Type 4...10mm and 12mm crank seals

[raygreenwood]

I seem to mention/warn about this issue whenever mysterious and plentiful bell housing oil leakage is the topic.

Too many times I just do not have all of the items in front of me to make it easy to take pictures of.

So I am building a 1.8L for someone right now for their 412 variant. This may or may not be the original case for that car but it is known to be from a 412.

It is an EA series. And while most of the case # lists show EB and EC for 1.8L and California 1.8L respectively....for the bus....I have found that not to be accurate for the 412.

Over the years I have found more than a handful of known to be original cases with 1974 412 cars with 1.8L L-jet that were very close to the line between late 1973 with D-jet and early 1974...that came with EA series cases.

Anyway...thats not the point right now.

This case came with the deep seal recess...12mm. I also have one case from a early 412 with the 10mm seal recess and one with a 12mm recess.

I have never been able to collect enough corresponding data to say when this started or why.

And.....this is what a deep seal recess versus a shallow seal recess looks like:

The case in question:

The new Viton Elring seal provided...part # 029 105 245 B.....measurements and data on seal read: 7.5 X 95 X 10 FPM/APM

The seal fit in the case when pushed in flush

Now....the correct fitting seal I have always found for these cases...to not cause a MASSIVE oil leak at highway rpms (seems to seal ok at low rpms in traffic) is 021 105 245 C...and is technically a Vanagon part. Note the part # prefix change.

Its seal data reads 7.5 X 95 X 12 LF

Here is the 12mm seal fit in the same case when pushed in flush.

The rhyme or reason for this seal depth/thickness change? Hmmmm.

Now this is purely speculation....I just do not yet have enough data to back it up....but with the engine case in question it is known that it came in a chassis with a 003 automatic transmission.

So looking at the flex plate for this transmission....bearing in mind that it does not have a radius like a flywheel....I measured the depth of the snout and it is 0.615" (with just a quick snap measurement with a cheap caliper).

The 12mm seal applied to the snout of the flex-plate and brought up to the faint wear/grease line that the last seal left on it.

The snout of the flywheel from a manual transmission happens to be 0.523" to the start of the radius.

Thats a difference of 2.33mm...which allowing the seal to ride just onto the radius about .010" to .015"....leaves a difference of right at 2mm.

Perhaps the deeper seal recess was used on engines that were destined for automatic trans cars (at least maybe in 411/412). Anyway...later I will inspect my 412 case that is known to have come from the factory with a four speed....and see what it had.

The real point of all of this is....when you are changing seals...if your engine was not built with its original case and you do not know what kind of vehicle it came from...check your seal recess depth and buy the correct seal.

Ray

[Spike0180]

Awesome information. Thank you ray.
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Brutis Patches Izabich: 1970 VW Transporter - 1776cc DP
Current State: Projects never truly end...
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[hazetguy]

another way to avoid massive oil leaks is to be sure the seating surface on the flywheel or flex plate does not have that worn groove as seen in the above pic, that the surface is extremely smooth with no pits, and that the seal does not ride in that groove if you are doing an emergency type repair. different seating seals will ride on different flywheel surfaces, so if you do have a groove, a deeper or not deeper seal might help in the short term.

[Wildthings]

[busman78]

When a case that used the 12mm seal had a crank with a wear groove I would install a internal retaining ring that I bought from McMaster-Carr that would compress enough to be tight on the case, they were 1mm thick, perfectly flat, allowed spacing a 10mm seal at 11mm, also ended up with some 10mm seals that were really 9mm thick, two retaining rings, either way ended up with proper seal placement and no leaks.

[raygreenwood]

[SGKent]

totally not T4 but someone who dropped by last summer had a failed seal on a T1 because it was inserted flush and the tapered part of the flywheel was riding on the lip. When a new seal was inserted until it stopped, the lip sat on the flat part of the flywheel race and did not leak. I kinda wonder now if some of the leakage problems on these seals don't come from some of the seals riding too far out, onto the taper in the flywheel. Also, I had one leaking but the place it was leaking was the case part line. I could see the wet line where the oil had been coming out along the part line. Attempts to use any sealers in that area caused the seal to creep out. It was a VR orange. I notice that the Elring have a black rubber sealing area on the exterior, instead of the all silicone VR. The ribs look deeper too. The arrow points to where my orange VR was leaking.

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"Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin

[Wildthings]

[raygreenwood]