[DeTomaso] Another brake question.

[pantdino at aol.com]

I bought my car with two stock rear calipers on each side. My understanding is that the proportioning valve was removed (and I believe the shuttle valve also) and that was OK because of the 4 rear-caliper situation.

I have been thinking I would like to remove the extra 2 rear calipers because they create more drag on the rear discs and increase the pedal motion. 

Just to be certain, I don't need to replace the proportioning valve if I?remove the extra 2 rear calipers?

My experience is that when a car?has a very hard pedal intermittently it is in fact the booster or vacuum problem.

Jim


-----Original Message-----
From: JDeRyke at aol.com
To: wdemelo at cogeco.ca; detomaso at realbig.com
Sent: Thu, Jul 9, 2009 8:54 pm
Subject: Re: [DeTomaso] Poor brakes


In a message dated 7/9/09 5:35:36 PM, wdemelo at cogeco.ca writes:

> It feels like I'm driving a '65 Ford with drum brakes. Every so often 
> they work (1 in 20 attempts), otherwise I've got to really step on the pedal. 
> I don't think my booster is working. How do I test it?
> 
Pull and plug the vacuum hose at either end and try them. There should be a 
difference in stopping power. Also, if they're working, there will be an 
audible 'hiss' when you step on the pedal or let it off. The true test though 
is to add a 0-1500 psi gauge to each circuit and check the pressures. 
Without a proportioning valve, you'll be hard-pressed to get 350 psi with the 
engine off, but you should see 1200 psi with the engine on and vacuum at the 
booster. I've found several Panteras in which the vacuum line was disconnected 
for some odd reason....
The shuttle valve under the booster often sticks in internal varnish at one 
end or the other of its travel, and it will not reset itself; the only fix 
is to take it completely out, remove the end fittings and tap the shuttle 
back into the valve center with a nail-set, then replace and carefully 
re-bleed the whole system. With the shuttle stuck, you essentally LOSE the 
brakes 
at that end of the car, which makes for p-poor stopping power. The shuttle 
can be safely thrown away and the various lines hooked together. Its only 
job is to warn you of worn brake pads, and only if you still have pads with 
ground wires embedded. 
Finally, if you also throw away the stock non-adjustable proportioning 
valve, ALL the brakes will run at full power rather than having the fronts 
hamstrung as they are stock. Deleting the prop-valve and the shuttle valve are 
often the only brake upgrade most street Panteras need. And its pretty low 
cost. Good luck- J Deryke


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