Brake master cylinder/bleeder valve method? (3 Viewers)

[jbyrd78]

Looking at replacing the front and rear brake pads and rotors this weekend. This is going to be my first brake pad/rotor replacement job on my 200. Originally, I planned to just pull the cap off the master cylinder to push the pistons in, vs opening the bleeder valve.
Am I going to cause damage to the master cylinder if I use this method? If I do the bleeder valve method, do I run the risk of introducing air into the fluid, and will I have to have the system flushed again, or will I just have to top off the fluid level? I just had a brake fluid flush & fill done last month.

 

[TeCKis300]

IIRC, it's bled through the calipers. Need techstream to actuate the bleeding functions.

 

[jbyrd78]

IIRC, it's bled through the calipers. Need techstream to actuate the bleeding .

IIRC, it's bled through the calipers. Need techstream to actuate the bleeding functions.

In one of the YouTube videos I watched. They just cracked the bleeder valves on the caliper, and used a caliper spreader to push the pistons back. When the pistons were fully pushed in, they closed off the bleeder valve.

 

[TeCKis300]

Sorry if I misread. Thought you were looking to bleed the master cylinder and calipers.

If you're only looking to change pads, what your suggesting can work. It's easier still in that you can use the worn pads themselves to leverage and push the pistons back enough for the new pads to drop in.

 

[CruiserFan88]

You can push the pistons back in without breaking open the bleeder valves and without causing damage, however you do need to keep an eye on your brake fluid level at the mater cylinder and remove some if the level increases past maximum with every piston you push back in. If your pads are really worn down and the fluid has been topped off to the max line recently, the system would be over-filled, in that case you might want to go the bleeder valve route to remove the excess fluid unless you have a easy was of pulling the fluid out the M/C. I used a small syringe.

 

[jbyrd78]

Sorry if I misread. Thought you were looking to bleed the master cylinder and calipers.

If you're only looking to change pads, what your suggesting can work. It's easier still in that you can use the worn pads themselves to leverage and push the pistons back enough for the new pads to drop in.

It's all good! I appreciate the reply. I just wanted to double check before I proceed. I was initially told to bleed at the caliper b/c just removing the master cylinder cap and pushing the pistons in, will push all the contaminated brake fluid into the master cylinder, which will in return cause the master cylinder to not work properly. I'm not looking to have to replace that anytime soon...those things are spendy.

 

[jbyrd78]

You can push the pistons back in without breaking open the bleeder valves and without causing damage, however you do need to keep an eye on your brake fluid level at the mater cylinder and remove some if the level increases past maximum with every piston you push back in. If your pads are really worn down and the fluid has been topped off to the max line recently, the system would be over-filled, in that case you might want to go the bleeder valve route to remove the excess fluid unless you have a easy was of pulling the fluid out the M/C. I used a small syringe.

Yeah, as far as fluid goes, I'm at the max line. If I open at the bleeder valve on the calipers, do I need to worry about air getting in, and do I need to have the system bled again?

When I do the rear pads, do I have to have the ignition on, or am I good with the vehicle off?

 

[CruiserFan88]

Yeah, as far as fluid goes, I'm at the max line. If I open at the bleeder valve on the calipers, do I need to worry about air getting in, and do I need to have the system bled again?

When I do the rear pads, do I have to have the ignition on, or am I good with the vehicle off?

Ignition does not need to be on for rotor or pad replacement. If you are super careful when attaching the hose to the bleeder and cracking it, you may get away with not introducing air into the lines. Or remove some brake fluid from the m/c, to the min line for example, then push the first one in and see. It’s not enough to where it’s going to shoot out everywhere but you don’t want brake fluid spilling over and eating up paint and such where it lands. That was easier for me with no risk of needing to bleed brakes. My understanding is the bleeding procedure on these is slightly more involved than other autos

 

[linuxgod]

Yeah, as far as fluid goes, I'm at the max line. If I open at the bleeder valve on the calipers, do I need to worry about air getting in, and do I need to have the system bled again?

When I do the rear pads, do I have to have the ignition on, or am I good with the vehicle off?

crack open, push in piston, close valve. At least that's how I've done it on much older vehicles. If you leave it open a small amount of air could get in. Attaching a one man brake bleeder will help as it'll suck old fluid back in instead of air. Just keep an eye on the MC and make sure the level stays between MAX and MIN and top off as needed.

That said I'd recommend just bleeding the lines. Why? Because unless you've changed your brake fluid in the last 2-3 years (or you've used some test strips and it shows as good) you should do that now. Brake fluid is hydroscopic and will absorb moisture over time which will eventually rust out the calipers. Also it will break down over time due to heat. A couple quarts of fluid is cheap and you can flush them yourself with a one-man bleeder in about 30 minutes.

 

[jbyrd78]

My understanding is the bleeding procedure on these is slightly more involved than other autos

I'm glad you mentioned this. Because I have seen mixed opinions on this, and like I mentioned. I'm just trying to go the safest route, while not trying to mess up my master cylinder b/c those things are around $2k for a replacement. I think for a piece of mind, I'm just going to have the system bled again at the dealership once I'm finished with the job. Right now, they have a special going on, and when it's all said and done, I'll be paying $75 for the job.

 

[jbyrd78]

That said I'd recommend just bleeding the lines. Why? Because unless you've changed your brake fluid in the last 2-3 years (or you've used some test strips and it shows as good) you should do that now. Brake fluid is hydroscopic and will absorb moisture over time which will eventually rust out the calipers. Also it will break down over time due to heat. A couple quarts of fluid is cheap and you can flush them yourself with a one-man bleeder in about 30 minutes.

Thanks for your response. I had the lines bled when I first bought her back in August. Like I mentioned though. I'm going to just have the system bled again at the dealership once I finish up the job, just for a piece of mind. It's only going to cost me around $75 after I use my Toyota dollars.

 

[linuxgod]

I'm glad you mentioned this. Because I have seen mixed opinions on this, and like I mentioned. I'm just trying to go the safest route, while not trying to mess up my master cylinder b/c those things are around $2k for a replacement. I think for a piece of mind, I'm just going to have the system bled again at the dealership once I'm finished with the job. Right now, they have a special going on, and when it's all said and done, I'll be paying $75 for the job.

My understanding is the bleeding procedure on these is slightly more involved than other autos

The bleeding procedure is easy so long as you don't introduce air into the master cylinder. Just keep the fluid level above MIN (top it off every few brake pumps) and you'll be fine. The order (below) is RF, LF, RR, LR.

If you do get air into the MC then you need Techstream so you can activate the MC and ABS sensors to bleed the entire system. But for normal brake pad replacement or brake bleeding/fluid flush this is not required.