I'm at my wits end- Master Cylinder issues..

I feel we're running in circles. I think what you call the secondary master cylinder, aka balancer, Toyota parts catalogs call the "master cylinder". The part that attaches to the fluid reservoir, Toyota parts calls the master cylinder sub-assambly.

Otherwise, if the terminology is as you say, then here is your part, correct?

 

Not sure that the rebuild kit you linked is for the two part master.

Second link looks like a different master completely...sub assembly might be refering to the whole system including booster and abs

 

Anyone found a potential different master cylinder & brake booster from another vehicle that will work?
- I used to have a 1 ton jeep with a hydraulic booster and master cylinder from a chevy astro van.

 

I'm hoping to change my booster to the pre 01 Tacoma booster, it's a dual diaphragm booster so it will improve pedal feel, as well as allowing an FJ80 1" bore master cyl to bolt up. Will report my findings once its done...

 

Now that’s the type of stuff I like to see! I’ve been hoping someone will just convert to a different year but this sounds like a cool idea.

 

Did you buy parts yet, or is this future plan. The reason I ask is when this thread was started I did a Google deep dive and was able to find that a 04-08 Sienna master cylinder looks like ours. I haven't yet attempted to cross reference the part numbers or rebuild kits but it does seem you might be able to buy the components. Food for thought.

 

I have the master, have to still buy the booster. I upgraded to the 13wl calipers and have a mushy pedal. I also plan to do a rear disc swap soon. I know the setup wotks really well, because I have it all on my Tacoma, 13wl calipers, fj80 master, pre 01 Tacoma booster(4 bolts to the master) and the Trail gear Tacoma rear disc kit. Locks up all 4 with 35s, just want my Tundra to do the same...

 

That would be good because my tundra with 35s has terrible braking. Sometimes I wonder if it isn't just a terrible abs system kicking in.

 

I had a CNC manual brake setup on a pre Tacoma pick up and it was actually great. If you size the master cylinder correctly they actually make for pretty good binders. Yeah the initial braking took some more work, but after that pedal pressure wasn't bad at all.

 

Might I suggest suck and fill (or bleed) your brake fluid a few times, adjust your rear drums star adjuster, and additionally LSPV adjust up to correct your brakes mushy pedal. Works great on my 2002.

Firm pedal
Equal braking on all 4’s
Responsive

This is with the WE (WEak calipers).

 

I have the same master cylinder and have had this same issue on my 06 Tundra double cab for the past couple of years. Pedal is mushy half way to the floor before the brakes kick in.

No external leaks or problems with the calipers/pads or drums/shoes. Have bled it repeatedly, including at the proportioning valve; and cycled the ABS with a bi-directional tool before settling on the master cylinder as the culprit.

I’ve since tried two different remanufactured Cardone 11-3300s and both leaked internally after a few days. It seems like an unnecessarily weird and ineffective cylinder that Toyota abandoned.

My latest effort is to convert to the 01-07 Sequoia master cylinder. This means modifying the brake lines and requires some unions and adapters etc. I found some prepackaged conversion kits online (sosperformance.com), but managed to buy the exact same parts myself for less than half the price. I’ll be installing in the next few days. Watch this space...

 

AFC1903, why try to convert an entirely different design? Why not try to adapt the master cylinder I noted in post #67? Either way I'm interested in the results. Just seems like your trying to build a house starting with tree branches when I've already shown you a stack of 2x4's.

 

Brakes are the single worst feature of these trucks. Despite all the rabbit holes people go down, at the end of the day they still suck. I've done all the various tricks and suggestions and while it helped a little I have realized these trucks are never going to stop like a modern vehicle. My truck is fine during everyday driving but where I notice the mushy pedal the most is when I press the brake while it's in park. Before shifting into drive my foot goes all the way down. I hate that.

I do have 1 question. If I'm in park with my foot on the brake, why is it that I can feel a pressure change in the pedal when I shift into drive or reverse?

 

Vacuum.

 

So this is normal then? Good. I do not notice it in my wife's Rav4 or any other vehicle I've ever owned so I wasn't sure.

 

Interesting... please report back with this outcome.

 

I just did the replacement on mine. I read through this thread several times and ultimately just purchased the part listed in post #34. I had fluid in the booster so while the whole assembly is pretty expensive at least the booster got replaced.

I'm really interested to see how this turns out for you.

 

How does your truck brake now? Better than before?

 

Honestly I can't tell a difference from before. I noticed I had a problem when my brake light came on as a result of the fluid being low. Everything externally looked fine so I separated the master from the booster enough to get a bore scope in there and sure enough found fluid. I don't know how severe it was as I had no other symptoms but since I let people borrow my truck sometimes I just didn't want to risk anything and replaced the whole thing.

Looking back on your previous post though I do not experience any change in pressure when I move from park to any other position (with the engine running obviously). With engine off and vacuum still in the booster my foot travels about 1/3 the way and stays when engine is started and put into gear. If I pump the vacuum out of the booster with the engine off I get about the same 1/3 travel when I start the truck. I'm pretty sure that's how it was before though.

 

I didn’t read this thread until recently and am already committed.

Also, I’ve had too many $200-300 punts on the remanufactured master/unicorn set up already, and there’s no way I’m paying a dealer for the OEM cylinder and booster (ridiculous gouging).

My experiment with the mod to the 01-07 Sequoia cylinder is costing me $70 for a new cylinder (not remanufactured) plus about $30 on add ons (lines, unions etc.). I just feel it’s worth a shot.

 

Could be the golden cheap fix everyone is looking for.

 

There is an easy test for brake boosters/cylinders. Goes like this:

1) With engine off, get in vehicle and step on brake pedal multiple times as if coming to a stop until pedal becomes hard. Do not full press.

2) With foot still on brake hard pedal turn vehicle on and pedal should only drop a 1/4”. This lets you know vacuum is working. If drops more then you have thingy problems.

Read this guys link. He has good philosophy.

http://www.agcoauto.com/content/news/p2_articleid/129

 

Pls do a write up (or a video) and post your experience. If it infact works, this would be an option to those needing a replacement MC, myself included.

Great link..

 

This is a bust so far. The Sequoia MC has the same two bolt pattern as the Unicorn, only the bolts are about 1/4” wider apart. I also noticed the push rod in the “unicorn compatible” booster is very deep set and impossible to adjust up to meet most cylinders. So my options are either change the booster to meet the MC, or buy yet another remanufactured 11-3300, or just live with it and bleed my brakes every couple of weeks. I read that virtually all Toyota boosters have an identical 4-bolt pattern to the firewall, so there must be some good alternative booster/MC combo that fits this darn truck. Seems I’m down a rabbit hole like everyone else.

 

Couldn't you just drill some new holes in the firewall? Or am I not understanding the problem?

 

Like cold pizza after a night of drinking...post #67 is starting to look good, eh?

 

Well that sucks.

I agree that Sienna assembly looks the same as what we have. It looks like that part number only gets you the master cylinder and not the unicorn part. Tundra FSM calls it the 3rd Chamber in the bleeding section. Because I had leaking into my booster I assumed that part has internal seals. I considered this when I replaced mine but ultimately chickened out and spent the $875 bucks on the OE replacement. I'd be super interested to see if that Sienna part provides a complete or partial solution.

 

https://www.ebay.com/itm/2006-2010-...-W-Master-Cylinder-In-Great-Cond/163912869608



I'll bet there's enough interest in this build to start a fund to defray the cost. I'll send you a $10 gift card to get it started.

 

Or a GoFundMe is probably easier.