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Thread: C5 Rs6 Boost leak test assistance

  1. #1
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    Question C5 Rs6 Boost leak test assistance

    Can I get some pointers on a boost leak test?


    I have a new to me 03 C5 RS6. Has intercoolers, apikol intake and a stage 1 tune. ZERO boost. Replaced one hose I found with a smoke test, but I think there are more issues. I was told possibly a passenger turbo is out but I should still see something if driver is still good. Trying to get a baseline for what to replace when I have engine out. (Everything is not an option right now).
    I know how to do a leak test on my 2.7's, I am probably over thinking this 4.2


    I have plugs for inlets, air source to passenger diverter valve hose. Plug diverter valve, remove oil cap. When doing that all air escapes oil cap. Do I need to remove a PCV and plug that line to hold air?

    This car is a mess and I need to get a good baseline of issues before engine pull.

    Thanks!

  2. #2
    Registered User hahnmgh63's Avatar
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    You would have to have a large boost leak (Intercooler/intake hose) to cause zero boost. It would definitely be a large whooshing sound when you put your foot in it.
    2003 White RS6 2013 Midnight Blue S5
    2013 Daytona RS5 2x944 Turbo's 1974 911 w/'91 3.6ltr motor
    Roy, WA

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    Quote Originally Posted by hahnmgh63 View Post
    You would have to have a large boost leak (Intercooler/intake hose) to cause zero boost. It would definitely be a large whooshing sound when you put your foot in it.
    Had a huge hole in one hose, the passenger outlet to intercooler, and it made no sound. I am not getting any of those sounds (familiar with the TTB going on a 2.7). I do think both turbos may be toast though with the huge amount of oil in the intercoolers. Given the inlet location, it would be pretty easy for someone to drop something in... Had someone do that to an S4, still made a little boost, but turbo cold side fins were GONE.

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    Registered User hahnmgh63's Avatar
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    With the intake off you should be able to use a video inspection camera down the intake to see what the compressor wheel looks like. Two separate intake tracts for both to get toasted unles it was intentional damage by someone.
    2003 White RS6 2013 Midnight Blue S5
    2013 Daytona RS5 2x944 Turbo's 1974 911 w/'91 3.6ltr motor
    Roy, WA

  5. #5
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    Quote Originally Posted by hahnmgh63 View Post
    With the intake off you should be able to use a video inspection camera down the intake to see what the compressor wheel looks like. Two separate intake tracts for both to get toasted unles it was intentional damage by someone.
    I tried that but neither of my cameras can get a good angle through the inlets based on the bends. I cannot get a decent straight on view of the CHRA or more than 1 fin. I was able to get enough pressure in the system to blow the inlet (plumbing stop) out, I see that as a positive.

    I did get a test drive in over the weekend and was able to get a code for N75. 17956. Never seen an open circuit for N75 cause Zero boost, normally defaults to wastegate opening, but going to swap that and see if it is the unit or wiring next.

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