Help please Hydroboost master cylinder

[aussiek20]

Hello , have just bought a Dorman M101267 1.125” master cylinder to mate to the hydroboost I got on Facebook , seems that the rod on hydroboost would be pushing on master 1.5 inches when assembled ? Should they have a pre tension like this or have a purchased the wrong master cylinder? Any help to get the right one would be appreciated , going on my Rhd Australian k20 that is getting a 4bt and 47re trans

 

[ali_c20]

Hello , have just bought a Dorman M101267 1.125” master cylinder to mate to the hydroboost I got on Facebook , seems that the rod on hydroboost would be pushing on master 1.5 inches when assembled ? Should they have a pre tension like this or have a purchased the wrong master cylinder? Any help to get the right one would be appreciated , going on my Rhd Australian k20 that is getting a 4bt and 47re trans

Welcome from Austria.
Post the part number of the hydroboost unit or the year and model it came from. There are deep and shallow master cylinders that has to match the rod from the booster.
You can get repair kits with different output rod lengths so it's possible to swap the rod.
The booster rod must never touch the back of the master cylinder, there needs to be a certain amount of gap. Use the search function of the forum or google it.
If you are not experienced with brakes seek help from a shop or someone who has experience with them and is trustworthy.
You don't want to die or kill someone cause you messed with your brakes.

 

[aussiek20]

thank you Ali, not sure what vehicle it came from, the only part number that i can see stamped into the hydroboost is 70748. Any links to where i can get those kits with rods would be greatly appreciated , or if someone has a rod similar to this and can say what master they used would be great too. DEfinately do not want to die or hurt anyone else

 

[ali_c20]

Here's a link on how to cut the output rod from long to short. I also added the files as .pdf to print em out for the shop.
https://powerbrakes.com/129496sh-kit/

Search for hydroboost push rod kit, results from shops and ebay will pop up.

 

[aussiek20]

Thank you Sir, That is greatly appreciated Ali.
Perfect, i can get in and modify it correctly, feel this would be super good information for the forum to make a sticky - would help heaps of people because I see lots of questions for on master cylinders and hydroboosts

 

[ss454elco]

I converted my 84 K10 to hydroboost. There was a removable spacer in the back of the master cylinder piston. Does yours? You need a small gap (about .030) between MC piston and brake pedal pushrod. MC piston must return fully so that there is no residual pressure to the calipers or wheel cylinders.

 

[aussiek20]

copy will check that, I followed the instructions in information provided by Ali (above) and it worked perfectly , will post up a pic after i do line work , ended up cutting approx 35mm from pushrod lenth and then slowly fine tuning until perfect