Break light

[intheric]

Afternoon all.

Now that the truck inspected (flying colors they said) and I’ve had the awesome pleasure of driving it for 2 weeks, I noticed the brake light came on yesterday on the way to work. Didn’t think much of it (pressed and released the e brake a few times) until I’m in targets parking lot today and I’m pulling into the spot and I notice the pedal goes all the way to the floor. This didn’t happen at the 3 other lights I just went thru. Didn’t really know until now that it’s also a low fluid light too...

so I pop the hood and check the brake oil and it’s sitting right above the min line. So I’m like “ok well ****, go figure”. I drive around the back part of the lot to see how bad it is and even tho the stopping time isn’t all that ideal, there’s still a good response. I don’t tailgate anyway so I’ll just be extra cautions. There’s an oreillys next to the house. All within 5 min of each other. So I buy a large bottle of fluid and top it off. The light on the dash goes out, and I pump the pedal a few times, but nothing changes. I remember when I got my brakes changed like 2 years ago, this happened but everything evened back out. Not happening now. I drove around my neighborhood a few times, doing some aggressive braking and pumping while coasting along.

I know I need to take it back to the shop, but any tips or tricks before I do that. I can’t think there’s air in the lines. The reservoir wasn’t empty. And with the truck off I can pump the brake and it gets hard after 3-4 pumps. Then back to squishy when running.

thanks again

 

[1998Exp]

There is a leak somewhere. An easy spot to check is the master cylinder - usually results in paint peeling off the booster, just underneath. Otherwise there are many possibilities: a leaking caliper, a torn flexible line, etc., etc... If this truck lived in the rust belt, a hole or a crack in one of the hard lines is a possible culprit. Don't drive the vehicle until the leak is diagnosed and repaired.

 

[fast_dave]

@intheric

"so I pop the hood and check the brake oil and it’s sitting right above the min line."

If you aren't seeing any obvious signs of brake fluid leaking onto the ground, or at your calipers,
then be advised that the brake master cylinder can leak directly into the vacuum brake booster (where the brake master cylinder is mounted).

 

[intheric]

There is a leak somewhere. An easy spot to check is the master cylinder - usually results in paint peeling off the booster, just underneath. Otherwise there are many possibilities: a leaking caliper, a torn flexible line, etc., etc... If this truck lived in the rust belt, a hole or a crack in one of the hard lines is a possible culprit. Don't drive the vehicle until the leak is diagnosed and repaired.

I’m in Virginia so not quite the rust belt

 

[intheric]

There is a leak somewhere. An easy spot to check is the master cylinder - usually results in paint peeling off the booster, just underneath. Otherwise there are many possibilities: a leaking caliper, a torn flexible line, etc., etc... If this truck lived in the rust belt, a hole or a crack in one of the hard lines is a possible culprit. Don't drive the vehicle until the leak is diagnosed and repaired.

This is after about 2-3 hours of it not running. Def some kind of leak. The area underneath is still moist to the touch. I wiped off that little black pipe coming off the grey pipe (forgive my lack of technical terms). Cant get to the underneath part to wipe that down (and I just showered for the day) so this pic will serve for a starting point for future ref.

 

[intheric]

from the other side. Seems clean

 

[1998Exp]

The rust on the booster (that's the black-painted round thingy behind the master cylinder) is clear evidence of leak from the master cylinder. It rusted because brake fluid dissolves paint, leaving it exposed. There is also fluid on the hydraulic lines coming out of the master cylinder - could be another evidence of same leak or simply a spill from your refilling. You will need a new master cylinder -- which is not to say that there are no additional leaks elsewhere.

 

[intheric]

The rust on the booster (that's the black-painted round thingy behind the master cylinder) is clear evidence of leak from the master cylinder. It rusted because brake fluid dissolves paint, leaving it exposed. There is also fluid on the hydraulic lines coming out of the master cylinder - could be another evidence of same leak or simply a spill from your refilling. You will need a new master cylinder -- which is not to say that there are no additional leaks elsewhere

The rust on the booster (that's the black-painted round thingy behind the master cylinder) is clear evidence of leak from the master cylinder. It rusted because brake fluid dissolves paint, leaving it exposed. There is also fluid on the hydraulic lines coming out of the master cylinder - could be another evidence of same leak or simply a spill from your refilling. You will need a new master cylinder -- which is not to say that there are no additional leaks elsewhere.

The rust on the booster (that's the black-painted round thingy behind the master cylinder) is clear evidence of leak from the master cylinder. It rusted because brake fluid dissolves paint, leaving it exposed. There is also fluid on the hydraulic lines coming out of the master cylinder - could be another evidence of same leak or simply a spill from your refilling. You will need a new master cylinder -- which is not to say that there are no additional leaks elsewhere.

The rust on the booster (that's the black-painted round thingy behind the master cylinder) is clear evidence of leak from the master cylinder. It rusted because brake fluid dissolves paint, leaving it exposed. There is also fluid on the hydraulic lines coming out of the master cylinder - could be another evidence of same leak or simply a spill from your refilling. You will need a new master cylinder -- which is not to say that there are no additional leaks elsewhere.

Ok. That makes sense. I had to think for a second about the booster and where and what everything else is. So I’ll order up a new master cylinder in the morning and check out YouTube for any tutorial videos. Everything else I’ve replaced myself has been relatively easy. Is this an easy fix? Or best to buy parts and take it to the shop?

The rust on the booster (that's the black-painted round thingy behind the master cylinder) is clear evidence of leak from the master cylinder. It rusted because brake fluid dissolves paint, leaving it exposed. There is also fluid on the hydraulic lines coming out of the master cylinder - could be another evidence of same leak or simply a spill from your refilling. You will need a new master cylinder -- which is not to say that there are no additional leaks elsewhere.

ok. Ok. That makes sense. I had to think for a second about the booster and where and what everything else is. So I’ll order up a new master cylinder in the morning and check out YouTube for any tutorial videos. Everything else I’ve replaced myself has been relatively easy. Is this an easy fix? Or best to buy parts and take it to the shop? Appreciate your help!!

 

[1998Exp]

ok. Ok. That makes sense. I had to think for a second about the booster and where and what everything else is. So I’ll order up a new master cylinder in the morning and check out YouTube for any tutorial videos. Everything else I’ve replaced myself has been relatively easy. Is this an easy fix? Or best to buy parts and take it to the shop? Appreciate your help!!

It's not hard to replace the master cylinder. You bench-bleed the new MC, disconnect the lines - very carefully, not to let them spill out, then replace the MC and bleed the system. Sounds easy, but if you've never worked on brake hydraulics, I would recommend taking it to the shop. Among other potential pitfalls, if you are not careful, you'll introduce air into the ABS controller, which requires an advanced scanner to correct. Also, a shop will check for other potential leaks. Good Luck!
Make sure you order an MC with the extra port for the Cruise Control disconnect sensor (where that brown plug goes). It may be a good opportunity to replace that sensor as well -- they had a long history of causing fires.

 

[intheric]

It's not hard to replace the master cylinder. You bench-bleed the new MC, disconnect the lines - very carefully, not to let them spill out, then replace the MC and bleed the system. Sounds easy, but if you've never worked on brake hydraulics, I would recommend taking it to the shop. Among other potential pitfalls, if you are not careful, you'll introduce air into the ABS controller, which requires an advanced scanner to correct. Also, a shop will check for other potential leaks. Good Luck!
Make sure you order an MC with the extra port for the Cruise Control disconnect sensor (where that brown plug goes). It may be a good opportunity to replace that sensor as well -- they had a long history of causing fires.

Thanks for the tip. Somethings are best left to the mechanics. Reading up on bleeding and this and that I’ll let them take care of it.

I’m going to post the MC before I get it to make sure it’s the right one. And the sensor too. I don’t need any fires. Thank you greatly!

 

[intheric]

It's not hard to replace the master cylinder. You bench-bleed the new MC, disconnect the lines - very carefully, not to let them spill out, then replace the MC and bleed the system. Sounds easy, but if you've never worked on brake hydraulics, I would recommend taking it to the shop. Among other potential pitfalls, if you are not careful, you'll introduce air into the ABS controller, which requires an advanced scanner to correct. Also, a shop will check for other potential leaks. Good Luck!
Make sure you order an MC with the extra port for the Cruise Control disconnect sensor (where that brown plug goes). It may be a good opportunity to replace that sensor as well -- they had a long history of causing fires.

I’m guessing going with something like Motorcraft is best? It’s pricy but worth going with that then some other brand. I’ve got the trifecta of auto parts stores down the street (oreillys auto zone and advance auto) which helps out

 

[intheric]

It's not hard to replace the master cylinder. You bench-bleed the new MC, disconnect the lines - very carefully, not to let them spill out, then replace the MC and bleed the system. Sounds easy, but if you've never worked on brake hydraulics, I would recommend taking it to the shop. Among other potential pitfalls, if you are not careful, you'll introduce air into the ABS controller, which requires an advanced scanner to correct. Also, a shop will check for other potential leaks. Good Luck!
Make sure you order an MC with the extra port for the Cruise Control disconnect sensor (where that brown plug goes). It may be a good opportunity to replace that sensor as well -- they had a long history of causing fires.

I see these 3 selection of various options. I think the motor craft one comes with the cruise control sensor your speaking of??

 

[donalds]

Seems about rite
Motorcraft has always been the most expensive date I've been on
but the day always ends with a happy ending

 

[Pete Deering]

There was a factory recall for the MC Fuse protection. 5 min Dealer fix free. I replaced all my brake line and hoses (95). For me the line running from front too back rusted thru. The brake line run in the frame rail. Everything rusted out in the rail. My fuel vapor line rusted out. If you can't find the brake fluid, it could be in the booster.

 

[1998Exp]

I see these 3 selection of various options. I think the motor craft one comes with the cruise control sensor your speaking of??

Yes, the Motorcraft is showing that sensor preinstalled -- but that can be purchased separately as well, as long as the master cylinder has the threaded port for it.

 

[Chris_A.]

Thanks for the tip. Somethings are best left to the mechanics. Reading up on bleeding and this and that I’ll let them take care of it.

I’m going to post the MC before I get it to make sure it’s the right one. And the sensor too. I don’t need any fires. Thank you greatly!

Would suggest that you replace your brake booster as well. The condition is not great - from your pictures. If not practical at this point, look at the back end of the master cylinder for evidence of leaking. If it has evidence of leaking, replace it. Having to replace it later is not easy and requires removing the master cylinder. Having a shop do this can end up pricey. The note on the cost is that they warranty their work. You warranty yours.