Brake porportion valve question.... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

locab36 · 06-05-2009, 09:19 AM

Getting ready to do some brake work on my Panel Truck. It has power brakes but doesn't have the 'Power' feel. I have a feeling that it has man drum brake porportion valve. It was converted to 5 lug and the hoses are routed correctly. All the brake lines have what looks to be factory bends w/rock guards. The porp. valve is on the front crossmember in front of the PS gearbox. Kinda like the later 73 on pickups. Is this where its supost to be? The pics I've seen have the porp valve off the side of the master. Any info will help....

John

Burbinite · 06-05-2009, 11:53 AM

http://www.67-72chevytrucks.com/vboa...d.php?t=241722

Check out this thread. It has pics of the correct porp. valve. Yes, it should be off to the side (driver's) and supported only by brake lines.

Hope that helps you out!

locab36 · 06-05-2009, 03:19 PM

Lots of info there. My brakes work just seem stiff. I will try some booster tests I saw on that one link. I did have to lengthen the brake rod as the pedal was too close to the floor and didn't rest on the rubber bumper. Even w/the threaded end there wasn't enough adjustment. Got some grease on the pivots too, that seemed to help some. Still don't understand why my combination valve is on the front crossmember. Looks factory w/all the clips and rock guards. Someone went to a whole lotta trouble if it was changed. The brown brake trouble light wire is still up by the master.

John

Suburban 72 · 06-06-2009, 01:08 AM

Check for kinks in the lines as well. I had a kink in the line to the back brakes and the braking felt stiff. The kink was behind the bracket that holds the hard line to the rubber line.

locab36 · 06-18-2009, 04:25 PM

Replaced front hoses and all is back to normal. Normal power feel in the pedal and stops straight now too:-)

mbgmike · 06-18-2009, 06:19 PM

Quote:

Originally Posted by locab36

Replaced front hoses and all is back to normal. Normal power feel in the pedal and stops straight now too:-)

More often then not the hoses are the culprit. Nobody replaces them as they should. The inner liner collapses on them. Glad you got them fixed.

mbgmike · 06-18-2009, 06:24 PM

And yes the prop valve was usually on the firewall by the mc but whose to say some plants may have put it down lower. Here is a pic of an unmolested truck

06-05-2009, 09:19 AM	#1
locab36 Registered User Join Date: Jun 2004 Location: Midland, MI Posts: 265	Brake porportion valve question.... Getting ready to do some brake work on my Panel Truck. It has power brakes but doesn't have the 'Power' feel. I have a feeling that it has man drum brake porportion valve. It was converted to 5 lug and the hoses are routed correctly. All the brake lines have what looks to be factory bends w/rock guards. The porp. valve is on the front crossmember in front of the PS gearbox. Kinda like the later 73 on pickups. Is this where its supost to be? The pics I've seen have the porp valve off the side of the master. Any info will help.... John __________________ Locab36 1936 low cab 1/2 ton 1956 BMW R25/3 1968 Moto Guzzi V7 1969 BMW R100/2 1986 Silverado SWB 2007 Harley FLHTP 2011 GMC SWB 4x4 Z71 http://www.flickr.com/photos/locab36...7623329816080/

06-05-2009, 11:53 AM	#2
Burbinite Registered User Join Date: May 2004 Location: North Little Rock, AR Posts: 63	Re: Brake porportion valve question.... http://www.67-72chevytrucks.com/vboa...d.php?t=241722 Check out this thread. It has pics of the correct porp. valve. Yes, it should be off to the side (driver's) and supported only by brake lines. Hope that helps you out! __________________ 1972 GMC 4x4 Suburban F&R A/C 1978 Pontiac Trans Am 400(Z) all stock

06-05-2009, 03:19 PM	#3
locab36 Registered User Join Date: Jun 2004 Location: Midland, MI Posts: 265	Re: Brake porportion valve question.... Lots of info there. My brakes work just seem stiff. I will try some booster tests I saw on that one link. I did have to lengthen the brake rod as the pedal was too close to the floor and didn't rest on the rubber bumper. Even w/the threaded end there wasn't enough adjustment. Got some grease on the pivots too, that seemed to help some. Still don't understand why my combination valve is on the front crossmember. Looks factory w/all the clips and rock guards. Someone went to a whole lotta trouble if it was changed. The brown brake trouble light wire is still up by the master. John Attached Images __________________ Locab36 1936 low cab 1/2 ton 1956 BMW R25/3 1968 Moto Guzzi V7 1969 BMW R100/2 1986 Silverado SWB 2007 Harley FLHTP 2011 GMC SWB 4x4 Z71 http://www.flickr.com/photos/locab36...7623329816080/

06-06-2009, 01:08 AM	#4
Suburban 72 Registered User Join Date: Jun 2007 Location: Colorado Posts: 17	Re: Brake porportion valve question.... Check for kinks in the lines as well. I had a kink in the line to the back brakes and the braking felt stiff. The kink was behind the bracket that holds the hard line to the rubber line. __________________ Ben '71 C10 Longbed

06-18-2009, 04:25 PM	#5
locab36 Registered User Join Date: Jun 2004 Location: Midland, MI Posts: 265	Re: Brake porportion valve question.... Replaced front hoses and all is back to normal. Normal power feel in the pedal and stops straight now too:-) __________________ Locab36 1936 low cab 1/2 ton 1956 BMW R25/3 1968 Moto Guzzi V7 1969 BMW R100/2 1986 Silverado SWB 2007 Harley FLHTP 2011 GMC SWB 4x4 Z71 http://www.flickr.com/photos/locab36...7623329816080/

06-18-2009, 06:24 PM	#7
mbgmike Registered User Join Date: Aug 2005 Location: Pasadena,Tx /Pto Pta DR Posts: 5,415	Re: Brake porportion valve question.... And yes the prop valve was usually on the firewall by the mc but whose to say some plants may have put it down lower. Here is a pic of an unmolested truck Attached Images

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