Help no/poor brakes

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d8moa

Active Member
Posts
313
Evening all.
Got a problem with my little 90 that I brought with a brake issue.
I have replaced the front calipers (as seized) and fully rebuild the rear brakes!
All bleed but still have a issue.
When running and the pedal depressed quickly it goes solid and stays solid,when I drive off and press the pedal it goes soft and almost to the floor!
I pulled the vac pipe off the booster and expected to hear a air noise from it being under vacuum but nothing! Tested with another 300tdi and I did get a air sound so I know I have a issue.
The vac pipe is sucking so I know the pump is OK so I am suspecting the booster/master cylinder
Any help would be appreciated
 
Well after changing the servo, master cylinder and vacuum pump I still have a brake issue.
Basically it feels like I have air in the system or the 1st stage of the master cylinder isn't working!
The only thing I haven't changed is the bias valve.. could this be the issue?

Dodgy seals in it etc
 
Clamp rear flex and try, drum brakes are ****e, I know some tosser is going to coma along and say best thins since sliced bread blah blah blah, ignore them and give the clamp test a try.
 
It's got rear discs lol I was going to clamp pipes but was unsure to do so with braided lines!
I'm going to make new copper lines tonight and bypass the bias valve see if that helps
 
I've found that it takes quite a while and a few bleeds to get all the air out of mine. I've had to leave it to settle and bleed it some more, then leave it overnight and bleed, and so on. Thank goodness for pressure bleeders. However, just before Christmas I replaced the factory made front to rear brake pipe with a new copper one that I'd bent myself with my fingers. The new pipe had no sharp bends in it and I got a firm pedal after a single bleed. So don't underestimate the amount of air that can hide in the system, especially if there are a lot of kinks in the pipework.
 
The symptoms you describe in your OP makes me think faulty seals in the master. I have had this on brand new parts, even the tiniest fault on a seal will result in what you have found. I once found drill swarf in a new brake cylinder, since then I always dismantle and inspect new brake parts before fitting. If you pump the pedal and there is no fluid loss / leaks and the pedal firms up, almost certainly a seal fault.
 
I was thinking the master too. I brought a 2nd had one and still have the issue...I then removed one of my friends 300 and still have the fault (so it's had 3 masters on in) worked fine when fitted back onto his car!
I am now at a complete dead end
 
Sounds like you still have air in the system. Landies are notoriously difficult to bleed. Try the brakes, make a note of how it feels, then bleed again. If it feels different after bleeding then you have air in the system. Sometimes it takes 4 or 5 bleeds to get all the air out, even with a pressure bleeder. If all this doesn't work, I would clamp off the rears - or even make up a pipe with a closed end to close the rear system. This will help you identify where the problem lies.
 
Clamp rear flex and try, drum brakes are ****e, I know some tosser is going to coma along and say best thins since sliced bread blah blah blah, ignore them and give the clamp test a try.

they are ****ing gash. they are 'okay' when adjusted ok but it took me 2 weekends and reverse bleeding, pressure bleeding and new adjusters. ****ing nightmare. discs are way bettererer. 1/8th of a turn on the adjuster made the most ridiculous massive difference it was unreal.
 
oh the ohter thing i did was clamp my brake pedal on overnight then rebled the following morning, that seemed to make a big difference
 
Might be worth a quick check of the one way valve on the servo (the right angled plastic bit the vac pipe goes on to) if the valve is intermittently sticking or leaking it will reduce effectiveness, fairly easy to pop out and do a quick suck / blow test:rolleyes:
 
The last time I popped out for a quick suck/ blow test ended very badly indeed...... I think my case comes up next month
 
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