Hard Brake Pedal During Panic Stops - Brake Booster?

[Friday88]

I discovered an issue with my braking system when a vehicle pulled out in front of me today. The pedal was rock hard and required a lot of force to get it down far enough to actually engage the brakes. This does not happen when I brake under normal stopping conditions, it only happens when I quickly try to press the brake pedal down hard.

I recently changed the brake hoses and put all new fluid in the system and bled it correctly with a partner. The pedal feel improved after I did that so I don't think it's related.

I'm wondering if my brake booster is failing? I've read that a hard pedal is one of the symptoms but I'm not sure since the hard pedal is only during hard stops. Any thoughts or advice is appreciated, thanks.

 

[thecole1098]

My old 99' had this issue and a new brake booster seemed to fix it. When you go to replace it, make sure there's not evidence of brake fluid inside as that will obviously be the root problem and will mean the seal of the MC is allowing it to leak into the booster.

 

[Scottyboy]

I have this issue too, but only in the winter when it’s freezing. Like -25 to -30 Celsius. In the summer and at any other temperature it’s perfectly firm and not spongy at all


Sent from my iPhone using Tapatalk

 

[thegipper]

Sounds like a failing brake booster check valve to me. Mine did the exact same thing on cold mornings.

Make sure you replace the grommet that check valve sits in also.

It's only like 25 bucks for both parts, I'd start there.

 

[catrains]

I had a booster leak . slowly the leak engine on got bigger so at first it did seam a bit hard to press down on a faster harder stop.. then normal easy braking pedal high and hard.. booster was worn over 200K on it..

with the engine off for an hour press down on brake if high and hard its a leak...

master fluid leak into it also causes the seal to break down as well as time and use ..

 

[Friday88]

Sounds like a failing brake booster check valve to me. Mine did the exact same thing on cold mornings.

Make sure you replace the grommet that check valve sits in also.

It's only like 25 bucks for both parts, I'd start there.

The valves can be replaced by themselves? I figured I'd have to replace the whole booster assembly which is pretty expensive.

 

[Friday88]

My old 99' had this issue and a new brake booster seemed to fix it. When you go to replace it, make sure there's not evidence of brake fluid inside as that will obviously be the root problem and will mean the seal of the MC is allowing it to leak into the booster.

I think I'll probably rebuild the MC anyway if I'm in far enough to replace the booster assembly.

 

[thegipper]

What year is your rig?

I believe the 01/02 its all one assembly.

The check valve on the brake booster on the 96-00 can be removed and replaced. It's stupid simple, takes 5 minutes.

 

[SpidermanGeek]

I have this issue too, but only in the winter when it’s freezing. Like -25 to -30 Celsius. In the summer and at any other temperature it’s perfectly firm and not spongy at all

This is 100% the Brake Booster Check Valve if you have a '96 to '00.

These were the parts I ordered for my '97 Limited
1- VALVE ASSEMBLY, VACUUM CHECK (FOR BRAKE) . VALVE,CHECK [44730-60060]
1- GROMMET, CHECK VALVE [90480-24015]

 

[Friday88]

This is 100% the Brake Booster Check Valve if you have a '96 to '00.

These were the parts I ordered for my '97 Limited
1- VALVE ASSEMBLY, VACUUM CHECK (FOR BRAKE) . VALVE,CHECK [44730-60060]
1- GROMMET, CHECK VALVE [90480-24015]

AWESOME! Thank you.

I have a 96. I'll order these parts today.

EDIT: McGeorge Toyota's website says the grommet doesn't fit my 96. Should I assume that's incorrect?

 

[SpidermanGeek]

AWESOME! Thank you.

I have a 96. I'll order these parts today.

EDIT: McGeorge Toyota's website says the grommet doesn't fit my 96. Should I assume that's incorrect?

These 3 part numbers should be the same part (all were replaced by/redirect to 90480-24015)

• 90480-24438
• 90480-24517
• 44673-25020

Does the site give you one of those?

 

[Friday88]

These 3 part numbers should be the same part (all were replaced by/redirect to 90480-24015)

• 90480-24438
• 90480-24517
• 44673-25020

Does the site give you one of those?

That first one says it fits. Perfect, thanks man.

 

[catrains]

That first one says it fits. Perfect, thanks man.

test the check valve and hoses for leaks . check valve flows one way easy to test .

 

[Andy in Pa]

This is 100% the Brake Booster Check Valve if you have a '96 to '00.

These were the parts I ordered for my '97 Limited
1- VALVE ASSEMBLY, VACUUM CHECK (FOR BRAKE) . VALVE,CHECK [44730-60060]
1- GROMMET, CHECK VALVE [90480-24015]

Very interesting, my 99 does this at first on cold mornings, but then it goes away. I'll have to look into this as well.

 

[greeney]

Hard Brake pedal:
Updating this thread to inform that I replaced my brake booster and have some suggestions. The most difficult part was inside the car. 3 of the nuts were easy, but not the upper right nut which is partially blocked by the brake pedal. I removed it with a socket wrench with 3" extension and DEEP 12mm socket, approaching from the door side of the steering column. To re-install, I had to get the nut started by holding it between 1st and 2nd finger to place it. Will be tough with big hands and don't drink too much coffee. Also you will drop it into the rubber boot around the steering shaft. Fortunately that is held on by velcro. But of course it will then fall behind the carpet and you will pull that up to fish around for it there.

Bad news is I still have the same hard brake pedal when making a downhill stop. Braking feels good for first 3/4 of the stop but by last 1/4, to come to FULL stop, I'm standing really hard on the pedal. Sigh

 

[AntleredRuin]

You may just need to adjust the nipple depth on the booster. The part that goes into the master cylinder.
You can simply pull the master cylinder back off the booster and use a small socket (I don't know the metric size; I have a 1/4" drive small socket set for work and just went down the list till one fit) and some small (preferably right angle) needle nose pliers. The pliers grip the base and the socket threads in or out. Just a few turns.

That, or the replacement booster is bad too. I had a bad one out of the box, but my 2nd one was fine.

Also, if you stand on the brakes *too* much, you risk getting the caliper pistons stuck. I had to crack the brake line, then compress the driver's side pistons back in, as they were stuck out and gripping the rotor even when not braking.
Then bleed the brakes, etc.

 

[greeney]

Thanks for those tips AnteredRuin. That gives me somewhere to go from here. I sure hope this remanufactured brake booster is ok. Don't want to go through changing that again.

 

[greeney]

I'll adjust the nipple out maybe 1/8" and check results.

 

[motorchris]

Brakes on 3rd Gen worthless

I have suffered through the exact same problem..

Replaced booster with a used one ... did brakes all the way around
better but still... I seen brakes on a fully loaded 15 ton straight truck
fully loaded that were more responsive and worked better..

Lately brake light was coming on on occasion added a small amout
of brake fluid .. Now brakes are hard as a rock... tried bleeding them
no joy... guess I will put another booster with check valve and master
cylinder from pick a part.. Anyone have great brakes on their 4runner?

Any ideas about it?

Best Regards

MotorChris

 

[motorchris]

brake booster

Update

Replaced the master cylinder .. And bled.. That makes replacing all of the normal parts including 2 leaking rear wheel cylinders originally.. The good news is I found a Chinese company on ebay and I purchased a new booster with a check valve made in China for 49 bucks shipped .. Installing this morning at first light.. New Booster and check value looks good . claims to have a 2 year warranty .. Compared to 450 from advance auto or 967 from toyota its worth a shot... I will update .. Quite a while ago I did the 140 amp Cadillac alternator upgrade rocks.. Also put the Bosch 1.8k starter on it and a honker of a deep cycle battery. 1/0 battery cables..

Regards
Motor Chris