Rock hard brake pedal pressure. No brakes (1 Viewer)

[maineidyl]

Been driving my 96 LX 450 and out of nowhere. Got tremendous brake pressure on the brake pedal and no braking. After pushing a couple more times the brakes actually caught avoiding me hitting a car. Then brakes worked fine until the next day. It happened again, two or three times. Added a little brake fluid but problem still remains. Is that my booster or?
TIA
Tom
96 LX450

 

[maineidyl]

Seems to happen more after I’m stopped at a stoplight. After keeping pressure on the brakes when I go to use it after leaving the stop light or stop sign I have zero brakes.

 

[BILT4ME]

Been driving my 96 LX 450 and out of nowhere. Got tremendous brake pressure on the brake pedal and no braking. After pushing a couple more times the brakes actually caught avoiding me hitting a car. Then brakes worked fine until the next day. It happened again, two or three times. Added a little brake fluid but problem still remains. Is that my booster or?
TIA
Tom
96 LX450

It's your booster.

Can buy a Seiken from @arcteryx or go to Toyota and buy an OEM for more $$$.

 

[Godwin]

Unclear as to how you are describing the issue. "Tremendous brake pressure" means what? If you mean that when you press the brake pedal it is very hard to press down then that indicates a brake booster issue. The brakes will still work but you have press much harder. May be time for a new booster.

Do you still have normal pressure pressing on the brakes but reduced braking effect? If so master cylinder may be going out.

 

[arcteryx]

Thanks @BILT4ME

Depending on your diagnosis, I have Seiken boosters and Advics (subsidiary of Aisin) MBCs in stock. They come with a 2 year warranty. I haev a lot of people buy both and tackle the system at one time since these trucks are 25-30 years of age and a lot are still on their original units. Buy once, cry once as the saying goes. It's better to be proactive than reactive IMO, especially when dealing with critical parts.

You can search/google/youtube and try some simple booster tests with how the pedal reacts while stationary. Regardless, it sounds like your truck is unsafe to drive in it's current condition.

 

[flintknapper]

Classic Brake Booster (failed or failing) symptoms, but check the vacuum at the supply line first, next the grommet and check valve on the booster, if all checks out OK....declare it dead and replace. Use the Seiken model.

 

[ajordan1975]

Bad booster

 

[Kernal]

One tip if you're working by yourself on this job; don't, get a helper.

The brake booster is attached via four studs that dive through the firewall with nuts on the cabin side to secure it. The studs however also pass through, and need to line up with, four holes in a bracket for the brake pedal on the cabin side. The same nuts for the brake booster studs also attach the brake pedal bracket to the firewall.

IME when the old booster is removed that brake pedal bracket can droop and if that happens it might become impossible to push the new booster studs through the holes in the firewall as the holes in the brake pedal bracket are no longer lined up with the holes in the firewall.

Point is, have helper ready to help line up the brake pedal bracket up/into position while you are working from the engine bay side pushing the booster through the holes in the firewall. Might save you some aggravation.

Many people have gotten this job done by themselves but it seems like everyone fights with it to some extent before the booster studs find their way through both the firewall and the brake pedal bracket holes on the other side. IME it was impossible to get things to line up working by myself as the brake pedal bracket had drooped maybe 1/4" out of line with the holes in the firewall.

FWIW

 

[maineidyl]

Thanks to all and advice about the pedal assembly saved my ass. Did it myself in about 2 1/2 hours. Had a bear of a time getting past the manifold then had to readjust the brake assembly to allow the 4 studs to go through. Shout out to ARCTERYX for his quick response and shipping. Did not even order until late Monday and had part in hands Thursday. New SEIKEN fit perfect and came with the two gaskets. Brakes are back. May do rotors and pads next. Put it behind me.
Tom

 

[flintknapper]

Thanks to all and advice about the pedal assembly saved my ass. Did it myself in about 2 1/2 hours. Had a bear of a time getting past the manifold then had to readjust the brake assembly to allow the 4 studs to go through. Shout out to ARCTERYX for his quick response and shipping.

^^^^

Yep, you basically have to 'force' the booster past the intake manifold, not Toyota's finest engineering moment.

 

[lumbee1]

^^^^

Yep, you basically have to 'force' the booster past the intake manifold, not Toyota's finest engineering moment.

Or remove the nut on driver's side engine mount and lift the engine like I did

I was able to remove the OE booster with a pry bar but I wasn't going to hammer my new booster in the same way with a lack of mechanical sympathy.

 

[flintknapper]

Or remove the nut on driver's side engine mount and lift the engine like I did

I was able to remove the OE booster with a pry bar but I wasn't going to hammer my new booster in the same way with a lack of mechanical sympathy.

Loosened my engine mount and tried to lift the engine with an engine hoist....but still didn't get enough room on mine. So I just used a thin, flat pry bar to force it past the intakes, same way I got it out.

 

[Malleus]

But the upper intake is so quick and easy to remove...

 

[another]

But the upper intake is so quick and easy to remove...

I made two modifications that, had I done them from the beginning, would have saved me three hours time.

1- Used a step bit and increased the hole size by one on the firewall (plenty of room for a cordless drill and bit).
2- Cut the indexing nub off the studs that go through the firewall (I measured the studs, difference of 1/4" between old and replacement booster).
This allowed me to angle the booster, putting the right side studs in first, sliding past the manifold, then rotating the left side studs into place.

The possibilities are endless as to why the manifold blocks the booster (motor mount bracket one millimeter too far back?)

These two mods eliminated all of that headache and, as far as I can see, with my limited mechanical engineering background, didn't harm a thing.

 

[Kernal]

Did you get photos of your modifications?

 

[DSRTRDR]

One tip if you're working by yourself on this job; don't, get a helper.

The brake booster is attached via four studs that dive through the firewall with nuts on the cabin side to secure it. The studs however also pass through, and need to line up with, four holes in a bracket for the brake pedal on the cabin side. The same nuts for the brake booster studs also attach the brake pedal bracket to the firewall.

IME when the old booster is removed that brake pedal bracket can droop and if that happens it might become impossible to push the new booster studs through the holes in the firewall as the holes in the brake pedal bracket are no longer lined up with the holes in the firewall.

Point is, have helper ready to help line up the brake pedal bracket up/into position while you are working from the engine bay side pushing the booster through the holes in the firewall. Might save you some aggravation.

Many people have gotten this job done by themselves but it seems like everyone fights with it to some extent before the booster studs find their way through both the firewall and the brake pedal bracket holes on the other side. IME it was impossible to get things to line up working by myself as the brake pedal bracket had drooped maybe 1/4" out of line with the holes in the firewall.

FWIW

PITA for sure, and it was two of us - but we didn't modify anything - just a lot of time, "figgering" and cursing

 

[WarDamnEagle]

Booster just went out on my '97 and I decided to punt and took it to a local shop I trust with two boxes of OEM parts: booster, master, new brake hoses, parking brake shoes, and all the assorted gaskets and nuts and bolts. Thankfully it's a shop that lets me supply the parts. Not that I couldn't do the work but it's not a job I cared to do.

 

[another]

Did you get photos of your modifications?

Negative.

 

[Kernal]

@another

The studs on the replacement booster should be in the same position as the original, 1/4" off is a mile (were they longer, shorter, in different positions or??). You mentioned an "indexing nub" of the studs, I don't recall an indexing nub on an OEM or the Seiken brake booster stud.

Do you recall what brand and part number booster you installed?

 

[another]

@another

The studs on the replacement booster should be in the same position as the original, 1/4" off is a mile (were they longer, shorter, in different positions or??). You mentioned an "indexing nub" of the studs, I don't recall an indexing nub on an OEM or the Seiken brake booster stud.

Do you recall what brand and part number booster you installed?

Length.

Unthreaded tip of the stud.

Don't recall the brand.