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Canadian Poncho Homepage -> Canadian Poncho -> Beaumont Chassis Tech Forum -> No front brake pressure after disc swap
Post Info TOPIC: No front brake pressure after disc swap
bowtieboy


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No front brake pressure after disc swap
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Just finished up a swap on my 67 Beaumont with a mbm power brake kit.

Bench bled the heck out of the master cylinder, brakes, etc, tested the prop valve that came with the kit to check that its centered.

Now for my problem, you can visually see the calipers/pistons move on the front brakes. But as soon as you drive the car it seems all the brake pressure is being applied to the rear. It has a nice firm pedal as well.

Ive done a whole lot of googling and havent really come up with any problems that relate to mine. 

Would a adjustable rear prop valve help my problem if installed after the current one?

Or would it be possible to run the front brakes straight off the mc and put an adjustable on the rear? If I were to do this would I be able to just plum the front lines off the mc as it has dual outlets?


Any input appreciated.



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67 Beaumont- Work in progress

83 K20- to much to list

97 GMC SLE: Cranked N Dualed

02 Cavalier, the sleeper that wont wake up.
pontiax


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Make sure you have plumbed it to the proper port , the front disc will have residual pressure, a small amount to keep the pads close to the disc and the calipers full of fluid, if reversed you would have to pump a lot to build up pressure to the discs.  And the drums would feel like they were dragging.

 



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pontiax- (canadian pontiac X frame)1964 Parisienne 2dr. Hardtop ,lagoon aqua metallic (Q) ,421 cid Dart Industries block and heads. 550 hp. 575 ft lb  of torque.

 
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Lefty


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on my kit the front was for the disks and the back (closest to firewall) was rear
i had to guess because there was no markings or instructions

valve layout.jpgvalve.JPG



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Surrey BC

1963 Acadian Beaumont Sport Deluxe
http://www.63acadian.com/
bowtieboy


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Everythings plumbed like it should, looks just like the pic's Lefty has shown.

The breaks are not dragging either.

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67 Beaumont- Work in progress

83 K20- to much to list

97 GMC SLE: Cranked N Dualed

02 Cavalier, the sleeper that wont wake up.
rabbit64cs


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What mc are you using? New supplied with the kit?



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later...rog

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OURWAGON


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USE A TEST LIGHT TO MAKE SURE THE VALVE HAS NOT TRIPPED !!

BEFORE YOU DO ANYTHING ELSE.



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rabbit64cs


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I never switched the prop valve on  my 70 vert a body.. Just changed the mc to a disc drum style. Prop valve just sets up the bias,  and I found the stock one worked fine.



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later...rog

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Beau67SD


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Converted mine to front discs a few years ago, and had a problem with the front doscs not working properly....bled and bled them, still no sustainable pressure. than sat and stared at it for a while...had the calipers on the wrong side of the vehicle...couldnt get all the air out so had no front pressure...LOL...just a thought!!

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rabbit64cs


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bleeder screw to the top .....

wink

learned that one when I worked in a garage when I was 16.... never forgot !



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later...rog

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JerryA


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I have had problems in the past with master cylinders not having a residual valving built in. I have used a 10lb residual valve on the front discs and a 5lb on the rear drums.



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bowtieboy


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Checked prop valve with test light a few times, checks fine.

Calipers are bleeder screw up.

It was a complete kit from MBM.

We were debating on using the factory drum/drum valve, even had it hooked that way first. But figured I should use the one in the kit, so I plumbed all new brake lines.

Jerry A, that is exactly what my dad was telling me about possibly adding.

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67 Beaumont- Work in progress

83 K20- to much to list

97 GMC SLE: Cranked N Dualed

02 Cavalier, the sleeper that wont wake up.
rabbit64cs


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BigSteve is having the same trouble with the 572 69 Chevelle the shop built. And another friends 70 Nova is acting the same way.  I'll get in touch with him,  I think the fix which hole the pedal is in pushing the MC...

stay tuned...



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later...rog

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OURWAGON


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YOU MAY HAVE SOMETHING THERE!!



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dualquadpete


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Was there a rubber cup or Boot on the back of m/Cyl.?? When i did the 64 conv. to dual cyl. that boot interfered with the push rod on booster. Threw the boot in garbage & got pressure to all 4 whls!! Just another thought?? Pete

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rabbit64cs


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Sounds like some of these kits are supplying mc that have a front bore that is 4 mm bigger than stock.  Using a stock mc for discs cures the problem, returning  brake feel.

 

bigsteve and Jesse  have discussed this already.....

 

soo...what's the conclusion?



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later...rog

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bowtieboy


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I beat you to bigsteve Rog, lol.

I dont think you could get the booster rod hooked to the upper hole in the brake pedal in this case the booster is mounted on a pretty good angle.

The only rubber boot I seen/we put on was the dust boot between the booster/firewall.

Another thing Ive been told to try was scuff the rotors up, but I dont think thats the case here.


I havent checked the bore size of the m/c yet as well, bigsteve had said to check that. But being I got a complete kit Id be suprised if it was the wrong one.

Would it be possible to eliminate that prop valve, and plumb the front brakes straight of the m/c(using the dual outlets) and putting an adjustable prop valve on the rear line? Ive been thinking about going that route.  It would be fairly easy for me re route/re do the lines at this point if I have too.

417863_10151629285001153_1432403935_n.jpg



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67 Beaumont- Work in progress

83 K20- to much to list

97 GMC SLE: Cranked N Dualed

02 Cavalier, the sleeper that wont wake up.
bowtieboy


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So first thing up on the to do list will be to check the bore size of the m/c when I get a chance.

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67 Beaumont- Work in progress

83 K20- to much to list

97 GMC SLE: Cranked N Dualed

02 Cavalier, the sleeper that wont wake up.
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dcneric


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Are there 3 lines coming off of the proportioning valve? I can only see 2?

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Beaumont4008


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dcneric wrote:

Are there 3 lines coming off of the proportioning valve? I can only see 2?

 Was going to say the same thing. The two front out lets are for left and right front brakes.



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seventy2plus2


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what does the manufacturer say?



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dualquadpete


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Beaumont4008 wrote:
dcneric wrote:

Are there 3 lines coming off of the proportioning valve? I can only see 2?

 Was going to say the same thing. The two front out lets are for left and right front brakes.

 Me too!!  But I can't see him not doing the new line to rt,frt whl.?? If he didn't & just hooked it up the "stock way" then he's got frt caliper & rear brakes on same line but would have had to plug rear outlet on valve?????



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JerryA


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You can use just 1 of the ports for the front and block off the other.



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Lefty


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would it be better to use both front ports ??

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Surrey BC

1963 Acadian Beaumont Sport Deluxe
http://www.63acadian.com/
GLHS60


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I'm very outdated on my brake schooling but as I remember the rear port on the master cylinder is often for the front brakes.
Any possibility this is your problem? Is the rear resovoir larger than the front?

Thanks
Randy


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JerryA


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I just used 1 of the ports on the valve for the front. Mine works fine



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