I bought my 2002 screw from a respected dealer in july of 2008. Got a car fax and their shop records. They did nothing to the brakes other than an inspection. I assume the topped off the brake fluid, but when I replaced the pads and checked the level it looked green, so I sucked some out and it smells like coolant. My trucked has only been serviced by me since i bought it. So am I crazy or could someone have put coolant in the brake fluid? How much of a problem is this? Would a brake flush fix it? I apperently have put 11,000 miles with it this way including towing and mountain driving and have not noticed any brake issues other than normal wear.

 

If the coolant seems to float on top of the brake fluid (I don't know if it does I've never a viscosity comparison of the two) I would just use something to suck the coolant out of the master cylinder, and replace it with the proper brake fluid.
If the coolant mixes with the fluid, I would still suck all of the fluid out of the master cylinder, refill it, and the do a thorough flush of the brake lines.

 

Its been there for 11000 miles so I'm sure its mixed through out the system. I guess i will take it to a shop and have it flushed.

 

I can't believe anyone, even in a bad shop, could be that stupid...but guess stranger things have happened. Anyways, I personally would imagine with that much of a foreign substance in the system, you'd know it. There should have been some serious symptoms over the course of that many miles.

 

I've seen brake fluid turn a greenish color over time before turning nasty blackish. It smells bad as well. I'm sure you know the smell of coolant, but did you try sliding it between your fingers? Coolant isn't oily like brake fluid would be.

I'm guessing it's NOT coolant, because during towing and mountain driving conditions, your brake pedal would have gone soft due to steam bubbles forming in the calipers/lines and you would have worried about it a lot sooner.

 

Thanks, I'll run it through my fingers, either way its time for a brake bleed.

 

Just make sure to replace te stuff in the master cylinder before you start

I'm sure you already know that, but it's just a friendly reminder. Sometimes when I get frustrated, I'll froget something like that.

 

I would flush the whole system. Brake fluid (except silicone DOT5) is hygroscopic (absorbs water) which lowers the boiling point. Like KOHARATX said, that would give you a soft/no pedal. The specific gravity of ethylene glycol is higher than brake fluid so it would sink to the bottom of the reservoir. That could cause it to get in the lines. Either way I would flush the system. Your brakes are the LAST thing you want to fail.

 

That's what I was wondering. It will take a lot of flushing to get that out of there. If that is coolant in there. You will have two compress all of the wheel cylinders and flush them individually. The anti lock system, master cylinder, and lines.
Man that sounds like a lot of work.

 

I'm betting it's not coolant. Like koharatx said, brake fluid will turn a greenish dirty color as it gets older. I would just do a normal brake flush to get new fluid in there and call it good.

 

Thanks for all the input. My best guess is it's not coolant since I haven't had any of those symptoms. Still it will be flushed by a shop, no time and its too cold for me to do it.

 

Sounds like you already figured out that its not coolant... but to explain with details...

If there are copper fittings in the brake system the copper will dissolve into the brake fluid (in very small amounts). The copper will turn the brake fluid slightly green. You will find copper at various fittings in the brake system - they use it to form a tight seal since the copper can be deformed around the steel connectors.

(this is based on FACT, not conjecture. I performed a materials analysis on green brake fluid a few years ago when an OEM returned a MC for "green fluid")

Chances are that your brake fluid is OK... but it would be good to bleed out the system just to make sure. (especially since you are not the original owner and you never know for sure what other people have done).

I doubt any damage was done.

 

A buddy of mine was running low on brake fluid once (many many yrs ago) and all he had on hand was hydraulic jack oil so he topped off the master cylinder with it. BAD IDEA!! All the rubber components in the system swelled up a lot and got REAL soft. I shouldn't have to tell you what comes next.

 

ha... "a buddy"... heard that one before...

thats because the hydraulic oil is a mineral oil... EPDM seals do not work with mineral oil.

And if you do that you can lose ALL brakes... bad news!