I will told by my mechanic today that I needed a brake fluid flush?? Any ideas on why that would be necessary and if it is really needed?

Thanks

 

Brake fluid is hydroscopic. Don't know the exact meaning but the short story is it holds water. Water = corrosion. It will save you grief in the long run to change it periodicaly. The old man always said never be cheap with brakes. I don't want to find out why the hard way.

 

A brake fluid flush is more or less just removing the fluid out of the master cylinder and replacing it with new. It is a good idea and is pretty common when doing any type of brake work. There is flushes for everything now a days and is usually a good idea to get them done.

 

FordPickupMan351w,

I'm sorry to have to call you on this, but brakes are too important to just let it go out of politeness.

Removing and replacing only the fluid in the master cylinder will NOT be adequate. That is only the first step in brake flushing. If you only did that you would still have nasty, moisture soaked fluid in all the cylinders where the damage is done. If that is all you do, the dirty fluid will not find its way out of the system.

After removing and replacing fluid in the reservoir with fresh stuff, you then go through the same procedure that you would use in bleeding the brakes. With pressure on the system, you open each wheel cylinder/caliper bleed screw until you see fresh, clean fluid coming out. This is the only way that you can force the old fluid out and fresh fluid in its place. While doing this you have to continue to add fresh fluid to the reservoir as it is used up.

I mean no offense in calling you on this, but as peppermrj indicated, don't take chances with your brakes. The life of your family, yourself and everyone that you share the road with are at stake.

Hope this helps,
Doc
ASE Master

 

Alright... Go ahead, just drag me out to the pasture an shoot me... Just kidding, but I do have to agree with you on that post. Changing the brake fluid in the master cylinder is the lazy mans way. I have bleeding the brakes. But then again there is a lot of debate on whether or not compressing the caliper and have it backfeed into the master cylinder is the correct way to change the brake pads. I bet you that 99% of people do it that way and supposively it can cause damage to the ABS system and master cylinder. What is your opinion on this? Should you clamp the brake hose and open the bleeder???

 

Just yesterday at lunch I was driving and truck seemed to pull slightly to the right. Headed back toward home (~10 miles), it got bad enough I pulled over and noticed the brakes were applied as I rolled to a stop. Got out, it was raining and windy so I didn't smell it, and the first three brakes I touched were cool. The front right wheel was very hot to the touch, covered with brake dust, and stunk of hot pads. Did the obvious, cracked the bleeder to make sure it wasn't hydraulic, tapped the pins to make sure it wasn't hung up with corrosion on the slider. Drove 1/2 mile or so to a shop my buddy works at with brakes hung up much tighter. Now is was hot enough to boil when you spit on the wheel. When we got the caliper off, the top piston wouldn't retract with channel locks. Bought a new caliper, had to pay his shop, and was cold and wet.

The really bad news, the fluid has been black for a couple of years. It's one of those things I've been meaning to do (btw, fluid attracts water, water makes the fluid dark) but never got around to. It was corrosion that screwed my caliper piston and kept it from retracting. One hour and $10 bucks of DOT 3 brake fluid turned into a couple of lost hours of work, a new caliper, and a shop bill.

There is another very good reason to change the fluid. As it gets water in it, its boiling point decreases. You get spongy brakes much earlier and can either loose your brake or the brake can self apply from steam. Neither is good. Stay off mountains with old brake fluid.

 

FordPickupMan351w,
To continue the thread hijack I will share what I have learned on the question you posed to MBDiagMan. I have an aquantence that owns a small brake shop in pgh. pa. (power brake xchange). His shop is more for rebuilding calipers,master cylinders, hydroboost units,vacuum booster,steering boxes,racks,pumps and so on. He also is a distributor for most major abs systems. Every time I come by his shop there is a dealer truck outside dropping off or picking up. That said his instructions to me on the matter was to definitely reseat the piston in a caliper by opening a bleeder with a clear hose attached to a catch bottle (don't pinch off a brake hose). He specified and I quote " The tolerances on those ABS units are too close". I am glad to have only RABS on my 98. He also insists on setting a brick under your brake pedal when bleeding to limit pedal travel to the used portion of the mastercylinder.
I have never done it this way on the crown vic with 4 wheel abs. I will in the future tho. I just looked up the price for an ABS unit!

 

The way I prevent these kinds of problems on my own vehicles is to keep the brake fluid clean in the first place.

If I were to change pads on a vehicle with dirty fluid, I would flush the entire system first then change the pads normally. The reason I would take this approach is that it must be done anyway and unless the system will be opened for some other reason while you're doing the work, it will be less overall work than to mess with a hose to bleed off excess into a bottle which would risk getting air in the system. Another reason is that if you push the dirty fluid out the hose with the caliper piston, you are pushing the piston through dirty fluid rather than the clean fluid that you would have after a flush.

Flushing a system just to get fresh fluid in is a quick and easy job. Bleeding a system that has air in it, can sometimes be frustrating with modern ABS systems.

Air in the system will make the brakes more difficult to bleed than it is to flush a system that does not have air in it.

BTW, I would STRONGLY recommend that you NEVER pinch a rubber brake line. If you do so, consider the line trash and replace it immediately.

Hope this helps,
Doc
ASE Master