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01-13-2015, 12:55 PM | #1 |
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Proportioning valve issues.
Just redid the WHOLE brake system on my truck, with the exception of a booster.
I bought a CPP factory style combination valve to replace the factory one that was in rough shape. All the brakes are plumbed correctly and the master cylinder and booster are in working order. I'm only getting some fluid to the rear brakes and the drivers side front caliper, the passenger side caliper is bone dry. I have a little pedal with the truck not running and no pedal when the truck is running (after some bleeding obviously). I know there's some crazy sliding valve in the combination block, but how do I get it to open up? |
01-13-2015, 01:07 PM | #2 |
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Re: Proportioning valve issues.
I assume the new valve has 2 ports for the front brakes, as opposed to a single port with a line running down to a tee fitting? Any pictures?
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Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
01-13-2015, 01:14 PM | #3 |
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Re: Proportioning valve issues.
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01-13-2015, 01:45 PM | #4 |
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Re: Proportioning valve issues.
Interested in what this might be because I plan on replacing all my lines too, what did you use and where did you buy the lines?
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01-13-2015, 01:50 PM | #5 |
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Re: Proportioning valve issues.
You need to push the button in on the front and hold it in while you bleed.
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01-13-2015, 02:53 PM | #6 |
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Re: Proportioning valve issues.
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01-13-2015, 02:54 PM | #7 |
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Re: Proportioning valve issues.
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01-13-2015, 04:59 PM | #8 | |
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Re: Proportioning valve issues.
Quote:
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Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! Last edited by MikeB; 01-13-2015 at 05:17 PM. |
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01-13-2015, 06:26 PM | #9 |
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Re: Proportioning valve issues.
Thanks for the diagram. I was able to get some fluid to the passenger side but I'm waiting for a second pair of feet to bleed them out.
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01-13-2015, 08:29 PM | #10 |
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Re: Proportioning valve issues.
I ran into a similar issue a few weeks back. My solution was
1. Clamp down the Combo valve button. 2. Remove the MasterCylinder cap 3. open the rear bleeders (both sides) 4. monitor the MC fluid level It took 48 hours to get good fluid out. All this should be able to be resolved with a two person bleeding job much quicker. I was told that slow 1 pedal pump bleeding works best because the volume of air stuck in the line after making such major changes. I was making the mistake of doing a two person bleed job allowing the person that pumped the pedal to pump it up multiple times to build pressure. This was causing my issue that filled the line with air and didn't allow fluid to the rear. |
01-13-2015, 09:05 PM | #11 |
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Re: Proportioning valve issues.
I ran into a similar issue a few weeks back. My solution was
1. Clamp down the Combo valve button. 2. Remove the MasterCylinder cap 3. open the rear bleeders (both sides) 4. monitor the MC fluid level It took 48 hours to get good fluid out. All this should be able to be resolved with a two person bleeding job much quicker. I was told that slow 1 pedal pump bleeding works best because the volume of air stuck in the line after making such major changes. I was making the mistake of doing a two person bleed job allowing the person that pumped the pedal to pump it up multiple times to build pressure. This was causing my issue that filled the line with air and didn't allow fluid to the rear. |
01-13-2015, 09:58 PM | #12 |
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Re: Proportioning valve issues.
The latter half of this video is a good demonstration of how the metering valve works. All it does is delay pressure to the front brakes. But you can see how both front ports should have the same pressure.
I still don't have a real handle on the inner workings of the prop valve, but I know that it limits maximum pressure to rear drum brakes in a disc/drum vehicle. Of course, you're stuck with the preset pressure determined by the spring. https://www.youtube.com/watch?v=PlElcEGjfd8
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Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
01-13-2015, 10:12 PM | #13 |
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Re: Proportioning valve issues.
Found a possible issue tonight. Somehow (dumbass me) didn't realize that I had the lines switch from the master cylinder to the valve, had the front reservoir feeding the back and back feeding the front brakes. BUT the bigger issue was the way the valve itself was machined. The valve is machined for a 3/16" line for the rear inlet (should be 1/4) and the front half is machined for a 1/4" (should be 3/16").
So this valve is getting sent back to summit and I have a line on a factory valve to put in its place. So beware if buying a CPP combination valve for your truck, may have been mishap in the machining process. |
01-14-2015, 07:55 AM | #14 |
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Re: Proportioning valve issues.
That's seems odd. Can you post pictures of this valve and its part number?
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Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
01-15-2015, 12:13 AM | #15 |
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Re: Proportioning valve issues.
CPP had a bad batch of valves a few years ago. I added discs to a 50 Chevy truck and the valve was leaking out the back with no miles on it. Googled it and found out there were many folks with this problem. I'm not too impressed with the quality control of some of CPP's stuff. Might be better off with a JY replacement.
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01-15-2015, 09:58 AM | #16 |
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Re: Proportioning valve issues.
I'll take a few pictures of the valve tonight, haven't been keeping track of responses.
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01-15-2015, 10:52 AM | #17 | |
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Re: Proportioning valve issues.
Quote:
I think most of their their stuff comes from China, and their customers do the QA. I will say that Aaron at CPP sent us both new sets of ball joints, but I ended up using Moogs. Buying CPP products from Summit Racing is the only way to go, because of their customer-friendly return policies.
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Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! |
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01-15-2015, 11:04 AM | #18 |
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Re: Proportioning valve issues.
There are two tools that might help
I'm using nomenclature, in quotes, from the cutaway pic in post #8... Kent Moore J-23709 is little more than a 90 degree bent piece of stiff metal with a slot that fits under the mounting bolt. The 90 degree tang depresses and holds the "bleeder rod" to center the "pressure differential valve" piston. There's another slick little tool that temporarily replaces the warning lamp switch and locks said piston once it's centered. This tool from Brothers Truck Parts --->http://www.brotherstrucks.com/prodin...number=PVBT087 There are many other suppliers.
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1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...
And please let us know if and how your repairs were successful. |
01-15-2015, 12:35 PM | #19 |
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Re: Proportioning valve issues.
I did have a GM tool to compress the bleeder, but found my real issue before trying it.
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01-15-2015, 06:08 PM | #20 |
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Re: Proportioning valve issues.
Should have made them bigger, oh well.
Last edited by 83swb; 01-15-2015 at 06:17 PM. |
01-16-2015, 03:18 PM | #21 |
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Re: Proportioning valve issues.
>> holds the "bleeder rod" to center the "pressure differential valve" piston.<<
The pin sticking out of the metering Valve (bleeder rod), has nothing to do with the "pressure differential piston". Moving that pin in or out DOES NOT move the pressure differential piston. I said "in or out" because on some combination valves, the pin must be held "out" when bleeding. This tool is a spring clip that holds the pin "out" for that type of combination valve.
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'67 GMC 2500, 292, 4spd, AC |
01-16-2015, 03:25 PM | #22 |
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Re: Proportioning valve issues.
Kent Moore J-23709 is shown below being used on a combination valve that requires the metering valve pin to be held "IN" while bleeding.
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'67 GMC 2500, 292, 4spd, AC |
01-16-2015, 04:44 PM | #23 | |
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Re: Proportioning valve issues.
The proportioning valve with the pin you hold is used on single reservoir master cylinder systems.
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