Brake master cylinder replacement

[Dee2]

90 Loyale, EA82, SPFI, automatic

Looks like I need to replace the brake master cylinder.  I have a few questions since I've never needed to do this before.  Manual looks straight forward but...

1.  Any recommendations or preferences regarding new vs refab. ?

2.  Any preferred brands to select or avoid ?

3.  How to videos are showing bench bleeding on units with only two ports.  Looks like this model  has four ports.  Any special instructions or tools needed to bench bleed this model ?

4. Any tips or tricks to suggest?

[idosubaru]

 

Subaru MCs rarely fail, hownsure are you that it’s bad?  Verify diagnosis first, they’re often erroneously replaced only to find brake issues still exist.

since they fail so rarely I doubt anyone but a long term Subaru shop is seeing enough volume to know but I wouldn’t worry much about brand for an MC.

Don’t sweat it, it’s so easy on Subarus. They don’t even need bench bled but of course do it, just dont freak out about how it goes or if you’re doing it right. As soon as you turn the thing over to install, fluid goes everywhere leaving air pockets anyway. 

Unbolt old one, bench bleed, install.  About as easy as it gets. 

If the lines are rusty you may have troubles getting new the fittings disconnected. 

 

[Dee2]

24 minutes ago, idosubaru said:

 

Subaru MCs rarely fail, hownsure are you that it’s bad?  Verify diagnosis first, they’re often erroneously replaced only to find brake issues still exist.

since they fail so rarely I doubt anyone but a long term Subaru shop is seeing enough volume to know but I wouldn’t worry much about brand for an MC.

Don’t sweat it, it’s so easy on Subarus. They don’t even need bench bled but of course do it, just dont freak out about how it goes or if you’re doing it right. As soon as you turn the thing over to install, fluid goes everywhere leaving air pockets anyway. 

Unbolt old one, bench bleed, install.  About as easy as it gets. 

If the lines are rusty you may have troubles getting new the fittings disconnected.

Basically, I have no brakes.  Pads and all,  look ok.  No leaks found.    I tried bleeding lines a couple of times over the last 2 years, readjusted rear brakes,  but poor braking has continued to worsen.  Now, pedal just goes to the floor.

So.... I'm 90% sure it's the MC.

Not sure what is meant by "turn the thing over to install".  I'm hoping to find a video for bench bleeding this old style MC with 4 ports.

 

[czny]

NAPA bench bleed video:

Beck-Arnley products are generally good choice:

https://www.rockauto.com/en/moreinfo.php?pk=485051&cc=1270055&jsn=372

Raybestos is usually my first choice:

https://www.rockauto.com/en/moreinfo.php?pk=309748&cc=1270055&jsn=381

Get a bleeding kit from NAPA or HF with universal fittings x 2, cheap clip set & a cheap wire separator set & make your own bleeder setup.

Edited September 22, 2018 by czny

[Dee2]

I think that video answers my questions.  Fill with new fluid,  gravity drain then plug all four ports and then pump the brake pedal plunger. 

I'll unplug one port at a time to reconnect the lines.  Hopefully, that will get me through without reintroducing air.  Somewhere, I came across an idea that said if the brake pedal is depressed the ports won't leak.  I'll try that and see if it is true.

Going to be messy....

A new Beck-Arnley looks like a good deal.  I just wish Rock Auto could ship faster.  Seems to always take a week to 10 days.

Edited September 22, 2018 by Dee2

[czny]

Method 2 for bleeding:

Install the M/C & connect all lines tight, but not too tight. Fill M/C resevoir to top line. Crack all connecting lines loose 1/4 turn. Go inside & pump the brakes slowly full strokes for 6-8 pumps. Go refill M/C & do it again until you can hear fluid squirting. Tighten up the lines then go thru bleeding at the wheels with a check valve bleeder tool into a soda bottle with some brake fluid in it. Fluid in bottle is to keep bleed tool from sucking air back up into system.

LF whl 1st, RR whl 2nd, RF whl 3rd, LR whl 4th, until no more air. May take a big bottle of fluid to get it done. One man operation. Done it for years this way. 

Just for giggles, check your brake proportioning valve under the car for leaks. DS under the back seat area. My 87 GL valve leaked so had to improvise with aftermarket proportioning valves up front in engine compartment. See my czny member car build.

[Dee2]

Connecting the lines dry should make it a lot easier.

Proportioning valve looks dry.  No sign of leakage.  I've never had to refill reservoir so that is a good check also.

Edited September 22, 2018 by Dee2

[Steptoe]

Have you ever replaced the brake flexible hoses? At this age I can totally recommend doing so. Recently watched a highly skilled brake specialist do a bench bleed just he was smarter - left it in vehicle and operator pump pedal as he bled not from bleeder nipples but the numerous output pipe nuts. The car was a basket case with morons working on it earlier. I have never seen anyone brave enough to bleed pipe nuts on absunits before either. A trick he advised was to jamb pedal on overnight in case air wanted to travel back up through valves in its own time. Better pedal next day

[czny]

33 minutes ago, Steptoe said:

Have you ever replaced the brake flexible hoses? At this age I can totally recommend doing so. Recently watched a highly skilled brake specialist do a bench bleed just he was smarter - left it in vehicle and operator pump pedal as he bled not from bleeder nipples but the numerous output pipe nuts. The car was a basket case with morons working on it earlier.

Especially when old brake hoses skive layers internally leading to a bulge. Lose pedal firmness when this happens then later on they burst. 

Definitely helps speed things up with a pedal operator behind the wheel. Then can pump it up a few times, hold down pedal hard & blow last of air out at the bleeders. 

 

[idosubaru]

Leaks that sometimes go unseen are rusty lines above the gas tank in the rear.  fluid drips out slowly and just coagulates with all the dirt and dust on top the tank so you never see it.  also leaking fluid can build up behind a piston caliper dust seal, but that's not going to take long before it's eventually seen and leaking. 

Subaru brake lines very rarely fail.  I've never seen it happen personally and it's never (rarely) a topic in subaru discussions.  Sure - diagnose properly and try to check them but I doubt you'll find your issue here. 

[Dee2]

Well....Good news, bad news.

 

good news.

Finally got the part and time to work on it.  Step 1 - get the old MC out

Only had to move a few things out of the way - tire rack, AC line, battery cables and coil.

The replacement is a Beck Arnley and is a new unit with a new reservoir and is made in Japan at a good price from RockAuto.

I installed it dry and did a bleed on the car with the brake pedal. 

Only noticed some improvement, so I did a couple of brake line bleeds to see if that would help.

 

Bad news...

Pedal is still going to floor.  I checked the brake booster and it seems to be working as it should be.  I double checked the manual adjusters on the rear wheels.  I opened a rear wheel and checked the brake pad thickness which is 3 to 4 mm.  1.5 is minimum.

So, I'm at a loss.  Not sure what went wrong.  Planning on doing more research to see how best to diagnose this so I don't end up redoing things too many times.

Also, I'm searching for the plastic plugs shown in the NAPA video to see if I can use those to block ports and test circuits separately.  I can't seem to find those plugs.  If anybody knows where to get some that would be helpful.

 

Edited October 3, 2018 by Dee2

[idosubaru]

Did you bleed A LOT?  when the systems are opened that far up the line they can take 2-3 large bottles to bleed - that's probably on ABS systems but nonetheless same thing still applies, once the entire system is opened up it can take a looong time to bleed it all out.  I can just replace one caliper or a hose close to a caliper and in those cases air is still close to the bleeder screw and easy to bleed - i've even opened and just bled one corner before if you can swap it quick enough and keep it from draining. 

it's more difficult when you introduce air that far up, have a leak further up, or replace an MC - it's going to take a lot more than a routine bleed to get it all out.  bleed, bleed more than you think necessary and then probably some more. 

Also - look for leaks above the gas tank...not sure how, but that's where they leak and cause pedal issues.  they leak just enough to cause issues but aren't yet spurting/spraying gobs of fluid.  there is no discernible "holes" or "leaks" - the metal lines get all flakey with multiple layers of scaled rust - the fluid just gradually pushes out of that without having a hole or significant leak.  so it's just enough to loose pressure but not enough to leak enough that it looses fluid fast or drips on the ground.  Anyway - i've seen it before, if it's got any rust try to check above the gas tank if possible. 

[Dee2]

I went through about 3 to 4 reservoirs, min to max levels, whatever that adds up to.  I'll try to bleed some more.    I'll keep looking for those plugs.  Hardware and auto parts stores don't carry them locally.  I thought NAPA would have them since it's their video, but no such luck.

I have an inspection camera, I'll try to look up on top of the tank.  Not sure how else to do that or if the camera will even work.

 

[idosubaru]

48 minutes ago, Dee2 said:

I went through about 3 to 4 reservoirs, min to max levels, whatever that adds up to.

 

I would guess that's not nearly enough for a completely aerated 4 line system.  I would guess that's 20 ounches and I'm sure i've used 50-60 or more before.  I've had some that just seemed to take forever..surely i had bled enough, then I asked what was wrong just like you're doing now, and simply needed to bleed it more and all was good.

 

fairtax and numbchux say they pull the MC forward after unbolting it or remove it to bench bleed in the car or off if there's air in it. 

 

 

 

[Dee2]

I tried to use the camera to see on top of the tank but it didn't provide anything useful.  The lens only focuses about two inches and only when it is perpendicular to the object.   Also difficult to direct the cable because of too many bends to get on top.

Tried one more bleed to use up last of brake fluid.  Didn't get any air bubbles from any wheel.  Just clean fluid.

Not sure about pulling the MC forward, it would have to be completely removed. In effect starting over...which is a possibility. 

To bleed the MC, I used the method described by CZNY above.

[czny]

You did use a check valve type brake bleeder at the wheels, right?

Try bleeding the MC this way then..with all MC lines tight but no too tight, crack one front line loose at the MC then allow it to gravity bleed until fluid is dripping. Then tighten that line. Go to one rear line,  crack it loose at the MC & allow it to gravity bleed until it is dripping. Tighten all MC lines.

Now go to each wheel in criss-cross pattern & bleed them.

Do all your bleeding with the engine off - no booster so you can get a solid feeling pedal first. You must have a solid pedal with no vacuum boost first or its pointless. 

Other things to check:

Pull down your lower kick panels & check out the clevis pin in brake pedal lever & the brake rod. Look for loose/worn parts.

While you've got the dash panel down check out firewall to see if fluid had leaked down inside the cabin.

Edited October 3, 2018 by czny

[Dee2]

44 minutes ago, czny said:

You did use a check valve type brake bleeder at the wheels, right?

No, I use the method of submerging the tube in a jar partially filed with brake fluid.  I watched the fluid carefully and no air was ever drawn back into the brake line.  The tube is tipped up from the bleeder valve so there is always fluid against the discharge point of the valve.

Engine is always off when bleeding.  All the connections look good. I checked inside and out for leaks around the booster and firewall, there are none.

I will try bleeding the MC again, after I get some more fluid.

[DaveT]

Only problem with that method, is that there is no seal when the bleeder is loose.  So air can be drawn back into the cylinder through the threads of the bleeder  on the release of the pedal.

[Dee2]

47 minutes ago, DaveT said:

Only problem with that method, is that there is no seal when the bleeder is loose.  So air can be drawn back into the cylinder through the threads of the bleeder  on the release of the pedal.

The 2 person method is the ideal way to do it.  Since I have no helper, i have to use the one person method.  So,  I can't close the bleeder valve to  seal the threads between brake pumps. 

I do think that if air was being drawn back in, there would have to be at least some bubbles showing up in the discharge line. I  haven't seen any in the last two cycles.

[idosubaru]

2 hours ago, Dee2 said:

The 2 person method is the ideal way to do it.  Since I have no helper, i have to use the one person method.  So,  I can't close the bleeder valve to  seal the threads between brake pumps. 

I do think that if air was being drawn back in, there would have to be at least some bubbles showing up in the discharge line. I  haven't seen any in the last two cycles.

You can bleed with that method. I'm not sure what dictates a successful/unsuccessful bleed and making sure no air gets past the bleeder/caliper connection but i've done it a lot without issue somehow.

[czny]

8 hours ago, Dee2 said:

The 2 person method is the ideal way to do it.  Since I have no helper, i have to use the one person method.  So,  I can't close the bleeder valve to  seal the threads between brake pumps. 

I do think that if air was being drawn back in, there would have to be at least some bubbles showing up in the discharge line. I  haven't seen any in the last two cycles.

https://www.amazon.com/gp/product/B000MXW2EM/ref=od_aui_detailpages00?ie=UTF8&psc=1

While you may not be seeing air when you get back to each wheel, air could be rising up the bleeder hose & remain trapped in caliper/whl cyl on last up stroke of brake pedal.  

[Dee2]

11 hours ago, czny said:

While you may not be seeing air when you get back to each wheel, air could be rising up the bleeder hose & remain trapped in caliper/whl cyl on last up stroke of brake pedal.

I keep the tube in an arch-shaped loop so air can't go back down into the bleeder valve.  Any air should rise up and away from the bleeder valve.   As the fluid goes back down, from the top of the arch into the bottle, it should create a slight vacuum at the bleeder valve.  At least that's my theory.....

On the threads of the bleeder valve, I think what happens is the first stroke of the pedal forces fluid around the threads and it becomes a wet seal.  Releasing the brake pedal slowly prevents the sucking of air back through the threads.  At least that's my theory.....

 

I also ran a little check test.  I have the rear end of the car up in the air with the wheels off.  So I pressed the brake pedal down and held it in place with a bar.  Both rear wheels will spin freely.  The shoes barely touch the drum.

I can lock the brakes if I turn the manual adjuster far enough, so I know they can work.  I'm not sure if that confirms air in the system or if the brake cylinders are both bad.

 

Edited October 4, 2018 by Dee2
additional info

[czny]

Drum brakes should always be adjusted first before bleeding, as I surmise you just found out.

Adjust & try again Dee.  Tighten until they're locked up then back off until they drag lightly.

By the time you get done here you'll qualify for your NIASE patch on your service jacket....

[Dee2]

36 minutes ago, czny said:

Drum brakes should always be adjusted first before bleeding, as I surmise you just found out.

Adjust & try again Dee.  Tighten until they're locked up then back off until they drag lightly.

By the time you get done here you'll qualify for your NIASE patch on your service jacket....

Yeah, I did adjust them before originally starting all the bleeding.  I just rechecked them again today.  So no changes.  I am rebleeding today again...and again....and again..........