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JBOYLE
08-19-2008, 11:39 AM
A quick question before I take the car to the (experienced Stude) mechanic...

I had my Avanti in the shop and they did a good job fixing various PS,PB leaks.

Now, I have a problem that shows up only some of the time...
When I apply the brakes the first few times in a drive...no brakes (scared the wits out of me at the end of the driveway!)
As I drive it gets better.
Other times, it's fine.

He didn't replace the brake booster...would that be a permanent solution?

63 Avanti R1 2788
1914 Stutz Bearcat
(George Barris replica)

Washington State

Dick Steinkamp
08-19-2008, 11:54 AM
What do you mean by "no brakes"? Does the pedal go to the floor?

Dick Steinkamp
Bellingham, WA

http://i149.photobucket.com/albums/s66/ddstnkmp/Stude-a-mino%20old%20pics/oldpics6asmall.jpg

JBOYLE
08-19-2008, 12:07 PM
Pretty much. Full brake pedal application, not much stopping power.
Like hot brake fade coming off a hill back in the bad old days.

63 Avanti R1 2788
1914 Stutz Bearcat
(George Barris replica)

Washington State

Dick Steinkamp
08-19-2008, 03:30 PM
I'm a little slow, but I'm still not understanding the symptom.

Does the brake pedal go to the floor like there is a leak or air in the lines but firm up if you pump it, or..

Does the pedal feel "normal" but the car just doesn't slow down when you press it, or...

Does it feel like there is not power assist, or...

none of the above.





Dick Steinkamp
Bellingham, WA

http://i149.photobucket.com/albums/s66/ddstnkmp/Stude-a-mino%20old%20pics/oldpics6asmall.jpg

N8N
08-19-2008, 03:33 PM
if the brake pedal goes to the floor and there is no leak in the system and it is still full of fluid, check your front wheel bearings. if they are loose they can knock the pads back and cause a low pedal on the first application, but the pedal will firm up if you pump it.

If it feels like a lack of power assist, check for vacuum leaks to the booster and/or the check valve.

I'm assuming that since you've had a mechanic look at it that all the brake hydraulics are in good shape...

nate

--
55 Commander Starlight
http://members.cox.net/njnagel

fmarshall
08-19-2008, 05:26 PM
It could be that you have internal leakage in the master cylinder also. If it gets better after a few applications, the seal could be expanding a little.

Two ways to test the system:

1. Pump the pedal and hold it with the engine off. If the brake pedal doesn't hold, then it is experiencing internal leakage. Try it cold with just 1 or 2 pumps.

2. With the car off, apply the brakes, then start the car. If the booster is working correctly, the pedal should drop about 1/2" when the car starts.



========================
63 Avanti R2, 4-Speed, 3.73 TT
Martinez, CA
http://i226.photobucket.com/albums/dd211/fmarshall_bucket/sigpic.jpg

JBOYLE
08-19-2008, 05:42 PM
quote:[
Does the pedal feel "normal" but the car just doesn't slow down when you press it, or...

Dick Steinkamp
Bellingham, WA



Yes. The pedal feels fine, just reduced stopping power.

63 Avanti R1 2788
1914 Stutz Bearcat
(George Barris replica)

Washington State

41 Frank
08-19-2008, 06:09 PM
Sounds like you have no power assist on the brakes.

buddymander
08-19-2008, 11:10 PM
Maybe a hose is leaking vacuum but seals up when it gets warm.

JBOYLE
08-20-2008, 12:08 AM
quote:Originally posted by fmarshall
2. With the car off, apply the brakes, then start the car. If the booster is working correctly, the pedal should drop about 1/2" when the car starts.


Yes, the pedal does drop.

63 Avanti R1 2788
1914 Stutz Bearcat
(George Barris replica)

Washington State

leyrret
08-20-2008, 05:41 AM
Not an authority on these but sounds like booster unit. The pedal drop indicates vacuum is getting to the main
piston, but control valve controls actual operation.