trosser001

The connector piece (I know, the name is not descript, but it is the formal name!) of my 95 993 non-varioram has oil in the lower tube.

Where might this oil come from?

Here is the part number: 99311002703 "Connecting Piece"

And I've attached a screen shot of the parts diagram - it is number 18. The piece has two tubes, I found oil in the lower one...it's the one the green arrow is pointing to...

Any ideas?

Ivan J

That is an air plenum that has a "resonance flap" inside of it to tune the volume within the plenum based on the rpms (similar concept; but, not the same thing as VarioRam).

Others are going to tell you that you've been overfilling your oil. I think that having some small amount of oil in there is normal, even if one is careful not to overfill.

I have some oil residue seeping out of that air plenum from the "round thing" right where the "find number" is pointing to the assembly. I believe the round thing is the shaft that the resonance flap rotates on. Nobody seems to know if there is a replaceable seal in there.... if yours is disassembled could you take a look at that area? I've been annoyed by the oil residue; but, not enough to remove all of that plumbing to have a look at it.

techman1

Not overfilling and I als get a small amount in my '95.

trosser001

Ivan - I will take a look to see if a) that shaft services as the axle for the resonance trap and b) if it has a replaceable seal.

Will shoot photos and post. Tomorrow...

Thanks for the reply, much appreciated.

trophy

The oil comes from the breather from the oil tank. Part of the emissions, oil vapour condenses in the intake and ends up in the lowest part of the plenum.

pp000830

+1

trosser001

I have more information on the source of the oil leak from the lower air plenum; it is from the bearing on the shaft used to rotate the resonance flap in the lower plenum.

I have disassembled and removed the shaft and resonance flap. There are "sealed" bearings at the top and bottom of the resonance flap shaft. These bearings are nice ideas but poorly executed (in terms of materials used to construct).

Having raced and wrenched on karts for a few years, I have come across sealed bearing that are durable and sealed. These are neither.

Before I go any further and press out the lower bearing, I wanted to post pictures and then open a dialog to get ideas on where we might find adequate replacements.

Here come Picts. The last picture is of that lower bearing and notice how the disk which would seal it is broken down and decaying!

trosser001

So they can stay in and will continue to work. And continue to leak. Does anyone have any ideas on finding replacements once I press the bearings out?

KNS

Just to add to the post - on my '95 (which I make sure not to overfill), I find a bit of oil in the same spot.

AllMine

Got my spoiler bearings from Boca Bearings... maybe try there? will need full dimensions though.
Curt

k722070

just remove it and take to a bearing company for sizing.
you might also be able to find a part number in the catalog.
this was covered for the varioram version in this thread with seal sizes and part numbers on page 2 and 3.
https://rennlist.com/forums/993-foru...anifold-2.html

Ivan J

Thanks for posting this! Can you measure the inner and outer dimensions without doing something that cannot be undone? If the bearing is a standard size, replacements should be available. There is a bearing supply place very close to my office... if you can post-up the dimensions, I'll see if they have replacements.

I'd be wary of cracking the plenum when trying to remove the bearings. It could get messy if the outer portion is glued to the plastic.

The Katalog indicates that the entire plenum is replaced as a unit, there is no further breakdown showing P/Ns for the flap or the bearings.

Sandia man

Help me understand. If the oil comes from the oil tank breather tube (#14 in the diagram) would not a bearing that is better sealed just trap more oil in the lower plenum chamber? I guess it would prevent oil from dripping out by way of the bearing but the mess inside the chamber would be worse.

trosser001

Ok guys, I'm pretty simple-minded in attempting to compare the "sealed bearings" used in kart racing to what turns out to be "oil seals" - as k722070 rightfully pointed out (thank you, btw).

And k722070 referred us to a varioram specific thread where they are attempting to seal up another shaft. The seal used there is identical to the seal used in this instance on my non-varioram.

The oil seal is dimensionally 8mmx12mmx3mm. The norm in referring to this size is "8x12x3". And this is a seal size readily available from a number of manufacturers, in a variety of compounds, with varying seal-lip designs for differing environments.

Coincidentally, you can get 3 different variants of the 8x12x3 seal, on of all places, Amazon. The manufacturer in this case is Dichtomatik. They range in price from 4 to 20 some odd dollars a piece. In my location I'm able to get the same one from the associated described in the thread listed above by k722070 (https://rennlist.com/forums/993-forum...anifold-2.html")

It's important to note that the seal is a plastic/rubber insert in a sleeve bearing. Removing it was simply an exercise in carefully lifting/prying it up with a tiny flathead.

I've included a picture of the oil seals I just removed. On the back I found the sizing specs...



two oil seals from my 1995 non varioram 993. out of the lower resonance chamber on the throttle body, these seal the flap shaft. Well, they don't actually seal it - the lower one is the source of oil on the top of our engines...




This is the side you see when you look at the seals installed (see the last picture for that view). <br/><br/>The one on the right was the lower seal. It's inner lip has completely disappeared. No wonder it leaks...



this gunky looking puddle of goop where the green arrow points, is the actual installed location of one of the two in the pictures above. The arrow is pointing to the area between the two seal lips, which is filled with a little grease. you can see that it appears to be non-metallic, and it has an inner race and an outer, between which is the moat of grease. the inner wall on this one is cracked. ....

trosser001

The lower plenum not only tends to capture oil, it is also the source of our non varioram engine's deep hearted growl that occurs when we step hard on the go-pedal - the air within that lower plenum is shared amongst our 6 air-hungry cylinders as they are called upon to go-faster. I'm pretty sure that there is much more magical stuff going on, but you get the point I hope!

And as that happens, that oil tends to find its way into the combustion chambers. Reminiscent of the PCV (positive crankcase ventilation) on my old Buick 455 tree stump puller.

So it doesn't just pool up in the lower plenum; some of it so nicely leaks out the oil seal which is the subject of this posting, and then much of the remaining oil goes poof! - as it gets burnt and comes out our exhaust.