Brake problem!

sharkey964 · Mar 4, 2020

OK.
Bear with me here peeps.
A few weeks ago,I came to move my 300tdi 90,& no brakes.Fluid reservoir was empty.
There was no signs of a major leak,but a slight leak on one of the front calipers,so, assumed that was the problem.
So,changed the front calipers for a bit of an upgrade to 110 vented,together with new disks & pads.
Whilst trying to bleed them up,I couldn't get any pressure at the bleed nipple,just a dribble of fluid when the pedal was pressed.BUT,when the brake pedal was released,fluid squirted out of the reservoir.I guessed the seales in the master cylinder were fubar,so replaced the master cylinder as well.
The problem still persists.Can't get any pressure at the bleed nipple,just a dribble,& altough i can get the pedal to have a bit of resistance,the front brakes dont work at all,i.e.with the pedal pressed,I can still turn the hub by hand.
I'm going to try reverse bleeding tomorrow.
Is there anything else I can do.
Oh,& it is still squirting fluid out of the reservoir when I release the brake pedal.I'm sure this isn't normal.I've never noticed it do that when I've bled the brakes previously.
Thanks in advance for any help on this.
Marc.

Gmacz · Mar 4, 2020

Only thing I can think off is there is high pressure being forced back. Maybe a flexi being forced to expand and then when pedal is released it is forcing fluid back. Fact you are not getting anything through to bleed nipple could be caused by same faulty flexi.

jamesmartin · Mar 4, 2020

id change flexis and 300tdi on 90 has same calipers as 110 vented or solid

Flossie · Mar 4, 2020

I wonder if over adjustment of the MC pushrod would cause that blow back?

jamesmartin · Mar 4, 2020

Flossie said:
I wonder if over adjustment of the MC pushrod would cause that blow back?

it would have to be pushing past the point reservoir port is open to master cylinder which would mean little if none fluid entering the master cylinder

sharkey964 · Mar 5, 2020

jamesmartin said:
id change flexis and 300tdi on 90 has same calipers as 110 vented or solid

Sme calipers,yes,but with a spacer between the 2 halfs to allow for the thicker vented disc.
The flexis are extended stainless jobbies,I wouldn't hav thought tey would baloon like the rubber ones do?
Thanks
Marc

turrican · Mar 5, 2020

I wonder if the bleed nipples on the new calipers are faulty. Because the calipers are still full of air and the air is being compressed when you press the brake pedal, this could cause the blow back at the MC.
Can you completely unscrew a bleed nipple and see if much air/fluid is released? If you still only get a dribble then I wonder if the calipers have a blockage inside?

jamesmartin · Mar 5, 2020

sharkey964 said:
Sme calipers,yes,but with a spacer between the 2 halfs to allow for the thicker vented disc.
The flexis are extended stainless jobbies,I wouldn't hav thought tey would baloon like the rubber ones do?
Thanks
Marc

yes the difference between vented not 90 and 110
undo the brake pipe at master cylinder and get someone to press the pedal slowly,block the hole fully with your finger before letting pedal up,try that a few times see the amount of fluid been pumped

sharkey964 · Mar 5, 2020

jamesmartin said:
yes the difference between vented not 90 and 110
undo the brake pipe at master cylinder and get someone to press the pedal slowly,block the hole fully with your finger before letting pedal up,try that a few times see the amount of fluid been pumped

Mmmmm,which pipe?
There are 3.

jamesmartin · Mar 5, 2020

sharkey964 said:
Mmmmm,which pipe?
There are 3.

one of the front and back

sharkey964 · Mar 5, 2020

OK,after trying to reverse bleed the system.....Not a chance,no fluid being forced up to the reservoir at all.
I'm thinking it could be the presure reducing valve on the bulkhead just under the servo.
Any thoughts guys?
Marc.

Wimblowdriver · Mar 5, 2020

sharkey964 said:
with a spacer between the 2 halfs to allow for the thicker vented disc.

Drillings in the spacer not lining up with the calliper halves? = blockage.

sharkey964 · Mar 5, 2020

Wimblowdriver said:
Drillings in the spacer not lining up with the calliper halves? = blockage.

After I tried reverse bleeding back to the reservoir.
I thought the same thing.
I disconected the feed pipe from the back of the caliper & reverse pumped fluid through with my syringe,that spurted out fine,so no blockage in the caliper.

flat · Mar 5, 2020

Could a bit of crap from the old MC have been forced down a pipe?

I would split the system at every joint and check if you can string fluid up each part, and the one you can’t is the blocked one.

The pressure valve you can carefully dismantle - it’s just a ball bearing on a slope to prevent rear lock up under hard breaking

sharkey964 · Mar 14, 2020

So,I fitted the new BBV today.

No real dramas,a bit fiddly but,I've done plenty of worse jobs.

The problem I now have is bleeding the brakes up.

I bled the front brakes with a Gunson pressure bleed kit until no air bubbles,tried the pedal & it was quite low & not very firm.Absolutely no brake operation at the caliper.

So,bled again & again & again,4 times in total.

Pedal now feels a little better & I have brakes at the front.But none at the back.

On a side note,& forgive me if I'm missing something obvious....Or,just being thick.

When I was testing to see if the rear brakes were working.The front wheels are off,car on axel stands.I jacked one rear wheel to spin it.It wont spin,like a locker is engaged?Car is in neuteral &high low lever in neuteral also.Surely with one wheel off the ground it should spin freely???

Marc

jamesmartin · Mar 14, 2020

not if hand brake is on

sharkey964 · Mar 14, 2020

I hope not!!!!!
I'll feel a right prat,if it is.
Can't look until tomorrow.
Marc

sharkey964 · Mar 15, 2020

I'm at the point where the Mrs is keeping all sharp object away from me...plus matches,as I want to set the bloody thing on fire.

I've pressure bled these brakes now so many times I've lost count.

STILL no brakes front or rear....

Fitted new calipers,discs,& pads,master cylinder & brake bias valve.

*Marc

Gmacz · Mar 15, 2020

Time to get someone else to have a look.

sharkey964 · Mar 15, 2020

That's a defeatist attitude,but,If I knew someone who could do more than me,I'd gladdly let them try.
Marc

Brake problem!

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