Oil in Brake system

Discussion in '80-Series Tech' started by corbs, Mar 24, 2004.

  1. corbs

    corbs

    Messages:
    231
    Location:
    Beaverton, OR
    I recently bought a 91 Cruiser and it runs fine but the brakes are rather "mushy". I took it in for 30k maintenance (since that includes servicing the diffs, transfer case & replacing spark plugs etc.) and the mechanic said that there was oil in the brake system (someone/previous owner? probably accidentally put something they weren't supposed to in with the brake fluid) and this oil may/has damaged the seals (or something like that), anyway he suggested replacing the Brake Master Cylinder and flushing the whole system.

    I agree with flushing the system but do you think I should go ahead and replace the master cylinder as well? If so I'm definitely doing the work myself as they estimated it to be about $500 (they're selling part for $250, but I can find online for $129 w/free shipping).

    I'd really appreciate any advice you can give this LC newb. ::)
  2. hoser

    hoser SILVER Star

    Messages:
    7,208
    Location:
    Bay Area, CA
    Flushing it is cheap. Do that first.
  3. Scamper

    Scamper

    Messages:
    1,460
    Location:
    Somewhere in NJ
    Do you know for a fact that there was oil in there? How did the mechanic know it? [never thinking to mix oil and brake fluid, I don't know how you would tell. Maybe it floats? who knows...]

    Seems to me that if there was oil in the brake system, that any damage done would not only affect the MC but also the calipers and/or brake cylinders. So why didn't the mechanic suggest replacing those too? It would be negligent to replace one but not the others I think.

    I can imagine that oil might slowly break down the seals in the brake system depending upon what kind of rubber the seals are made of, but I'm doubtful of this. If you flushed and replaced with brake fluid, and it held pressure fine, I'd be inclinded not to believe this fella.

    Spongy brakes are not surprising in a truck of that vintage, and it could just be air in the lines. There have been many posts here about fixing this--often suggested is a replacement of the rubber brake lines at the wheels which get soft over years of use. Use the search button to find threads associated with brakes and you'll find what you need to do to fix your brake system.

    If in the end, you do need to replace expensive parts, come back here and look up CDan to get the OEM parts...you'll be happy you did. I would not go aftermarket on important parts like this.

    Tom
  4. Seminole

    Seminole

    Messages:
    106
    Flush/bleed it FIRST! The PO who had mine obviously NEVER bled the LSPV(or anything else) and it FULL of crap when I flushed it. Also check to see if the LPSV is leaking. I wonder if your fluid is just OLD. Old brake fluid breaks down to a dark cloudy mixture that could look like oil. Like the others have said, flushing is cheap, don't throw parts at it or throw money at the dealer. :beer:
  5. landtank

    landtank SILVER Star

    Messages:
    17,222
    Location:
    Groveland MA
    If your going to go and flush the entire system I'd rebuild that MC first. It's a cheap kit and nothing more than replacing O-rings. Doubt it's more than $25.00. Then flush away. Might take you an hour and a half from start to finish.

    My understanding though was that brake fluid was really hard on seals, more so than motor oil.
  6. corbs

    corbs

    Messages:
    231
    Location:
    Beaverton, OR
    There was a slight different color liquid visible, sort of floating on the top, when I added some brake fluid when I first picked it up . . . but I don't know for sure if that's what he was talking about as he had finished his shift before I could pick up the truck.

    Actually he did mention the possibility of damage to the rest of the system (like you mentioned), said he couldn't garuntee the rest wasn't damaged, suggested the Master Cylinder replacement & Flush as a minimum . . .

    So you think I should just go ahead and flush it (and possibly replacing the rubber brake lines) and see if it holds the pressure. If it does then I shouldn't need to replace the MC, right? Sounds good to me. . . :D THANKS.

    [quote author=Scamper link=board=2;threadid=13649;start=msg126407#msg126407 date=1080154096]
    Do you know for a fact that there was oil in there? How did the mechanic know it? [never thinking to mix oil and brake fluid, I don't know how you would tell. Maybe it floats? who knows...]

    Seems to me that if there was oil in the brake system, that any damage done would not only affect the MC but also the calipers and/or brake cylinders. So why didn't the mechanic suggest replacing those too? It would be negligent to replace one but not the others I think.

    I can imagine that oil might slowly break down the seals in the brake system depending upon what kind of rubber the seals are made of, but I'm doubtful of this. If you flushed and replaced with brake fluid, and it held pressure fine, I'd be inclinded not to believe this fella.

    Spongy brakes are not surprising in a truck of that vintage, and it could just be air in the lines. There have been many posts here about fixing this--often suggested is a replacement of the rubber brake lines at the wheels which get soft over years of use. Use the search button to find threads associated with brakes and you'll find what you need to do to fix your brake system.

    If in the end, you do need to replace expensive parts, come back here and look up CDan to get the OEM parts...you'll be happy you did. I would not go aftermarket on important parts like this.

    Tom
    [/quote]
  7. Scamper

    Scamper

    Messages:
    1,460
    Location:
    Somewhere in NJ
    The quick and dirty way to go is just to flush and refill.

    But Rick makes a good point. A '91 has lots of use by now, so it would not be a bad idea to rebuild the MC since it is pretty easy to do (and cheap). If it were my truck, since it requires a complete flush/refill, I'd not only do the MC, but I'd do the calipers and/or BC's too thought that will take a bit more time and effort. I'd also replace the rubber lines at each wheel and put new pads/shoes on it. At that point, you'd essentially have a pretty new brake system assuming your rotors are still good. All in all will cost you much less than what the mechanic wants to charge you and you'll be lots further ahead.

    If you don't have a FSM, search the forum for the brake bleeding procedure.

    Tom

    Edit: PS -- dealers always want to replace things even though it costs YOU more than a rebuild kit (e.g., $250 vs $25 for your MC). That's just one more reason to stay away from dealers and learn to do the work yourself.
  8. sjcruiser

    sjcruiser

    Messages:
    839
    Rick & Tom,

    I never thought of an MC rebuild kit available. Are these OEMs or aftermarkets ? It's handy to know this fact.

    Frank.
  9. Scamper

    Scamper

    Messages:
    1,460
    Location:
    Somewhere in NJ
    Frank,

    They're OEM as far as I know. Uncle Dan (CDan) can get you fixed up.

    Tom
  10. Jiggy

    Jiggy

    Messages:
    60
    Speaking from experience as someone who has put oil (or was it power steering fluid??) in my MC, it didn't do anything bad. It wasn't in an LC tho, it was a Dodge Stratus. The brakes were crappy anyways, and I didn't notice a difference. Just bled them all out, and it was good as new. It may be that being a Dodge and having an inherently crappy brake system made it immune to the oil, (or was it power steering fluid?) but somehow I don't think so.
  11. firetruck41

    firetruck41

    Messages:
    5,736
    Location:
    Camas, WA USA
    I was thinking the same as landtank, brake fluid is way harsher stuff than motor oil, I would think a flush might do the job.

  12. Rich

    Rich

    Messages:
    1,805
    Dot 3 & Dot 4 brake fluid is composed of glycols and glycol ethers. There are no petroleum products in brake fluid. The seals in a brake system are not compatible with petroleum products. The result of adding petroleum products (oil, power steering fluid, hydrualic fluid, etc) to the system can be seal failure, resulting in total brake failure. It has happened many times in the past.

    Rich
  13. corbs

    corbs

    Messages:
    231
    Location:
    Beaverton, OR
    So where can I get a MC rebuild kit, I haven't been able to find one online. . . rebuilt master cylinders yes, rebuild kits, no.

    Thanks again for everybody's help! :beer:
  14. landtank

    landtank SILVER Star

    Messages:
    17,222
    Location:
    Groveland MA
    Go to a Toyota dealer. :doh:
  15. corbs

    corbs

    Messages:
    231
    Location:
    Beaverton, OR
    I was never able to find a MC rebuilt KIT, so I just bought a rebuilt MC. I also found out that my driver's side wheel cylinder was leaking, so I also replaced that. Breaks are now SOLID (knock on wood).

    I wanted to thank you guys for the GREAT ADVICE. Total price of parts was about $55 (including break fluid). :cheers:

    Domo Arigato!
  16. DanKunz

    DanKunz

    Messages:
    7,516
    Location:
    Woodstock, GA
    rebuild kits are like 30 bucks on the high side...OEM.

    I priced one, but opted for a new one anyway since I wanted a spare.

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