Mushy brakes
 

Recently my brakes have become mushy and the pedal travel is more than usual. I pulled all 4 wheels off, no leaks found, no bulging brake hoses and brake pads are almost like new. The fluid res. level is sitting about 1/3 below the max mark. Could the recent real temps. have anything to do with it. This is my second winter with this car. I don't recall having this problem last winter. Also as a related question. I am going to add brake fluid, but I don't know what is in the car now, DOT 3 or 4. If it is DOT 4 and I add DOT 3, would that be ok. I need to take care of this ASAP. It'd bad enough braking in snowy weather, nevermind with mushy brakes.
Thanks in advance.

If you have a warm place to work, sounds like a great time to do a brake fluid flush and change. No worries about mixing ;),

How does the pad thickness look? 1/3 down on fluid with no leaks points to a fair amount of pad wear.

After I posted I went right to Walmart and bought some DOT 4. As I was pouring it in, the level wasn't changing, then I noticed what was REALLY low. When I said the level was a 1/3 down from max., I was looking at the front part of the res. It was the rear section that was damn near empty. I had bought a 12 oz. bottle of fluid and it took a little over half of that to fill her up. After a couple pumpings of the brake, she was good to go. TO be honest with you, ever since I bought the car a year or so ago, I always just looked at the front compartment. I ASSUMED that what was in the front, was representative of the entire res. Of course forgeting that the sys. is designed as such that in the event of a major brake fluid lost in one brake circuit, that would not fail the other. So basicly I am going to watch the level, in both parts, particullarly the rear, now that I know that it is full. Again, the rear hoses are bone dry, as is everything else. Maybe all along the level was low and as my brake pads wore down a bit, the lack of fluid reared it's ugly head. I will also have test the low fluid light, because I didn't get a light. The pads themselves have a long way to go.

Better bleed the rears. If they were that low , they prob now have air ......

You're probably right. I just wish Walmart sold DOT 4 in larger containers. They had the big bottles of DOT 3. Speaking of bleedy the brakes. Just how do you know when the old fluid is out. The brake fluid that is in there now isn't dirty per say, for me to notice when the new stuff has made it to the bleeder screw.

I use a clear tube attached to the bleeder screw. You can see the difference in new/old fluid as it moves through the tube. Added benny to the clear tube, you can see any air bubbles as they push out with the fluid.

Yes, using the clear tube helps alot.

You should flush and bleed. Since it's been at least two years since they were flushed, it could easily take a quart of fluid to get everything properly flushed out.

Flushing these brakes thoroughly every year is a very small price to pay to keep from having to rebuild hydraulics. If you do it every year, your cylinders can last virtually forever.

Good luck,

you can use ATE brand fluid which comes in blue and gold colors so you can see the old color being pushed out...

Unless you are likely to use it all, big containers are not really the best way to go with brake fluid.
Once the seal is cracked, the fluid can absorb water just sitting on the shelf.

When I flushed the brakes on my first Benz, the '80 SD, the old fluid was real dirty. So when putting in the new fluid, you could see the old stuff coming out and then the new clear fluid. If the brake fluid that is in there now is relatively clean, how would I know when the new stuff has pushed out the old? BTW Mike, what is "benny"?

It would have to be REALLY new for you to not be able to see the difference. It darkens noticibly in just a few months.

Also, don't sweat it too much.
If a small amount of the old stuff remained, the world would not end. The worst of it is in the caliper itself (the lowest point in the line). That is where the water and sediment settles to over time.

only way to tell is if you use something like the ATE Blue fluid. they make gold and blue colors so that you can alternate and clearly tell the difference when doing the flush. BTW, benny=benefit.

cheers

I had flushed my fluid a couple of years prior to doing a recent caliper rebuild. There were no leaks, but the dust boots were cracked. When I pulled the pistons, I found jelly on the back sides and in the calipers. This stuff had been in there a long while. No way had the previous owner been flushing the fluid. Even my flushing was not enough to get this stuff out. While I had everything down, I replaced the hoses too. What a difference! Pedal feel is like a new car.

Thanks for covering for me while work interupted.