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Hydroboost WTH am I doing wrong

jekquistk5

jekquistk5

Weld nekid
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Alright been awhile since I've messed around with my rig, but last time I had it out brakes were squealing, and in the slippery stuff noticed front right caliper was dragging. So I decided to go ahead and replace the calipers, pads, rotors in the front, and shoes and wheel cylinders in the rear. Upon removing old calipers and wheel cylinders I snapped of the fittings on the lines. Replaced lines from the proportioning valve to the calipers(new steel and new 2wd longer lines from napa). Then replaced the line on both sides of the T in the rear. I tried bleeding the system starting in the rear farthest away from the master cylinder as I always did. Pumped the pedal for ever and no fluid ever came out? :confused::confused: The reservoir is full and I do not see any leaks from any lines anywhere. Anyone have any suggestions?

After half hour of trying to bleed the rear I tried the front. I bled those no problem until no bubbles were left, but the pedal was still spongy as all hell with almost no engagement of the calipers. I assume this is due to the lines still having air in it. Any suggestion on where to go. New proportioning valve? Vacuum based bleeder? :dunno::dunno:
 
I think if you got the fronts, that the prop valve may be the culprit. Can you crack a line at the frame above the rear diff to see if you have any fluid flow there?

Also are the rear shoes adjusted out to the drum to make contact when the pedal is pressed.
Just trying to cover the basics here.
 
76zimmer said:
I think if you got the fronts, that the prop valve may be the culprit. Can you crack a line at the frame above the rear diff to see if you have any fluid flow there?

Also are the rear shoes adjusted out to the drum to make contact when the pedal is pressed.
Just trying to cover the basics here.
Click to expand...

Yes shoes are adjusted, and I guess I could do that, I may just take the sender line from the valve and take it off see if any fluid comes out. If it doesn't I'll replace it but if it does, replace the steel line all the way back?
 
There is that little release pin on the side of the combo valve, but I think it's supposed to force pressure to the front even if the there is none to the rear. If the the fronts bleed, there is pressure to the front. If there was no pressure to the rear, the brake light should be on.

PropValve.jpg


So there must be a problem with the rear plumbing or the wheel cylinders. If the wheel cylinders aren't new, I would suspect that the bleeders are plugged. Just start cracking lines to see how far back the fluid makes it.
 
Blue85 said:
There is that little release pin on the side of the combo valve, but I think it's supposed to force pressure to the front even if the there is none to the rear. If the the fronts bleed, there is pressure to the front. If there was no pressure to the rear, the brake light should be on.

PropValve.jpg


So there must be a problem with the rear plumbing or the wheel cylinders. If the wheel cylinders aren't new, I would suspect that the bleeders are plugged. Just start cracking lines to see how far back the fluid makes it.
Click to expand...


Gonna have to start cracking lines :) but I have to move the gf to the mitten from new york so It will have to wait.
 
I have gone to vacuum bleeders. The only one I have found worth the money is the Mity Vac. It has a metal body and will hold up to years of use unlike the cheap plastic ones sold at the autoparts stores.

http://www.mityvac.com/
 
Oh, thanks for reminding me. Once I had trouble bleeding the rear, so I built a power suction bleeder, which did the job. I used a mason jar and punched two holes in the lid and epoxied two tubes in place. One tube reached near the bottom of the jar and had plastic tubing running to the bleeder. The other tube ended near the lid and got vacuum line running up to the intake manifold. A 5.7L vacuum pump can move some brake fluid!
 
Blue85 said:
Oh, thanks for reminding me. Once I had trouble bleeding the rear, so I built a power suction bleeder, which did the job. I used a mason jar and punched two holes in the lid and epoxied two tubes in place. One tube reached near the bottom of the jar and had plastic tubing running to the bleeder. The other tube ended near the lid and got vacuum line running up to the intake manifold. A 5.7L vacuum pump can move some brake fluid!
Click to expand...

I got fluid to the rear wheel cylinders now, just have to finish bleeding properly. I didn't have my helper yesterday so hopefully she will be available tonight :) If not I'm gonna grab a vacuum bleeder.
 
jekquistk5 said:
I got fluid to the rear wheel cylinders now, just have to finish bleeding properly. I didn't have my helper yesterday so hopefully she will be available tonight :) If not I'm gonna grab a vacuum bleeder.
Click to expand...

Glad you got it, I was just going to say the last time I replaced my rear line and calipers in my truck, it seems liked forever before I finally got fluid in them. In fact, I am ashamed to say I even excanged the new master cylinder as faulty and then realized the new-new one did the same thing. So I just keep bleeding forever and then it finally worked.
 
folkenheath said:
Glad you got it, I was just going to say the last time I replaced my rear line and calipers in my truck, it seems liked forever before I finally got fluid in them. In fact, I am ashamed to say I even excanged the new master cylinder as faulty and then realized the new-new one did the same thing. So I just keep bleeding forever and then it finally worked.
Click to expand...

Yah I ended up taking of the lines from the T in the rear, and pumped forever till there was a puddle on the floor. Hooked the lines up and started bleeding. I hate when I over troubleshoot a problem.
 
Well had help but something still isn't right. I have no pedal off the start, but if I pump it a few times back to back, it will firm right up, let it sit for 5 seconds and no pedal again, goes straight to the floor. I'm thinking I just need to bleed it more and more. I'm having a love hate relationship with hydroboost right now. Love it on my dmax, hate it on the k20!
 
I like the compressed air version like this

image_2567.jpg


Gotta have some decent airflow though. My 6 cal compressor wouldn't work for crap, but the 25 gal runs it just fine.
 
cdoggwsu said:
I like the compressed air version like this

image_2567.jpg


Gotta have some decent airflow though. My 6 cal compressor wouldn't work for crap, but the 25 gal runs it just fine.
Click to expand...

No problems with compressor size, I picked one of these up a few weeks ago, how much does one of those cost. It may be worth it for me to buy one of them suckers.

images
 
Well even after replacing the Master Cylinder still no luck. I have bled the damn thing like crazy. I'm thinking the reman unit from advance auto may be bad as well. The issue still is there I can get pressure if I pump the pedal and it remains there as long as I hold the pedal down, release the pedal all the way and then no pressure and the pedal goes to the floor. Yes I bench bled the new master cylinder but when I put it in and tested for the pedal there was resistance but wasn't firm at all. I did notice when I had the cover off when i released the pressure and my foot off the pedal 2-3 seconds later there a gush of fluid that almost hits the hood. This doesn't seem right to me. Anyone have any ideas this is really starting to piss me off. Its just a simple brake system and I've been stuck with no brakes for almost 2 weeks.
 
Last time I ran into a dilema like yours was on my friends CJ-5 --we replaced the master cylinder and both front calipers,and bled a gallon of brake fluid thru the thing for three nights in his frigid garage one winter,and all we could get was a nice firm pedal after several pumps,and it would hold pressure fine--till you let off the pedal and the next time you pushed it down it'd go right to the floor with ZERO resistance!..we gave up and I took it to a guy who ran a brake & muffler shop..

When I got there he put it on the lift and took one front tire off,and went "OH,I see what the trouble is--you might as well wait,I'll have it fixed in about 10 minutes!..
He removed the caliper,put a block of wood between the pads,and flipped it around so the bleeder screw was pointing straight up,and he bled it while I pumped the pedal..but it back on,did the same to the other side,and the pedal was perfect,first pump it stopped 1" down and it had excellent brakes..
Evidently someone or the factory had swapped the left & right calipers around,and though they'll bolt on fine and the hoses dont look kinked or stretched,even though they are on the "wrong" side!..and the bleeders end up pointing down at the ground,instead of straight up like they need to be!..:doah:..

I've seen my share of faulty rebuilt master cylinders ,but for every one called "defective" many are not,its just something like this keeping it from bleeding properly..a bad rubber hose can block flow in one direction like a check valve and cause all kinds of greif,and many folks fail to properly bench bleed the master cyl. before installing it--doing it "on the vehicle" doesn't always work for some reason,maybe its at too steep an angle or the stroke of the push rod is too short to get a full "pump"...good luck with your bleeding,I have been there myself many times,I usually end up using my home brewed vacuum bleeder because I am alone most of the time when my brakes need to be bled!..It's THE best way I have found ..
 
Brake fluid is for all intents and purposes noncompressible. So, no matter how much pressure you put on a system with the pedal, its not going to spew back because the fluid was under pressure.

With drum brakes, there might be a small amount of fluid going back due to the springs compressing the brake cylinders, but the only way you get a big geyser like that is if there is air in the system to compress.

I know you have bled gallons through it, but there has to be something in the system that is compressible.
And that is air.

The mighty vacs are great, make things a lot easier, but they do have one drawback.
They put negative pressure on a system that is designed to only have positive.

Say you have rear drums. I don't know, I can't go back and look at the first post while I am writing.
If you have ever seen the inside of a drum brake cylinder, you know the little rubber cups are designed to expand against the cylinder when pressure is applied to them from the inside.
But, you put pressure from the outside, and they will allow air in. And a vacuum inside is the same as pressure outside.

Unless your bleeders are on the bottom like the other poster mentioned, and has happened more often than you would think, I suspect you have a restriction somewhere that is causing you to pull more vacuum on one of the bleeders than the seal can stand.

Of course you were having this problem before the vac, so check the location of the bleeders.

Instead of the vacs, consider making a pressure bleeder. I think there are plans here somewhere for them.
Might be able to force enough flow through to move that bubble from where it is hiding.


Edit: Found one of the links

http://coloradok5.com/forums/showthread.php?t=138124&highlight=pressure+bleeder
 
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