What would be your next step for dealing with this brake booster/master cylinder issue?

I had leak in my brake booster so I replaced it myself with an aftermarket one from autozone.

I am a novice mechanic, and it turned out to be a much more difficult job than I had anticipated, just getting the old one out. I had to remove the charcoal canister, push the master cylinder to the side, not damage the brake lines, and snip one of the bolts off the brake booster to get it out. To the new brake booster in, I had to cut the same bolt 1/4” short to get it past the intake manifold.

Finally, I got it in, reconnected the master cylinder and canister, and took it for a spin. I noticed that about halfway down my pedal stroke, there was a new click in the brake petal. After driving for about 2 miles, pumping the brakes periodically to test them, the brakes were all seizing. Clearly the master cylinder wasn’t letting fluid back in. I barely got it home, let it sit overnight, and the next day the brakes worked but the same thing happened when I took it for a spin. This time, I disconnected the master cylinder from the brake booster to take a look and the brakes let up. So fluid will recenter the master cylinder, but when it’s connected to the brake booster, it won’t.

I’m guessing that either I damaged the master cylinder’s push rod, the brake booster is bad, or there’s an issue with the connection between the two.
I don’t have the tools (or experience) to bleed the brakes so I’m hesitant to take the master cylinder off and inspect it more closely.

Has anybody had an experience like this? What could this click be? What would you do first? Warrantee the brake booster, order a new one and reinstall?

 

What engine and drive train? Sounds like the master isn't returning to its float position. You should be able to find an adjustment procedure. I don't know about the click is there a hitch in the pedal when you hear it?

 

Not a brake expert, but does your truck have ABS?

 

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$12 (Upgraded) Brake Adjustment Tool, Brake Booster Rod Adjustment Tool, Brake booster with master cylinder,Pushrod Power For Adjustable Braking Distance of Brake Pedal(N48 Magnetic CNC Aluminum)

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The length of the pushrod that comes out of the new booster needs to be adjusted.

 

It’s a 2.7L engine, standard transmission, 4x4

What do you mean by a hitch in the pedal?

Theoretically it does, but the previous owner took out the ABS solenoid and I’ve never tried to get it to work.

Wow this looks like the push rod on the booster is likely the issue. Only problem is that the nut and push rod are recessed inside the brake booster and will be nearly impossible to adjust without removing the booster and using a special tool (see here https://www.toyotanation.com/thread...the-pushrod-inside-the-brake-booster.1721720/)

The previous booster had a 1" spacer plater between the booster & the firewall, and I wonder if removing that would help. It would certainly make it easier to fit the booster in, but I bet I would just need to adjust the push rod in the other direction.

Wish I hadn’t already given the original booster back to autozone for the core rebate…

Any other thoughts about how to go about this?

 

The rod must be adjusted correctly because if it pushes on the booster without pressing the pedal the brakes would be engaging unintentionally. Check FSM if there is a tiny gap specified. Was the booster you removed the original and same as what you replaced with? Did you use the original pushrod or did it come with a new one? Isn't the rod adjusted behind the master so why would the booster need to be removed again to access the rod and nut to make the adjustment?

 

I don’t know if the booster was the original, but it was made by Toyota. The new booster was an aftermarket, made by Duralast.

The gap should be 0.5mm.

You’re right, the booster does not need to be removed to adjust it. It just requires a specialized ”brake booster push rod adjustment wrench” (sst 09737-00020) which I currently see on Ebay used for $50, but won’t get here until the 27th at the earliest. It’s my only vehicle and I’m trying to drive home for Xmas so this doesn’t help as much as I would like it to.

 

Update: After taking a closer look at the aftermarket brake booster push rod, I see that it doesn’t need the same specialized tool that the OEM Brake Booster Push rod would need, but it can’t actually be adjusted any shorter on that end.

I am at a loss for ideas as to what to try next. Any ideas would be greatly appreciated.

Note that for this photo, I wedged a pipe between the brake petal and the seat, forcing the push rod to its maximum extension so it could be seen more easily.

 

It looks like there are still some threads exposed if you back the jam nut off it should spin in more if not take the acorn off and grind/cut the shaft a little shorter or adjust the push rod on the pedal side it might be too long.

As for the noise the "hitch" I as asking about do you feel anything in the pedal when you hear the noise?

 

There’s only about 1mm of thread exposed. How big of a margin would make the difference between no pressure on the cylinder and the cylinder being permanently compressed enough that the brakes heat up and seize after a couple miles?

On the brake assembly side of the booster, I can only screw in the nut on the push rod another 1/4” max before I would have to cut it to get it in further.

 

Is that a pushrod already in the master cylinder in addition to a pushrod in the booster? Shouldn't there be just one?

If you are considering using one over the other,
have you measured the difference between the new and old pushrod lengths? Have you determined if the old pushrod will fit the new booster and backing off the nut 1/4" is enough to get the .5mm clearance you need? It seems if using the old pushrod then would need to make sure the OD matches the new push rod so it mates to the seal.

Could also return this booster and get a different one that has an adjustable rod if the old rod doesn't fit it or is corroded.

BTW the push rod in the booster looks really dirty or is that just new grease? It should be clean and smooth and slightly greased (check specs but perhaps with silicone grease) so the seal is not ruined. If the booster leaks then it doesn't do it's job. It needs to hold vacuum.

What symptoms were you fixing when replacing the original booster? You said it had a "leak" so assuming it failed a vacuum test? Have you tested the new one to see if it is worth your trouble to install?

 

I was replacing the booster because I got a lean run code and had an issue with the brakes feeling hard when I was accelerating (cruise control on going up a hill). My mechanic helped me realize both these were due to the brake booster having a leak. Check engine light hasn’t come back on so I think I took care of it.

In the photo, there is a push rod in the booster, none in the master cylinder. The grease came off the inside of the tube going into the the master cylinder. It looks more solid than normal because it’s 10 degrees outside and the grease is cold.

I unfortunately can’t return this new booster nor replace it with the old one because I had to chop a bolt off the old one and snip a bolt short on the new one to get them past the intake manifold.

I haven’t tried to take the push rod out of the old booster yet, but my next steps are:

1) Go back to autozone to retrieve the core I dropped off yesterday
2) measure the depth of the push rod
3) adjust the back of the pin on the new booster to try to get the depth right
4) If that doesn’t work, cry a little then buy a higher quality new booster with an adjustable push rod.

 

What Glamisman saying

 

Thanks for the reminder. I ordered this tool earlier today on Amazon. Theoretically, it will be here on Tuesday. It will tell me if there’s any hope of adjusting the push rod and if not, I’ll have to get a different booster, unless I can swap it out for the old one.

In the meantime, tomorrow I’m going to try adjusting the “clevis” on the other side.

 

Braking during accelerating? Did the brakes work before or this is a new to you truck that came with the ABS turned off as you noted and the brakes have never worked right for you (with a hard pedal)?

 

Despite what “we” are saying…..it’s not rocket science.
However, totally ness. to adjust this rod when RR’ng both MC/booster
(Especially if AM(what I would pay for))

try to figure out what your issue is as far as lack of pressure or too much pressure provided by position of rod
Your description is all brakes lock
I’m guessing Too Much pressure

There are rod adjustments on MC/booster and B pedal throw
GL
Keep everyone posted

 

Hi all, here’s an update. I got that tool on Amazon, adjusted the push rod so there is a tiny gap between it and the master cylinder, took it for a ride, and it’s still seizing when it gets nice and hot. The push rod is at its minimum length, down to the acorn nut. To make it any shorter, I would have to remove tue lock nut or grind down the acorn.

There’s still a tiny click half way down the pedal stroke when the master cylinder is connected. I’m wondering if that could be something inside the master cylinder. The strange thing is that when my brakes are seized and I disconnect the master cylinder from the booster, the brakes still release their pressure.

Any more ideas?

 

I would of probably removed the lock nut and blue loctite the push rod all the way

and see what feel that extreme position gives you

if its still stiff....I would suspect booster is not releasing

or have been given totally wrong booster


I would always hang on to a core for 30days......to compare and rob do-dads off....


you said 'The previous booster had a 1" spacer plater between the booster & the firewall'......

you should of placed old and new flat on table and made sure old w/spacer is same height on that ball tip....and same receiver depth.

 

Ok. So this is the same master since you said you didnt disconect it right? And it never seized up before swapping the booster? And it didnt have a click sound prior? You had the opposite problem with a hard pedal (indicative of a failed booster)? And your sure you've measured the pushrod gap correctly? How much did you have to adjust it, back? About 1 mm?

Have you reconnected the return spring on the pedal?

 

Yep, same master, haven’t disconnected it from the brake lines yet, never seized up before swapping the booster. Maybe have gotten banged around a little bit, disconnecting the old booster and reconnecting the new one. Had a hard pedal when accelerating, indicator of a failed booster. The click is felt in the pedal, but not heard.

I measured the push rod gap to the best of my ability, which was a little difficult to do because the tool I got isn’t made for this type of master with the tube that goes into the booster. I modified the tool to make it longer (taper rulers into either side, installed a longer metal rod) and believe i got a good measurement.

I adjusted the push rod approximately 2-3mm back in total (tightening the lock it and grinding the top of the acorn nut. But oddly enough, when I installing washers (about 2mm thick) between the master and booster to serve as a spacer, that seemed to work as a temporary fix. Tomorrow I’m going to grind another mm off the acorn nut and see if that works.