V10 5.2 FSI Y plenum assembly - read before you mess with it

A6 All/ S6 All
#1

Having just replaced Y plenum with new one, and taking it off and putting back on multiple of times I thought i would write a fair warning to everyone, who will either take the manifold off, replace throttle body gaskets etc.

  1. Audi manual states that bolts, that hold Y plenum down to the intake manifold itself should be torqued to 9Nm. This is bullshit, as OEM bolts are aluminum (they have to be - if they are steel they will corrode the threads in the intake manifold getting them stripped), and they break at 7.3 Nm. In my expirience 6.5 Nm is totally fine.
  2. Throttle bodies should be torqued to 9 Nm according to Audi. In my opinion this is too much as well. My unit is new, and I dit torque it to 9Nm, however the next time I will do 8, as it is max I was comfortable doing. I think that getting older unit to 9Nm might crack the thing.
  3. Throttle bodies bolts - I have bought 8 OEM new bolts, and 2 of 8 are just a little bit bent, or the thread is cut in a wrong way - hard to tell. Also all of them have their heads offset just a little bit from the bolt core center. I would highly recommend trying every single bolt first with screwing them in with just your fingers - they should go to the end no issue. If you feel it gets locked just a little than don’t use that bolt.

TL;DR

  1. Torque for bolts holding Y plenum to the manifold should be 6,5 Nm
  2. Torque for the throttle bodies bolts should be 8Nm
  3. Check every throttle body bolt first. It should go all the way in the Y plenum effortlessly.

Hope this helps someone in the future.

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#2

Great advice. To be honest on many of these bolts and several others. I do a Tq to feel. So I don’t use a TQ wrench. I tighten till I feel it’s snug then start with 1/4 turns after that until I feel the right amount of force has been used. As you said with some bolts you tend to feel like it’s very easy to over tighten them and instinct is one important tool to utilize.

#3

I agree!
I have recently worked on my intake/plenum assembly and one bolt broke in the manifold.
Very good advice!

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#4

Torqued a Mercedes gearbox as factory spec once. The whole block cracked. Will not do that again.
Thanks or the tip!

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#5

One snapped on me last week when I was trying to torque to spec. :frowning: Have you got the part number for those bolts?

#6

N 106 919 01 - Y plenum to the IM
N 105 303 04 - Throttle Body to Y plenum

2 Likes
#7

Thank you!

#8

Lots of great in this thread.

Might help to drop some of the intake part numbers in the original thread.

#9

I recently torqued all these bolts to factory spec, thankfully without issue BUT I did calibrate the torque wrench and checked the calibration as I worked if something “just didn’t feel quite right.”

#10

Great FYI from @Dlugi11 - WAY too many people over tighten these bolts.

#11

I just recently snapped two following the torque specs, wish I’d seen this thread before lol

I have a weird issue with mine, I can’t get it to seal to my new intake manifold. It’s doesn’t seem to line up quite right and it’s leaking near the fire wall on the passenger (right) side. Has anyone ever heard of this happening?

#12

Is it getting caught on the throttle body wiring or passengerside low pressure fuel rail?

#13

It doesn’t seem to be, I thought that at first as well so i removed it got a new gasket and removed the throttle bodies. Then reinstalled, it’s doing the same thing again. When I test fit it on the old intake it fits perfectly but on the new intake the front two bolts barely catch the threads

#14

The issues with the intake and Y pipes and all of those collecting pieces is they tend to warp. So it’s best you use the gasket but on all of those parts I always use a small beed of permatex

#15

Thanks, that was going to be my next option. I was just curious if anyone else had come across this

#16

Many people have had leaks at the throttle body and the Y sections. It has been the recommendation to use a silicone gasket aid on those parts.

#17

Yeah I did that, it seems to have sealed up with some rtv, I smoke tested it and couldn’t see a leak anywhere