Never had this much trouble with brakes

[Breadfather]

okay, first off I apologize if this is a repeat but I have been reading for hours and can't find an answer to my issue.

The vehicle in my sig is what I'm working on.  I bought is a few weeks back and the brake light was on in the dash and the brakes were week.  The rear brakes were a mess and look like they had both leaked at some point from the wheel cylinders.  So I redid everything on the rear, drums, cylinders, hardware, shoes, steel lines from the T. After the job I couldn't get them to bleed, there was no pressure.  Plenty of pressure up front, but nothing in the back.

After a ton of time online, I was convinced the combo valve was the issue as I had the warning light on in the dash.  After a ton of issues with the 5 brake lines I finally got them loose.  Disassembled the combo valve and cleaned it out and re centered the switch thing.  It was very dirty in there.  Put it back on the truck.  Refilled the master, gravity bled it at the master, then going into the combo valve. Front brakes gravity bled easily.  But after 2 hours I still couldn't get anything out of the rear. If I start the truck the brake light stays off so I don't think the combo valve slid over.

After more dickering around I removed the line from the rear master and it just would not let any fluid out, nothing more than a drip every 5 seconds. The front one pours out.  Is this is sign of a bad master?
These thing are driving me nuts as I've been working on the, for2 weekends now.  I've never had this much issue with brakes before.

[roundhouse]

I'd replace the MC too
Not expensive
Get a new one.  Not a rebuilt one


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[zieg85]

You could try to bench bleed the master to get all the air out but may be shot due to being empty with all the repairs that were needed.  As roundhouse stated, they are not that expensive.

[Breadfather]

Installed new master this morning bench bled it with no problems.  The good news is that the flow from the rear reservoir is now what it should be and flowing well to the combo valve and the pedal feels much better than before so I'm sure I needed a new master or if I didn't it was only $34 new from Napa.

The bad news, I still cannot get fluid to the rear brakes.  It flows well to the combo valve but will not come out the back section of the valve.  I ran air through the lines before putting the valve in, and they are not blocked.  I also ran air through the rear section of the valve before re installing it, and it came through.  It was definitely reduced flow but it did come through, so I am assuming the reduction of air flow is how the valve is designed?  Anyways, I bolted it back in and can't get fluid through the rear section of the valve and the warning light came back on after a very light pedal push to try and assist the fluid through the valve.

My diagnosis, the valve is also bad. Now I have to try and find another one. Anyone know if the PV-2 from Summit is a direct replacement? I don't want to have to redo lines or fittings. I'm gonna do some searching on here before I order it.

[bd]

The combination valve is just doing its job.  Frustrating as it is, there is still air in the lines and the valve tripped to isolate the front from rear brakes.  You need to recenter the valve and bleed.

[Breadfather]

The combination valve is just doing its job.  Frustrating as it is, there is still air in the lines and the valve tripped to isolate the front from rear brakes.  You need to recenter the valve and bleed.

I cannot bleed the rears at all as it will not let any fluid through the valve.  Even if I redo everything, and hook it back up, it will not gravity bleed through the valve.  Am I doing something wrong? I have also noticed that the little pin on the front of the valve does not move no matter what happens.

[Flyinhillbilly]

If you can get your hands on a vacuum bleeder try sucking the fluid through. I've got several proporting valves working again like that.

[zieg85]

All you have to do is open both front bleeders mash on the brake pedal to center the valve back and without letting the pedal up have someone close the bleeders.  Then it will gravity bleed.  Done this procedure more times than I care to remember.

[Breadfather]

I don't know anyone that has a vacuum bleeder and buying one is the same as buying a valve.

I've tried the front bleeder mashing thing and it hasn't worked.  Even when I know the valve is centered(after I remove it, disassemble, manually center it, and re install it) it will not let any fluid through the rear section of the valve.

There is no telling how long the truck was driven without rear brakes before I got it.  By the look of the rears when I did them, it was a while.  I am wondering if the spring inside of the valve is weak or if there is something else wrong inside of it.  There isn't that much to it when you disassemble it but the red plastic thing that is attached to the switch section was a little bent when I pulled it out.

[Breadfather]

Well im looking at the valve from inline tube, before I buy it, does anyone have any other suggestions on how to get this thing going assuming the stock valve is functioning? I've tried the open bleeder/pedal stomp thing and no dice. I don't have access to a vacuum bleeder and I don't think the DIY pressure bleeder thing will work as it seems like it would put the pressure in the wrong side of the valve.

Any other ideas?

[Flyinhillbilly]

I don't know anyone that has a vacuum bleeder and buying one is the same as buying a valve.

I've tried the front bleeder mashing thing and it hasn't worked.  Even when I know the valve is centered(after I remove it, disassemble, manually center it, and re install it) it will not let any fluid through the rear section of the valve.

There is no telling how long the truck was driven without rear brakes before I got it.  By the look of the rears when I did them, it was a while.  I am wondering if the spring inside of the valve is weak or if there is something else wrong inside of it.  There isn't that much to it when you disassemble it but the red plastic thing that is attached to the switch section was a little bent when I pulled it out.

Got a shop vac? Wrap a ball of duct tape around some vacum hose, cram it in the end of the shop vac, tape the crap out of it, turn on shop vac, slip vac hose on brake bleeder, open bleeder, keep master cyl full.

[Dr_Snooz]

Can't you get a friend to cycle the brakes while you operate the bleeder? On-off-on-off...? I've tried lots of different ways of bleeding and there really isn't a substitute for the old-school two man way. I wouldn't expect gravity bleeding ever to get air out of the lines.

[Dr_Snooz]

If you absolutely have to do it alone, you can get a length of clear plastic tubing small enough to slip over the bleeder end and stay there without falling off. Run the tubing up and over a suspension member before letting it descend into your bleed receptacle. When you pump, you want the fluid to run uphill in the tube before falling into the receptacle. Basically, you'll have a column of fluid above the bleeder at all times. Open the bleeder and leave it open while you pump the brakes. Air bubbles will rise to the top of the column, while fluid is sucked back into the bleeder when you let off the brakes. It's harder to determine when the air is all out, but this is the only other method of bleeding that I've found to be close to practical.

[roundhouse]

A hand held vacuum pump bleeder is not expensive

I've had to use em a few times

You could take the valve apart and remove the guts and reinstall
I don't think it's a proportion valve
I think all it does is turn on the light when the pressure is not balanced


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[Breadfather]

I'm going to try the shop vac thing but what I have had an issue with is that the fluid flows very well to the prop valve. Once it gets in the prop valve it flows out of the front section into the lines going toward the front brakes with no problem. The fluid flows to the rear section of the valve very well now with the new master, but it will not flow out of the rear section of the valve even if the rear brake line is totally removed from the valve.  That is why I suspect a valve issue.  Since I cannot get the valve to re center using the pedal, the only option that I see is to remove the valve, re center, re install, and see if I can suck the fluid through without tripping the valve.  I have heard people talk about a pin that is supposed to stick out of the valve when it trips, the pin in the valve never moves, no matter what position the valve is in.  Is this another sign of a bad valve?