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Cause of sludge in rear calipers? #2828688 12/08/12 09:38 PM
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The Critic Offline OP
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Co-worker had me take a look at her 2006 Sedona w/64k, the original complaint was front brake noise.

The front pads had 5mm left but whoever did the job last at the dealer, did not reinstall the shim kit. (Not sure why it took so long to make noise, perhaps the noise had gotten worse lately?) I noticed the brake fluid was getting dark so I advised and got approval for a brake flush. I used the Motive 1117 cap and 15-20 psi to do the flush in the LF, RR, RF, LR sequence (had a brain hiccup and realized that LF, RR, LR, RF is the correct one - but brakes work great so no harm done).

The fluid in the front calipers was moderately dark, but the fluid from both rear calipers was the grey/black and had the viscosity of 10w-40 motor oil. I would guess that over 8 ounces of this nasty stuff came out from each of the rear calipers. The thick stuff took a long time to come out, but the fresh fluid escaped at a much quicker rate thereafter.

Overall, I flushed through two quarts of BrakeBest DOT4 fluid. There was no complaint of a low pedal before I worked on the car, and the pedal felt pretty good on the test drive after.

My question is....how in the world can brake fluid turn into thick, grey/dark sludge? This car does not have a lot of miles on it at all.

Ideas?

Last edited by The Critic; 12/08/12 09:45 PM.

2020 Ram 1500 5.7L eTorque - <1K - Factory Fill
2011 Toyota Prius 1.8L - 209K - Valvoline Premium Blue Restore 10W-30
2007 Honda Accord 2.4L - 146K - Valvoline Premium Blue Restore 10W-30
Re: Cause of sludge in rear calipers? [Re: The Critic] #2828690 12/08/12 09:43 PM
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eljefino Offline
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Moisture.

You should have seen what came out of my 1982 yamaha virago caliper, it squeezed out of the bleeder screw like gelatinous toothpaste.

Someone should start a BITOG experiment of brake fluid in various situations exposed to humidity.

Re: Cause of sludge in rear calipers? [Re: The Critic] #2828694 12/08/12 09:46 PM
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NHGUY Offline
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Subgrade brake fluid? Everybody is concerned about the Japanese companies cheaping out,but its the Koreans that need scrutiny now.My 88 Aries had the original brake fluid in it when I bought it.The calipers and wheel cylinders had never been changed.I changed front hoses and flushed the fluid at the time.A brake fluid tester showed 5% water content.The fluid was not thick or dark.Gotta love the quality of the older stuff,things are just not up to par now.

Re: Cause of sludge in rear calipers? [Re: NHGUY] #2828697 12/08/12 09:49 PM
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The Critic Offline OP
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Originally Posted By: NHGUY
Subgrade brake fluid? Everybody is concerned about the Japanese companies cheaping out,but its the Koreans that need scrutiny now.My 88 Aries had the original brake fluid in it when I bought it.The calipers and wheel cylinders had never been changed.I changed front hoses and flushed the fluid at the time.A brake fluid tester showed 5% water content.The fluid was not thick or dark.Gotta love the quality of the older stuff,things are just not up to par now.

I've never seen this problem on Japanese cars, even on ones with far more miles. Then again, I'm sure they are out there too.

What I'm curious about though, is why this was an issue on the rear calipers but not with the fronts.

I have also noticed that on the two Korean cars I have worked on, the lug nut QC isn't so great. My socket fits tighter on some of them than others. LOL


2020 Ram 1500 5.7L eTorque - <1K - Factory Fill
2011 Toyota Prius 1.8L - 209K - Valvoline Premium Blue Restore 10W-30
2007 Honda Accord 2.4L - 146K - Valvoline Premium Blue Restore 10W-30
Re: Cause of sludge in rear calipers? [Re: The Critic] #2828698 12/08/12 09:52 PM
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Chris142 Offline
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Lowest point in the system and all the nasties will settle there.


02 Wrangler Napa high milage 10w40
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Re: Cause of sludge in rear calipers? [Re: The Critic] #2828699 12/08/12 09:53 PM
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Chris142 Offline
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Lowest point in the system and all the nasties will settle there.


02 Wrangler Napa high milage 10w40
87 F250 Valvoline 15w40
07 fjcruiser Car lube plus 10w30
Z400 castrol T 10w40
Can am Maveric edge 5w40
57 case tractor Chevron sae30
Re: Cause of sludge in rear calipers? [Re: Chris142] #2828705 12/08/12 10:03 PM
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SuperDave456 Offline
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When I first got my Father-In-Law's truck the brake fluid was black.
He did a bunch of fishing and used the truck to tow his boat. You could easily get the petal to the floor, but somehow it passed inspection year after year.

I flushed a couple bottles though it also. The longer runs always are the worst. Most folks only bleed their brakes, never think about a flush, and so the junk builds up on the longer lines.

Other than that the truck was in good condition.
He instilled my wife with the "It will blow up if you don't get the oil changed at or before 3,000 miles." attitude.

Unfortunately her little sister never got the message. But that is another story.

Re: Cause of sludge in rear calipers? [Re: The Critic] #2828717 12/08/12 10:20 PM
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Gabe Offline
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I think the flexible rubber brake lines were starting to break down.

Re: Cause of sludge in rear calipers? [Re: The Critic] #2828732 12/08/12 10:45 PM
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Obos Offline
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Could there have been an error on a prior "top up all fluids"?

Re: Cause of sludge in rear calipers? [Re: The Critic] #2828764 12/08/12 11:47 PM
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djb Offline
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Originally Posted By: The Critic
I used the Motive 1117 cap and 15-20 psi to do the flush in the LF, RR, RF, LR sequence (had a brain hiccup and realized that LF, RR, LR, RF is the correct one - but brakes work great so no harm done).



It doesn't really matter which wheel order you do a brake fluid flush in. If all else is equal, you might as well follow the age-old advice and do the longest line first. But if you are already working on a different wheel, start with that one.

Re: Cause of sludge in rear calipers? [Re: The Critic] #2828794 12/09/12 12:44 AM
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Noticed the same exact thing on my wife's Civic. We picked it up from a friend who kept up with every other maintenance item except the brake fluid, and what came out of the rear drums looked nasty after 60k miles.

The reservoir and what came out of the front calipers was a dark amber.

Last edited by gathermewool; 12/09/12 12:45 AM.

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Re: Cause of sludge in rear calipers? [Re: The Critic] #2828843 12/09/12 03:49 AM
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L_Sludger Offline
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ot: Critic, I hope you're getting some money for all the car repairs you do for friends, acquaintances and family.

Re: Cause of sludge in rear calipers? [Re: L_Sludger] #2828856 12/09/12 04:43 AM
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The Critic Offline OP
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Originally Posted By: L_Sludger
ot: Critic, I hope you're getting some money for all the car repairs you do for friends, acquaintances and family.


Charging for repairs creates a whole can of worms in terms of expectations, liabilities, etc.


2020 Ram 1500 5.7L eTorque - <1K - Factory Fill
2011 Toyota Prius 1.8L - 209K - Valvoline Premium Blue Restore 10W-30
2007 Honda Accord 2.4L - 146K - Valvoline Premium Blue Restore 10W-30
Re: Cause of sludge in rear calipers? [Re: The Critic] #2828860 12/09/12 04:50 AM
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Obos Offline
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In that case, I was just wondering if ..............

Re: Cause of sludge in rear calipers? [Re: The Critic] #2828941 12/09/12 08:43 AM
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Water is one cause. Some use DOT5 silicone which is not hygroscopic. But there is danger of contamination with other brake fluid so it is risky to use. She may drive through water also.

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