I was told that some of my poor braking symptoms sounded like very old fluid. I have changed the fluid in the system yesterday. This has not made any difference at all. The old fluid had dust in it and was brown in the calipers, I got rid of it until new clear fluid showed up.
Once that was done, I could still press the pedal to the floor with the engine running. A few facts that I know for certain:
- the fluid level never changed in 5 years that I owned the car and I never had to top up.
- braking is inconsistent, sometimes it's better, sometimes worse, but generally the more I rev the engine, the better is braking power.

Should I install a MC repair kit? Should I install caliper repair kits? It sounds like two separate problems to me: one is that there is not enough boost, which is vacuum and I am leaning towards replacing a booster; and two that there is not enough pressure created in the MC or in the calipers, but if it were the calipers, I would be loosing the fluid, so it is the MC. Do I make sense at all?

 

does the car have ABS

it sounds like a MC or booster problem

 

Check the vacuum lines running from the booster cylinder to the intake manifold. You might have a crack somewhere.

When most mater cylinders fail they usually leak fluid, and since you did not then I'd guess its still good (but cannot say for sure). I mostly hear that the fluid actually leaks into the booster itself, so you don't see actual fluid leaking.

Are you sure you bleed the system properly? When I bleed my entire system, braking improved significantly.

 

No ABS........

 

MC can leak a bit and not really show it. You have to get under the dash and peel back the carpet and see if it's leaking down the firewall.

 

Well when you say that the braking seems to get better when you rev the engine, it sounds as if the booster has a leak in it.......if this is the case hit the junk yard and pick up another one.

However, when you say that the pedal goes to the floor, it seems as if the booster would be okay. If the booster had a leak then it would be harder to apply the brake due to the lack of the assist that the booster provides. It sounds to me as if you have some bypassing goin on in the master cylinder. In other words the cup seals in the MC are bad (prolly due to the old fluid being in there scratching them up) and are letting fluid pass by them when you step on the brake, which would let the pedal fall to the floor because the MC cant build the pressure. Just my 2 cents....good luck

 

Jeff:
But if the level always stays the same in the container - does it mean that there is no leak?

Drivin Max:
That is what I have been thinking!

 

How did you Bleed your break system?? If your pedal goes to the floor, sounds like there is air in your break system. Im no expert but I would suggest you post how you performed the bleeding for the breaks.

 

Air in the system is definitely a possability, although air in the system leaves the pedal with more of a spongy feeling rather than just a sheer collapse to the floor upon depressing...........however, because it is a possability there is a quick test you could try to see. It is better if you had another person, but start by taking the cap off of the resevoir and set it aside. Wrap a towel or a few rags around the master cylinder (and this is where its better to have two people cause the other person can hold the towel around the MC and above the resevoir to make sure that the fluid doesnt shoot too high and get all over your paint). Pump the brakes a few times (slowly) and hold the last pump. Now with the pedal held down, let your foot slide off of the pedal causing it to pop back up. If there is air in the system then the fluid will jump about an inch or higher out of the resevoir. If the fluid doesnt jump that high then you can almost definitely rule out air in the system. Just make sure that if you do it by yourself or even with somebody else you do your best to catch any fluid that might jump out or the resevoir.

Also while Im thinkin of it some cars require the person bleeding the brakes to disengage a safety button on the combination or pressure differential valve. Im not sure if Maximas require this but if you bled the system without doin that then the pedal falls to the floor when done. Give the test a try if you want....good luck

 

this would be the correct way to bleed the break system:

Correct way

Guaranted you wont have air, but all so try adjusting the break pedal, unlikely but still a possibility.

adjusting break pedal hight

EDIT:"If the height is under these specifications, check the system for leaks, accumulation of air or damage to the components, such as: master cylinder, wheel cylinder or etc.; make the necessary repairs. " ---autozone----

 

What makes you think that I do not know how to bleed the system?

 

Just covering the basics, dont know your experience level, my bad

 

Lighten up Tarzan..these guys are just trying to help!...now go tell Jane to go to auto parts store or junkyard and get you a booster cause it is shot.

 

I was just asking the question to see if anything I had mentioned above sounded like an obvious mistake! I did not mean to sound irritated and I am not an errogant person, sorry if it was a rude comment in any way!

 

I dont think the MC has to leak to be bad all the time. my MC went out and it didnt leak a drop of fluid...

 

Here you go! I agree, because it has a complicated system of seals and even if one or two go, but not the outermost one, there would not be enough pressure created in one or both circuits.

And Maxima does not have an equalizing valve. My old Accord'91 did have one and I removed it, thus obtaining ideally equal braking on the left and right sides. The old valve has seized and my right side had almost no braking.

 

Tarzan. I'm surprised you haven't just replaced the master cylinder. This is my guess. Here is a link from the stickies:
http://www1.autozone.com/servlet/UiB...3d801f5aa3.jsp

has general info about the brake system. Also if you click back it has small sections on teh ms and booster.

 

That's what I think I will end up doing: replace the MC with the booster. It does not make sense to spend money on an MC rebuild kit and booster separately when I can get them both for almost same money.

 

You should be able to test the booster via the link I gave.

 

Negative. It tests fine, but where is the line? It does hold the vacuum for much longer than 1 minute but I still can prove that amount of braking depends on how hard I drive. It is quite low in comfort mode and much higher in power mode of AT and if I give'r a kickdown it feels like a new car's brakes.

 

Very odd. Cheap check. Pull the line to the booster. Remove the 1 way check valve and make sure it's still a 1 way valve. How did you check the booster if you don't know where the line is??? There is a pic in the link?

 

By 'line' I mean imaginary line between good and bad booster. The test procedure described above tells me to run and shut off the engine, wait 1 minute and check if I still have vacuum by depressing the brakes several times. That checks fine.