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940 Brake Bleeding Question: Village Idiot Is Back

Djw21a

New member
Joined
Dec 29, 2009
Location
Central Georgia
Hey guys, Village Idiot here again.

Car: 93 940 ABS
Current Conundrum: Brake Bleeding Sequence etc

Done so far:
Got car's butt on axle stands.

Decided to replace and flush my brake system while my rear axle was in need of love. I installed IPD SS lines after compressing each brake caliper and examining the pads. Now when I pump the brakes with car off 3+ times I get the pedal slowly *under constant pressure of my foot mind you* going to the floor. When I crank the car up I get almost no pressure at all. Pedal just goes to floor with slightest pressure of my foot and returns each time.

This just screams that air is still in the system to me, but hell i've been wrong before

All this above happened after I bled the system the first time going from right rear, left rear, right front, left front. Then because I was told I needed to bleed the MC tits I attempted to do that as well. Some where along the line the MC got really low/ almost empty of DOT 4 on first bleeding*I didn't check fluid level between calipers like an idiot*

Question:
Can I attempt to use the MC nipples to get the air outa the system or should I leave them alone an continue to bleed the system via the calipers? And am I doing the correct sequence?
 
Forgot to mention I've been using a mityvac bleeding unit as well as while bleeding i've been tapping the hard brake lines to get any air out of the system that might be locked.

Lastly the brake fluid before installation of the new lines was fairly clear. System was bled entirely about 4 years ago so it wasn't completely neglected.

Master Cylinder thats on the car is Original. Just thought I'd toss that out.

Just finished attempting to bleed the system again. No go. Pedal still has firm but not solid pressure w/ engine off. W/ engine on I get no pressure. Some help or suggestions would be really appreciated right about now.

Thanks
DJ
 
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Guys this car is supposed to be my reliable vehicle. My truck i've got a feeling i'm have to rip the transmission out and i'll definitely have to replace the MC on it. So what should I do? I've got to get my dog to the vet soon also, she has some abnormal skin growths.

I've bled the brakes, on this car, three-four times now. Still same results ideas/ suggestions? Criticism's?
 
Did you try doing it by pumping with a foot first? I bet you bottomed the master and tore the seal doing so

Did not try doing it w/ foot first. Been doing solo w/ MityVac. The Master Cylinder being Fubar has crossed my mind though since it is original. Any way I can test to see if this is whats wrong?
 
How many bleeders are on the front calipers? Never used a MityVac. Try gravity bleeding just the back calipers starting with right rear, and then the left to see if you get any pedal. If it has a lot of air in it, it could take a while to get a good flow of fluid coming out. Just use some tubing for bleeder valve, open it, and just let it sit there until it starts flowing good. Don't mess with the brake pedal until after you have done the gravity bleed, and closed the bleeder valves. If you can get some pedal like this, then I think the master cylinder would be ok.
 
Did not try doing it w/ foot first. Been doing solo w/ MityVac. The Master Cylinder being Fubar has crossed my mind though since it is original. Any way I can test to see if this is whats wrong?

Well it would produce symptoms like you talk about. you should be able to pump it up and get it to kinda work. Does that happen?
 
Bleed it manually without the mityvac. Find a helper. Put a ton of fluid through it.

Too bad SuperBlue isn't still around, it was nice to have a visual indication that the line was flushed.
 
Did not try doing it w/ foot first. Been doing solo w/ MityVac. The Master Cylinder being Fubar has crossed my mind though since it is original. Any way I can test to see if this is whats wrong?

Here's how you can tell if the old master is gone:

It is gone if (1) it is not new, AND (2) you allowed the pedal to travel any further than it had before you started working on your brakes, for any reason.

For those who need proof, I have a couple cut-off and soldered-shut brake line ends one could plug the master's ports with.
 
Alright Update Time:

Went at car again and did the following

1) Checked Master Cylinder Fluid Resvoir and Topped off
2) Pumped Brakes 3-5 times until hard (it'd get firm by 1st, hard by 2nd, 3rd was just to make sure 4th i'm wasting time)
3) Let rear left gravity bleed for 75 seconds.
4) Tightened bleeder, pumped pedal again 3 times + topped off it needed
5) Put MityVac on system @ max I could get.
6) Tightened Bleeder + topped off
7) Repeated 1-6 for rest of wheels

Finally I tested w/ engine on. Pedal had no firmness like before the lines were changed. I put in drive then revved engine an hit brakes to force engagement of ABS system. Pedal only got spongy at best. Still stopped car but if on road an accident woulda happened.

Again I repeated steps 1-6 and am only able to get a spongy pedal at best. Also It appears the e-brake is maladjusted or not properly seated but thats easy to fix. Additionally, I noticed that brake calipers seem not to be disengaging as well as before.

My Opinion
I think the Master Cylinder or Brake Booster is fubar based on the fact that pedal will not firm up with engine on. I'm 96% certain no air is in the system (or almost no air is still in the system) since I've used 3 large bottles of DOT4 brake fluid and 2 small containers. Whats more the fact that the rear calipers seem to be disengaging less efficiently further convinces me.

Question
Guys what is your verdict? I know the MC is original because of Volvo stamp. I am slightly certain brake booster is original because of a Bendix sticker on it. Do I need to replace the Booster and Master cylinder or can I get away with just the MC?

Thanks Guys
DJ
 
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This is important, do not ignore it:
Here's how you can tell if the old master is gone:

It is gone if (1) it is not new, AND (2) you allowed the pedal to travel any further than it had before you started working on your brakes, for any reason.
What happens is the old cylinder wall surface is rough further down in the bore, and when you press the pedal further than normal, the rubber seal gets chewed up on the rough bore area and is not able to pressurize as be

Also: I know the mityvac is fun and easy to use, less messy for bleeding the brakes but results are often unsatisfactory. My experience was that air gets drawn in thru the loosened bleeder threads. I had to resort to old-fashioned 2-man bleeding process to get firm pedal back.
 
@tintintin

I think that's what is happening with the bleeder valves and the MityVac. That's why I mentioned earlier to just gravity bleed both back brakes to see if he could get any pedal.

If it has multiple bleeders on the front, I would use the two man method, and open all the bleeders at the same time with the pedal down. Use tubing on all the bleeders, and drain it into a bucket. Then close all the bleeders, and do the process all over again. Use a block of wood under the pedal, so it don't go all the way down.
 
This is important, do not ignore it:

What happens is the old cylinder wall surface is rough further down in the bore, and when you press the pedal further than normal, the rubber seal gets chewed up on the rough bore area and is not able to pressurize as be

Also: I know the mityvac is fun and easy to use, less messy for bleeding the brakes but results are often unsatisfactory. My experience was that air gets drawn in thru the loosened bleeder threads. I had to resort to old-fashioned 2-man bleeding process to get firm pedal back.

I get mostly around this via using white teflon tape on the bleeder screw threads. However after all this bleeding and re-bleeding it's mostly gone. I'm all for not having to go out and spend $127.21 for another Master Cylinder but after doing the above 6 steps in addition to doing the "old-fashioned 2-man" method multiple times and not having hardly any satisfactory results I have to look elsewhere for the cause of the problem.

Also I've gone under this car and followed the brake hard lines as well as examined the new IPD SS lines to and have found no leakage from them.

@tintintin

I think that's what is happening with the bleeder valves and the MityVac. That's why I mentioned earlier to just gravity bleed both back brakes to see if he could get any pedal.

If it has multiple bleeders on the front, I would use the two man method, and open all the bleeders at the same time with the pedal down. Use tubing on all the bleeders, and drain it into a bucket. Then close all the bleeders, and do the process all over again. Use a block of wood under the pedal, so it don't go all the way down.

The Volvo 940 only has 1 bleeder screw per caliper as well as 2 bleeder screws on the Master Cylinder.

I may try one more time in the morning but then i've got to admit i've done all I can do. I'm down to 1 working vehicle and even that vehicle is not completely reliable.
 
I feel your pain. I have had the same type of problems before. One time I had to resort to bleeding the master cylinder on the car with the two man method, and it got that last bit of air out of the system. It was an old Chevy Chevette from many years ago. It was a royal pain in the behind.
 
Give up on the power bleeder.

I used to use a Vacula at the shop and it was good for flushing the majority of the fluid but you still had to bleed it manually a little because the power bleeder introduced a small amount of air into the system.
 
OP, I'm not seeing anything you've written to convince me you understand the difference between a master bypassing and an air bubble.

Do this: Engine running, apply moderate but steady pressure to the brake pedal. Over the time it would take you to wait for a green light, keep the pressure steady. Does the pedal (whether firm or not) sink slowly? If so, that's the $127 answer.

You can dead head the ports if you're an enthusiast bent on learning, but I take it you just want the car available to take you to work every day.
 
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