Master Cylinder how bad does this look? w/ pics

[71threequarterton]

I pulled my master cylinder lid off this morning. You can see the diaphragm that covers the front part of the reservoir was partially collapsed and you can also see that front reservoir has an angled side rather than just vertical.

I'm assuming the collapsed diaphragm is a result of the slanted inside of the reservoir. Does that sound like a fair assessment and is that normal?

From the looks of this, is it possible to flush and bleed until I get all my new parts for a rebuild or how bad does this look?

[Stocker]

Sounds like a fair assessment to me.

If your brakes have been working, I'd probably leave the fluid alone until your rebuild, if it's gonna happen soon. That is kinda ugly.

[HO455]

Your diaphragms look fine. Before you put the lid back on compress the diaphragms so they are flat.
The fluid is very dirty as I am sure the inside of the reservoirs are too. If it was me I would suck the old fluid from the reservoirs and as much of the crud with it. Then carefully blot the inside of the reservoirs a dust free rag to get more crud. Then rinse the reservoirs with clean fluid until you can't get any more crud. Doing all of this before bleeding the system means none of the crud you remove will end up inside of your system. It will add about 45 minutes to the job. I've used a hand vacuum pump, a shop vac, and even big syringe clean the bad fluid and crud out. It is a good idea to protect things below with plastic and rag to absorb the drips.

Stocker makes a valid point about waiting. Sometimes if nothings broke don't fix it. When you say rebuild are you talking all new components and tubing?

[71threequarterton]

Thanks, guys. The brakes are sketchy at this point - they work most of the time but the pedal will often go all the way to the floor and I'll need to release and pump again to get full braking power. I'd call the situation urgent, based on that alone.

I was going to flush and bleed for starters, just to see if that helped but I tried hooking up a power bleeding system and couldn't even get it to seal up properly. It's the Motive black label system with rigid aluminum MC lid and I'm using an Irwin one handed clamp(which should be plenty of pressure) to hold the lid down on the reservoir. When I pump the system up to between 5 - 10 lbs I can immediately hear the air leaking out - it sounds like it's coming from the lid/MC connection but I'm going to test it on something else to see if I have a bad fitting or something on the bleeder system.

Ultimately, I am planning to rebuild the whole system: power booster, MC, prop valve, hard lines, flex hoses and wheel cylinders. I want to have a completely new system in there so at least I know what I'm working with. I wasn't sure if I would do it all at once though...

Thanks for any advice!

[Stocker]

Originally Posted by 71threequarterton

I tried hooking up a power bleeding system and couldn't even get it to seal up properly. It's the Motive black label system with rigid aluminum MC lid and I'm using an Irwin one handed clamp(which should be plenty of pressure) to hold the lid down on the reservoir. When I pump the system up to between 5 - 10 lbs I can immediately hear the air leaking out - it sounds like it's coming from the lid/MC connection but I'm going to test it on something else to see if I have a bad fitting or something on the bleeder system.

The top of the MC is so crusty & cruddy that I would be surprised if it didn't leak.....

[HO455]

The symptoms you describe are classic for a failed master cylinder. Some of that crud has made its way to the lip seals in the bore it is causing them to allow fluid past. In addition I would bet the bore has rusted and there are pitted areas that will never allow the lip seals to seal. Time to tear the master cylinder down and inspect. If it has a flawless bore then rebuild with new seals and a complete cleaning. If the bore is pitted then get a new one. I would avoid rebuilt ones due to the lack of quality control by rebuilders these days.
The up side is that if you install a new master cylinder now you can still use it later as it is the first component in the system and won't be contaminated by other old components. You can work your way to the ends later.
Good luck.

[71threequarterton]

Originally Posted by Stocker

The top of the MC is so crusty & cruddy that I would be surprised if it didn't leak.....

Good point and a test of the power bleeder system tells me that it is OK so what you're saying makes sense.

Originally Posted by HO455

The up side is that if you install a new master cylinder now you can still use it later as it is the first component in the system and won't be contaminated by other old components. You can work your way to the ends later.

That sounds logical to me and I was hoping that was the case so thanks for that.

I keep reading over and over about all the Chinese junk that's out there, otherwise I'd have bought a new MC already but at this point I don't trust anything that's out there unless I know it is made in USA and gets good reviews from guys on here.

[Steeveedee]

Originally Posted by HO455

The symptoms you describe are classic for a failed master cylinder. Some of that crud has made its way to the lip seals in the bore it is causing them to allow fluid past. In addition I would bet the bore has rusted and there are pitted areas that will never allow the lip seals to seal. Time to tear the master cylinder down and inspect. If it has a flawless bore then rebuild with new seals and a complete cleaning. If the bore is pitted then get a new one. I would avoid rebuilt ones due to the lack of quality control by rebuilders these days.
The up side is that if you install a new master cylinder now you can still use it later as it is the first component in the system and won't be contaminated by other old components. You can work your way to the ends later.
Good luck.

Yup, it is bypassing and is a clear and present danger for you and the people around you when you are driving it. If you replace the master with a Chinese product, it probably just means that it will possibly fail sooner than a US-made product, but there are no guarantees either way. Be sure to bench bleed the new master per the directions, and then try to gravity bleed the system before pumping the pedal. The nasty fluid at the outlet of the master can surge up into the master when you pump it. In fact, if it is that bad, I'd do like was mentioned and mop out the old fluid, but then flush the lines with brake fluid before putting the new master on. That's only a couple of bucks' worth of brake fluid. When you take the old master off, you will be able to assess the quality of the lines. If they have corrosion inside, you may as well chase the lines all the way out to the wheels with replacements.

[mike16]

No dont leave the fluid alone. protect all surfaces around the MC. then, using as many paper towels as needed. blot the fluid from each reservoir until the reservoirs are empty. then get more paper towels and soak them in Isopropyl alcohol 93%. then continuing to be carfull of the surfaces around the MC wipe out the interior of the reservoir until it is spotlessly clean. then get so Q tips and soak them in Isopropyl alcohol and then carefully clean out the several bleed and drain holes in the bottom of each reservoir.

now when you add new fresh fluid to the system it does not cary filth and rust to the rest of the system and you can be confortable knowing that that filth will not damage the rest of the system as you flush.

[AussieinNC]

IMHO...that master cylinder needs to be swapped out ASAP....the top seal is being sucked down by internal pressure bypassing inside the old cylinder...

New units are available for around $50...

The brake pipes also look sketchy...lots of rust...should be swapped out ....

Pull some wheels off and the drums / calipers...check for leaks...

Biggest issue when it gets to this stage are the rubber hoses between chassis points to each wheel and chassis to rear axle...they swell internally and can either balloon or develop internal issues that prevent full release...

GOLDEN RULE ....never shortcut on Brake Systems

[71threequarterton]

Originally Posted by AussieinNC

GOLDEN RULE ....never shortcut on Brake Systems

Agree

[Steeveedee]

Originally Posted by AussieinNC

IMHO...that master cylinder needs to be swapped out ASAP....the top seal is being sucked down by internal pressure bypassing inside the old cylinder...

New units are available for around $50...

The brake pipes also look sketchy...lots of rust...should be swapped out ....

Pull some wheels off and the drums / calipers...check for leaks...

Biggest issue when it gets to this stage are the rubber hoses between chassis points to each wheel and chassis to rear axle...they swell internally and can either balloon or develop internal issues that prevent full release...

GOLDEN RULE ....never shortcut on Brake Systems

The top seal sinks into the master reservoirs when the fluid disappears, right? Such as into the calipers to take of the wear volume of the pads.

[HO455]

Originally Posted by Steeveedee

The top seal sinks into the master reservoirs when the fluid disappears, right? Such as into the calipers to take of the wear volume of the pads.

That is correct. The seal has the accordion (?) pleats in it to do just that. The idea is to limit the fluid's exposure to air and the moisture it contains. The fluid will absorb moisture out of the air which leads to internal corrosion. (It is best to check your brake fluid on days with low humidity. Not that I ever remember that. You folks in the southwest once again have it better). When the fluid level drops the seal drops without pulling fresh air into contact with the fluid.
If you just put an air tight lid when the fluid dropped it would pull a vacuum and nature being abhorrent would end up pulling air into the reservoirs through the end of the master cylinder. Don't ask how I know that.

[lil hoodlum]

My master cylinder is about the same shape yours is in less the rust on the top. I have another MC waiting to go in.

Question, how do you go about flushing the brake system? I know my brake fluid is in about the same condition as 71 theequartertons.

[HO455]

Originally Posted by lil hoodlum

My master cylinder is about the same shape yours is in less the rust on the top. I have another MC waiting to go in.

Question, how do you go about flushing the brake system? I know my brake fluid is in about the same condition as 71 theequartertons.

You will have to bleed the brakes. To start I would gravity bleed the system until you get clean fluid before you remove the old master cylinder. Then bench bleed the new one, install and gravity bleed the system. If you have a "good pedal"" you're done. If not may find that bleeding by pumping or a vacuum method will be needed. On an old system if you have problems getting fluid out a bleeder with the gravity method I would replace the hose associated with that wheel. Old hoses are problematic as they can degrade internally.
I really feel they should be changed for no other reason than they bleed easier. I couldn't tell you how many hours I have fought with brakes only to find it was a bad hose. They are cheap and make life easier.
Here is a link with more info and there are plenty of YouTube videos too.
http://67-72chevytrucks.com/vboard/s...d.php?t=166034

[71threequarterton]

Originally Posted by lil hoodlum

Question, how do you go about flushing the brake system? I know my brake fluid is in about the same condition as 71 theequartertons.

I bought the Motive power bleeder system which seals on top of your MC and you pressurize and pump new fluid into the system. I haven't used it yet but it seems like it will be really handy. Check out the videos online: https://www.youtube.com/watch?v=2MmKaa3IVMo

[S_Gibson]

Mine was just as nasty as yours. I sucked all the fluid out of the reservoir with a turkey baster and filled it up with fresh fluid. I then opened the bleeder valves up and let the crude drain for a bit while filling the reservoir up as needed. After that I bled the brakes until it looked clean. Fluid is cheap so I ran quite a bit of new fluid through the system to clean the old out.

[brown7373]

Rebuilt master cylinders are cheap. Accidents are expensive. I would replace or rebuild ANY questionable brake components. IMHO

[71threequarterton]

Any place that I've called or looked at online near me says they have to order an MC so I ended up just getting one from Summit.

Soon as I took it out of he box I could see that it was made in China and one of the bales that holds the lid on was floating around loose inside the bag

So I went to put the second bale on and it was so loose that it just flipped back and forth inside the groove on the lid, putting no pressure on the lid.

What, no QA over there at Cardone???

I took the bale off and bent it to see if I could get it to fit better and it does now but I don't know - should I even trust this thing now?

Maybe I could see if the bales off my old MC fit better...

From many of the stories I've read, I pretty much already expected to get cheap Chinese crap and figured I'd write this off as an opportunity to learn my system but I'm still kinda pissed about it.

[sick472]

Summit isn't know for selling junk parts even if it's china made. I would not have any trouble installing the MC, but do NOT hesitate to call them and ask them what to do about the bail. They will likely send you a new MC. Notice I said.. "ask them what to do about the bail". I have found that if I call customer service anywhere and am pissed off...it shows and I get less than desired results. If I call and am somewhat passive and ask what should I do about this part that does not seem to be right, then I usually get a new part coming with no worries about returning the other. Just my experience with customer service. Good luck!

[71threequarterton]

Originally Posted by sick472

Notice I said.. "ask them what to do about the bail". I have found that if I call customer service anywhere and am pissed off...it shows and I get less than desired results. If I call and am somewhat passive and ask what should I do about this part that does not seem to be right, then I usually get a new part coming with no worries about returning the other. Just my experience with customer service. Good luck!

Yep. I learned that one too. Kill 'em with kindness=much better results

[71threequarterton]

I got the new power booster, MC and prop valve installed over the weekend. I knew that the brake lines would not line up with the new setup but I pretended that it didn't matter and just kept on working

Good thing I already have my new NICOPP lines, stainless gravel guard, tube cutter, flaring tool, bending tool all handy and ready to go! I wasn't planning on having to do that just yet but I'm glad to be prepared for it.

This was/is my first time doing ANY of this stuff. Hat tip and a salute to the gentleman who said to drop the steering column when working with the pushrod/brake pedal assembly. Had I done this from the get go I would have shaved an hour or so off the job - for those of you who have not done this, if there's any question about whether or not you should drop the steering column, just do it.