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

Thanks for the update!

Any notes on the install? Or pics?

 

Hello Again,

This whole episode is the gift that keeps on giving! Like I said above, the SOS Sequoia MC conversion went pretty smooth and seemed to perform acceptably with no tweaking of the LSPV. SOS sent me another MC to replace the one that leaked, and guess what:?? It leaked too!! And, like that wasn't enough, the Toyota OEM booster/MC assembly that I had ordered "way back when" finally showed up on my doorstep. So, considering the problems with the SOS MC leakage, I decided to just return the SOS stuff and install the stock assembly. That's what I did, and the truck seems to be fine now. Wow, what a nightmare!! Tom at SOS was very nice about returning the kit for a refund, and stated that he had had some leakage problems with his particular supplier's MCs. I told him that, if I ever have occasion to go the Sequoia MC route again, I will just plan to pay extra for an AISIN Toyota OEM MC, just for the added peace of mind.

So ........ I guess this saga is overwith, at least for now. Sorry, no pics from the SOS installation. And really nothing to show in a pic right now - the truck looks exactly like stock (because it IS exactly like stock).

Cheers and good luck to all!!

 

Good to hear from you, Mac.

That really stinks you've been having problems with the MC from SOS. At least you're back to stock at least for now -- without any issues I hope. I didn't have a problem with mine leaking, but mine was ordered and installed well over a year ago and could be from a different source. I was actually concerned at first that the SOS MC I received wasn't stamped with Aisin. It hasn't caused me problems yet, but I'll probably eye it over ever so often.

Not really related, but I've started to look into retrofitting one of the fancy hydro-boost boosters onto a vacuum booster truck like ours. I found a company that sells the parts for a conversion, to be paired with an even larger(!) Wilwood master cylinder. I'm still looking into this and may do it at some point as a way to upgrade my brakes even more without going to bigger wheels. If I find more information or pursue this, I'll include some info on this thread.

 

Des2Mtn ---

Thanks for the reply. I quite enjoy the back & forth, and the updates on what folks are up to with their trucks. I had no complaints about the SOS update, other than the fact that they have a MC supplier who apparently does not have a robust QA system. In the industry I retired from, Aerospace & Aviation structural component manufacture, a QA system that allows a defective part to get shipped is a huge no-no. When you let a bad part slip out the door, it's a HUGE deal, and the FAA, NASA, the prime contractor, your QA system certification body, and many other people get very excited and very testy.

On both of the SOS MCs I dealt with, the fluid dripped out of the cavity on the side of the reservoir, where you install the level sensor. It wasn't a gushing leak, just a steady drip, but enough to just about empty the reservoir overnight. Completely unacceptable for a key brake component. I have no idea how the manufacturing process for the plastic reservoir goes, but I suspect some kind of secondary bonding or fusion process with a detail-part (the "well" for the sensor) that's molded separately from the body of the reservoir and added during an assembly operation. However it works, it's a process that needs some attention.

The hydro-boost system sounds interesting, and I hope you have good luck with it if you decide to go that route. I would be interested in hearing about your progress, although that sounds like something that's never going to happen with my truck. As long as I can haul my camper around in the back-country, and have good enough braking to be reliable and safe, I'm happy. Back in my sports-car days, it would have been a different story, but those days are probably gone for good - other priorities, limited budget - you know the story!

This has been fun. I will keep an eye on this thread and see if anyone has any updates along the way. Many thanks to you and everyone else. My best!!

P. Mc.

 

I am selling my used master cylinder with booster. Before I put it on eBay wanted to give first dibs on this site since you guys been really helpful. It needs to be rebuilt. Let me know.

 

Is this the website you used? Can you confirm if you were ever able to receive the unit? I'm thinking of getting a 2004 Dbl Cab for my son but remembered this thread. It seems the 2004 Tundra to avoid is the one with stability control.

 

FREE OEM Toyota unicorn master cylinder available for diagnostics / rebuilding - you pay the shipping charges. I missed my core return window.

Former 2006 Tundra Double Cab 4x4 owner here. I struggled with ongoing brake issues similar to many of you and replaced most of my brake components over the course of a few years. I replaced the unicorn master cylinder with a rebuilt BrakeBest 11-3300 master cylinder from O'Reilly after finding my brake booster was doubling as a brake fluid reservoir / swimming pool earlier this year. I still had spongy brakes after several bouts of brake bleeding. I have my original master cylinder available to anyone interested in tearing into it do determine its failure point and potentially rebuild it - just message me and pay me shipping charges and it is yours!

Location: Minneapolis, MN