Jump to content

Front Right brake won't bleed?


Alex3000
 Share

Recommended Posts

I've done a bunch of searches and it seems like the answer is always "air in the lines"  but maybe someone here has some more practical advise?

 

The car is a first gen rx7 that I have put second gen front 4 piston calipers on.  I hooked up the whole system and using a vacuum bleeder bled rear pas side, then rear driver, then I go to bleed front pas side and nothing is coming through?  So I go to the driver side, and bleed that caliper and it works fine.  But the front passenger side just won't pull any fluid through??? And believe me I sat there for awhile pumping away at the vacuum bleeder.

 

Any thoughts?  How would you proceed?

 

Honestly, I am just running out of time with all the stupid crap that keeps popping up so it could be worth it to me at this point to lets say, buy a new master for 50 bucks, if that's going to solve it.  So tired of chasing things...

 

 

Link to comment
Share on other sites

  • Technical Advisory Committee

Something is blocking the line . Remove the brake hose blow through it,  open the bleeder blow slightly onto it does air come out the hose connection ? If yes disconnect the hard line and blow through it.  There is a blockage somewhere,  the next would be proportioning valve . Way back in the day I found a bleeder that was not drilled all the way through , or yours could be stopped up . 

Link to comment
Share on other sites

  • Technical Advisory Committee

First thing I would do is check if that brake works or not.  Do you have a firm pedal or a really soft pedal?  Get someone in the car that can apply brake pressure, see if you can spin the wheel when brakes are applied. 

 

If you have a really soft pedal and or it goes to the floor, use your helper to  bleed the system.  pressurize and open.  Repeat until air is out and that corner works.

 

If you have a really hard pedal and you can still spin that wheel with someone standing on the brake pedal, start taking things apart to figure out where the blockage is.  Remove brake line from caliper, does fluid come out when brake pedal is depresses (slowly)?  If yes, caliper may have an issue, time for rebuild.   If no fluid comes out of the line, start tracing back until you find the section that has the block.  Crimped hard-line, junk in the line clogging things up, fitting somewhere.  etc.

 

Link to comment
Share on other sites

On a Miata one of the fronts runs thru the proportioning valve but I don't remember which one at this point with out a look.

Point is you might have a stuck piston in that and not letting anything to the front caliper?

 

Again I would look for a blocked or plugged line as was said.

Link to comment
Share on other sites

A firm pedal but not a bled line indicates a blocked line.  If all lines were open but one caliper not bled should have a soft pedal.  

 

Does it have a distribution block after the master?  I would guess it is seized and not communicating with the one caliper.  The distribution block (larger brass rectangular cuboid) is the factory bias adjuster.  Ours is removed in favour of a manual adjuster.  

Link to comment
Share on other sites

1 hour ago, 55mini said:

On a Miata one of the fronts runs thru the proportioning valve but I don't remember which one at this point with out a look.

Point is you might have a stuck piston in that and not letting anything to the front caliper?

 

Again I would look for a blocked or plugged line as was said.

 

Oh interesting. I really am not a pro with hydraulics so its all a bit black magic to me, but if I understand what you are saying it looks like the FL caliper comes directly out of the master (which bleeds fine), while the FR (non-responsive) goes through a proportioning valve that splits to the rear?

 

So, how might I unstick this valve?

 

    brp.thumb.jpg.27904f52e3d8caf1ed57b076266bb565.jpg  

Link to comment
Share on other sites

  • Technical Advisory Committee

Blowing air through the system/component can help un-clog.  Pressurize from the outlet side,  since the clogged portion is most likely at an inlet.

 

If the only thing you have changed out are the calipers and now you have a problem, I would take a close look at where the brake line goes in (unless damaged, the rest of the system should be OK).  Make sure the brake line fitting types match between hard-line, soft line and caliper (bubble flare vs. double flare).  Or you could have some junk in the inlet if the caliper in which case pull the piston out clean out the inlet with reverse flow air pressure and/or brake clean.

Link to comment
Share on other sites

10 minutes ago, NigelStu said:

Blowing air through the system/component can help un-clog.  Pressurize from the outlet side,  since the clogged portion is most likely at an inlet.

 

If the only thing you have changed out are the calipers and now you have a problem, I would take a close look at where the brake line goes in (unless damaged, the rest of the system should be OK).  Make sure the brake line fitting types match between hard-line, soft line and caliper (bubble flare vs. double flare).  Or you could have some junk in the inlet if the caliper in which case pull the piston out clean out the inlet with reverse flow air pressure and/or brake clean.

 

I'll just cop to it right now.  I removed the entire brake master and booster unit and undid all the lines attached.  When I did this I shoved paper towel chunks in all the fittings to stop fluid from dripping everywhere.

 

So yes,  at this point I'm thinking there is a 99.99% chance I may have reassembled with some paper towel in the system. 

Link to comment
Share on other sites

The valve will also come apart and the piston will come out if not too stuck.

Large nut on the end of the valve and back that off and everything should come flying out :-) or not if it is stuck.

 

Blue rags can play hell on lines if you leave them in and reconnect. I know of a guy that did that very thing on an oil cooler line. 

It happens.

 

 

Edited by 55mini
spelling
Link to comment
Share on other sites

10 minutes ago, Alex3000 said:

 

I'll just cop to it right now.  I removed the entire brake master and booster unit and undid all the lines attached.  When I did this I shoved paper towel chunks in all the fittings to stop fluid from dripping everywhere.

 

So yes,  at this point I'm thinking there is a 99.99% chance I may have reassembled with some paper towel in the system. 

 

You may hear about this for the rest of your racing career.  Just make sure to put a gag order on your teammates so they dont tell your wife about it...! 😉

  • Like 2
Link to comment
Share on other sites

Like everyone else I agree that it sounds like you have a blockage somewhere.

 

I will give a nugget of advice that could save you from a lot of frustration down the line. When you install second gen rear brakes on a first gen car you have to flip them right for left. There is a R and L cast into the calipers but if you install them this way the bleed nipples will be pointing down and they will never bleed. I got lucky since I didn’t even notice the R and L in the calipers and just installed them with the bleed nipples up like any other caliper, but a friend of mine followed the marks and was really frustrated.

 

The reason you have to do this is because on a second gen RX7 the rear calipers are mounted in front of the axle and on the first gen they are behind the axle.

Link to comment
Share on other sites

3 hours ago, mhr650 said:

Like everyone else I agree that it sounds like you have a blockage somewhere.

 

I will give a nugget of advice that could save you from a lot of frustration down the line. When you install second gen rear brakes on a first gen car you have to flip them right for left. There is a R and L cast into the calipers but if you install them this way the bleed nipples will be pointing down and they will never bleed. I got lucky since I didn’t even notice the R and L in the calipers and just installed them with the bleed nipples up like any other caliper, but a friend of mine followed the marks and was really frustrated.

 

The reason you have to do this is because on a second gen RX7 the rear calipers are mounted in front of the axle and on the first gen they are behind the axle.

 

Interesting.  But, since my car is a gsl-se I'm keeping the stock rear brakes with the second gen fronts. 

Link to comment
Share on other sites

Outside the paper towel issue the flexible lines to the caliper - especially stock type - sometimes will collapse internally and you cannot visually tell.  This will create the same problem and others - like a caliper that won't release pressure.

 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...