Brake booster vacuum line is 20 years old. How can I seal this connection perfectly air tight? On left side of picture is check valve built into hose, so I cannot replace the hose and part is not available. A very slight vacuum leak is very detrimental as it causes front brakes pads to touch rotors and run hot. Can I use pipe dope like they use with natural gas fittings between the rubber hose and metal pipe?

Here is context of vacuum hose. On right side of picture (left of car) is brake booster, on left side of picture is intake manifold out of sight where hose feeds into. You see on brake booster side I was able to install a new hose but I cannot do that with hose containing check valve so I have to seal the connection between rubber and metal as is.

 

You do not need the check valve. That's in case the car dies while moving and gives you a little braking power.

Replace it with a standard hose until you can get the correct one in or use a standard hose and splice in a check valve.

 

Thanks Child_uv_KoRn,
I wish things were working the way you describe, and then I wouldn't have this problem. But the way my brake booster is working, after getting a vacuum, if some atmospheric pressure gets back into the booster it pushes the master cylinder to make the pads contact the rotors with mild pressure. Normally pressure enters into the booster by pressing the brake pedal, but this is happening without applying the brake.
It is enough pressure to interfere with the handling of the car and it the front wheels run hot. The more the vacuum hose leaks, the hotter my wheels get. I think my booster is defective but it tests ok and holds a vacuum. I don't want to replace the booster unless I am guaranteed to fix it, so I'm trying to 100% fix any vacuum leaks.
Also regarding replacing check valve, I bought a cheap ATE valve with 3/8" ends but it leaked. The original check valve in the rubber hose is perfect after cleaning with brake fluid and gentle compressed air. Finding the proper check valve is difficult because it goes by make and model of car and they don't carry it any more for 2000 Infiniti. I would have to adapt an OEM (high quality no leaks) from another type of vehicle circa 1980-1985 but the size of the ends is not published, even dealers don't know from cars that old.

 

You just described to a tee a failing booster. Ditch the check valve, install a straight hose, and replace your booster. Your leaky hose connection is actually whats allowing you to drive around still. Once you have full vacuum, your brakes will only have more rotor compression.

 

So is the check valve built into a new booster? There has to be a check valve to hold vacuum in case the engine dies.

 

Every braking system in every car will work manually without vacuum. I'm not aware of the check valve component in your car. My 5th gen with a 7th gen motor uses only a hose from the booster to the manifold. I think you're focusing on a secondary issue with the check valve as you have a faulty booster to figure out.

 

The check is in whatever hose that has a hard spot in it. I don't recall which (probably the one that attaches to it)...I've never seen a hose/valve go bad.

But like User1 said, the booster is bad.

 

Faulty valve on the atmosphere side of the diaphragm along the actuator rod. Or some obstruction blocking the pedal from making a complete release/keeping it depressed -not to be confused with a throw adjustment-.

 

I've tried braking without vacuum and it is like doing bench presses, and I'm a strong guy. My wife usually drives this car and she has issues so she could never step hard enough on it.

 

Your car is also broken.

 

Well this is certainly enlightening. If I buy a new booster then I hope it will be like yours and I can just run a hose without a check valve. But in my original equipment there is indeed a check valve that can be seen in the first picture of my original post as slight bulge in the rubber hose. If I remove the hose from the booster there is a whoosh of air going into the booster because the check valve is holding the vacuum. Now I am really encouraged by your post that despite being told my car is broken (no offense) that I can get a new booster with a built in check valve to hold the vacuum internally without our ever having to know about it.
Thanks for the quick response, it has helped me on my way

 

I haven't seen or messed with a check valve, so I don't know anything about it. Whatever you need to know though is always in the FSM.

My go-to site for parts research does not list a check valve for 2000 through 2003 Maximas.

https://www.nissanpartsdeal.com/part...html?PNC=47210

 

I will be ordering a re-manufactured Cardone brake booster that has a built in check valve. They have improved original equipment like that. That is after messing around with the vacuum hose and check valve to the point where there are no leaks. But I still get vacuum leak symptoms so I assume it is happening in the old booster. Nissan dealer says the booster reacts to vacuum leaks by putting pressure on the brake line fluid without applying brakes.

 

It would only be labeled as booster hose.

 

Ah, makes sense.

 

That shows it for 2000 maxima, part 47474. The hose has an imbedded check valve.

 

Just fix it already!

 

So I replaced the booster. What came to light was the tightness of the booster input rod against the brake pedal needed to turn off the brake light. That pushes the pedal stoppers against the stop lamp switch and ASCD switch. There is supposed to be around one or two mm of free play. In this case there is none. In particular the pedal stopper against the ASCD switch has zero free play and the pedal stopper against the stop lamp switch has a gap of one or two mm. Looking at the picture it looks like the stop lamp switch socket is not seated straight on the bracket. I don't know if it is broken or the bracket is bent. Hopefully I can just loosen it and reposition it.

 

Paid $13 bux a piece for my stoppers at the dealer. Replaced them both myself. That your switches/brackets are broken/bent would concern me -what happened?-.

Bend them up and make them work. But those are just the switches. How do the brakes feel now?

 

The question I'm asking myself is, does the force on the booster input rod and the leaking booster vacuum have the same effect on making the pads ride on the rotors?
The new booster seems to improve ride quality but is that because I was careful to keep the force low on the input rod just enough to turn off the brake lights?
I will be fixing that switch but not before I find out availability of parts as things are sort of working now.