Do I need to change brake fluid?

Hi guys. I was wondering...my jeep is a 95, so the brake fluid in there is 8 years old. Do I need to change it?

If I do change it, how far do I push in the brake pedal? I read in Popular Mechanics once that on an older master cyl, light crud and corrosion builds up on the inside of the cylinder beyond the furthest extant of the pistons stroke. This means that when you are bleeding and push the brake to the floor, the seals in the cylinder walk over this crud and get roughed up. This can ruin the master cyl.

So...is this true? It would take forever to bleed the brakes pumping it an inch at a time, and it would be hard to make a stop that is exactly the right length. A bit too long, and you might as well not have a stop at all. A bit too short, and you are pumping all day.

Its true about the crud build up in master cylinder. So what you could do is go to a place that can pressure bleed them or you could buy a one person vacuum bleeder. Thats what I would do.

I'm an advocate of replacing the brake fluid. Unless you have silicone fluid, it absorbs water. Use a turkey baster to empty the master cylinder and refill it with fresh fluid before you begin to bleed.

PaulJ said:

I'm an advocate of replacing the brake fluid. Unless you have silicone fluid, it absorbs water. Use a turkey baster to empty the master cylinder and refill it with fresh fluid before you begin to bleed.

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OK. Yeah...I was going to use a suction pump to empty the resevoir (you know...those big syringe things).

So, when you change your brake fluid, how do you keep from pressing the pedal down too far and ruining your master cyl?

And how much does it cost to have this done at a garage?

I just flushed my brake fluid yesterday. Its a 99 with only 33k on it and the fluid was pretty nasty. I used a Mighty Vac that I bought at Harbor freight for about 30 bucks. It's a tool you can use for alot of other things too so it's a good investment. It's alot easier and safer than pumping the brakes. I would guess it would cost you 40-50 bucks to have the same done in a shop and maby more so it makes sense to just but the tool and some good quality brake fluid and do it yourself. BTW, if you do use the Mighty Vac don't forget to get some teflon tape to wrap the bleeder threads in before you start bleeding.

Where else can I get a mighty vac? Does it just attach to the bleed screw and suck? I thought the bleed screw just looked a bit like a zerk fitting, and you just stick a hose on it. What threads are you talking about?

Vac Pump

As Walt said Harbor Freight. Any good auto store will have it. I bought one at auto zone years ago. Make sure it comes with the brake bleeding kit. They really work. Just make sure you bleed in the sequence specified in your manual. If you don't then you won't get a complete bleed.

The threads mentioned are on the bleeder where it screws into the wheel cylinder or caliper. If you don't wrap it with the teflon tape it will leak and you'll be sucking air past the threads instead of brake fluid.

PaulJ said:

The threads mentioned are on the bleeder where it screws into the wheel cylinder or caliper. If you don't wrap it with the teflon tape it will leak and you'll be sucking air past the threads instead of brake fluid.

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I've found the amount of air that comes through the threads isn't really critical. You'll still suck plenty of fluid too. The only drawback is that when bleeding, you can't be sure when to stop, because there will always be bubbles in the jar. But that doesn't really matter when you're just flushing.

No "Harbor Freight" where I am, or at least that I know of.

So how exactly does this thing work? Do you totally remove the bleed screws that are already there? Do you just turn it on and let it suck brake fluid while you add it at the resevoir?

www.harborfreight.com

J. C. Whitney also sells the Mighty Vac. As someone already posted, if you buy one be sure to get the model with the brake bleeder kit.

You don't completely remove the bleeder screws. You open one, press the suction tube over the tip of the bleeder, and squeeze the handle om the Mighty Vac to start sucking. The old fluid will be drawn through the vacuum pump into a little jar that attaches to the vacuum pump. When you see clean fluid coming out, shut that bleeder and move on to the next.

BTW, 8 years is much too long. Brake fluid should be flushed out at least once every two years, preferably every year. Unless (again as someone posted) you use silicone brake fluid. Silicone fluid is not hygroscopic, so you can leave it in for a lot longer and not worry about it. I fringe benefit is a much higher boiling point than even synthetic brake fluid.

It is handy to have two people around, the second person keeps the master cylinder full so you don't suck air thru it. If you start the bleed and drain the master you get air in the lines and have to start over again . Eastwood company has an upside down bottle that you stick in the master cylinder resevoir that has a float in it that adds fluid as as you draw it down. Handy....
The might vac is sold all over the place, as others have said, get the one with the brake bleeder parts, it will have a plastic bottle with it. Advance auto, National, NAPA, all sell them, I've also seen them in walmart and a few other places.

I just got one of these pressure bottle babies from motive products and it works like a champ. One person can do the job easy. Just suck out the old dirty fluid from reservoir add clean fluid add clean fluid to pressure bottle hook to top of reservoir w. adapter pump up pressure bottle to 15-20 lbs and simply put clear hose on brake bleed niple at wheel farest from master cylinder (passenger side rear) and drop hose into clear container. Then open niple and the pressure in bottle pushes out fluid and replaces w. clean fluid from pressure bottle. Then move on to next wheel and finish at the one closes to master cylinder (driver side front). I used the ate fluid they sell in blue color so I could see when the old fluid was all gone and replace w. dark blue coming out of brake nipple into the container. They also have ate (dot 4) in gold color so next time I can do the color change the other way. I just did this on a family passat and am going to do it today on the older daughter's passat and then soon on the family jeeps. Changing the brake fluid every two yrs is a must on abs brake systems -- big $$ for a wasted hydraulic modular. http://www.motiveproducts.com/
Greg

OK...thanks guys. I'll go ahead and get whichever of those products my auto parts store sells today. If the tool costs as much as the service there is no reason not to.

I know my fluid is old, but I have only had the Jeep for about 3 years now.

You know what is weird? I looked through the manual, and it never gives an interval for changing either the fluid, or the cap & rotor for that matter!

So how do I fix my adjuster?

You generally don't 'fix' adjusters, you replace them. You can clean them with a steel brush and some elbow grease but at around $5 an ajduster or around $12 for a complete hardware kit it is easier to replace them.

OK guys, I gotta chime in. Although all these bleeder boosters are great, and save time, but you don't need them to change all the fluid in your system easily.

You can "GRAVITY BLEED" the system most of the way. This involves connecting a drain line and catch container to all four of the bleeder fittings, and opening them all up without pumping. Gravity will drain most of the fluid naturally, and you can then follow up with the traditional peddle pump bleeding at the end, using a assistant.

I am surprised no one else suggested this method. Eagle, you are probably, like me, one of our more senior members, and can remember gravity bleed being done all the time in the old days.

Admittedly, it's not real fast (may take 1/2 hour to bleed the whole system), but it requires no special tools.

When I have time, I usually just gravity bleed. Then finish up with the tried and true... Pump-Hold, bleed. I have tried several other methods over the years, but I stay with this.
Glenn