Where does this pin go? Brake Master Cylinder

Hello everyone, long time forum lurker here that never gets around posting any cool pictures but is really thankful to have this awesome source of information for figuring out all the little things that have been wrong with my 4th gen.

This time around, I found a brake fluid leak around my master cylinder, and to me it seemed like it was coming from the gasket between the solenoid and the body of the master cylinder. After a lot of careful consideration, I of course took the easiest, least intrusive and most sensible approach: I removed the entire unit from the truck and completely disassembled it .

Here are some pictures where you can first see the leak around the solenoid (half the cover is "shiny black" while the other half is nice and dusty). And then a couple of pictures with the unit disassembled and the gasket I am talking about.









Here is the problem I'm having. After I took everything apart, at some point I found this little shaft that came out of "somewhere" in the master cylinder body, but I didn't notice where or what it came out of. I've only found one whole in the master cylinder face where it fits completely, but I am not certain that it is supposed to go in there. Has anyone here disassembled theirs and knows for sure if this pin is supposed to go in the whole I point at with my finger in the picture? or does it go somewhere else I'm not aware of yet?





Any help is greatly appreciated!!!

 

Try this. Second page. At a glance it looks like the 'shaft' under the brake booster accumulator assembly.

 

Also, for reference

 

Thanks for the response @iamincrediboy I saw that picture in my copy of the manual too and unfortunately that's not it. The one you are referring to (in red below) is much longer than the one I found. It was a good try though

 

Is that a shaft or roll pin?

 

Not really sure about the difference. I'd call it a roll pin too. I saw your other message about it coming from some other part in my bench. That is very very possible, but it suspiciously showed up under the master cylinder as it was "sitting" in the bench, plus the fact that it perfectly fits that whole made me very suspicious. Anyways, for those finding this thread in the future, I went to the stealership and after a lot of struggle, they decdided they couldn't find the part (gasket only) and could only sell me the entire assembly (of course they did ), and the whole assembly is $1800 . So tomorrow I'm surfing as many junkyards as I can to find a used one and try to save my rig. Thanks for the help guys. I still appreciate it if anyone recognizes the pin and can tell me if it is part of the assembly or not.

Cheers.

 

That looks like a shaft or straight Pin the picture shows what a "Roll Pin" looks like and generally are used for alignment of items;

 

wild guess

 

yeah, I looked at many diagrams and youtube vids and NO one disassembled a unit this far down it seems.

The pin I was wondering about is what HornedOwl has circled above. But am not sure.

Work clean, my man. Only "AVE" can master the "healing bench".

If you get another unit, you could always open it up and look for that pin again

 

Yeah after seeing your picture, I can say it is NOT a roll pin since there are no slots on it and it is not hollow. It is a solid straight pin. I also thought it would be for aligning something but that means it shouldn't go all the way into the body of the master cylinder. However, if I try the only other whole where it fits (but doesn't go all the way in), it would be hitting the flat face of the gasket and therefore I wouldn't be able to assemble it.

 

I saw that other pin that @HornedOwl circled, but then I noticed that the diagram that shows that pin is not representing the exact same assembly that my 4runner has. My fluid reservoir screws into the body of the master cylinder with 3 screws, 2 in the back and 1 in the front. So that pin circled in red doesn't exist in my assembly. I guess Toyota has 2 different master cylinder assemblies depending on the year of the truck?

Thanks for helping me scout the internet for more info, I haven't been able to find anyone else that has done this level of disassembly either .

I went through 3 junkyards in my area already and the 4runners in their lots didn't have master cylinders in them anymore. But I found some part recyclers like 2 hours from me that might have a functioning one. I might drive down there this weekend to get this over with.

 

You can always check Tacos and Tundras and Lexus. Go find your part number for this unit. Then google it and use dealer web sites to get a full list of cars that use this unit. Take that list to every junkyard. Take pictures of a your unit (or same unit found online) to show the guys at the yards.

Maybe you can get lucky, find a cheap non-working unit and tear it down and verify how your original should be assembled.

 

That's a pretty good idea. So far I've been looking at tundras of similar years and I think their system is different but looking it up through part number I'll probably get more accurate results. Thanks!

 

I have Multiple Sources for Toyota Parts Drawings and Service tech manuals So if Give me the Year and model Number (first 4 digits of Serial number tag it should look like --->5TFA) I may be able to pull up the correct layout drawing for that assembly.