Odd Brake Problem

[Cyclone101]

Hey guys,

I have had rock hard brakes on my malaga 02 for quite some time now, I always just wrote it off to bad boosters, but yesterday I had a little more sprited drive than usual, and BOOM! I almost wet myself, cause my brakes worked normally, and in my usual "stomp-the-brakes" mode I locked all 4's.

So, I now suspect a vacuum leak, as it only happens when the rev's are up and when I am quick off the throttle onto the brakes, otherwise its the old hard pedal. oh, and the pedal travel is MUCH less when the booster works...

Any other explanations?

Regards

Jacques

[Swiftus]

So I agree that it could be a vacuum leak... Or possibly a faulty one way valve in the booster line. If the valve is broken, then the booster will not keep vacuum for any assist when you need it... Unless you are constantly providing a high vacuum for the booster...like a high rpm full-off throttle condition...

HTH

[c.d.iesel]

....and of course this important point before you become a "opps - i shouldove

not driven the car with broken brakes?!?!"

figure out if you have the booster hose check valve backwards?

or the inside of the booster is broke, or your pedal linkage

is seized from rust or inproper 'rebuilding'?

you should not be driving this car untill fixed .

[Cyclone101]

....and of course this important point before you become a "opps - i shouldove

not driven the car with broken brakes?!?!"

figure out if you have the booster hose check valve backwards?

or the inside of the booster is broke, or your pedal linkage

is seized from rust or inproper 'rebuilding'?

you should not be driving this car untill fixed .

Haha, yeah I guess you are right cd, but its hard not do drive the little falla.

The check valve is working as it should an the right way round(the wrong way round the booster would never work btw...)

Its a RHD car(no brake linkage), with twin remote boosters, so my reasoning is that its highly unlikely that both don't work, and then both works again at the same time. Thus my thinking its got something to do with vacuum.

Could still be a relatively small tear in the diaphragms, although as I am writing this, I realized it can't be as the pedal would slowly drop with a small hole in the diaphragm. my pedal stays firm and responsive, but when I release the pedal and step on it again it drops down far and is hard again.

Sorry for the essays but I am trying to describe every effect in the best possible detail.

Regards

Jacques

[TobyB]

Hmm- this is a wild- assed guess, but have you confirmed, when the pedal

drops and is hard, that you're getting both brake circuits? The

long/hard pedal's a classic symptom of one leaking (usually in the master,

if you're not losing fluid.)

A single- booster system will have a hard and HIGH pedal when the booster's

not working- when it get vacuum, it sinks slightly.

...but that's on the single system, and doesn't explain why they work with

high vacuum...

t

[Napes]

Smokin' rockets, Commander. That braking system out of a RHD looks like something Honda would come up with. I'm glad mine's a little simpler.

Bob Napier

[Cyclone101]

Smokin' rockets, Commander. That braking system out of a RHD looks like something Honda would come up with. I'm glad mine's a little simpler.

Bob Napier

TELL ME ABOUT IT! Ever tried getting air out of this one? No pressure bleeder? Now that would be quite a funny thing to watch! Its like a damn nuclear reactor, only more complex!! haha

And, if you want to rebuild your MC, you don't, cause you have to rebuild 3 MC's. I realy don't like the system, but I have to live with it.

At least RHD cars don't have the same RUST-O-PEDALBOX problem.

So I guess the main question would be what can cause a high, normal pedal at high rpm(doesn't always work though), and a low, hard pedal at low rpm...

Jacques

EDIT: I bled the brakes a while ago, and im sure fluid moved from all nipples(one line supplies one set of pistons on the caliper iirc). But I think I should go bleed again and double check. What do you think the effect of running on one line would be? It can't change pedal hight can it?

[tim385]

RHD here to , hmmm hard pedal ...boosters probably not getting vacumn, I know the vac hoses are a bit of a maze on the RHD cars check that you have the right type of hose on your boosters ...not heater hose ...yes ive seen it before....the T piece between the two boostere is not cracked (poss vac leak . The one way valve is working properly . With the engine not running pedal should be quite hard , whan you start it the pedal should drop a bit and feel not so hard with a little bit of spongeyness ... if that makes sense. Ive gone boosterless on one car and the pedal is hhaarrd.The other car has boosters , and they are a real bitch to bleed usually I have to do it a few times .Best way to date to bleed , get another master cyl cap put an air line fitting in it hook it up to the compressor with the regulator adjusted to 15 psi then crack off the steel lines first 1 at a time and retighten when clear(no air)(start LHS rear ,RHS rear LHS front , RHS front (this is for a RHD car )then do the same again on the bleeder screw, should come up alright after that .

[tim385]

I also run single line boosterless, High revs lotsa throttle not much vac.

[Cyclone101]

Ahhh, a fellow common-wealth-bottom-of-the-world guy! What's weird is, my pedal is hard, but manageable. If i disconnect the vacuum hose my pedal is very hard. So the booster works a bit, or maybe that is a sign of a vacuum leak. Either that or just one booster is working. I'm going to replace the valve and hoses this weekend just to make sure, and then run a straight line to only 1 booster and see if I can notice a difference.

About the bleeding, did u mean the reservoir cap?

Regards

Jacques

[tim385]

Yes the reservoir cap oh dont forget the bleed screws on top of the boosters,yeah try the one way valve , could try blocking off 1 booster at a time see what that does.What carb/s you running ?Twins usually dont give much vac at the manifold.

[Guest Anonymous]

Im runnung a 40pdsi, std solex single bbl. So vacuum signal sould be good at the manifold.

Regards

Jacques

(posted from phone, and too lazy too log in)

[Cyclone101]

Okay, today I bought new vacuum hoses and valve and that was not the problem. It still behaves the same.

So I was thinking, can there be a vacuum leak inside the booster that is small enough to cause this?

On a side note, all this heavy braking made me notice a slight pull to the right under heavy braking and the right front locks up first, so i might have to rebuild my calipers.

Regards

Jacques

[tim385]

Hmmm, are you getting vac. to your boosters ?