Master cylinder brake lines, Hydroboost vs Vacuum Assist

[Rob_85Ttype]

Why are the brake lines on the 84-85 hydroboost master cylinder opposite from the brake lines on the vacuum assist master cylinder? The HB MC lines are "small" up front and "large" in the rear, where as the Vacuum MC lines are "large" up front and "small" in the rear.

If converting from HB to Vacuum assist, what do you do about this? Do you remove the lines from the distribution block and reverse them to match up with the vacuum MC?

 

[turbonut85]

Just the way the reservoirs are set up in the master...the HB master is reversed from the PM and the vac setup. Simply "tweak" them to reverse them. The front brakes use a separate reservoir from the rear in all 3 setups...don't change anything on the proportioning valve...Just curious, why you would swap from hydroboost to vac??

 

[INEEDAGN]

Just curious, why you would swap from hydroboost to vac??

VACUUM BRAKES FOR THE WIN!!!!!!!!

Sorry couldnt resist

 

[Rob_85Ttype]

The original hydroboost is leaking (I realize I can get a rebuilt one from Cardone), and the hydraulic lines that I have plumbed from the '87 pump are a crowded mess, even though I think I've done a fairly good job of routing them. I also lack one line that I need to have made from the pump to the HB. I'm still in the consideration phase of doing this (HB vs Vacuum boost). I don't race the car on the track so I'm not concerned with pedal force on the line when building boost.

So is the small diameter line the supply for the front or rear brakes? I take it that it is for the front brakes, since on the vacuum master cylinder it is connected to the larger well, and on the proportioning valve it appears to supply the forward portion of the valve associated with the front brakes.

 

[charlief1]

The smaller line is usually the rear and the larger line is usually the front.

 

[turbonut85]

If it functions, and is just leaking...they do make a rebuild kit for the HB system which includes housing seals...if its leakin out the back into the car, then it needs to be replaced or rebuilt by someone. As far as the lines...the 84-85 replacement lines are available from the parts store...and the pump to HB line will work fine with a minor tweaking of the steel end at the pump. HTH ---Keith

 

[lolo86GN]

The original hydroboost is leaking (I realize I can get a rebuilt one from Cardone), and the hydraulic lines that I have plumbed from the '87 pump are a crowded mess, even though I think I've done a fairly good job of routing them. I also lack one line that I need to have made from the pump to the HB. I'm still in the consideration phase of doing this (HB vs Vacuum boost). I don't race the car on the track so I'm not concerned with pedal force on the line when building boost.

So is the small diameter line the supply for the front or rear brakes? I take it that it is for the front brakes, since on the vacuum master cylinder it is connected to the larger well, and on the proportioning valve it appears to supply the forward portion of the valve associated with the front brakes.

I don't think you need to have any custom lines made for the hydroboost... I put the hydroboost out of an Astro on my car and the two pressure lines only cost about $30 from rock auto... Any pics? Curious as to the hose routing on your car...

The smaller line is usually the rear and the larger line is usually the front.

 

[Rob_85Ttype]

Yep - leaking out the rear and inside the car. Hydraulic hose routing that I have is correct - just a lot of stuff in a conjested area with the 86-87 pump reservoir in place on the fender. I'll look into all the other tips prior to doing anything drastic. Thanks.

 

[TexasT]

I guess I'm not understanding your problem. Your name has 85 in it so I am assuming a hydroboost setup unless it is a late car with a powermaster.
I put the hb setup on mine with 84 parts from rockauto. I got the lines, master cylinder, and hydroboost and bolted them on. Works real good.

 

[Rob_85Ttype]

It is an '85 with original hydroboost that's leaking, that has been configured to work with '86-'87 engine and power steering pump. The hydroboost supply line to the pump is not standard, as it has to mesh the '86-'87 pump with the '84-'85 hydroboost.

The original question was why are the big and little brake lines reversed on hydroboost master cylinders as compared to vacuum boost master cylinders, as I have considered changing to vacuum.

 

[lolo86GN]

Rob, if you do convert don't worry about the brake lines. Easiest thing to do is to leave the installation of the master for last. The front and rear lines can be moved around pretty easily and if the master is not bolted to the vacuum reservoir it should be no problem lining up and screwing in the lines. Once you get the lines on the master, just bolt the master to the vacuum reservour and you are good to go. And for what its worth. Both TexasT and I have 86/87 engines and where able to use stock 85 lines for our conversions... That's why I guess we are showering you with questions about hose routing on your car. When I was doing my conversion TexasT posted pics for me and helped me with tips too. Your car and your decision, but if you need help with how to keep the hydroboost or even upgrade to the hydroboost with the accumulator then we are your guys..

 

[TexasT]

Not sure what you did but I used a stock line from pump to hb unit and from unit to steering box. I did have to "adjust" the line at the pump as seen here.

http://turbobuick.com/forums/threads/installing-a-1985-hb-system.379401/#post-3039385

I would look into getting a reman hb and a stock line and doing the "massage" but your car , your call. Good luck! Keep us posted on your progress.

I will add I wouldn't hesitate to good hb again, though I can see the allure of the vacuum. I figured the money each way and they both seemed pretty comprable so I went with what I already knew worked as I had an 84 before my current whip.

 

[Rob_85Ttype]

I see now how that line HB to pump line is slightly modified. Does that then tie into the triple 90 degree hardline on the '87 pump, or directly into the '87 pump? Thanks guys.

 

[TexasT]

I see now how that line HB to pump line is slightly modified. Does that then tie into the triple 90 degree hardline on the '87 pump, or directly into the '87 pump? Thanks guys.

I believe it went right into the pump. Here is a link to a writeup on our local clubs page. Plenty of pix. Post up with any questions.

http://www.lspbcforums.net/lspbc.yaf/yaf_postst544_86ing-the-powermaster-for-a-HydroBoost.aspx

a pic of the line at the pump

 

[lolo86GN]

I see now how that line HB to pump line is slightly modified. Does that then tie into the triple 90 degree hardline on the '87 pump, or directly into the '87 pump? Thanks guys.

That line ties into the pump directly... but I have the part number for a pressure hose that connects to the hard line you are referring to. Read the thread below and look at the pics i posted for that pressure hose. I'm currently using it on my car and have no problems with it..

http://turbobuick.com/forums/threads/another-hydroboost-question-universal-push-rod.379750/