Help Please - Brake Problems

[econhonda]

Hi Everyone. I have searched and searched, but have not been able to reach a conclusion regarding an issue I'm having.

Starting a week ago, my 4runner's brakes have suffered from intermittent hard pedal syndrome. I seem to have plenty of vacuum going to the Booster. I pulled, cleaned, and sucked the check valve. Seemed to work fine although it made a fluttering noise when I sucked air through it. Brake fluid is full. No fluid leaks that I can see.

This seems like a Booster issue to me, but it's strange to me that it works and then doesn't again with no rhyme or reason. Also, I don't hear a vacuum leak except when the peddle goes hard I hear a slight hiss from down by the peddle.

One thing I can't stop thinking about is even when the brakes seem to be working normally the peddle slowly falls under constant pressure. Could my master cylinder be bad as well? Could the Booster be fine and a bad master cylinder be causing all of these issues?

Thanks everyone.

 

[shootmymime]

It does it during cold morning after the truck has not moved in a while or while driving and or coming back out to it after it's been parked for lunch?

What year is it?

 

[ajonesnv]

This sounds like the break booster.

I had this happen, first it was intermittent then quickly became regular. The randomness is just signs of impending full failure. I would recommend getting it done sooner than later because these brakes are not designed for use without it. When pressing the brakes without the booster you can actually see the firewall bow from too much pressure.

I had to replace it on a Overland trip with a Napa comparable one, which ended up going out 1.5 years later. Long story short buy an OEM.

Good luck...very easy job and the good news is you don't have to worry about all the fancy stuff on the newer models.

 

[econhonda]

It's a 99 and it happens warm and/or cold.

Do you the master cylinder is fine? Not liking the idea of throwing 800 at a Booster. Might have to pull one from a junk yard.

 

[nevada]

It's a 99 and it happens warm and/or cold.

Do you the master cylinder is fine? Not liking the idea of throwing 800 at a Booster. Might have to pull one from a junk yard.

if you hear hissing when you push the pedal, that is the booster leaking vacuum.

to check the MC, with the engine OFF pump the pedal a few times then hold it. if the pedal slowly drops, the mc is bypassing internally(or you have a leak somewhere) and is bad.

you can also hit the pedal quickly, if its hard at first, then slowly fades down, same thing. its bypassing and needs replaced.


check for any brake fluid leaks before changing the MC, just to be sure.

 

[ajonesnv]

Do the above check, but just because the booster goes does not mean the MC is gone too. My MC survived both bad boosters.

Bummer on the cost. I bought mine from a mechanic that gets them much cheaper. I only paid 400.00. But the first one still ran me 200.00, so I am not too far behind OEM cost.

 

[LittleCaesar]

Booster I would bet.

Try Car-Part.com--Used Auto Parts Market for a junkyard near you. I picked up one that had 67,000 miles on it for $12.

 

[econhonda]

Thanks everyone. Did the MC test above. No fade. Going to replace the Booster.

 

[econhonda]

Just to wrap up this thread, brake Booster replaced. All good now. Master Cylinder seems fine. Thx again.