Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Changing brrake fluid

My repair shop says my brake fluid is discolored. Does this mean I need to change it?

Should be replaced every 3-4 years. check your owners manual.

Your brake fluid can look dirty after a few months, so that isn’t necessarily an indicator. If it has been in the system for more than a few years, yes, you need to have it changed.

There should be a schedule for brake fluid replacement is the “maintenance” section of the owner’s manual.

Brake fluid needs to be replaced periodically.

It depends on how much it is discolored. A little is OK, Much more than that is subject to opinion. I agree, 3-4 years is good.

I know that most of you guys say to change the brake fluid every 3 or 4 years, but I have NEVER changed brake fluid and I doubt very much if it is mentiioned in my owner’s manual, I will check and see. I know that a Chevy HHR is not old enough to worry about.

Whether or not it is recommended in your owner’s manual, it is still a good idea. Moisture can contaminate your brake fluid and lead to the breakdown of your brake system. Pay a little now or a lot later when your brake pistons begin to leak.

With ABS brakes, changing the fluid now and then is cheap insurance…

Problems with ABS can get expensive! I would change the fluid anytime the brakes are worked on or every 3 years or so.

As mentioned, the color is not the final answer to the condition, although if it looks like very strong black coffee, I would change it. If it’s slightly amber colored, and not muddy, I would not worry about it.

With non ABS systems, the brake fluid should be flushed with every pad replacement. This is not in the maintenance schedule because the brake pad replacement can vary so widely. I think it is just assumed that it will be done at that time, but I’ve seen it left off or some quotes in order to get the price down.

If it has turned a dark brown, do change it, it will save you money in the long run.

Everybody here is correct. You need to change the fluid according to your owners manual. Brake fluid absorbs moisture, it is hygroscopic, and that can and will rust the metal brake lines. Then one day you are cruising down the road and need to depress the brake pedal and you will find you have none. What you will find then is a collision about to happen. I have seen this twice, it happens.

Well my van is 14 years old with 130k miles on it. I plan to wait until it is 15 years old with 150k on it before I change the fluid. I hope it makes it.

I can tell you from experience that it is wise to change that fluid. It only takes one experience of approaching a busy intersection and having the light turn red, hitting the brakes only to have the pedal go to the floor with no effect because a rusted line blew. I was lucky. I have my brake fluid changed on a regular basis these days.

If every time the brakes pads / shoes are changed, the brake fluid is bled (to remove any possible air), that is removing some of the old brake fluid and replacing it with new brake fluid (as the brake fluid reservoir is replenished). Thus, over time, most of the brake fluid is changed. Also, though I’ve never measured the water content, the water absorbed in the brake fluid MAY have collected at the brake caliper, since water is heavier than brake fluid. If this theory is correct, the water would be concentrated at the brake caliper, and would be drained with the brake bleeding. As always, I ask any curious mechanic to verify, or disprove, this theory. It does have PRACTICAL applications.

Sorry to go off topic, but are there any automotive brake engineers on this board that could tell us why a non hygroscopic brake fluid can’t be designed for modern cars? It would be so nice to not have to replace the fluid periodically. We all know the polyglycol based fluids should legitimately be changed periodically, but the the car owners’ perception is that it’s a rip off.

, since water is heavier than brake fluid. If this theory is correct, the water would be concentrated at the brake caliper, and would be drained with the brake bleeding.

I do not know if water is heavier than brake fluid but there is an error in your post. You claim water is heavier and I cannot argue that but if it is then the water is in the bottom of the wheel cylinder and the bottom of the caliper. Now, where is the bleeder screw? It’s in the top because air rises. But, no matter, exchanging the fluid gets rid of old water saturated brake fluid and air.

On second thought I do not think it is heavier since the water is neither on top nor bottom of the fluid. It is IN the b/fluid. When you crack open a bleeder you do not get a rush of water then fluid or fluid then water. That’s why fluid boils if it gets to hot. But again, it’s a moot point. Exchange the fluid and no water.

I believe the DOT5 silicon based does not absorb water but I do not know why it is not being used in passenger cars. All seals/rubber parts would need to be different but again I do not know why.

I understand DOT5 is used in military vehicles and certain collector cars that do not get driven much.

I think since brake fluid isn’t petroleum base, but alcohol base, the water will mix with the brake fluid. Also, I’ve read that brake fluid is so hygroscopic that it actually pulls moisture right out of the air through the brake hoses, but I can’t verify this.

I did a little reading up and found that silicone based DOT 5 doesn’t mix with water; the polyglycol DOT 3 and 4 do. DOT 5 doesn’t pull moisture into itself, like 3 and 4 do, but if you do get some water in DOT 5, it could freeze, boil, or cause corrosion since it stays separate. DOT 5 is much more expensive, too. The polyglycol DOT 3 and 4 swell the seals slightly in a positive way to prevent leaks, which DOT 5 wouldn’t do.

I guess the entire auto-making industry would have to agree to a change in any across the board change in brake fluid, necessitating partial redesign of all brake systems. If just one manufacturer did it, the wrong fluid would invariably end up in that car. Actually,

Citroen and Rolls Royce use hydraulic system mineral oil (HSMO), the ultimate in automotive hydraulic fluid, 'cept you can’t use it in systems that need DOT 3 and 4 since HSMO isn’t compatible with seals used in those systems.

Thanks for your reply