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Advanced help needed, non abs standard brakes VR Ute.

Gthayes

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Thanks to everyone's help so far, but I failed the pits again for poor brakes.

The brakes are poor but not dangerous so I figured in may be basic so I changed the pads to benix and changed out the piston seals and dust boots. Lightly regressed all moving parts.

The pedal is low and spongy with a hiss when depressed from under the dash.

Vac tests being the pedal drops slightly when I start the car. 3 pumps to clear vac pressure when car off. Sweet.

Bled with dot 4 maybe twenty times. Not even small bubbles since finishing the 2nd bleed.
Using 1 and two man bleeds.

Slightly better.

Machined the rotors, and re stripped out the calipers to ensure they are moving freely. Changed out MC unit. Bench bled it first and depressed the caliper pistons when connecting to get the last air out. Then bled again from calipers.
No change.
Changed out the vac booster hose and found that the check valve does not hold suction when engine is off and yr finger is over the end. Obviously this will we changed first thing but will this affect braking while the engine is running? Simply cannot find symptoms for this on the site?

Also when I benched the MC the pressure for the rear lines sent fluid across the garage but the front outlets just gently spurted when I fully depressed the piston? Is this the norm?

I have also checked the rotor temps after each road test and they seem fine.
Checked the electric switch under the MC for good measure.
Tomorrow I will throw in a new booster for the hell of it as I am totally stumped???
No vac or liquid leaks detected but when I disconnect the booster vac hose the engine purrs at 2k rpm??
Could that be related?
Lastly I changed the fuel reg as the vac hose was full of fuel. Runs sweet now, just can't stop!
Thanks for your time
 

VR38

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Did you fit a brand new M.C?
 

VR38

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Hiss sounds like you need another booster too.
 

Brett_jjj

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Theres a load sensing proportioning valve on the rear brakes on utes,(utes also use a different master cylinder to sedans etc) and if this proportioning valve is closed or near closed when the rear brakes are bled, it can hold or trap air in the rear brake lines. Before bleeding the rear brakes, make sure the proportioning valve is held fully open by removing the chain and/or clamp that connects the proportioning valve to the panhard rod, and holding it in the full open position whilst the brakes are bled... This proportioning valve works by cutting brake line pressure to the rear wheels when the vehicle is unladen and it also lets more line pressure through to the rear brakes when the rear end is weighed down with a heavy load. It also stops the rear brakes locking up by controlling the brake line pressure to the rear wheels as the rear end lifts up under heavy braking.
 

Gthayes

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Again another superb response, let you know how it goes thank you!
 

VrWagz1

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Its not just the 1 way valve leaking and bleeding air back out of he booster(The white right angle plastic bit that plugs into the booster)?
 

Gthayes

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Its not just the 1 way valve leaking and bleeding air back out of he booster(The white right angle plastic bit that plugs into the booster)?

You mean the check valve we have already covered....thanks
 

Gthayes

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Theres a load sensing proportioning valve on the rear brakes on utes,(utes also use a different master cylinder to sedans etc) and if this proportioning valve is closed or near closed when the rear brakes are bled, it can hold or trap air in the rear brake lines. Before bleeding the rear brakes, make sure the proportioning valve is held fully open by removing the chain and/or clamp that connects the proportioning valve to the panhard rod, and holding it in the full open position whilst the brakes are.....

Followed Brett's advice and got my best bleed yet!
Enabled me to get some trapped air and dirty fluid through.
Pedal travel is better as is no longer hitting bottom.
Real hard to depress so it's a new booster in the a.m to complete the set! Yay. Ta Brett

Guy working the counter at ABS assured me the booster check valve does not affect braking while the engine is running.
Although I have the slow release of vac when engine is switched off, also pedal drops a little as expected when engine started? Just left with a med hard pedal that does not grip...Grrr
 
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VR38

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Glad to hear your getting on top of it.
 

Not_An_Abba_Fan

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Bed the brakes in properly as well, Bendix are **** until they are bed in.

Find a nice quiet area.

Get up to 60 and brake HARD down to ~10 (without locking the brakes). Repeat 5-6 times until you can really smell the brakes and they tend to fade a bit. Then drive for 10 or so minutes avoiding braking as much as possible to cool them down. Then give it a go. Should get a nice high and hard pedal that stops pretty good.
 
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