Hydroboost motor failure?

[biederboat]

Hey, fairly new to the whole 4Runner thing (love my 2003 so far!) but I'm fairly certain there's an issue with the brake boost system. The only "negative" symptom that I can tell is that there is a high pedal effort. If you push hard enough, the stop is good and short but it's way more effort than what I consider "normal" but I haven't been able to compare it to a known-good 4Runner (just other cars). To the best of my knowledge, there is no extraneous "humming", air-sucking, etc. I'm first interested in just trying to diagnose the problem to make sure it's the boost system.

Does anyone have a procedure for this? I'm assuming it's somewhat different than the typical vacuum booster behind the master cylinder system.

Any help is greatly appreciated. I searched and only found info on how to replace it and not diagnose it.

Thanks,
Biederboat

 

[fourwd1]

Simple:
Disconnect the vacuum hose from the booster and plug it (the hose).
Drive around and note the difference. If no change you may have a booster problem.

 

[BlackWorksInc]

What do you mean by pedal effort? Do you mean length of travel or amount of pressure (effort) to push the pedal?

These hydraulically assisted units don't take a lot of pressure to move the pedal and they often feel like they have a long travel on the 4Runners in particular. It tends to be a different braking feel than most people are used to.

[MENTION=1857]fourwd1[/MENTION]

He has a Hydraulically Assisted Master Cylinder unit, there's no vacuum source or hoses for these systems at all, its all internally managed between the accumulator tank and accumulator pump. All North American 4th Gen 4Runners (and some 2001-2002 3rd gens) came equipped with these units as standard. The 5th Gen 4Runners, FJ Cruisers, GX470/460 and even the Tacomas starting in 2010 (IIRC) sport these units as well.

 

[biederboat]

What do you mean by pedal effort? Do you mean length of travel or amount of pressure (effort) to push the pedal?

These hydraulically assisted units don't take a lot of pressure to move the pedal and they often feel like they have a long travel on the 4Runners in particular. It tends to be a different braking feel than most people are used to.

It's the effort (force). Definitely seems like a lot. The travel I'd say is good (not a lot needed). The rig stops in a nice straight line, no vibration, etc. so unless there are two frozen front or rear calipers, I'm thinking it has to be somewhere up in the master cyl.

Thanks,
BB