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post #1 of 5 (permalink) Old 05-31-2016, 08:01 PM Thread Starter
Join Date: May 2016
Location: Butler, IN
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Odd unknown brake fluid leak

Anyone had a brake fluid going low yet no sign of a brake fluid leak anywhere? Any ideas where it could be going? 2008 Cobalt LT. Wife said brake fluid light came on. Checked reservoir and it was indeed very low. I refilled it. Pressed the brakes and held. Pressure was good. No noises or signs of leaking. Then a couple months down the road and same thing happened. Checked reservoir and fluid almost gone again. At this point I assumed it was a rear brake drum wheel cylinder leaking slowly. I disassembled both brake drums to find both cylinders perfect and not leaking (I had already replaced one of them a couple years prior). Boots good. No leaks at all and no signs of previous leaks or any fluid at all. Traced brake lines, all in perfect condition. Checked connections at front calipers etc. All perfect. Any ideas where the fluid is going that is leaving no sign of a leak at all?
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post #2 of 5 (permalink) Old 06-01-2016, 07:21 PM
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Doesn't the clutch hydraulic system use the brake fluid? I've heard the clutch slave cylinder can leak and is a pain to fix, gotta drop the tranny. I'm not looking forward to that repair...I regularly put in fresh fluid by bleeding and/or turkey baster, hopefully it's putting this job off a couple years. If you've got a standard transmission that might be your culprit, look for leaking from the bottom of the tranny bell housing.
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post #3 of 5 (permalink) Old 06-07-2016, 12:06 AM Thread Starter
Join Date: May 2016
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Yikes! That would be unfortunate. Though I have not noticed any leaks/fluids there either. I was under there not long ago and pulled the trans pan, replaced the trans filter and removed the magnet and replaced with two stronger magnets (per tsb) and replaced the trans fluid. Everything appeared clean and perfect. That's why this was so confusing to me.
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post #4 of 5 (permalink) Old 06-07-2016, 04:23 AM

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ive had this issue as well but what if you dont have a manual trans then where else would it go? i notice every couple months it gets low and the light comes on when i make a hard corner or i put G force on the car lol.

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post #5 of 5 (permalink) Old 06-07-2016, 05:55 AM
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If you have an auto, there won't be any use of brake fluid there.

If you have a leak - you'd definitely find it if it's near any painted surfaces - as it'll take the paint right off.

I had the Cav piss out all the brake fluid once, and never leak it again. Could've been one of the calipers I replaced, though.

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