[DeTomaso] master cylinder

John Buckman jb841 at cox.net
Tue Jun 15 23:53:14 EDT 2010


Yes, the front and rear braking systems are independent of each other.  The shuttle valve can be "stuck" in any position and there will be no loss of braking.  When one braking system has a hydraulic failure, the shuttle valve just moves to the "side" that has a significantly lower pressure and activates the warning light switch.  That is all that the shuttle valve does.  It does not stop the flow of hydraulic fluid.

What calipers are you using?  If they are stock or modified stock, they have been known to trap air.

John



On Jun 15, 2010, at 5:34 PM, Justin Greisberg wrote:

> 
> 
> My guess is that the shuttle is frozen in the middle and not doing anything, so that the front and rear systems are simply independent of each other?
> 
> 
> 
> I had an older car as my daily driver, and when the brake line rusted through to the rears, the pedal would not pump up presumably because the shuttle valve was frozen inthe middle.  I have convinced myself that the problem is not in the valve/distribution block, BUT I DONT KNOW WHAT THE PROBLEM IS so who' to say.  I was kind of hoping someone would say that master cylinder is just not right, but I really don't think that is the prblem.
> 
> 
> 
> I plan to actually take the car out of my driveway when I get the new tires mounted and see how the pedal feels on the street in front of my house.  Hopefully, i wont crash into the mail truck.  justin
> 
> 
> 
> 
> 
> 
> Date: Tue, 15 Jun 2010 20:28:44 -0400
> Subject: Re: [DeTomaso] master cylinder
> From: rob at dumoulins.net
> To: justingreisberg at hotmail.com
> 
> 
> If it is not triggering the light, it has not shifted (at least all the way).  Does it stand to reason that if it is not shifted, is not bleeding pressure to the other side?
> 
> On Tue, Jun 15, 2010 at 8:25 PM, Justin Greisberg <justingreisberg at hotmail.com> wrote:
> 
> 
> 
> no.  of course who knows if the shuttle valve actually moves at all anymore.   i would bet it is frozen in place and now irrelevant.
> 
> 
> 
> Date: Tue, 15 Jun 2010 20:12:07 -0400
> Subject: Re: [DeTomaso] master cylinder
> From: rob at dumoulins.net
> To: justingreisberg at hotmail.com
> CC: mikeldrew at aol.com; detomaso at realbig.com
> 
> Is your brake warning light illuminated? 
> 
> 
> On Tue, Jun 15, 2010 at 7:47 PM, Justin Greisberg <justingreisberg at hotmail.com> wrote:
> 
> 
> I do have the stock distribution block.  But all cars of this vintage have one just like it, and I have always bled brakes with the block and shuttle valve in place.  interesting thought -- I now really regret not throwing it away, since I had it out and cleaned it all up, but wonder whether the shuttle valve is a problem...
> 
> 
> 
> From: MikeLDrew at aol.com
> Date: Tue, 15 Jun 2010 09:53:22 -0400
> Subject: Re: [DeTomaso] master cylinder
> To: justingreisberg at hotmail.com; detomaso at realbig.com
> 
> 
> In a message dated 6/14/10 5 23 13, justingreisberg at hotmail.com writes:
> 
> 
> 
> I have bleed the system with mity-vac and motiv pressure bleeders over and over again, yet pedal still is soft.
> 
> 
> Do you still have the stock differential pressure valve in place, which displaces in the event of a blown line and illuminates the idiot light on the dash?  If that valve displaces during the bleeding process, it can reportedly make it very difficult to get a solid pedal afterwards, until it's centered again.
> 
> Mike
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