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Discussion Starter #1
Im having trouble diagnosing weak brake problem following complete overhaul of entire system recently my car is 105 2000 gtv rhd with tandem master cylinder and dual servo/boosters. Yes the car been bled thoroughly with every method known and no leaks. The local garages seemed unfamiliar with the setup to help so bit lost any help much appreciated.

How do i check if servos/boosters are good? How should they feel and operate correctly?

How do i know master cylinder? How much pedal travel and effort before the brake lights come on?

Does the rear brake proportioning valve have any adjustment in it?

Is there a detailed brake line diagram for this car i can double check against line are to correct ports?

Many thanks
 

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When you say weak, what do you mean? - the pedal travels a long way before anything happens? The pedal is firm but it doesn't stop very well?, the pedal needs pumping up or the pedal feel is firm but excessively heavy with little result - they should feel firm, progressive and effective, not in a modern light switch sort of way but heavier with lots of feel, as standard they are very good brakes
 

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Discussion Starter #3
The pedal goes 1/2 - 3/4 way down before resistance is felt then its firm (not spongey or like trapped air feeling) however the wheels can be turned by hand on axle stands regardless of how hard pedal is pushed.
Pumping the pedal has no effect in feel or pedal position or retardation.
 

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Even without the servos (engine off) they should work, from what you are saying nothing is happening, I assume the RHD GTV has the same set up as the spider with the MC under the floor?, so to me that sounds like something may not be connected correctly, I've got a RHD brake line diagram but cant attach it for some reason so here's the link to the ARBB forum with the diagram, suggest you join the ARBB as there is a lot of tech stuff on there

https://www.alfabb.com/bb/forums/gt-1963-1977/156378-what-does-switch-do.html
 

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Discussion Starter #6
Thank you thats very helpful i can now trace all the brake lines.

Yes standing pedals same as spider with MC under the floor and yes all calipers have nipples upwards.

The entire brake system is brand new not reconditioned hoping i would avoid these problems...

Im looking at rear bias valve thing theres large threaded bar with allen key type hole and locknut, what does that do?
 

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Im looking at rear bias valve thing theres large threaded bar with allen key type hole and locknut, what does that do?
that sounds like the setting screw to adjust the plunger spring, described in this alfa tech pdf (which also notes the setting must never be altered!)
https://www.alfabb.com/bb/forums/808060-post60.html

the rear proportioning valve is described in detail (+how to refurbish it etc) in this long thread:
https://www.alfabb.com/bb/forums/su...es/152693-rear-proportioning-valve-105-a.html
 

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The trouble with having 2 remote servos is that it's like having 3 master cylinders and it's possible that the rods in the servos get stuck in the wrong position. If they're stuck "fully in" than that might explain the symptoms?
 

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I suspect that pressure bleeding from the reservoir might not work with this setup (never tried it myself). The last time I bled my system I used the vacuum method from each bleed nipple.
 

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I suspect that pressure bleeding from the reservoir might not work with this setup (never tried it myself). The last time I bled my system I used the vacuum method from each bleed nipple.
I've done it and it does work but i always find having a bottle of brake fluid under pressure a bit scary... prefer to use my Pella extractor on vacuum
 

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Discussion Starter #11
After going though everything several times the only thing i could find is pushrod/clevis not allowing brake pedal to return fully therefore MC pushrod always preloaded/ pushed inwards. With tandem MC i think (please correct me if im wrong) the front part of MC is for rear brake circuit and rear part for front circuit, so if pushrod always pushed in it stops that front chamber (rear circuit) from refilling and goes into fail safe mode mechanically pushing rear piston for front brakes rather than hydraulically hence really poor rear brakes, low pedal and iffy front brakes.

The solution was 10mins with hand file, now brake pedal sits considerably higher at rest 30mm higher! I also made sure clevis and pedal linkage as 0.25mm of play at rest anymore like 1mm felt too much under my foot. New clevis pin made world of difference here, if your can even slightly feel grooves on the pin swap it out!

Should clutch and brake pedal be at same level as throttle pedal?

Brake lights now come on earlier and i don't have to stomp on pedal like emergency stop level of leg effort, however during light press as per normal driving i have approx 20mm of pedal travel. Results much better however im still not happy and somethings still amiss...

Seriously considering redoing brake lines rather than use automec brake line kit as i did before because the lengths were a bit short or long and i might have slightly crushed a pipe or bend too tight to make them fit.

Anyway i hope pictures help solve other peoples low brake pedal issues.
 

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