Leaking hydraulics - proportioning valve

**SJAndrew** · 12-08-2010

I've spent the last couple of weeks tracking down and fixing oil leaks in my engine compartment. I've since pressure washed my driveway and have found a brake leak on my now pristine driveway

I got my trusty inspection mirror and tracked it down to the proportioning valve. It's leaking from the body of the valve itself - the portion where the two halves meet is leaking (not the connection to the brake hose).

This is the first time I've ever seen a proportioning valve leak so I'm wondering if this is a common failure.

Have any of the rest of you had proportioning valve issues?

Also, my Hayne's manual has nothing in it re: the proportioning valve. Other than removing the old one, getting its orientation correct, and bleeding per normal procedure, is there anything else I need to do?

**matt5112** · 12-08-2010

its near the rear brakes right? if so, just buy a new one from the dealer then bleed the brakes.

**SJAndrew** · 12-08-2010

Yup - right next to the fuel filter. If they're not too expensive, I will replace both.

**TheOtherNick** · 12-09-2010

Just replace the lines while you are doing it. They will probably break anyways. Should only be like $30 for the lines and fittings.

**SJAndrew** · 12-10-2010

Are you talking about the hard lines or the flex lines? I replaced the flex hoses with braided lines a while ago.

I'm going to pressure bleed my brakes again tonight - I'm not sure I got all the air out last night (plus I only did the back circuit). I would have done all four but I ran out of time when my pressure bleeded blew a hose and spewed brake fluid all over my garage

**matt5112** · 12-10-2010

There is no back circuit.

Its front left and rear right on a circuit and front right and rear left on a circuit.

**SJAndrew** · 12-10-2010

Good to know - I assumed each wheel had a separate circuit given the 4 hoses exiting the ABS assembly.

Even more reason to re-bleed the entire system.

**matt5112** · 12-10-2010

Technically yes, each corner has its own circuit after ABS but before abs theres two.

**SJAndrew** · 12-10-2010

Right - it looks like out of the master it's two in an x-pattern then split into four.

**matt5112** · 12-10-2010

yup

I can post the ABS diagram if you want.

Its in the GM service manual over on GPONA.

**SJAndrew** · 12-10-2010

If you have it handly, by all means.

I was using this as a reference. It has the same modulator assembly as mine (Bosch 5.3)

**matt5112** · 12-10-2010

(1) Master Cylinder
(2) Master Cylinder Reservoir
(3) Pump
(4) Left Front Master Cylinder Isolation Valve
(5) Left Front Prime Valve
(6) Brake Pressure Modulator Valve (BPMV)
(7) Damper
(8) Right Rear Inlet Valve
(9) Accumulator
(10) Right Rear Brake
(11) Right Rear Outlet Valve
(12) Left Front Outlet Valve
(13) Left Front Brake
(14) Left Front Inlet Valve
(15) Left Rear Inlet Valve
(16) Left Rear Brake
(17) Left Rear Outlet Valve
(18) Right Front Brake
(19) Right Front Outlet Valve
(20) Accumulator
(21) Right Front Inlet Valve
(22) Damper
(23) Right Front Master Cylinder Isolation Valve
(24) Right Front Prime Valve

**guimond47** · 10-20-2011

i remove the porportioning valves on my grand prix thinking i don t need them as they were leaking.... i wanted to know if its a need to have them. and now i cant bleed my system.... i have steady fluid sprying out through the bleeder screww nicly all around but the peddle is mush.... any ideas guys? thanks

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