Problem with vacuum brake conversion

[Mike70gtx]

Brake light came on my hydro boost system and the brakes were getting spongy. So I decided to follow the conversion to vacuum boost system. Got a new vacuum booster and master cylinder for an 84 4-barrel regal. Put in a new foot pedal. I have bled them several times but my brake light is still on and I barely have any brakes.
Any suggestions?

 

[turbowrenchhead]

Did you bench bleed the master?

 

[Mike70gtx]

I did it as per instructions. I never really felt like it was getting any stiffer. Maybe I didn't get it good enough. Should I take it off and do it again?

 

[Mike70gtx]

Another possiblity. I can't loosen the little vents to bleed the front calipers because they are so rusty and the heads are rounded. I loosened the bolt were the line attaches and would bleed the fronts. Could it still leave air in the calipers since I'm bleeding at the bottom where it comes in instead of the top?
If so I might need to get new calipers.

 

[BuickTV6]

I had this exact same problem with mt car as well. Turns out it was one of the rear wheel cylinders that blew out on me. I'm no brake expert, but as far as I remember there was this valve that stuck open which trips the brake light to stay on. Its been a few years since I did it, but I remember I had to replace this valve cause it was stuck open.. I hope that gives you some ideas. but I am sure someone else in here can answer you in better detail

 

[HOTSIX]

I did the conversion this summer.

Even a lil air in the system will screw up the feel in the pedal. You definitely have to get rid of ALL air in the system.

I think you can get new bleeder screws if your calipers are still saveable. I ended up getting new calipers though...mine were toast after all those years of service.

Get new screws or calipers...then bleed the system again. Work from the furthest away...ex: Do rear pass side...then rear dvr side, pass front then dvrs front.

ALSO check the electrical connection to the porportioning valve mounted on the driver's side frame below the master cyl.

If you bench bled the system...you got no problems...if not - gotta do it...or everything else after that is no good.

HTH

 

[Mike70gtx]

Thanks for the advice. I had just decided today to get some new calipers ($12 I think). I'm sure I have some air that I am not getting out. I just ordered a line lock and decided to do that to while I have the system open again.
BTW. The master cylinder fittings were just the opposite of my brake lines. Two adapter from NAPA and it worked. Could that be a problem having the smaller line on the other end of the master cylinder? (The MC was from an 84 non injected)

 

[HOTSIX]

Not too sure what you mean by 'smaller line' on the other end of the master cyl.

If you are asking is it okay to have reversed the lines (front line to back and back to front) i'm pretty sure thats not right. Your brake pressure will be different...where most pressure is supposed to be at the fronts...it would be at the back...and that's not safe.

I may have misunderstood you here though....

 

[Mike70gtx]

Just an update. Got the brakes working great. Thanks for all the advice. I replaced the calipers and the rear brake cylinders (one was leaking). I did have to switch the lines on the master cylinder, the replacement model must have been opposite of my original. The front brakes didn't work very well till I switched them. I also added a line lock and it is sweet.

 

[HOTSIX]

Great.

How hard was the line lock to install ?

 

[Mike70gtx]

Line lock was not to hard at all. I did a search in General Buick Turbo Tech for "line lock". The thread titled "Sam Biondo rebuildable line lock"., had some good info in it. John Larkin had a picture to access on his reply. With the instructions on my Summit line lock (Morosso brand I think, about $40 and the kit to go with it for the electronic button, about $70 total with 2 day shipping) and the picture from John Larkin it went alright. I couldn't mount mine down by the porportiion valve because in got in the way of my linkage to my shifter. I mounted mine on the firewall by the master cylinder, got two 3/16 in brake lines 30 inches long and ran the lines down to the valve. You remove the front brake lines off of the front of the porportioning valve and hook them together with a "t". and run one of the 30" lines from the front (the end closest to the wires) of the line lock down to the t on the front brake lines. The other 30" line goes from the back of the line lock to the top hole on the valve that the front brake line came off of. Then screw a plug in the bottom hole that the other front brake line came off of. The instructions that came with the switch were pretty easy to follow to hook that up. You with also need to 90 degree connectors to hook the brake lines into the line lock. Just make sure all your connectors are for brake lines. Advance Auto had everything I needed. Hope this helps.

 

[HOTSIX]

Hey thanks a lot.

I'm gonna do mine soon as I finish the heads and intake...

 

[Rob_85Ttype]

Mike,

I will be attempting this conversion soon, as I have collected all of the parts. I too noticed that the smaller line was on the front, which is opposite of everything that I've ever seen. Without considering the linelock, could you or did you simply remove the lines, put the rear on the front, and the front on the rear, then reassemble?

 

[Mike70gtx]

Yes, even without the line lock, just switch the lines front to back and back to front. At least that is what someone told me and it seems to work great.