What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Proportioning Valve Reset

swettysblazer

swettysblazer

Swetty The Yeti
Vendor
GMOTM Winner
Joined
Jul 20, 2009
Posts
5,922
Reaction score
2,624
Location
North Jersey
I am trying to reset my proportioning valve on my 1991 K5. I have searched and tried most of the methods on the forum, short of vacuum bleeding it. Does any one have any tips or tricks? I am not getting any fluid to the rears at all and this is the only thing holding me up from the one ton swap being driveable.
 
I had this happen to me after replacing the rear brake line.
Had an air bubble in the rubber loop of the extended brakeline.
I removed the proportioning valve from the frame.
Reset it manually by moving the piston back to center with a pick tool through the hole after removing the warning light switch.
Then re installed and bled the rear brakes first.
I left the front bleeders open and pushed the pedal slowly.
Eventually the air came out and i got the rears bled.
Then i bled the front.
The whole process took 3 bottles of brake fluid.
Never had so much trouble bleeding brakes.
 
Chevy305 said:
Have you tried hitting it with a hammer?
Click to expand...

I did do that, no good.

K5wrench said:
I had this happen to me after replacing the rear brake line.
Had an air bubble in the rubber loop of the extended brakeline.
I removed the proportioning valve from the frame.
Reset it manually by moving the piston back to center with a pick tool through the hole after removing the warning light switch.
Then re installed and bled the rear brakes first.
I left the front bleeders open and pushed the pedal slowly.
Eventually the air came out and i got the rears bled.
Then i bled the front.
The whole process took 3 bottles of brake fluid.
Never had so much trouble bleeding brakes.
Click to expand...

Yeah, this is driving me up the wall. I changed the rear wheel cylinders because one was blown out and now I can't get anything. I was worried about taking the prop valve off because I wasn't sure if it would cause more issues. I will try that and see what happens tonight. If not, I may go the adjustable route.
 
Every time I touched the PV I ended up ruining them--tried holding that pin under the rubber boot in or out (whatever the instructions said to do)--to help get the brake light to shut off and re-set the PV,and they leaked afterwards,or the light still kept staying on--ended up getting a good used one from a junkyard off another truck or 70's GM car (same one!)..

I avoid touching them now,its like asking for trouble if I do..

I had no luck getting the brake warning light to stay off in my '82 GMC despite it being perfectly bled--you stomp on the pedal hard & fast and it would blink off for a few seconds,them come back on again..I pumped at least a quart of fluid thru all 4 bleeders and NO bubbles ,and it has a nice firm pedal without having to pump it up..

I just unplugged the wire off the dam thing..truck stops fine,there is nothing wrong with the brakes..and the light in the dash still comes on when you apply the E-brake and I think it comes on when the key is on,with the engine not running still too..
 
Try stumping the pedal real hard a few times, has worked for me
 
diesel4me said:
Every time I touched the PV I ended up ruining them--tried holding that pin under the rubber boot in or out (whatever the instructions said to do)--to help get the brake light to shut off and re-set the PV,and they leaked afterwards,or the light still kept staying on--ended up getting a good used one from a junkyard off another truck or 70's GM car (same one!)..

I avoid touching them now,its like asking for trouble if I do..

I had no luck getting the brake warning light to stay off in my '82 GMC despite it being perfectly bled--you stomp on the pedal hard & fast and it would blink off for a few seconds,them come back on again..I pumped at least a quart of fluid thru all 4 bleeders and NO bubbles ,and it has a nice firm pedal without having to pump it up..

I just unplugged the wire off the dam thing..truck stops fine,there is nothing wrong with the brakes..and the light in the dash still comes on when you apply the E-brake and I think it comes on when the key is on,with the engine not running still too..
Click to expand...
I have taken those things apart and cleaned them and they work as they should
 
As I recall the only thing that is SUPPOSED to be needed is to push the pin in. If required. I've never had to do it setting up a system with a used valve, but maybe that is because they were not "tripped".

My understanding is that if the brake light is on, that means the valve has moved and until the light resets (since it's driven from the combo valve innards) you won't see flow to the front or rear, whichever circuit tripped it.
 
dyeager535 said:
As I recall the only thing that is SUPPOSED to be needed is to push the pin in. If required. I've never had to do it setting up a system with a used valve, but maybe that is because they were not "tripped".

My understanding is that if the brake light is on, that means the valve has moved and until the light resets (since it's driven from the combo valve innards) you won't see flow to the front or rear, whichever circuit tripped it.
Click to expand...
That's true but some trucks never see a fluid change and end up with moisture and sludge forms in the unit and gets sticky.
Cleaning it frees it up
 
imiceman44 said:
That's true but some trucks never see a fluid change and end up with moisture and sludge forms in the unit and gets sticky.
Cleaning it frees it up
Click to expand...

Is that what the pin is supposed to do? Like I said I've not needed to use the pin method, but perhaps with a sticky valve, that is why the pin exists. Either way, it sounds like the light should tell you if the valve is the problem.
 
The light is on, and then went off but i am still not getting any fluid to the rear. I will take it apart but my hopes are low.
 
This wouldn't have anything to do with the rear ABS would it? I've never dealt with the system, but I know it's rear-only.

Have you tried with the engine running? Wonder if the assist would help.
 
I've have to run the engine to get the brakes bled before,the power assist seems to help..but 90% of the time I just did it with the engine off if I bled them manually...I usually use my home made vacuum bleeder if I'm alone though..

I had no fluid flow to the rear wheel cylinders in my van after I replaced the long 1/4" steel line all the way from the PV to the rear end where it joins the rubber hose..

I could only get the pedal to "pump up" after pumping it like 20 times,then as soon as I let off it,and stepped on it again,it went right to the floor again with zero resistance..

I assumed I ripped the seal in the master cylinder piston,because it master cylinder was actually "stuck" from sitting and it took some foot pressure to get it to break free...so I bought a master cylinder,bled it on the bench ,installed it--and got the exact same results..:doah:..(van has manual brakes BTW)..

Then I took the new steel line off at the rear rubber brake hose and fluid gushed out..hmm..so it was getting that far at least..

I connected it back up and removed both rear wheel cylinder bleeder screws completely--got in the van and pumped the pedal again,it took many pumps before it got pressure and then I held my foot on it,it didn't bleed down at all!..soon as I let off,it was back to zero resistance..not a drop came out of either wheel cylinder!..

I concluded the rear rubber brake hose had somehow sealed itself off,and I found a good used one I had off another GM truck that was identical,I installed it and instantly I had fluid to both rear wheel cylinders,and 5 minutes later it was all bled and working fine again..
All along it was that dam hose !..probably original..
There was probably nothing wrong with the master cylinder,but it was original from 1981,so I felt it was due to be replaced anyway..
 
diesel4me said:
I've have to run the engine to get the brakes bled before,the power assist seems to help..but 90% of the time I just did it with the engine off if I bled them manually...I usually use my home made vacuum bleeder if I'm alone though..

I had no fluid flow to the rear wheel cylinders in my van after I replaced the long 1/4" steel line all the way from the PV to the rear end where it joins the rubber hose..

I could only get the pedal to "pump up" after pumping it like 20 times,then as soon as I let off it,and stepped on it again,it went right to the floor again with zero resistance..

I assumed I ripped the seal in the master cylinder piston,because it master cylinder was actually "stuck" from sitting and it took some foot pressure to get it to break free...so I bought a master cylinder,bled it on the bench ,installed it--and got the exact same results..:doah:..(van has manual brakes BTW)..

Then I took the new steel line off at the rear rubber brake hose and fluid gushed out..hmm..so it was getting that far at least..

I connected it back up and removed both rear wheel cylinder bleeder screws completely--got in the van and pumped the pedal again,it took many pumps before it got pressure and then I held my foot on it,it didn't bleed down at all!..soon as I let off,it was back to zero resistance..not a drop came out of either wheel cylinder!..

I concluded the rear rubber brake hose had somehow sealed itself off,and I found a good used one I had off another GM truck that was identical,I installed it and instantly I had fluid to both rear wheel cylinders,and 5 minutes later it was all bled and working fine again..
All along it was that dam hose !..probably original..
There was probably nothing wrong with the master cylinder,but it was original from 1981,so I felt it was due to be replaced anyway..
Click to expand...
1981 van with no power brakes?
Didn't know it was an option.
 
More like a non-option!..it was a "stripped down" straight six G-10,it even has 2 round headlamps,which doesn't show up in GM's listings,they say they only came with 2 square headlamps or a 4 square headlamp optional..I put a 1978 grille in it and it looked identical---I assume it was either a "fleet" vehicle or just a entry level strippie that some dealer had..?.

Its only options it has are P/S and a TH350 with a lockup converter..
It had a 250 straight six originally,I put a '73 307 in it hoping to gain some power & speed,but I think the six had more low end--I also put a 2:73 rear diff in it after the 3:08 in it ate the diff case at the side gear..(that killed acceleration quite effectively,but it'll cruise at 70 at fast idle)..

When I went to buy the master cylinder,there was a listing for manual brakes,but only in "brand new",no rebuilt ones available,and prices ranged from $80 to $150..:eek:...

Good thing I decided to take the original off and find the casting numbers,because all the ones listed for '81 had a different looking cover ,though the listings did say "may not look identical,but will fit and function as OEM"..they showed one with a bolt holding the cover on,mine had the usual spring bail clip type cap..

I looked up the casting numbers online and it cross referenced to a "1980 G-10",and the same number was listed to fit many older years,and many C-10 pickups with manual brakes..looked just like mine!..
Autozone had one listed with the same number,it costed $19.99 exchanged!..:D..
 
dyeager535 said:
This wouldn't have anything to do with the rear ABS would it? I've never dealt with the system, but I know it's rear-only.

Have you tried with the engine running? Wonder if the assist would help.
Click to expand...

I don't think so- I tried that as well and same results
 
dyeager535 said:
Is that what the pin is supposed to do? Like I said I've not needed to use the pin method, but perhaps with a sticky valve, that is why the pin exists. Either way, it sounds like the light should tell you if the valve is the problem.
Click to expand...
Well the valve is supposed to move with the fast flow of fluid and block the path in case of a major leak.
The reset button is to put it back where it's supposed to be after you fix the problem.
Bleeding brakes sometimes will trigger it.
If there is sludge from moisture it doesn't reset properly because it's spring loaded to stay in the middle and sludge will get it stuck sometimes just off the middle.
I struggled a lot with my 73 k5 and changed everything until it was the last thing and I had to open it up and see what it did.
 
Learned something new today, I was wondering why the brake light stayed on after I changed the rear calipers and bled the brakes.
 
You must log in or register to reply here.

Latest Posts

Top Bottom