[s-cars] Re: Pressure testing

chris chambers fastscirocco_2000 at yahoo.com
Wed Jul 21 08:02:44 EDT 2004

Dave, Tom

My air compressor has a 60 gallon tank, so that should do right?

The breather hose on the back of the valve cover is leaking so much air
I can't hear anything else. Sounds like my first step is to put new
clamps on the breather hose and stop that leak. Then after sealing that
leak continue testing for other leaks.


--- Djdawson2 at aol.com wrote:
> Hey Chris,
> Here's the deal....  When you simply put a fitting in the turbo
> intake line 
> and pressurize it, you're actually pressurizing a whole bunch of
> things that 
> don't require pressure.  This isn't a problem, provided you have an
> adequate 
> supply of air to compensate for the losses.  I use a 60 gallon
> compressor.  
> Needless to say, I can regulate the pressure down to about 10 psi
> (very safe for 
> all things involved) and it would take quite some time to empty the
> tank.
>   If you don't have a large volume of air to work with, you will have
> to more 
> adequately isolate the intake tract.  Going in through the turbo
> intake will 
> pressurize the entire crankcase, valve cover area, etc...  You will
> have to 
> remove and plug any and all breather lines that would allow this to
> happen to 
> effectively test with a small volume air tank.  Keep in mind that it
> may still 
> be difficult.  When pressurizing the intake, you will also be
> pressurizing any 
> cylinder whose intake valve is open.  You will also potentially loose
> large 
> volumes of air rapidly through any cylinder that is in a position
> where valve 
> overlap is occurring (intake and exhaust valves partially open in the
> same 
> cylinder).  Likewise, if you have any significant leakdown in a
> cylinder receiving 
> pressure, you will again be pressurizing the crankcase, leading to
> rapid 
> depletion of a small volume air tank.  No matter how hard you try, a
> test of this 
> nature will loose air somewhere, so large volume is your best weapon.
>   Bottom line... IMHO, it is best to find someone with access to a
> large 
> volume tank.   Pressurize the whole system to a reasonable level (10
> psi), and 
> then isolate your leaks.  Likely, opinions will vary.  But this has
> worked 
> exceptionally well for myself, and numerous lister's cars that I've
> helped test.
> Good luck, and HTH,
> Dave in CO

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