Possible brake booster failure, looking to cross check my diagnosis (1 Viewer)

[CharlieS]

Hi Mud,

I was on a trail this week where my brake pedal was becoming progressively more firm and the stopping power seemed reduced. Then I stopped to check out an obstacle, and when I moved the 80 from park to reverse with my foot on the brake pedal the vehicle lurched back as if I wasn't on the brake and only stopped when I stood on the brake pedal with both feet.

From that point on, the pedal was as hard as a rock, I had to stand on the pedal to get any braking, and it wasn't much stopping power when I did get braking.

The pedal doesn't go down when I start it up, like it used to. It stays rock hard and doesn't move.

I've never had a bad brake booster, but this sounds like what I've read on this board as symptoms of one failing.

If I need to R&R it I don't want to put in a rebuilt unit, or a crappy one.

Are the main good options still Toyota factory, Seiken, and City Racer?

Does anyone recommend upgrading to a double diaphragm like the Terrain Tamer style?

Thanks!

In case it matters, I have a few month old Toyota master cylinder, ABS is completely removed, no LSPV, slee stainless lines. No fluid loss, and reservoir is at full line. Other than initial pedal travel to engage being more than I like, the brakes have been fine as long as I've had it. Prior to this failure, I could lock up all four tires on dirt with this braking setup. Now I don't have enough force to lock them up.

 

[robnicko]

test it by the following
with engine turned off pump the pedal and hold it firmly, start engine and if working properly you should feel the pedal go a little softer as the vacuum kicks in
It may be a faulty one-way valve that is not holding vacuum / operating as it should

replacement wise, Toyota / Aisin / Seiken i would choose

 

[Godwin]

You have a bad brake booster. As already stated replace it with a quality unit. Avoid Cardone. Toyota unit from Partsouq is not cheap but you know it will be of high quality.

 

[Azca]

Yep, booster is gone. The pedal is hard because you have no vacuum assist. Before you jump off the ledge, check the vacuum line from the booster to the intake manifold, you may just have a bad hose.

 

[CharlieS]

Just tried that test - pumped several times, held, then started, the pedal didn't move down at all.

Also, my idle is super odd now - high 1900 rpm at cold start, dropping to 800 in D, then idling low and erratically, like when I've had vaccum leaks previously. This is new. It is normally 1100 cold start in P, then a steady 650+/-50 rpm in drive. Could I have a vacuum leak in the booster diaphragm cause that?

Also, hopefully not the check valve since I installed a new factory Toyota vacuum hose, check valve and grommet (about 1 year ago).

 

[CharlieS]

Yep, booster is gone. The pedal is hard because you have no vacuum assist. Before you jump off the ledge, check the vacuum line from the booster to the intake manifold, you may just have a bad hose.

Good call. First thing I checked. Booster line is connected, and relatively new.

 

[CharlieS]

I do have the old hose and check valve (that I replaced preventively while chasing idle issues) that I could swap in to eliminate hose and check valve as the problem.

 

[CruiserDave]

I would swap in old check valve with the newer hose first and go from there. Then old hose with old valve. Worth a shot to potentially save money.

 

[77mustard40]

If it’s the booster, this is the replacement. Buy with confidence.

New Toyota Land Cruiser FZJ80 LX450 OEM Seiken Brake Booster Gaskets 44610-60792

New 80 series, FZJ80, FJ80, 1991, 1992, 1993, 1994, 1995, 1996, 1997, brake, brake booster, OEM, Seiken, japan, 44610-60792

www.cruiseryard.com

 

[ALX4X4]

Just plug the manifold hose barb to isolate the whole booster hose assy to see if it fixes your idle issue.

 

[CharlieS]

Just plug the manifold hose barb to isolate the whole booster hose assy to see if it fixes your idle issue.

Brilliant! Thank you.

Capping the manifold nipple fixes the idle issues.

Sounds like I have a vacuum leak downstream of the plenum nipple. Since the hose, check valve and grommet test good (see next post) it seems to point to a vacuum leak at the booster.

 

[CharlieS]

Did a rudimentary test on the hose and check valve. After removal, I applied pressure and vacuum. Both are leak free and functioning as designed. The check valve allows movement only in one direction and blocks it in the other. The grommet is supple and undamaged.

Also, a correction, when I replaced the parts recently I replaced the hose and grommet, but not the check valve. I confused that with the check valve and hose I replaced recently on my son's Land Rover Discovery 2.

 

[CharlieS]

Seiken brake booster ordered and on it's way later today. Many thanks to CruiserYard for getting it out today!

 

[GORDA91]

Seiken brake booster ordered and on its way later today. Many thanks to CruiserYard for getting it out today!

Bought one and recently installed on my 91. Immediately fixed the problem.

 

[Fj80oregon]

Did you buy from cruiseryard? I thought I remember @cruiseroutfit having them for around the $300 range. If it was cruiseryard list price of $449 why not go OEM for $469? Just curious I will be replacing the entire system soon calipers, lines, master and the only thing left to purchase is the the booster.

 

[CharlieS]

Did you buy from cruiseryard? I thought I remember @cruiseroutfit having them for around the $300 range. If it was cruiseryard list price of $449 why not go OEM for $469? Just curious I will be replacing the entire system soon calipers, lines, master and the only thing left to purchase is the the booster.

I don't have a great answer other than someone here recommended the Seiken at CruiserYard. It does come with both gaskets, which seems good. I don't want to wait around for Amayama or Partssouq, since this is my prime offroading season before snow flies. US Toyota dealers didn't have great deals, and I didn't think to check cruiser outfitters. I should be back on trail within a week if the booster arrives in a reasonable time.

 

[GORDA91]

Did you buy from cruiseryard? I thought I remember @cruiseroutfit having them for around the $300 range. If it was cruiseryard list price of $449 why not go OEM for $469? Just curious I will be replacing the entire system soon calipers, lines, master and the only thing left to purchase is the the booster.

Yes bought at cruiser yard. Needed asap and I think Seiken is essentially OEM.

 

[Fj80oregon]

@cruiseroutfit do you have the Fzj80 boosters in stock seiken? Msrp$? Not trying to hijack the thread just getting another purchase option out there for future readers.

 

[CharlieS]

The only one I found on their site that fit my '94 was genuine Toyota. If they do have the Seiken, it isn't easy to find.

 

[jonheld]

The only one I found on their site that fit my '94 was genuine Toyota. If they do have the Seiken, it isn't easy to find.

I would double check with @OGBeno, but I believe Seiken is the OEM for Toyota.
Toyota part number 44610-60792 includes the check valve and grommet. $469.62 from our friends in Dubai if you have to have the red and white box.