# Brake Master Cylinder Gone???



## Zilverado (Sep 25, 2002)

OK, so I did a little searching on this topic before posting, and I think I know what I'm up against, but I thought I'd still ask...

This afternoon, on the drive home, we lost a good portion of our braking power. The truck still stops, but the pedal is extremely soft and can't be "pumped" up - just stays soft. A heavy push on the pedal will still result in fairly good braking, but no where near what it was this morning.

I did the usual checks around the master cylinder and all 4 wheels - no leaks - brake fluid is still full (a couple of bubbles in the reservoir).

So, I am assuming the MC is pooched.

Is there any way to replace the MC without having to bleed the entire brake system afterwards? I know this is not the greatest idea, but with the winter in full swing here, I would like to avoid all the under-vehicle work here. Oh well, I assume things could be worse.

Any other helpfull tips???


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## Zilverado (Sep 25, 2002)

Or should I consider a Master Cylinder rebuild kit?


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## NPath (Dec 12, 2004)

Zilverado said:


> Or should I consider a Master Cylinder rebuild kit?


I can't see how you can avoid bleeding the brakes after taking the master cylinder off.

I don't know if you should or not get a rebuild kit, but my supervisor told me a short story last week that he'd lost his clutch master cylinder and a shop replaced it and gave him back the old one. He cleaned up the old one later on in the year and reinstalled it to see if it worked or not, and it did work.


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## Oldnissanguy (Jan 6, 2005)

If you mess up on a clutch master rebuild and it fails, worst case you get towed home because you can't shift. A brake master rebuild failure is much more serious. Some things just aren't worth the risk no matter how much money you can save.


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## Zilverado (Sep 25, 2002)

Well, for the $120 (CDN) price a store-bought MC, this is the way I will go.

As for bleeding the brakes...

My shop manual talks about bleeding the entire system (from all wheels) prior to replacing the MC. I have never done this before. In the past, on other vehicles, I have had success simply bench-bleeding the MC and reinstalling the "full" brake lines onto the cylinder. I realize that bleeding the whole system after the fact basically removes all the existing fluid, but the way I see it, this does not introduce as much air into the system as purging it all before hand. This means less air to be removed and less chance of an airlock in the system???

Any thoughts on this?


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## Oldnissanguy (Jan 6, 2005)

Your reasoning seems sound. That's the way I would do it, and this is a good time to flush out that old fluid for some of the new (to me) synthetic stuff.


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## Zilverado (Sep 25, 2002)

So, despite everyone's help, it seems I may have jumped to conclusions - at my expense...

I replaced the MC tonight, and to my disappointment, nothing changed. The pedal is still softer than it was (or at least has more travel). I performed a successful, bubble free, bench bleed of the new MC, and then placed it on the vehicle, and it feels the same.

I have not bled the entire system yet, but in my experience, even with air in the lines, you can still "pump" the pressure up. Here there's just the same pedal travel all the time - no build up of pressure.

So what else could I be dealing with here? Is it possible my brake pedal/push rod somehow got screwed up causing more pedal travel? Or could a bad calliper(s) cause something like this? I would assume that would lead to binding or pulling or...

Any words of wisdom here???


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## NPath (Dec 12, 2004)

Is there a spring connected to the break pedal? If there is, is it possible that the spring has been broken or disconnected? 

If you still have fluid and a new MC hasn't changed anything, must be something simple. 

Bleed the entire system first and see how it feels. When the entire system hasn't been bled, it'll still feel soft.


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## LiquidLunch (Dec 1, 2006)

You will need to bleed all four wheels. Once the master cylinder has been removed, air will get into all 4 lines. You wioll probably need to bench bleed the master cylinder again since you didnt bleed the lines prior to use.


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## 88pathoffroad (Jun 6, 2004)

Bleed the lines. There's no way to avoid air in the lines when you disconnect the MC from the lines. The air is probably present in the lines at the top end still.


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## Zilverado (Sep 25, 2002)

Yeah, I guess that's the next step. I think I may take LiquidLunch's suggestion and remove the MC again and repeat the bench-bleed. Mayb take the time to clean theh reservoir as well. Removing it is not too tough, so it'll just add a little bit of work. But I think this will heave to wait until I have some time. Since the brakes are still working quite well - - tight, just soft - - I think I'm ok to wait a little.

What's the best way to clean the reservoir. I know it's got some black "gunk" on the bottom, but getting down there is a little tight. Any suggestions?

Thanks for all the tips guys.


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## golfer (Aug 21, 2006)

Zilverado said:


> Yeah, I guess that's the next step. I think I may take LiquidLunch's suggestion and remove the MC again and repeat the bench-bleed. Mayb take the time to clean theh reservoir as well. Removing it is not too tough, so it'll just add a little bit of work. But I think this will heave to wait until I have some time. Since the brakes are still working quite well - - tight, just soft - - I think I'm ok to wait a little.
> 
> What's the best way to clean the reservoir. I know it's got some black "gunk" on the bottom, but getting down there is a little tight. Any suggestions?
> 
> Thanks for all the tips guys.


Hope you're working in a nice heated area these days.

Use methohydrate or isopropanal alcohol (99%) don't use the 77% , it's contains too much water.


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## Zilverado (Sep 25, 2002)

golfer said:


> Hope you're working in a nice heated area these days.
> 
> Use methohydrate or isopropanal alcohol (99%) don't use the 77% , it's contains too much water.


Well it's not exactly heated, but I did build myself a 26x30 garage this summer that I can now park and work in. The heating pipes are in the floor, but I won't be heating it until I have it all insulated...

As for the methohydrate or isopropanal alchohol - what is this and where is it available? Does Canadian Tire sell this?


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## golfer (Aug 21, 2006)

Zilverado said:


> Well it's not exactly heated, but I did build myself a 26x30 garage this summer that I can now park and work in. The heating pipes are in the floor, but I won't be heating it until I have it all insulated...
> 
> As for the methohydrate or isopropanal alcohol - what is this and where is it available? Does Canadian Tire sell this?


I built a garage this year as well and like yours not insulated yet, but , the wood stove does help to take the chill out.

The methohydrate may be hard to find.

For the isoproponal (alcohol ) go to a place like Shopper's Drug mart ( or any pharmacy ) , you have to get from the pharmacy counter. They don't put it out on the shelves because of those who may buy it for the drink... if you know what I mean.
The cans of brake cleaners that you can buy at auto part stores or Can. Tire are basically alcohol , but they may evaporate too quickly for what you want to do.


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## Zilverado (Sep 25, 2002)

Thanks for the tips man. Maybe I'll try and spray the reservoir out with brake cleaner and see how that works.

Yeah, on a morning like today, the garage - insulated or not - is a HUGE benefit. I love mine! I have bought all of the wall insulation, but have yet to get the attic stuff (I have a 6/12 pitch with a "walkable" attic space - sweet). And once that floor slab is heated, maybe next winter, it'll be a super place to hang out and "tinker".

Just curious, what area of the City are you in. No street names if you don't want to - just an area. We are in St. Boniface.


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## golfer (Aug 21, 2006)

Zilverado said:


> Thanks for the tips man. Maybe I'll try and spray the reservoir out with brake cleaner and see how that works.
> 
> Yeah, on a morning like today, the garage - insulated or not - is a HUGE benefit. I love mine! I have bought all of the wall insulation, but have yet to get the attic stuff (I have a 6/12 pitch with a "walkable" attic space - sweet). And once that floor slab is heated, maybe next winter, it'll be a super place to hang out and "tinker".
> 
> Just curious, what area of the City are you in. No street names if you don't want to - just an area. We are in St. Boniface.


Hey Z... been working out of town for a few days. I'm out in St. James.

I was also thinking ... have you checked your rubber brake flex hoses ??
They will eventually get "soft" and when applying the brakes they will actually swell giving a spongy feel to the brake pedal. Since they are soft they don't handle the hydraulic pressure that's exerted .


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## Zilverado (Sep 25, 2002)

Ah - St. James - nice area of town...

Yeah, I was thinking about the brake lines too, but since it seemed to come up suddenly, I was looking more at a sudden mechanical failure. Also, since it's an "overall" problem, not obviously right or left side, again that led me to the central point of of the MC.

I guess I'll repeat the R&R together with a bench bleed and wheel bleed and see where it takes me. Fortunately, it sounds like a warm weekend ahead...

Thanks again.


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## golfer (Aug 21, 2006)

Hey Zilverado... how did you make out with the brakes ??


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## Zilverado (Sep 25, 2002)

Thanks for asking - I haven't actually taken the time to redo everything. Besides being a little "soft", they are working fine, so with Chirstmas preparations in full swing, "tinkering" in the garage is lower on the priority list.

Now, it may be my imagination, but it seems almost like the pedal has firmed up a bit in the last while. But I'm thinking this is just me getting used to it, since there's really no way the air (if that's what it is) would get purged out of the system.

Maybe the Christmas break will give me some time to play...


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