Conference vmsnet::car$note:carbuffs

I have a 96 Jetta with ABS brakes.  It has about 17k on it now.  Somewhere
between 15k and 16k the brakes started squealing slightly.  I mentioned this
when I brought it in for the 15k service.  They replaced the front pads with
upgraded pads.  Didn't say anything about a problem being found.  Finally got
around to calling and asking the service manager about it (I had picked the car
up late so couldn't get an explanation at the time it was in).  He said that
because they can no longer use asbestos in brake pads, the new pads have a 
higher metallic content.  As the pads begin to wear the metal in the pads 
rubbing against the rotors causes the squealing.  The upgraded pads have less
metal content so they won't do this.  He said the original pads were not overly
worn; that this is a common problem; there is no safety issue here but only the
sound to deal with; that some customers choose to keep the original pads even
with the squealing.

This all sounds plausible to me but I wanted to check it out.  I was very sur-
prised that my breaks would start squealing at 15k miles!  Is this guy (Tulley
VW in Nashua, btw) telling me the truth, and the whole truth?

Thanks!
Barb
    

    Brake dust can cause the brakes to squeal.  
    
    Brakes can squal for many reasons, the dust, they're worn out, the
    rotor is ground up, they're cold....
    
    Metalic pads don't last long, but they stop your car better.  They
    could squeal more than non-metalic pads.  Non-metalic pads may not
    squeal, but they don't work as well as (semi)metalic pads.  They'll
    fade easier, etc...
    
    It depends on what type of driving you do and how you maintain your
    brakes.  For example, have you driven through a puddle lately?
    Did you slam on your brakes recently to avoid a road hazard?
    Do you ride around with your foot on the brake?
    
    A slight squeal is ok.  A chirp means the pads are worn out, a DRAGGING
    SQEALING GRINDING noise is bad.
    
    Metalic pads are generally "high performance" stuff.  High performance
    stuff isn't expected to last as long as normal stuff.  
    
    MadMike

    re: squealing brakes
    
    WE have an Acura and a Honda with 4-wheel disc brakes and metallic
    pads at all 4 corners.  Each vehicle, after 5K miles, started having
    minor brake squealing - not on hard braking, but on softer braking,
    especially right before the car stops.  There's almost nothing you
    can do to prevent this, due to the the way the pads break in and the
    way they wear on the rotors.  Other vehicles, like Volvo, have even
    worse squealing problems.  Mostly it's the nature of the braking
    system and materials.
    
    Some dealers will replace the pads with ones with less metal content
    to reduce squealing - but the downside is they wear much quicker and
    tend to grab when they get hot.  If you car wasn't designed with
    non-metallic pads in mind, you may get braking behavior you don't
    expect - especially when warmer weather hits.  From what you describe,
    the pads weren't an upgrade - but rather a "downgrade" to keep you
    happy with less noise, but bring you in earlier for pad replacement
    down the road.
    
    So - keep an eye on the braking ability of your car once spring/summer
    arrives - you may notice a difference from before.
    
    andy
    

The squeeling is either due to the pad material or the lack of brake shims
and/or lack of grease behind the pads and on specific areas of the caliper. I
own two Volvos and cured the dreaded Volvo squeel by going to an aftermarket
pad (Friction Tech), two shims behind each, and high temp grease on the back of
the pads and shims.  I also greased all the contact areas for the brake
hardware.  BTW, the shims were Teflon coated as well. 

If I owned your VW, I would start by investigating aftermarket pads and
installing them exactly (shims, grease, etc) as VW recommends. Ask in this
notefile what people use.  There are plenty of VW owners here.

Jim 

    I have a holley 4150 double pumper carb.  I have power brakes.
    I used to pull vacuum from my intake manifold to the brake booster.  
    My new manifold has no port to draw vacuum.  I am wondering if I can
    route a hose from the PVC plug on my carb to the brake booster.
    Is this OK.  Currently, the pvc plug on the carb base is plugged.
    
    MadMike

    
    	Yeah, pipe the vacuum through to the PVC plug.  8^)
    

    Be careful!!!
    
    The PCV valve is letting crankcase air into the manifold so there is not
    the max vacume available for the brakes like you would get in a
    seperate port.
    
    Steve

>    The PCV valve is letting crankcase air into the manifold so there is not
>    the max vacume available for the brakes like you would get in a
>    seperate port.

Everything under the throttle blades is at the same relative pressure (or 
vacuum)

A T fitting in the PCV (not PVC) hose worked on my old Wagon.

The only "problem" you'll run into relative to crankcase fumes is that they 
tend to be dirty and. as such, tend to fill the port with deposits that 
eventually clog up the PCV port.  If you don't keep on top of it, there 
won't be enough VOLUME to replenish your booster's vacuum.

If you have a PCV port on the back of the carb and aren't (I can't see any 
valid reason NOT to be using positive crankcase ventilation) using it, the 
brakes will work fine on it.

Running an engine w/o positive crankcase ventilation produces an oily 
engine (blowby) and a sludgy engine (moisture buildup)

    Skip, I disagree. Depending upon where the 't' fitting is, the size of
    the pipe/hose etc, by letting in air from the PCV you can be lowering
    the overall vacume suction available to booster. As a matter of fact,
    all my trucks and I assume cars too have a check valve to hold the
    maximum vacume (throttle closed) so that the booster will start off
    with it's 'best shot' of boost pressure.
    
    Steve

    I think in most modern cars, the booster check valve is at the
    booster.. so there is no way to get "behind" it with PCV air..
    
    Using the PCV fitting for both PCV and the brake booster is probably
    not optimal, but it will work.. as skip says, the port is at the same
    vacuum level as the manifold; the only question is volume and dirt..
    
    ...tom

    
    
        Many vehicles come right from the factory with a "TEE" fitting
    in the line to the PCV and then going off to the brake booster.
    As long as the booster hose is higher (it is) than the crancase vent
    valve, no crud will ever end up in the booster. One of my chevys is
    built that way. Works fine.
    
    -john

    The hazards of nite-noting... ya, it's PCV.  I'm working on 4 cars
    at once and I was a little bit dizzy from pulling an engine out of
    one of them, taking the heads off another and rebuilding the bottom
    end of the third.  (The 4th... my wife accidently shoved into reverse
    while she was cruising down the hiway)...
    
    So... the PCV nipple on the carb will be sufficient to run my brakes.
    This is not street driven, so I'm not concerned about "streetability".
    What I AM worried about is being able to stop the car from 120 mph
    in a decent distance.  
    
    MadMike