Changing oil in master cylinder?

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  #1  
Old 06-15-06, 06:58 PM
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Smile Changing oil in master cylinder?

I have a 93 GMC JImmy 4x4 last week we replaced a leaking wheel cylinder and rear brake, pads, drums, spring kits etc.
We bled off the brakes. My husband noticed that the oil in the master cylinder seemed very dirty while topping it up(probably never been changed) we have owned the truck for 4 years.
Is this something that you should do often? I checked with the local GMC - Chev dealer and they infomed me that they dont do it, and had never heard of changing or flushing the master cylinder before and to try one of the local muffler shops, upon doing this the guy told me it should be done every year just like a rad flush.......as oil breaks down......any thoughts?
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Old 06-15-06, 07:07 PM
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I think every 2 years is adequate. the brake fluid is actually more comparable to radaitor fluid than oil. The main reason why it needs changes is because it attracts water. The moisture gets in there and corrodes the inside of you brake lines and calipers. if you and your husband want to replace it, just bleed it out, making sure to keep putting new fluid in the resivour so no air gets sucked in. start with the rear passenger tire, then the rear driver, then the front passenger, than the front driver. I did this with my car. I put a short length of clear tubing over the bleeder screw so I could see when the clean fluid started coming through.

~Bill
 
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Old 06-15-06, 07:08 PM
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Well it is not "oil" in the sense that most people speak of oil but is brake fluid. This is a special fluid dsigned fore use in brake systems.

Yes, the fluid should be flushed occassionally. I generally recommend it whenever brake work is being done. Brake fluid is hygroscopic which means it absorbs water. The amount of moisture absorbed does not seem great but it does a couple of things;

1. it lowers the boiling point of the brake fluid making the chance of actually boiling the fluid greater. This causes air pockets to develop in the brake system which reduces the effectiveness of the entire system

2. it cause corrosion within the system, damaging some seals and requireing replacement of parts.
 
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Old 06-16-06, 05:51 AM
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Originally Posted by gmcladee
I checked with the local GMC - Chev dealer and they infomed me that they dont do it, and had never heard of changing or flushing the master cylinder before
Unless the guy (or gal) you were talking to misunderstood your question, I would find a new dealer or garage to use. They may not ever do it, but I would have expected them to at least know the points mentioned by zzzzz and nap.
 
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Old 06-17-06, 07:30 AM
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Thanks........

Thanks for the replies, although I did explain fullyto the dealer what i wanted done, i think because they werent making a big buck on the whole job they were discouraged in doing it, who knows lol....My husband will follow the advice given by the above and change it ourselves, we purchased a bleeder kit to do the job.

After doing some checking, for all that read this post Midas Muffler does do this if you are unsure about doing it yourself for $39.95Cdn

Thanks to you all again!
Carol
 
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