UK GN brake problem

[allkiller]

My problem is there are only 4 of these cars in the UK and most American car shops over here wont touch them ??
I really need to get this car working again properly and need some experienced advice.

I have an 86 G.N. and again P/M brakes are playing up, motor burnt out, fuse went and pressure switch gave up all within seconds.

I changed out the Motor, fuse and switch...and followed the bleed proceedure....motor runs for about 15-16 secs then switches off, but the pedal is still very soft and spongy, virtually no brakes.
I have bleed the system over 10 times now with no improvement
...could this be the accumulator or master cylinder.

Any advice would be grateful,
Many thanks

 

[turbo nasty]

Try this lil test.
Key OFF
Pump the pedla until it get firm/hard should take 15 is trys if teh accum is good.

Now turn the key ON and watch the inboard reservoir it should drop to a 1/4 " (not a typo) in 10 ish seconds.

You may need to place something on teh Pro valve to keep it from popping out while bleeding. That is the clicking you are most likely hearing whil pressing the pedal,

 

[zeus87gn]

Which procedure did you follow for bleeding?
Did you remove the master cylinder from the vehicle to replace the components?
Have you run the diagnostic procedures yet?

Please remember, these units are tricky and can be troublesome.
If you take care of them properly, they can be made to last a long time.
Feel free to PM or email me if you need specific answers.

Z

 

[allkiller]

OK The inboard resevior drops more than 1/4", i'd say about 1/2 ".

i did not check prop valve ? if this pops out does this void the bleeding ?

 

[allkiller]

Checked again, the resevior level drops about 3/4" in 10 secs and 1" in 15 when motor stops.
Motor recycles for 2 secs at 1 min 35 sec everytime. checked it 5 times after pumping down.

Also pump will instantly run again for a few seconds, if you even slightly touch the brake pedal.

 

[turbo nasty]

let me reclarify.
With the key off and you pump the pedal until its hard what you are doing is depleting teh acuum ball.
This will cause the inboard res to fill.
Turning the key on on start.... the pump should pull the level DOWN to 1/4 " from full. NOT A 1/4" FROM THE LEVEL AFTER THE RES IS CLOSE TO FULL.

i.e. pedal pushed till hard...inboard res full....turn key on...pump energizes and the levels drops until there is only 1/4'ish of a inch in the res in a 10 ish seconds.

Now for the pro valve while bleeding. You start as normal with et furthest brake form teh MC which is the pass side rear. if someone is helping you and you have pressure on te hpedal and they crack the bleeder you fott falls to teh floor. As its falling you will mostl likely hear a click and teh BRake light coming on. That is your pro valve jumping over to the circuit that doesnt have a leak /the front.
If you look at the pro valve you will see a little plunger stick out and thats whats jumping out. and you can put something in there to stop it from doing so while bleeding.

IMO if i were you I would switch to VAC and never worry with the stupid high $$$$$ PM again.

You can get a whole vac MC, booster and pedal for less than what the Accum or the sw costs. Advance, napa, auto zone auto parts, vendor, etc can ship it across the pond to you. Then youll be done.

I spent around 800 bucks rebuilding teh insides of the PM, new pump, new sw, new accum. And it lasted about 4 years on a DD before the switch started screwing up. No way I was going to spend that much cash for what they are going for i swapped to vac and never looked back...Ha HA that was a pun.

Cheers mate the PM is Rubbish with a capital R

 

[allkiller]

Thanks Turbo...
yes it does pull the fluid down to about a 1/4 " from the bottom in about 10 secs YES.
but i did not hold plunger in on Prop valve when bleeding... (is this the key) ?

Because the pedal is pants with a capital 'P'

I re-bled the M/C again today to be sure....seems fine, was a little air, but not much, then re-bled the 4 corners...still no better pedal.

Just in case, Whats the best price youve seen for a complete vac system ?
thanks Mate

 

[charlief1]

You can get them from $100 US and up. The other option is to go with the hydroboost set up. A little more expensive but the brakes work better. Welcome aboard btw. Do some searching and make up your own mind on what you want to do. Good luck and come back on a regular basis.

 

[turbo nasty]

Dont worry with the plunger unless its clicking on you while you are pressing the pedal to the floor.
Are you bleeding it with te key on?

 

[zeus87gn]

Don't listen to the converts!
It just has air in it!

 

[allkiller]

Bleeding with Key off.

Also if the i pump down and pump up... when i touch the brake pedal it starts to cycle for about 2-4 secs again, even if i just lightly touch it.

The problem i have is all the stuff you guys can get easily, i have to send back to the U.S. for, or make... as even simple things like bench bleed kits are all metric (european) sizes. so imagine the delay time in repair

 

[allkiller]

ok... new M/C, pressure switch, and motor...still not a good pedal and now blows the fuse after about 10-15 seconds.

it cant be this difficult to solve...its throwing everything at me