Rear Main Seal: Install new seal completely dry? Lightly oiled? or Silicone greased?

[S4Gibbs]

Hi All,

There's no mention in the Erwin Audi doc of any pastes/lubricants needed when installing a new RMS, but that doesn't mean that lubrication is unspoken and implied.

Any guidance is greatly appreciated!

[JRYtheS4]

Do you like it dry? Neither do seals when they're assembled. All the shaft seals I've ever done on electric motors get some silicone based o ring lube to aid assembly, can't imagine it's any different for an engine shaft seal.

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[RPMtech147]

Do you like it dry? Neither do seals when they're assembled. All the shaft seals I've ever done on electric motors get some silicone based o ring lube to aid assembly, can't imagine it's any different for an engine shaft seal.

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Most modern crank seals, including Audi use a PTFE, IE plastic, seal and should be installed clean and dry.

The older, rubber seals, I would always use just a dab of molylube/grease. If you get a PTFE seal, it may have the "no oil" logo.

[S4Gibbs]

Yeah after deeper research in non-B8 forums, I came across this thread(check last two replies #17,18). The posts state that an OEM for seals(Victor Reinz), as well as the factory manual mentions that PTFE seals should be installed dry.

https://www.audizine.com/forum/showt...e#post10421374

[S4Gibbs]

Here's our final answer for others' future reference. While I don't see an OEM brand name on my new seal, I do clearly see "PTFE" printed.

https://www.victorreinz.com/EN/Servi...on.aspx?region

"Installation of PTFE Oil Seals

• Only remove PTFE oil seals from their protective packaging immediately before installation, to protect them from dust and other contamination.
• The sealing lip of PTFE oil seals is protected by a plastic sleeve, which can normally be used as an assembly aid. Therefore, the sleeve should remain in place until the seal has been installed.
• If the seal is to be installed without the sleeve, use the special tool provided by the manufacturer.
• Both the PTFE sealing lip and the shaft surface must be completely dry. Do not use any grease or oil.
• The shaft may not exhibit any sharp-edged chamfers – if necessary, have the edges removed by an engine expert.
• The shaft surface must be in a perfect condition – also here, possible damage must be repaired by an expert.
• Position the assembly sleeve with the PTFE oil seal on the shaft.
• Make sure that the sealing ring is aligned correctly – the sleeve must be located so that the seal can be pushed onto the shaft smoothly.
• Push the sealing ring onto the shaft with an even motion.
• When replacing, the PTFE lip of the new seal should not run in the same position as the old one.
• You can now remove the assembly sleeve.
• Do not start the engine sooner than four hours after installation – this permits the new sealing lip to adapt perfectly to the shaft.

Failure of PTFE Oil Seals
Damaged PTFE Sealing Lip
The most frequent cause for failure is damage to the PTFE sealing lip during assembly. If the seal is installed without the help of a sleeve or special tool, and is shifted or even turned inside out, reliable sealing will hardly be possible. Similarly, the use of oil or grease – as with classical oil sealing rings – will result in total failure of the PTFE oil seal immediately after installation."

[JRYtheS4]

Really nice info. Haven't dealt with a PTFE seal yet, have to log that away for future reference!

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[S4Gibbs]

Really nice info. Haven't dealt with a PTFE seal yet, have to log that away for future reference!

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Happy to help man. And in response to your earlier reply, I agree, o-rings and other rubber seals should generally all be lubricated. Silicone paste like this, stays put better and is more waterproof than a silicone spray IMO. Plus, silicone grease is great to have around for most plastic-plastic friction points too.

Oil generally degrades rubber, so the only rubber seal that I apply an oil-based lube to is motor-oil onto oil filter housing o-rings, because they're already being exposed to engine oil -- which might be why they need to be replaced so frequently...

[minman26]

Had rear main seal done a couple years ago. Has a $85 charge for paste. AMV-188-001-02

[S4Gibbs]

Had rear main seal done a couple years ago. Has a $85 charge for paste. AMV-188-001-02

From what I can google, that looks like an RTV-type adhesive. 2.0T engines require an RTV bead when reinstalling the rear main seal mounting plate to engine block; 3.0T's don't use such a mounting plate.

The shop either billed you for a paste your 3.0T's RMS procedure didn't need, used the paste to seal something else legitimate on your engine(did you get a new oil pan installed too?), or the next person who tries to replace your RMS will have a REALLY rough time.

[JRYtheS4]

the next person who tries to replace your RMS will have a REALLY rough time.

If it doesn't seal, just add more sealant!
I'd wager oil pan sealant or timing cover sealant.



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[minman26]

Interesting. Appreciate the feedback. I’m sorry I can’t offer an further insight. Hopefully I won’t have to find out before I sell the vehicle!

[RPMtech147]

From what I can google, that looks like an RTV-type adhesive. 2.0T engines require an RTV bead when reinstalling the rear main seal mounting plate to engine block; 3.0T's don't use such a mounting plate.

The shop either billed you for a paste your 3.0T's RMS procedure didn't need, used the paste to seal something else legitimate on your engine(did you get a new oil pan installed too?), or the next person who tries to replace your RMS will have a REALLY rough time.

I've seen a number of mechanics smear a small amount of sealant on the outside of new seals where it seals to the block. I don't feel it's necessary so I don't.

but yeah...$80+ for a tube of sealant? Got-damn. We exclusively use MB factory sealant and that's $25/tube, and from my experience, it's the exact same thing as Audi D176501A1..even uses the same "caulking gun".

I don't recall ever using AMV-188-001-02. Is that the factory brownish stuff, say like when you removed the valve cover on a 2.0T? (That stuff is such a pain to clean). That stuff is pricey from my googing...almost $60/toothpaste tube

[chi123]

As you may have already found out, it's installed dry. First time I installed it, I applied some oil to help it slide onto the crank snout more easily but then my friend who is an Audi tech said that the seals are PTFE and should be installed dry to form a good seal to crank. Otherwise, it'll leak. You have to install it dry, making sure the lip doesn't roll or get kinked going onto the snout. Not other sealants or lubricants go onto the seal that meets the back cover.