Cause of sludge in rear calipers?

Status
Not open for further replies.
Joined
Aug 30, 2004
Messages
31,869
Location
CA
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:
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.
 
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.
 
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.gif
 
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.
 
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.
 
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:
ot: Critic, I hope you're getting some money for all the car repairs you do for friends, acquaintances and family.
 
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.
 
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.
 
You need to get a job with higher end outfit. All your co-workers seems to be driving lowly Hyundai and Hondas :)
 
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 hear you, but IMO, you can't really compare the brake systems from back then, with what's out there now.

There's a whole lot more movement going on with today's 4-wheel disks, ABS systems, VSC systems, etc. A lot more fluid gets shoved in/out of calipers than it did on wheel-cylinder equipped rear drum brakes. Maybe that speeds up the fluid break-down? I dunno.

Joel
 
In addition to above suggestions, perhaps this was a first flush and what came out was factory debris, break-in debris, and assembly lube from the component manufacturer.
 
Yah with 4 wheel discs and ABS, there must be more wear and tear on the fluid. The recommended flush interval is 2 yrs. Racers change before every race. Best thing is frequent activity keeps the bleed screws free. If I can free up the bleeder, I can overhaul a caliper and re-assemble using Sil Glyde brake lube. Worst comes to worst, I stop before shearing the bleeder completely off and trade it in on a rebuilt caliper. Last set was only 19$ apiece with a good core.
I have done 2 major brake repairs this year. I dont even start the job without a liter or qt of fresh fluid. on hand. If you keep the MC full whilst doing line work, you will keep air out of the ABS. I make an airlock with some tubing and a 4 oz hot sauce bottle full of brake fluid . Hook this to a bleeder and pump the pedal with my hand. I pump by hand because I am checking the bottle for air bubbles. No bubbles in clear fluid and you 're done. Onto the next wheel.
 
Internal seals and hoses break down and make fluid dark.
BIG heat also can contribute - fluid breakdown.
I wouldn't worry about what corner you bled first, unless it's ABS with specific instructions.
 
Status
Not open for further replies.
Back
Top