Author Topic: Cannot get brake pressure - Can a reservoir be fault?  (Read 1501 times)

Offline imebgo

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Cannot get brake pressure - Can a reservoir be fault?
« on: November 15, 2015, 04:21:22 PM »
Hi,

Obviously doing something wrong or something is faulty here:

1) Fitted KSPort front and rear
2) Replaced master cylinder with 929 for larger brakes
3) ABS unit is OK
4) Replaced all lines with copper/nickel lines
5) Bench bled master cylinder
6) Bleed brakes in correct order

No pressure build up at all can pump and pump and pump but nothing.  System does not have any visible leaks.

So, I figured I would loop the connections at the master cylinder together to see if I can build up pressure just with the pedal and cylinder, but same result.

I am using the original reservoir of the old MC, can these things develop faults? 

Thanks,
James



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Re: Cannot get brake pressure - Can a reservoir be fault?
« Reply #1 on: November 15, 2015, 06:27:37 PM »
Is the pedal returning after applying pressure?. If the master cylinder was at fault i would expect it togo to the floor and stay there. 
Seems strange the k sport brakes have they a bleed both sides of calipers? Wondering if you still have air in system.
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Offline imebgo

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Re: Cannot get brake pressure - Can a reservoir be fault?
« Reply #2 on: November 15, 2015, 06:51:54 PM »
Pedal returns back no problem.

Strange it doesn't build pressure even when the two circuits are blocked of the other connections near the MC.

It's bled multiple times and there;s no air coming out of the lines.  I bleed the KSport on the outside nipple first, then inside on the caliper.  Just curious why its the same problem even with all of the brake circuits blocked off.

Im not sure the MC is at fault as I first tried with the original MC, and thought the problem might be an undersized MC so I upgraded it to 929 anyway due to larger brakes, but fault still exists.

Reservoir is original though, can these go wrong in anyway?

Thanks!

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Re: Cannot get brake pressure - Can a reservoir be fault?
« Reply #3 on: November 15, 2015, 09:10:15 PM »
reservoir is just that supplys fluid to MC...and as you have fluid at calipers with no air does not seem to be at fault.....strange.

Like you say closed ends should pressurise.

i had a similiar problem when replacing a front to rear brake just could not get a pedal and a mated suggested breaker bar on pedal and used seat to apply pressure. left overnight and voila.

but in this case with the closed ends does not make sense.

umm you pressurised with engine running so servo assisted?

92 FD rx7 Twins 13.5psi. Track car
94 Westfield Se 231 rx8 street port powered. Race car
EAT SLEEP ROTOR REPEAT.

Offline imebgo

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Re: Cannot get brake pressure - Can a reservoir be fault?
« Reply #4 on: November 15, 2015, 09:17:52 PM »
Engines not running, so no vacuum assist.  Can the brake booster fail to fully operate the push rod? 

Im thinking at the moment, pedal play, or push rod clearance, maybe pedal is bottoming out before MC is bottoming out?

/J

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Re: Cannot get brake pressure - Can a reservoir be fault?
« Reply #5 on: November 15, 2015, 09:21:20 PM »
Was it the same with the standard mc? Id run her up with servo assisting and see what it feels like.
92 FD rx7 Twins 13.5psi. Track car
94 Westfield Se 231 rx8 street port powered. Race car
EAT SLEEP ROTOR REPEAT.

Offline imebgo

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Re: Cannot get brake pressure - Can a reservoir be fault?
« Reply #6 on: November 15, 2015, 09:28:29 PM »
Yea, same with standard MC. got some work to do before car will start, so not an option at the mo.  I would have thought a badly operating booster would just make the pedal much harder?

Thanks,
James

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Re: Cannot get brake pressure - Can a reservoir be fault?
« Reply #7 on: November 15, 2015, 09:36:32 PM »
Yes pedal would be hard....how does the pedal feel...travels all the way to stop? Then returns or goes hard but no pressure at calipers?
If the push rod was not operating on mc you would not be able to bleed....personally i alway manually bleed with 1 in car and me at nipple....always had fun and games with those ezi bleed systems.
92 FD rx7 Twins 13.5psi. Track car
94 Westfield Se 231 rx8 street port powered. Race car
EAT SLEEP ROTOR REPEAT.

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Re: Cannot get brake pressure - Can a reservoir be fault?
« Reply #8 on: November 15, 2015, 09:45:00 PM »
If the brake pedal is very hard but no pressure at the calipers i think youve got to wait til car running as servo will amplify your foot pressure. My westy has no servo assist and i really have to push them hard and there tiny calipers as opposed to them huge k sports. Id personally wait til up and running and see if you still have a problem.
92 FD rx7 Twins 13.5psi. Track car
94 Westfield Se 231 rx8 street port powered. Race car
EAT SLEEP ROTOR REPEAT.

Offline imebgo

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Re: Cannot get brake pressure - Can a reservoir be fault?
« Reply #9 on: November 15, 2015, 09:51:19 PM »
Pedal travels to a stop, then returns, can repeat over and over again with no build up of pressure, no resistance.  Pedal is not firm, and does not change after pumping.

/J


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Re: Cannot get brake pressure - Can a reservoir be fault?
« Reply #10 on: November 15, 2015, 09:58:39 PM »
Should go hard even without the servo...stuck myself now mate...ill run it by a mate tomoz. Master mechanic.
92 FD rx7 Twins 13.5psi. Track car
94 Westfield Se 231 rx8 street port powered. Race car
EAT SLEEP ROTOR REPEAT.

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Re: Cannot get brake pressure - Can a reservoir be fault?
« Reply #11 on: November 15, 2015, 10:06:05 PM »
Cheers - any help appreciated.

/J

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Re: Cannot get brake pressure - Can a reservoir be fault?
« Reply #12 on: November 15, 2015, 10:08:09 PM »
No worries...got all the symptoms of failed seal in the mc....but new and did it on std....perplexed!
92 FD rx7 Twins 13.5psi. Track car
94 Westfield Se 231 rx8 street port powered. Race car
EAT SLEEP ROTOR REPEAT.

Offline imebgo

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Re: Cannot get brake pressure - Can a reservoir be fault?
« Reply #13 on: November 16, 2015, 12:48:58 PM »
I have a third (old) MC from a 92, probably original so I will give that a go.

If the problem is still present that could mean 3 broken MC seals, so that might make it less likley to be the MC.

Im going to try rebleeding the MC and then bleeding at each joint just incase it is air

But any other suggestions are more than welcome!

Cheers /J

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Re: Cannot get brake pressure - Can a reservoir be fault?
« Reply #14 on: November 16, 2015, 01:17:06 PM »
I had a word with my mate and he said air or mc fault....did you try closed end with the original mc?
He also said slow movement on the pedal to protect the mc seals.
92 FD rx7 Twins 13.5psi. Track car
94 Westfield Se 231 rx8 street port powered. Race car
EAT SLEEP ROTOR REPEAT.