I just replaced the #3 fuel injector in my Q. All went well despite having to reuse a O-ring because the dealer gave me the wrong one. Anyways I made sure the fuel system held pressure for longer than 10 minutes (23 to be exact). Right after the replacement though my brake pedal was somewhat hard sometimes, Not always. I can sometimes hear a hissing noise under the dashboard.

I checked the vacuum at idle and its at 20 inches of mercury. I reused the plenum gaskets after cleaning them of oil/crud. I also reused the AAC/IACV gasket because it seemed fine. I know I have done a lot wrong so far. But how can a engine maintain 20" of mercury and have a leak somewhere? When I press the brake pedal the vacuum goes up. I tee'd in between the Fuel Pressure Regulator to test engine vacuum.

After starting the car and shutting it off I pump the brake pedal. The first time it goes down pretty far, The second time it goes down less and so on. PASS

The second test in the Service Manual says to press the brake pedal with the engine off. Start the engine and then stop it. The brake pedal should not move. FAIL My brake pedal wants to rise when I shut the engine off.

I tested the one way check valve and the hoses to make sure they are not restricted.

Please tell me I don't need a new brake booster. I don't mind the price (Autozone/Cardone Remanufactured)Could I have misaligned one of the 8 plenum gaskets? Could they be leaking? The idle was high (1000 RPM's) when warm but I adjusted the AAC valve... I must have adjusted the bypass screw before for some reason. I cleaned the Throttle Body and some of the plenum when I removed them.

Thank you for any help you can offer.

Do the brakes feel normal?

I don't think minor engine vacuum leaks are going to have much of an impact on brake pedal feel...

Heath

Heath,

The brakes feel harder than ever, almost no power brakes. Some is there for a second or two then gone, Leaks out?

I found a one of the plenum bolts loose but tightening it made no difference. I have a feeling the grease I applied to the brake pedal to solve a squeaking noise may have eaten though the rubber diaphragm or dry rotted it out.

I removed the hose from the brake booster leading to the plenum to find that the plenum is indeed fine and not clogged. There is plenty of vacuum at the plenum. I haven't measured how much yet.

You never should have listened to me and used that 0W-20 oil!
I kid

Based on your experiences though, it sounds like the brake booster to me. I had similar issues with my Lexus - hard pedal, felt like i had to push down really hard to stop the car. It only got worse and worse until I finally replaced it. I learned after the fact that it could have just been clogged and to try using seafoam to clear out the booster lines before replacing the whole unit. It's worth a shot IMO, I would try it if I could do it all over again.

Hissing noise under the dashboard is your best indicator of a bad booster.

Thanks all for the help!

I picked up a remanufactured unit (Cardone). I will throw that in as soon as I get the gasket that goes between the firewall and booster. I will try to make a write up on this if anyone is interested.

The Cardone unit is remufactued in Mexico and powder coated silver

I replaced the brake booster on my car a few painful days ago. I found that it can be replaced in ~5 hours. Thats with all the right tools needed to do the job. I have removed and reinstalled some pieces of the dashboard on my car. So I am missing some nuts/screws and bolts which sped up removal.

Step one: Remove center window switch controls

Step two: remove the radio/HVAC controls trim piece.

Step three: remove the lower knee trim piece that house the drivers foot well light.

Step four: remove the two nuts and two bolts that hold the steering column up, Properly support steering column. Make sure one of the airbag connectors does not come off or break. On my car it popped out but I popped it back in. The airbag light blinked but reset following the procedure posted here: http://www.nicoclub.com/archives/reset- ... light.html

Step five: locate and remove all 4 nuts holding the brake booster to the vehicle. Notice how I say locate. Well the nuts are not in plain sight especially the upper right hand one. I just used the lower right hand one as a guide.

Step six: once all the bolts are loose but still in the studs remove the safety pin and clevis pin on the brake pedal. Push the tabs on the clevis pin in as to not break it like me. The tabs are plastic I think.

Step seven: remove the two flare nut fittings from the brake master cylinder and then remove the two nuts from the master cylinder. Put a pig mat or paper towels under the lines before removing them so you don't take paint away from the dripping lines.

Step eight: remove the old gasket from the firewall and clean the firewall area where the brake booster was.

step nine: install new gasket and brake booster. Be careful of the brake lines so they don't get bent. Also be careful of the plastic brake line anti-vibration retainers.

Step ten: Depending on where you get your brake booster it may have the "U" shaped piece that the lock nut goes against and the clevis pin goes into already installed. If not you must count the threads on the old one you removed. Then re-install it on the new one.

But ever since installing the brake booster my front brakes are sticking. At least I think its just the front brakes. I checked the brake pedal free height and it is with in specifications. Any idea's?? I will remove the brake master cylinder tomorrow weather permitting.

I will take some pictures when I get around to it. I know this is not a job I want to do again!

Just an update.

My A1-Cardone brake booster is rusting some how. It was powder coated (RE-made in MEXICO), Not the USA as one of the reps. that I spoke with on the phone. Besides the rust it also makes a noise that sounds like a small metal pendulum dropping. Not sure what that is?

So in the future I will be looking for a low milage brake booster. As ~$1000 for a OEM new is a little out of my reach. Its very hard to justify that price for such a simple device. Just as ~$300 for hood struts?!?! Infiniti really wants these cars off the road it seems.

Infiniti wants to stay in business. The overall goal of any business is to make money. Customer service is second. You know how these cars work. Labor, cost of operations, and precious metals is at a constant rise. Any other out dated luxury sedan from this era will be as expensive.