How do I check brake fluid level on our W22 ?

[Scooter]

I can see the reservoir OK, under the hood, but it is not see-thru plastic like our old P32 chassis. You could get up behind it and shine a bright light thru it to see the level.

Our 2002 or 2003 W22 has opaque plastic. There are two caps. Why is that?

Does one stick your finger in or use a clean stick or something to find the level. And what is the correct level?

Thank you

[Skip426]

There are two caps to allow you to figure out if the front or rear brakes are low or leaking fluid. The filler neck in the resivoir will project into the fluid and have slots up the sides, to allow air out while adding fluid; do not fill past the top of those slots. A small mirror will help you see the fluid level, may need a flashlight too. If you have to add a lot of fluid , or have added a little fluid often; it's time to have the brake pads checked for wear. Fluid stays in the calipers as the pads wear down and only returns when the caliper pistons are pushed back to allow the installation of the new ; thicker ; pads.

[dieselclacker]

Scooter,

I usually just use my finger to check the level. The level will vary with the amount of pad wear.As the pads wear, the level of the fluid in the reservoir will go down. It is really not necessary to add fluid to the master cylinder unless your system has an external leak. There is enough fluid reserve within the reservoir so that even with the pads worn down to the backing plate, your system will still be able to maintain hydraulic pressure. If you do insist on keeping the fluid level to the top of the reservoir as the pads wear down, do be sure and cover the master cylinder with a shop towel, or remove some of the fluid with a suction bulb before replacing the brake pads. Forcing the caliper piston back into the bore of the caliper during the act of replacing the pads will push the brake fluid back into the master cylinder, and causes it to overflow.

Dieselclacker

[Clay L]

I don't know why there are two caps. There is only one fluid chamber in the master cylinder.
I verified that when I flushed the brake fluid. Sucking fluid out with a baster or adding fluid to one opening removed or added to both places.

[DriVer]

Quote:

Originally Posted by dieselclacker I usually just use my finger to check the level.

Not my favorite practice. Use a mirror and flashlight.

Yes - Keep the master cylinder filled to the recommended level but there is no need to check it every day. I would be sure to check it every year, top off the fluid to the bottom of the fill neck and that's it. We have already established (per the new maintenance recommendation) that we would like to do a brake system flush every 2 years.

In doing a brake job on one of these chassis, I would start off by vacuuming out all the fluid in the master cylinder as step 1 in preparation for a system flush.

[Scooter]

The plastic is too thick to see thru with a flashlight. But I will try again using a mirror. Question: Fluid is in the plastic reservoir but yet, master cylinder is referred to. Master cylinder is metal and below the reservoir. Am I being too picky?

[dieselclacker]

[QUOTE=DriVer;979100]Not my favorite practice. Use a mirror and flashlight.


Sorry DriVer, didn't know you had such a delicate finger. Guess you could also use a sterilized popsicle stick as a gauge if you couldn't find your flashlight and mirror to check the level.

Dieselclacker

[Clay L]

Quote:

Originally Posted by Scooter The plastic is too thick to see thru with a flashlight. But I will try again using a mirror. Question: Fluid is in the plastic reservoir but yet, master cylinder is referred to. Master cylinder is metal and below the reservoir. Am I being too picky?

It's probably sloppy speaking but I have always referred to the whole assembly as the master cylinder.

[DriVer]

Quote:

Originally Posted by dieselclacker Sorry DriVer, didn't know you had such a delicate finger. Guess you could also use a sterilized popsicle stick as a gauge if you couldn't find your flashlight and mirror to check the level.

Dieselclacker, You may not buy this but it's largely a contamination issue. Being a mechanic for so many years (about 8) I couldn't find in my curriculum where they advised me that I should use a finger as a dip stick!

You could poke the fluid with your finger however the only reliable indicator is a direct visual.

[dieselclacker]

Quote:

Originally Posted by DriVer Dieselclacker, You may not buy this but it's largely a contamination issue. Being a mechanic for so many years (about 8) I couldn't find in my curriculum where they advised me that I should use a finger as a dip stick! You could poke the fluid with your finger however the only reliable indicator is a direct visual.

Well DriVer, in my 37 years in the mechanical field, I can recall NO other vehicle that I maintained that required anything other than a visual check on the brake fluid level. Workhorse being the exception. As for using the finger as a dipstick, weren't you ever instructed how to check the differential level, or the transmission level on standard trans equipped vehicles by seeing if the lubricant could be touched with the finger inserted through the fill plug hole. If the lubricant could be touched with the index finger inserted no farther than the first joint from the tip, the level was OK. This method allowed for expansion of the lubricant when it got up to operating temperatures. Just one of the many things taught in "service station 101" a long, long time ago. Still valid today.

Dieselclacker

[DriVer]

Quote:

Originally Posted by dieselclacker Just one of the many things taught in "service station 101" a long, long time ago. Still valid today.

Dieselclacker, I was a mechanic (not technician) before I went into the service in 1969. I worked new car dealerships and when I got out of the Army, I went back in the trade and worked on heavy duty trucks, loaders and dozers for about 6-7 or years however that was too much like work.

I moved on into the electrical field. I came very close to taking my mechanic's license (electrician) however .... that turned out to be too much like work but the work was great.

I went back to school and wound up as a network engineer. Still a lot of work but big difference hardly any dirt.

Being a Professional Firefighter also got plugged into the mix and that took me 28 years to finish up. One day while working with a new firefighter we had a small leaf fire. He started to stomp it out with his boots. I suggested using a tool like a broom or shovel.

I will still suggest the same procedure especially since their isn't any room on the top of the Bosch Hydro-Max to do a lot of stuff but a light and my wife's compact mirror shows me how much fluid is in the tank.

Today a "tech" would have heart failure if a finger were stuck in a hydraulic brake fluid reservoir so I try not to let any of those types see me.