cboyd
GOLD Star
Brake components deep in the heart of the system? OEM always, IMO. Pads and rotors are a different story...
Master Cylinder Rebuild - DIY (2 Viewers)
- Thread starter Skidoo
- Start date
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I don't have any braking trouble and the pedal seems to behave just fine but I do get this screeching noise every morning when I start the truck. A few minutes later, the noise goes away. Sounds exactly like:
The only time I did not get this noise in the morning was when I was in Tahoe in December. No noise when I started the truck in the morning but the dash lit like a Christmas tree with Brake, ABS, and other brake related lights on. Braking still worked fine. Drove around for 10 minutes and the screeching noise came back - once it was done, the dash lights went to being normal.
Today, the mechanic pulled codes from history and said there is a code for some hydraulic pump failure on the ABS/MC unit. Does the rebuild kit sound like a good fix?
The only time I did not get this noise in the morning was when I was in Tahoe in December. No noise when I started the truck in the morning but the dash lit like a Christmas tree with Brake, ABS, and other brake related lights on. Braking still worked fine. Drove around for 10 minutes and the screeching noise came back - once it was done, the dash lights went to being normal.
Today, the mechanic pulled codes from history and said there is a code for some hydraulic pump failure on the ABS/MC unit. Does the rebuild kit sound like a good fix?
- Thread starter
- #103
The brake booster pump is separate from master cylinder, so don't think rebuild kit is the answer. Was a thread a while back on having an electric motor shop rebuild the motor for booster pump you might take a look at. Thats not for everybody as need to find a shop you really really trust and if it turns out to be in pump section, you haven't fixed it.
Thanks. Reading other threads, I reached the same conclusion that the rebuild kit won't help with the pump. So either a new pump ($1099) or a used one for $500, right? But I might be able to do without the whole MC assembly.
All,
I've rebuilt my Brake master cylinder twice in the last 6 months to still have a spongy pedal. I thought I botched the first job, so attempted it again. After having a spongy pedal again on the 2nd time I'm thinking my master cylinder was fine and I instead should have done the following. This is an adjustment that I found in the FSM and wanted to share with everyone. This is a 10 minute job that requires a 14 mm open ended wrench, needle nose pliers and no dis-assembly of anything. This is a step you should take before attempting a rebuild and it is also a step that needs to be performed if you do rebuild your master cylinder.
Below is a diagram that IDs the brake push rod location. This is where the brake master cylinder connects to the brake pedal. I only performed steps (e) - (g) in the service manual shown in the pic. You can reach the push rod by laying on your back on the drivers side and reaching up past the gas pedal and over the steering shaft.
This image shows the measurement of the adjustment you would be making. To adjust this measurement, first, loosen the 14 mm push rod lock nut. Then use the needle nose pliers to turn the pedal push rod (I would describe this as a screw). At the base of the push rod, there is a geared surface that is perfect for grabbing with the needle nose pliers. You may need to push back the rubber boot to see this geared surface.
Adjusting in the red arrow direction will give you a firmer brake pedal. Be careful not to adjust this too much or you will have too much pressure which will cause your brakes to always be applied (ask me how I know). Adjusting the push rod in the blue direction will give you a softer (spongy) pedal.
*Note: The only place that I could see the master cylinder leaking would be in the foot well on the drivers side. If you don't have brake fluid leaking onto the floor in the foot well or if you remove the rubber boot and don't see any brake fluid, then it is most likely not your master cylinder. You likely just need to make this adjustment.
I've rebuilt my Brake master cylinder twice in the last 6 months to still have a spongy pedal. I thought I botched the first job, so attempted it again. After having a spongy pedal again on the 2nd time I'm thinking my master cylinder was fine and I instead should have done the following. This is an adjustment that I found in the FSM and wanted to share with everyone. This is a 10 minute job that requires a 14 mm open ended wrench, needle nose pliers and no dis-assembly of anything. This is a step you should take before attempting a rebuild and it is also a step that needs to be performed if you do rebuild your master cylinder.
Below is a diagram that IDs the brake push rod location. This is where the brake master cylinder connects to the brake pedal. I only performed steps (e) - (g) in the service manual shown in the pic. You can reach the push rod by laying on your back on the drivers side and reaching up past the gas pedal and over the steering shaft.
This image shows the measurement of the adjustment you would be making. To adjust this measurement, first, loosen the 14 mm push rod lock nut. Then use the needle nose pliers to turn the pedal push rod (I would describe this as a screw). At the base of the push rod, there is a geared surface that is perfect for grabbing with the needle nose pliers. You may need to push back the rubber boot to see this geared surface.
Adjusting in the red arrow direction will give you a firmer brake pedal. Be careful not to adjust this too much or you will have too much pressure which will cause your brakes to always be applied (ask me how I know). Adjusting the push rod in the blue direction will give you a softer (spongy) pedal.
*Note: The only place that I could see the master cylinder leaking would be in the foot well on the drivers side. If you don't have brake fluid leaking onto the floor in the foot well or if you remove the rubber boot and don't see any brake fluid, then it is most likely not your master cylinder. You likely just need to make this adjustment.
PabloCruise
SILVER Star
2nd pump issue? The other day I drove the wife's LX and noticed brake pedal not great, I lifted off the brake and then pressed brake again, pedal felt much better. Is this 2nd pump issue?
Thanks
I had the same issue on my LX. I would double or triple pump to get a firm pedal. Try the adjustment I posted about. This fixed it for me. Adjusting in the red direction created a firm pedal on the first application of the pedal.
PabloCruise
SILVER Star
I ruined a MC this way. When I poured all that nice, clean fluid into the reservoir, it re-suspended the dirt that had settled out of the fluid and then (I think) ran into the MC bore...
PabloCruise
SILVER Star
Does the rebuild kit come with new rubber seals for the reservoir?
PabloCruise
SILVER Star
Am I looking at the image correctly that you are making the push rod shorter by adjusting in the direction of the red arrow?
PabloCruise
SILVER Star
Last question, and then I will stop hammering this thread, I promise!
I have heard of folks bleeding their brakes, and ABS, by using Techstream to actuate ABS? Anyone here done that?
I have heard of folks bleeding their brakes, and ABS, by using Techstream to actuate ABS? Anyone here done that?
No, actually the opposite. You would be making the push rod longer by unscrewing it from where it connects to the brake pedal.
Is there any concern that this fix is only masking a problem ?
From my understanding of the design of the master cylinder (on a '99 LX), the only way it leaks is if there is fluid coming through the firewall. This would mean that the rubber boot that protects the cylinder shaft would be filling up with brake fluid. If there is no fluid in the boot or leaking around the shaft bushing, then you do not have a leaking master cylinder. If anyone knows any different please correct me.
I honestly believe that a few people here that performed the rebuild, did not need to do this rebuild. They fixed the issue when they put everything back together and then they properly adjusted the push rod (most likely by dumb luck). When you see people say it "kind of fixed the soft pedal issue," this is because the push rod was adjusted more so then they had it before but not to its' maximum potential.
I don't see this adjustment masking anything. What it does, is it pushes the master cylinder far enough into the housing so that the MC is just starting to apply pressure to the system. The result is that very little brake pedal movement will apply the proper pressure for braking (hence the firm pedal). When this push rod is too short, the MC must travel a good distance before it starts applying pressure to the system. The distance the push rod must travel is exaggerated in the movement of the brake pedal based on geometric design. This is where you need to double or triple pump the breaks in order to build up sufficient pressure to stop the vehicle.
By making this adjustment you are just shortening the distance is takes for the MC to travel before it has applied the sufficient amount of pressure in the system. The only watch item here is if you make the push rod too long, your brakes will constantly have pressure and will be constantly applied. You'll know if this is happening.
Well that is a well thought out, perfectly constructed and informative post. Thank you sir!
All,
I've rebuilt my Brake master cylinder twice in the last 6 months to still have a spongy pedal. I thought I botched the first job, so attempted it again. After having a spongy pedal again on the 2nd time I'm thinking my master cylinder was fine and I instead should have done the following. This is an adjustment that I found in the FSM and wanted to share with everyone. This is a 10 minute job that requires a 14 mm open ended wrench, needle nose pliers and no dis-assembly of anything. This is a step you should take before attempting a rebuild and it is also a step that needs to be performed if you do rebuild your master cylinder.
Below is a diagram that IDs the brake push rod location. This is where the brake master cylinder connects to the brake pedal. I only performed steps (e) - (g) in the service manual shown in the pic. You can reach the push rod by laying on your back on the drivers side and reaching up past the gas pedal and over the steering shaft.
This image shows the measurement of the adjustment you would be making. To adjust this measurement, first, loosen the 14 mm push rod lock nut. Then use the needle nose pliers to turn the pedal push rod (I would describe this as a screw). At the base of the push rod, there is a geared surface that is perfect for grabbing with the needle nose pliers. You may need to push back the rubber boot to see this geared surface.
Adjusting in the red arrow direction will give you a firmer brake pedal. Be careful not to adjust this too much or you will have too much pressure which will cause your brakes to always be applied (ask me how I know). Adjusting the push rod in the blue direction will give you a softer (spongy) pedal.
*Note: The only place that I could see the master cylinder leaking would be in the foot well on the drivers side. If you don't have brake fluid leaking onto the floor in the foot well or if you remove the rubber boot and don't see any brake fluid, then it is most likely not your master cylinder. You likely just need to make this adjustment.
I have 3 follow up questions:
1) Any advice for knowing the right amount to adjust or is it just trial/error?
2) Will it be obvious if I've gone too far and the brakes are now slightly on all the time?
3)
OK, googled #3, but my guess is that people just estimate tightness most of the time.
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1) Honestly, i just did trial and error. While you're adjusting you can use your hand to feel the pressure on the brake pedal. I found the sweet spot by just adjusting a bit, and then putting the truck in reverse and drive and going back and forth only about 10 feet until i found an adjustment setting i liked. I would recommend a low speed 5-10 mile drive to confirm you like how you adjusted.
2) Yes. Make sure the brake booster pump has completely pressurized the system before you confirm your final adjustment. I did mine a little too tight and it felt good at first, but after a 5 mile drive, all of a sudden my brakes were constantly applied. This was obvious because it took a lot of engine power to get the truck moving. The sweet spot I found was that you will still have some play in your pedal. I had about 1/4" of pedal travel before I got stopping power. I guess it's something i'll have to live with. However, before I had to press the pedal about 1.5" before getting any brakes, much improved.
3) That's just a recommended torque value. In this case you can just hand tighten with a wrench.
- Thread starter
- #118
Trial and error is not the best way to go about this, getting this wrong can lead to brake failure.
The FSM manual covers THREE pedal measurements in adjusting and checking operation of brake system.
Pedal height, freeplay and Reserve distance are specified.
While you can tell heavy drag by feel you can not tell light drag that may leave your pads and rotor so hot they lose their efficiency.
Best to have the FSM in hand when doing this adjustment. This adjustment does not hide issues and FSM mentions that if some of the adjustments can not be made to spec that other areas of brake system need to be addressed. I see that @Eliot posted the part of the FSM on height, if you undertake this you should also check the FSM for the other two.
The FSM manual covers THREE pedal measurements in adjusting and checking operation of brake system.
Pedal height, freeplay and Reserve distance are specified.
While you can tell heavy drag by feel you can not tell light drag that may leave your pads and rotor so hot they lose their efficiency.
Best to have the FSM in hand when doing this adjustment. This adjustment does not hide issues and FSM mentions that if some of the adjustments can not be made to spec that other areas of brake system need to be addressed. I see that @Eliot posted the part of the FSM on height, if you undertake this you should also check the FSM for the other two.
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@Skidoo You make good points. I went to attempt this today and stopped after realizing I don't think it's quite so simple.
1. The FSM seems to indicate the verification of correct MC "pre-tension" or starting location is solely based on pedal location. To measure the pedal location accurately you have to remove the carpet from that area to get your floor reference point. It's hilarious to me that they call out the measurement to three decimal places in inches. Nobody is going to adjust that pedal with that kind of accuracy.
2. Adjusting the push rod without using the pedal height measurement seems risky. Determining if there's a small amount of contact or pre-tension on the pads at various temperatures is nearly impossible and if you're dragging your brakes ever so slightly you can really wear them without really realizing it.
3. If your pedal is already low (mine seemed to be at the bottom of the spec at best) the FSM seems to indicate you need to address why the pedal pressure isn't building up as quickly as it should via other complicated tests and bleeding processes. The Reserve Distance measurement seems like it would be very telling, too. If the pedal height is correct and you fail the reserve distance then the master and booster aren't capable of providing stopping force they're meant to.
I compared the tests for the hundy with the tests for my 90 Supra... The Supra tests are a few pages in total. The hundy has a few dozen pages, half of which require SSTs or service computers.
So trial and error has worked for me and has caused no noticeable issues with 5 months of daily driving. This does not mean there isn't an issue. As @Skidoo and @suprarx7nut have said, I could have my brake pads dragging slightly and not even know. I also could have adjusted the system to spec by luck. My luck is terrible so I doubt it. I just wanted to post to agree with these two that trial and error is not the way to go about this. After reading through the entire process in the FSM, it has become obvious to me that this process is much more involved than just adjusting a nut and a screw on the MC piston and it is very important to adjust this system to spec.
