Master cylinder issue and SERVICE BRAKE LIGHT ON

[Gus04Runner]

So on my way to work my brake service light popped up (the one with the "(!) And BRAKE" underneath. I pulled over and checked my master cylinder for fluid. Past the low level. Luckily i had a bottle and topped it off. Keep in mind i had a full master cylinder two days prior. Yet i could not locate any leaks from the lines, calipers, or mastercylinder. Im stuck as to how i lost so much fluid in 2 days. Any help greatly appreciated. I also checked the parking brake but it was not the case........UPDATE: the light slowly dimmed down on its own and has now completely turned off. Im confused to whats going on. Should i take it to toyota to have it checked out?

 

[TechWrench]

So on my way to work my brake service light popped up (the one with the "(!) And BRAKE" underneath. I pulled over and checked my master cylinder for fluid. Past the low level. Luckily i had a bottle and topped it off. Keep in mind i had a full master cylinder two days prior. Yet i could not locate any leaks from the lines, calipers, or mastercylinder. Im stuck as to how i lost so much fluid in 2 days. Any help greatly appreciated. I also checked the parking brake but it was not the case........UPDATE: the light slowly dimmed down on its own and has now completely turned off. Im confused to whats going on. Should i take it to toyota to have it checked out?

If you lost that much fluid in just two days, you have a leak. You didn't mention what year vehicle you have, but if it is an older one, you probably have a small rust hole in a line somewhere. If you are not noticing any stopping issue, or soft pedal, then it is probably just a pin hole at this point, but it will get worse soon. Sometimes these leaks are difficult to spot early on. If possible, park someplace level and dry, with s smooth surface. Apply the brake firmly, and hold it for 2-3 min. If the pedal starts to lower during that time, pump it to bring it back up and continue to hold it for a while. Then, being sure to make note of where exactly the 4 wheels are, move the vehicle off the spot, and check for fluid on the ground. If you see some, note where, in relation to the vehicle the spot is, and then carefully check that area on the vehicle. You should find the source of the leak.

Try to do the leak check someplace close to home or the repair shop, because it is possible, that with strong enough pedal pressure, that the small hole could become larger in a hurry, and result in a much faster rate of fluid loss and the brakes not working at all. And be sure to have extra brake fluid on hand if necessary.

I know, been there, done that.

 

[Gus04Runner]

If you lost that much fluid in just two days, you have a leak. You didn't mention what year vehicle you have, but if it is an older one, you probably have a small rust hole in a line somewhere. If you are not noticing any stopping issue, or soft pedal, then it is probably just a pin hole at this point, but it will get worse soon. Sometimes these leaks are difficult to spot early on. If possible, park someplace level and dry, with s smooth surface. Apply the brake firmly, and hold it for 2-3 min. If the pedal starts to lower during that time, pump it to bring it back up and continue to hold it for a while. Then, being sure to make note of where exactly the 4 wheels are, move the vehicle off the spot, and check for fluid on the ground. If you see some, note where, in relation to the vehicle the spot is, and then carefully check that area on the vehicle. You should find the source of the leak.

Try to do the leak check someplace close to home or the repair shop, because it is possible, that with strong enough pedal pressure, that the small hole could become larger in a hurry, and result in a much faster rate of fluid loss and the brakes not working at all. And be sure to have extra brake fluid on hand if necessary.

I know, been there, done that.

Ive got the 2004 sr5 v6 with 162k. I will try that. And no i have not noticed any pedal difference. But i will try that out.

 

[V8Man]

[MENTION=115850]Gus04Runner[/MENTION]. What is the build date on your truck? Look at the drivers door tag. 03 & early 04 use the same master cylinder and they have problems.

 

[Gus04Runner]

[MENTION=115850]Gus04Runner[/MENTION]. What is the build date on your truck? Look at the drivers door tag. 03 & early 04 use the same master cylinder and they have problems.

Found my problem, like the other guy mentioned above, there was a small hole in my rear line and it finally broke completely and now i have a severed rear brake line. Glad its not a faulty master cylinder. Looks like more maintenence for this hog tomorrow!

 

[TechWrench]

Found my problem, like the other guy mentioned above, there was a small hole in my rear line and it finally broke completely and now i have a severed rear brake line. Glad its not a faulty master cylinder. Looks like more maintenence for this hog tomorrow!

Not surprised, I have had to replace three different sections of brake line on my '03 in the last year. Each one failed about 2-3 months after the previous one. Check the rest of the lines carefully, especially the ones near the frame in the front. If one has gone, more may be ready to fail in short order.