Implications of Contaminated Brake Fluid

[Justin]

Do you need to replace nearly all the brake components when contaminated brake fluid is found?

Just bought a used 2007 Pontiac Grand Prix GT with ABS & traction control at a dealership a couple weeks ago. 70000 miles on it. It had what felt like a bad master cylinder (pedal will fall to the floor after lightly pumping the pedal). Had that confirmed by the dealership and an independent mechanic who said he’d charge $150 to replace it. So I got the dealership to drop another $100 off the price of the car and drove it home.

After researching the repair (ericthecarguy.com of course), I figured I could do it myself. So I start by checking the brake fluid (which I stupidly didn’t do myself before buying 😳 ). After removing the cap I find a swollen cap diaphragm. Pictured here next to a new one.

After some research, I found this commonly means that the brake fluid has been contaminated by power steering fluid, oil, etc. It certainly looked contaminated…

I removed what I could out of the master cylinder reservoir using a turkey baster. Here’s the bottom of the nearly empty reservoir.

So I had already bought the master cylinder, but Alldata says I need to replace almost everything due to the swollen cap gasket. Do I really need to be looking at replacing all the calipers/hoses (about $500) and the Brake Pressure Modulator Valve (about $350)?

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[Lorrin Barth]

Anything metal can be cleaned. Anything rubber needs to be replaced.

[Joeseph Mama]

I think you are on to something with your contamination diagnosis. furthermore, i have legitimate concerns being that alldata specifically addresses this issue with total replacement of the major brake components. It may be possible to conclude that the seals in the master cylinder and caliper pistons may also be compromised as a result of the contamination.

Brakes are high-liability; it’s a matter of life and death. I would hate for your brakes to fail at the wrong time. The good news is that if you decide to replace your calipers, it’s a relatively easy DIY job… save some $$$ by doing it yourself.

[edit:]
it is possible to do a rebuild of your calipers, replacing the piston seals with new ones. this is not a common practice and perhaps could be considered a lost art; however, in your case i believe you might benefit from learning to overhaul calipers. the main issue of course is just being able to find a rebuild kit specific to your application:

[Justin]

Thanks Ratchet!

I may actually give that a try or at least inspect the outer seal for swelling. Doesn’t look as complicated as I thought. Found the Dorman part# for the front(D35885) and back (D670095). More parts involved for the rear caliper. About $30 for all four calipers.

[Lorrin Barth]

The only hard part to rebuilding calipers is replacing the dust boot. The first time I did one of these I was at it for hours. The trick is to put the dust boot in the groove in the caliper bore, put it on the piston and then insert the piston. It seems like the dust boot should be the last thing to go on but it doesn’t work.

If you find any rust on the caliper piston get a new piston. Use brake fluid for lubrication. Brake fluid will make your skin crack so wear gloves.

[george gonzalez]

Sorry to have to mention it, but there are many seals and valves and a pump inside the ABS and traction control manifold. Those may be suffering from the contamination too.

[Joeseph Mama]

In that case, I would probably just pull an ABS module out the junk yard and save some $$$.

[EricTheCarGuy]

It’s hard to say if that fluid was contaminated or just old. As the fluid ages it will change color and also leave the debris you showed in your pics. You might consider sending the fluid off to be analyzed before you commit to replacing all the major brake components. You may just need a master cylinder and a system flush. That said, if it is contaminated fluid you will need to replace all the major brake components. Personally, I don’t recommend rebuilding calipers to the DIY. One of the main reasons is that it’s often more than just the seals that go bad. If the piston or bore gets a great deal of corrosion, replacing the seals likely won’t be enough to repair the problem.

Good luck and keep us posted.

[Justin]

Thanks Eric.

Will automotive shops or dealerships analyze the brake fluid? I seen there’s some strips you dip into the fluid to judge water content. Is that what your thinking?

I read that you could test for oil content by placing the fluid in a clear container and see if a layer of oil rises to the top, because brake fluid is heavier. Did that today and here’s the fluid after six hours. No visible separation. Is this a good sign?

Keep in mind this bottle consists of about 2/3 brand new brake fluid. I attempted to flush out the reservoir a bit by adding new and removing it a couple times.

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[pilotvp]

I just replaced my front calipers on 2000 4Runner with an after market brand, to which I was discussed with their dust boot retainer- didn’t fit snug at all! So I returned it and got OEM calipers- no problems :woohoo:

[Lorrin Barth]

All I have to do is look at the cap seal in the first picture and I am convinced.

[EricTheCarGuy]

I honestly can’t say by looking at the fluid. Dealerships and shops would send the fluid off to a specialist to make that determination. They don’t normally have anything in house for that. The test you were talking about just checks for moisture content, not other contaminants. I just spent some time trying to find a place that could test brake fluid. I found lots of places that do engine oil but not brake fluid. My concern here is that we go on the assumption that the fluid is contaminated and you replace a bunch of stuff. That could be expensive. The other concern is that you don’t make that assumption and you have another issue down the road. Perhaps someone on the forum will be able to offer up a place that could do the testing for you.

[Author]

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