New here so please be gentle, LOL.

Recently bought an 03 G35 Sedan (5AT, non-Brembo). Six weeks later started noticing car was decelerating quickly after lifting off the accelerator - like it was braking lightly. Then, noticed a whirring or hissing sound coming from driver's side dash area. The hiss would stop when I depressed the brake pedal, then re-start once I released the brake pedal. Drove cautiously home. Last week, took it for a test drive, driving about one mile before stopping at a stop sign. Lifted off brake and noticed that it was a little harder to get rolling, as I started to accelerate, it got harder to do so. Looked down at brake pedal and it was depressing itself. Tried to lift it and could not. Got off the road, let it sit and was later able to get back to the driveway before it flared up again. Here is what I've tried...

1) Research and symptoms seemed to indicate a failing booster. Tested the booster via the FSM's "operating check" and "air tight check" and it seemed to be operating normally. Test drove - no change.

2) Some research indicated a bad check-valve. I replaced both rubber hoses (one from the booster and one into the manifold) with salvage yard hoses since it was a week or more to get one delivered. My understanding is that the check valve is in the hose that connects to the manifold. Test drove and same issue occurred. Removed the vacuum line from the booster and calipers immediately released and car rolled freely (albeit without power brakes).

3) More research indicated I might have a bad/sticking caliper that was heating/expanding the brake fluid and causing the other calipers to stick too. Examined the calipers and determined they were the likely culprit. This weekend, I replaced the calipers, rotors and pads, then, flushed/replaced the fluid and bled the system. Test drove it and it seemed to be fine (drove 2-3 miles) before it seized up again. Removed the vacuum line and limped home - defeated.

Suggestions???

ARNOLDKNOX wrote:New here so please be gentle, LOL.

Recently bought an 03 G35 Sedan (5AT, non-Brembo). Six weeks later started noticing car was decelerating quickly after lifting off the accelerator - like it was braking lightly. Then, noticed a whirring or hissing sound coming from driver's side dash area. The hiss would stop when I depressed the brake pedal, then re-start once I released the brake pedal. Drove cautiously home. Last week, took it for a test drive, driving about one mile before stopping at a stop sign. Lifted off brake and noticed that it was a little harder to get rolling, as I started to accelerate, it got harder to do so. Looked down at brake pedal and it was depressing itself. Tried to lift it and could not. Got off the road, let it sit and was later able to get back to the driveway before it flared up again. Here is what I've tried...

1) Research and symptoms seemed to indicate a failing booster. Tested the booster via the FSM's "operating check" and "air tight check" and it seemed to be operating normally. Test drove - no change.

2) Some research indicated a bad check-valve. I replaced both rubber hoses (one from the booster and one into the manifold) with salvage yard hoses since it was a week or more to get one delivered. My understanding is that the check valve is in the hose that connects to the manifold. Test drove and same issue occurred. Removed the vacuum line from the booster and calipers immediately released and car rolled freely (albeit without power brakes).

3) More research indicated I might have a bad/sticking caliper that was heating/expanding the brake fluid and causing the other calipers to stick too. Examined the calipers and determined they were the likely culprit. This weekend, I replaced the calipers, rotors and pads, then, flushed/replaced the fluid and bled the system. Test drove it and it seemed to be fine (drove 2-3 miles) before it seized up again. Removed the vacuum line and limped home - defeated.

Suggestions???

Currently your almost fifteen year old vehicle is a hazard on the road.

You should have had the vehicle towed to a dealer prior to just guessing and throwing parts at it.
Call AAA & have it towed to the nearest Infiniti dealer.
Just tell them there is a brake problem and let them tell you what parts are required to fix it & how much its going to cost.
Don't mention what you've done.

Just my $.02

Good luck

Telcoman

If you are hearing a hiss then it seems something under pressure is releasing. If you are still getting the hiss then try and track it down and troubleshoot from there.

You said you heard a hiss from the drivers side dash area. It is still there after you changed all this? The lines from the ABS come thru that area on the outside of the firewall. You might have a pin hole in one of them or just one of them leaking and getting air into your whole system. Also, have you read your ABS codes? Do you have any brake/VDC/parking brake lights on all the time?(oreillys or advance auto will read your abs codes for free) Did you bled the lines properly(best is with a reverse bleeding system), Did you bled once only if you used the normal bleeding method or did you bled several times? Did you go back to the booster as a possible culprit even if your initial test said it is ok? Did you check your parking brake shoes, that they are not staying all on the time due to improper rigging of the parking brake cable?You mentioned that you changed rotors, so I guess you rigged the parking brake shoes properly??Post all these info for a better troubleshooting.