the original builder of our engines. The push rod tubes move a bit in their bores as the engine goes through hot/cold cycles, so I don't see how a sealant would help much. My seals installed with no sealant stay dry for quit a few years before time to renew. The Viton seals may last even longer.

Lots of folks on the 'world do use sealant and have success with that method and will no doubt be here soon to tell you their way of push rod tube reseal...and that it is best. The topic has been debated before here. You'll need to decide for yourself...sealant or not

Posted by: cuddyk Jan 13 2017, 12:45 AM

Thanks mark.

My preference would be to go with no sealant as well. But then again, I also didn't want to run a starter solenoid . Our cars aren't getting any younger and I wonder if sealant becomes more inevitable...or at least practical...as time goes on.

I read the previous threads / debates. Will be interesting to see if anything has changed since then.

Posted by: johnhora Jan 13 2017, 10:57 AM

As Mark said oil only ....no sealant...
many VW and 914 builds later no problems

Posted by: Keith914 Jan 20 2017, 03:21 PM

Hmmm! I just finished carefully, no O ring damage, re-installing the existing tubes with a coating of engine oil, after very carefully cleaning their grooves of paint and flexible sealant ("snot") using new Viton O rings. All eight "popped" into place. After several short runs with engine up to operating temperature, perhaps 30 or so miles, three tubes appear to be leaking with thin oil trails along the bottom of the tubes. There is also oil on the underside of the lower tins just above these tubes.

The oil leaks have been reduced by at least a third, now about 4 to 5 drops after cool down, on the passenger side, and some oily surfaces, but no drops, on the driver side. I remain suspicious of the cylinder/case seals which may be the remaining leaks with oil dropping onto the tubes where it gravitates to the underside of these tubes. I am considering pulling the "leaking" tubes enough to put Yamabond on the O rings and reinserting them with the engine in place -- not easy, but quicker than pulling the engine again. If this does not fix the leaks, I will then have to address the only remaining possible leaks -- the cylinder/case seals -- which will require removing the drive train again Any comments?

Posted by: Mark Henry Jan 20 2017, 05:05 PM

NO to any sealant!
BTW Yamabond (threebond) although a different curing type is still RTV based. It's excellent stuff, but this is the wrong app.

I have used liquid teflon, for the most part it worked but I didn't like it.
I now use DOW 55 which is made specifically for O-rings. The DOW 55 is a lube (Molykote), but it also makes the O-ring swell a bit, giving it a tighter seal.

Two big tricks when installing the tubes.
1/ Smooth out and deburr the radius and hole on both the heads and case holes to make sure there are no sharp edges to cut the O-ring.
2/ As you insert the tube do so with a slight spinning action on the tube.

Posted by: HAM Inc Jan 20 2017, 07:32 PM

I only used oil. I've fixed drips from newly installed pushrod tubes by simply rotating them. I think the orings get bunched up during install on occasion and twisting unbunches them.

Smoothing the sharp edges at the case and head entries is important.

QUOTE(Keith914 @ Jan 20 2017, 02:21 PM)

Hmmm! I just finished carefully, no O ring damage, re-installing the existing tubes with a coating of engine oil, after very carefully cleaning their grooves of paint and flexible sealant ("snot") using new Viton O rings. All eight "popped" into place. After several short runs with engine up to operating temperature, perhaps 30 or so miles, three tubes appear to be leaking with thin oil trails along the bottom of the tubes. There is also oil on the underside of the lower tins just above these tubes.

The oil leaks have been reduced by at least a third, now about 4 to 5 drops after cool down, on the passenger side, and some oily surfaces, but no drops, on the driver side. I remain suspicious of the cylinder/case seals which may be the remaining leaks with oil dropping onto the tubes where it gravitates to the underside of these tubes. I am considering pulling the "leaking" tubes enough to put Yamabond on the O rings and reinserting them with the engine in place -- not easy, but quicker than pulling the engine again. If this does not fix the leaks, I will then have to address the only remaining possible leaks -- the cylinder/case seals -- which will require removing the drive train again

Any comments?

Posted by: Keith914 Jan 20 2017, 10:33 PM

Thanks sgain for your advice -- will try spinning first.

Posted by: Keith914 Jan 22 2017, 12:49 PM

Rotated the tubes 180 degrees (surprisingly easy -- little torque?), some improvement but still three to four drops from the passenger side pushrod/cylinder area while idling the engine for about 15 minutes while checking timing etc. Looks like I am going to have to reseal the cylinders to the case, Plan on using Yamabond for both the cylinders and the tubes.

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