Proportioning Valve and Bleeding

[Goldie Driver]

Where did you get your proportioning valve and what was the part number????

Not sure who you are asking, but mine came from Amazon and was a PV2. Around 30 bux. I'd buy a used OE as a 1st choice if one can be found.

 

[hack_man]

I got mine from a local GMC dealer in 2006 "just in case" the old one had a problem. Looks like this part is still available at not much different a price than I remember paying for it.

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[Raoul Ross]

Where did you get your proportioning valve and what was the part number????

Inline Tube It was very reasonable and appeared well built. The PR100 is the P/N for front disk/rear drum and PR101 for Disk/Disk. Search for proportioning valve. It'll ask you Year/Make/Model.

Some things to think about before topping-off the MS reservoir. The reason fluid level drops is because the pads/shoes are wearing. Think of it as an indicator of how much they're wearing. Now think about replacing those pads/shoes and pushing the fluid back to the reservoir as you push the caliper pistons/wheel cylinders back in. Yup, big mess on the floor!

This was how I sold brake jobs when I worked the service station life many years ago. If I saw the fluid low, (as you're under the hood 'Checking the Oil Ma'am!') you could visually explain to the customer what was happening and at least get them to agree to an inspection. I never ripped anybody off and usually the customer was appreciative as I'd offer to do it for free. Obviously that was back when there were Full Service Stations but the same principal still applies today... If the fluid is low, there's a reason!

 

[idahovette]

I drain the master cylinder before I do a brake job with a turkey baster or a Mighty Vac, clean it out as best as possible and refill with fresh brake fluid. I NEVER push the fluid back into the master. I always open the bleeder and push the fluid into a bottle. Close the bleeders, then push the brake pedal a couple of times and recheck fluid, then back to the bleeders and open to check for air. Gravity works

 

[hack_man]

Cracking the bleeder so the fluid doesn't get pushed back into the m/c has the added benefit of keeping the bleeder unfrozen during every break job. As far as gravity bleeding, I'm a believer, I went nuts once trying to bleed my brakes with the 2 person pump method but it just wasn't working and my pedal was mushy. Someone suggested gravity bleed and bingo! it worked.

 

[Raoul Ross]

So a new problem has arisen. Rear brakes won't release... sometimes. Come to a stop and then release the pedal and wait. Sometimes it releases and sometimes it doesn't. Hit the pedal again and it might release. It's not a gradual release, very abrupt.

At first I thought, because the rear adjusters were so far out, that the shoes were cocking and then became uncocked if I'd put it in reverse but that doesn't seem to be the case. Replaced the rear shoes and drums (the drums were paper thin from being turned many times)

I'm gonna have a helper hit the pedal and then release. With the rears still locked, crack the line at the master to see if there's pressure there holding the rears. I'm starting to wonder about the replacement proportioning valve too.

The owner says if he brakes gently they don't lock.

 

[hack_man]

It could be the flexible brake line that is common to both rear wheels. If you crack the M/C and it does not release the brakes, I'd then crack one of the rear bleeder valves.

 

[Raoul Ross]

It could be the flexible brake line that is common to both rear wheels. If you crack the M/C and it does not release the brakes, I'd then crack one of the rear bleeder valves.

Good Point, I'll try that... Thanx!

 

[edgephoto]

If the hoses are more than 5-6 years old you should replace them as a matter of maintenance.

Brake fluid should be flushed every two years regardless of mileage. Brake fluid absorbs water and that water not only corrodes the brake parts it lowers the boiling point of the fluid significantly. If the fluid boils you pretty much have near zero braking. You can Google charts that show you the drop in boiling point over time. It is pretty eye opening if you did not know this.

Our trucks use DOT 3 brake fluid. You can go to DOT 4 for the increased boiling point. You will need to stick to the 2 year flush schedule as it can absorb water a bit faster the DOT 3 but you get a higher boiling point which is good for towing and heavy loads. Do NOT use DOT 5 as it is silicone based and not able to be mixed with DOT 3 or 4.

There is a DOT 4 plus fluid that European cars use. It is the same as DOT 4 just with a higher boiling point. Your high performance autobahn cruisers like Mercedes, BMW, Audi, Porsche all use DOT 4+.

There are some bleeders designed for easy brake bleeding. I never used them but I know people who have and they are happy with them. They are Russel Speed Bleeders. These might help some of you.