New to the G35Drive forum. Bought a used '03 G35 5AT sedan (non-Brembo) with approx 78k miles. Drove it for about six weeks and started experiencing some odd braking issues.

First noticed that when I lifted my foot off the gas (no brake applied) the car started decelerating faster than usual, as if the brakes were being applied softly. It would only do this after a couple miles of driving. Also began noticing a hiss sound behind the driver's side of the dash that would stop when I applied the brakes and start back as soon as I released the brakes. This hiss only occurred after driving for a while.

Last week, I left home, drove about a mile and everything seemed fine. Stopped at a stop sign, accelerated, then lifted my foot of the accelerator. When I lifted the car quickly came to a stop. I had to force it to the side of the road using a lot of gas. When I looked down the brake pedal was engaging itself and I could not lift the pedal. Let it sit for a while and managed to get it back home before it flared up again.

Here is what I've tried.

1) Assumed it might be a booster check valve, so I replaced the vacuum lines into the booster and on the passenger side into the manifold (used parts due to length of time to deliver). My understanding is that the check valve is in the passenger side hose. Nothing changed, though I did find that disconnecting the vacuum line from the booster immediately released the calipers, making the car drive-able (without power brakes).

2) Calipers looked rough so figured I might have a bad/sticking caliper that was heating up the fluid and causing the system to lock up. Replaced calipers, rotors, pads, and did a fluid flush and bleed. Car drove about 3 miles without any issues then suddenly started the spontaneous braking. Pulled to side of the road, disconnected the vacuum line which was under a LOT of suction (loud thud when I finally got it to release). Limped home - defeated.

Anybody experience similar issues? Suggestions? Do I have multiple issues here?

 

http://forums.nicoclub.com/post6744835.html#p6744835

Telcoman

 

To my knowledge, the only thing the check valve does is prevents air from leaking back into the brake booster which would make it harder to operate, not the opposite.
Seems to me that there's an issue with the brake booster itself. Maybe whatever part, spring, or whatever that normally keeps the engine vacuum from pulling too much on the diaphragm failed.

 

ArnoldKnox, before you start replacing un-needed parts you need to find out what the cause really is! Find a "Independent brake/alignment shop" in your area, they deal with brake issues all day long and will be able to solve yours! Every town has at least one, find yours...Gary

 

Agreed with Gary, you could throw money at it all day and not solve the issue. Id take it in and have it diagnosed. from there you can have them do the work or you can do it yourself. In the end it will be a lot cheaper.

 

My local dealer is not super expensive



You get a free loaner and everything works when you leave

Telcoman