[Vwdiesel] Weird brakes

James Hansen jhsg at sasktel.net
Wed Jan 2 20:11:53 PST 2008

  He recently put a new master
> cylinder and one new brake line on the car, and afterwards is when this
> started.

I would suspect that the rod length between the master cylinder and the 
vacuum booster is incorrect.  This is accomplished by not seating the 
rod properly, or losing the o ring that goes between the two. What 
happens is the cylinder stays just depressed a tad, and this keeps the 
brake fluid from going back to the master cylinder  like it does if your 
foot was off the pedal in a normal situation.  Now, the fluid heats up 
in the brake line, particularly on the brake end, it gains volume, and 
slowly applies more brake due to fluid expansion.

If this is not the case, then you have to look at the booster- the 
vacuum valve may be leaking, holding the brakes on just a tad, as if you 
had a partially depressed pedal.  Maybe you could tell if freeplay in 
the pedal diminishes a lot with vacuum on the system versus no vacuum on.

> My opinion is that the new master cylinder is somehow faulty, but I really
> don't know. This is a strange one that I haven't seen before. Does anyone
> else out there have any ideas?

That's doubtful Eric, but there is always a first.


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