Replace master cylinder and bleed the brakes. Do not use synthetic fluid as the ABS does not work well with it. I like Ford high performance fluid. Twice the boiling point of regular brake fluid.
Thoughts on potential brake issue
New CTS-V owner. Had the car for almost 3 weeks now and counting the long drive from PA to GA to bring it home, I've put about 1,500 miles on it since I got it. That's plenty of time to get a good feel for some essential items -- including the brakes.
The issue I am having which seems to have just started last night is the brakes are stopping the car on initial application of the pedal but if I continue to sit still (stoplight, etc.) the car will start to creep forward and I need to push the pedal down further. It eventually works its way almost to the floor. I wasn't having this issue prior to last night. Once I noticed what was going on, I did take it out and perform a number of hard stops (to the point of triggering ABS in one instance) and it stops. The sharpness doesn't seem quite as good as it was, but it stops just fine at speed. This morning on the drive to work, stops just fine but same persistent issue with the pedal not holding at a stop.
There are a couple things that come to mind, but wanted to get everyone's input on where to start with this. Had I not been familiar with the feel before last night, I'd be questioning if this was "normal" because the car still stops but there's a noticeable difference from today and the braking feel I've had for the first 1,500 miles. Any thoughts before I start the process of bleeding?
The issue I am having which seems to have just started last night is the brakes are stopping the car on initial application of the pedal but if I continue to sit still (stoplight, etc.) the car will start to creep forward and I need to push the pedal down further. It eventually works its way almost to the floor. I wasn't having this issue prior to last night. Once I noticed what was going on, I did take it out and perform a number of hard stops (to the point of triggering ABS in one instance) and it stops. The sharpness doesn't seem quite as good as it was, but it stops just fine at speed. This morning on the drive to work, stops just fine but same persistent issue with the pedal not holding at a stop.
There are a couple things that come to mind, but wanted to get everyone's input on where to start with this. Had I not been familiar with the feel before last night, I'd be questioning if this was "normal" because the car still stops but there's a noticeable difference from today and the braking feel I've had for the first 1,500 miles. Any thoughts before I start the process of bleeding?
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First and foremost, thank you. Second -- well, crap. The car has 14K miles on it. Is that truly an indication of a permanent MC failure or is it your opinion that starting with the MC replacement is the easiest/most likely best path to resolving the underlying issue?Replace master cylinder and bleed the brakes. Do not use synthetic fluid as the ABS does not work well with it. I like Ford high performance fluid. Twice the boiling point of regular brake fluid.
Also, thanks for the detail on the fluid -- that comes as a surprise to me. My "go to's" for my track car has always been the ATE Superblue (now ATE Type 200) and Motul RBF 600. Guessing I definitely want to stay away from those on this car?
Motul is great too. I have had lots of old cars with leaky master cylinders. The seals fail internally and bleed off pressure like you describe. My Corvette is 30 years old and it did exactly as you describe. Check out rock auto and get a master cylinder and some fluid from the local dealership. Cracks me up when I go into Ford and the guys don't know what they have. They try to sell the regular fluid in the blue label bottle. The High Performance fluid is red label. They have both DOT 3 and DOT 4 now.
You can try just bleeding the brakes with a quality fluid first and see if that does the trick before diving into a brake master replacement. Motul is a great option, RBF600 will be more than adequate in a street car but if you want to hit a road course with it I would be looking for Castrol SRF.
Thanks for the detail. It is definitely in the plans to hit the road course in the future, however I haven't fully sorted out my brake mod plans for that yet (pads, upgrading to stainless lines, fluids, etc.). The Castrol SRF looks like the absolute top tier option for a road course car, however I may stay a little lower on the cost in attempting to see if fresh fluid and a bleed resolve the current issue.You can try just bleeding the brakes with a quality fluid first and see if that does the trick before diving into a brake master replacement. Motul is a great option, RBF600 will be more than adequate in a street car but if you want to hit a road course with it I would be looking for Castrol SRF.
Thanks for this additional detail. Let's see -- 30 year old Corvette equals LS1 C5. My track car is a 2002 Camaro SS (same LS1 platform).Motul is great too. I have had lots of old cars with leaky master cylinders. The seals fail internally and bleed off pressure like you describe. My Corvette is 30 years old and it did exactly as you describe. Check out rock auto and get a master cylinder and some fluid from the local dealership. Cracks me up when I go into Ford and the guys don't know what they have. They try to sell the regular fluid in the blue label bottle. The High Performance fluid is red label. They have both DOT 3 and DOT 4 now.
The fact its behaving differently than it was before and is now bleeding off pressure that it was holding before yesterday does seem to indicate a seal of some form is just not holding the way it was before. I can do a bleed here with no issue at all if I can convince my wife to help me, however I'd probably take it to my buddy's shop for a MC install if that's the path we need to go. Will start getting my ducks in a row for that. If you don't mind my asking, how long did this persist on your Corvette before you solved it with the MC replacement?
I screwed up and bled the Corvette with synthetic fluid and the ABS went nuts. Reading a corvette magazine and it suggested Ford High Performance brake fluid. Pedal felt is great and as hard as you track the car the fluid holds up. I have Baer brakes all round.
If the brake system isn't holding pressure, IMO the problem is more likely a MC seal than the fluid. I could imagine maybe the wrong fluid (too low a weight) could contribute. But I'd expect that to be a problem only after the system was good and hot, not when it was still cold as described...
In all my years of wrenching, a pedal that sunk slowly to the floor has always been a bad Master Cylinder. One or both of the brake circuit rear seals starts to leak, so you get decent brake action (maybe with a slightly spongy feel) when you step on the pedal, and when you keep your foot on the pedal, the fluid pressure leaks past the seal and into the equalization port on the back side of the seal where it returns to the reservoir, and the pedal slowly descends to the firewall.
It's an unusual failure on a low mileage car, though, unless someone put the wrong kind of fluid in at some point in the past and that degraded the seal(s).
Also, I wouldn't trust it. The seals are rubber (of some kind). If they're leaking because they're degraded, that failure mechanism could progress to a tear (especially under hard braking) and if one does tear, you'll lose brake function on that brake circuit completely.
In all my years of wrenching, a pedal that sunk slowly to the floor has always been a bad Master Cylinder. One or both of the brake circuit rear seals starts to leak, so you get decent brake action (maybe with a slightly spongy feel) when you step on the pedal, and when you keep your foot on the pedal, the fluid pressure leaks past the seal and into the equalization port on the back side of the seal where it returns to the reservoir, and the pedal slowly descends to the firewall.
It's an unusual failure on a low mileage car, though, unless someone put the wrong kind of fluid in at some point in the past and that degraded the seal(s).
Also, I wouldn't trust it. The seals are rubber (of some kind). If they're leaking because they're degraded, that failure mechanism could progress to a tear (especially under hard braking) and if one does tear, you'll lose brake function on that brake circuit completely.
Could be contaminated fluid. Brake fluid is hydroscopic, if it’s sitting a long time it could absorb water and attack aluminum surfaces.
Sent from my iPhone using Tapatalk
Sent from my iPhone using Tapatalk
These cars don't like sitting, as Karch alluded to.
Mine was a low mileage car (under 5k) in its first five years...and had to do rear shocks within a couple of thousand more miles.
So entirely possible for water in the brake fluid or seals. Start with the easy.
Mine was a low mileage car (under 5k) in its first five years...and had to do rear shocks within a couple of thousand more miles.
So entirely possible for water in the brake fluid or seals. Start with the easy.
Thanks for all of the insight on this one. I found a new AC Delco master cylinder for $92 so not much of a cost deterrent to just replacing it. Certainly a possibility there's really old fluid in there that needs to be changed, however given the fact the brakes were solid before yesterday and now they're not I went ahead and pulled the trigger on purchasing it. Should be here early next week. I'll get it installed and will report back.
Hopefully this fix is easy enough and I can come back to the planning for future track-oriented brake upgrades.
Hopefully this fix is easy enough and I can come back to the planning for future track-oriented brake upgrades.
Good news update: Replaced the master cylinder and gave it a good bleed with ATE Type 200 DOT 4 fluid and the brakes are good to go again. Solid pedal with good feel and it's no longer bleeding off pressure when sitting at stop lights. Thanks all for your help and pointing me in the right direction on this fix.
Still some work to be done before the brakes are track ready (primarily focused on the pad upgrades) but at least the fluid situation is much better prepared for track duty.
Still some work to be done before the brakes are track ready (primarily focused on the pad upgrades) but at least the fluid situation is much better prepared for track duty.
Did you buy OEM master cylinder or…. Figure I should get one now and avoid the pain in the future…
Yes, bought the AC Delco/OEM one off of Rock Auto for $92 + shipping. I didn't have the time to get the work done myself so had a local hot rod shop do the work and it was $150 in labor. Already had a new bottle of ATE DOT 4 fluid at home so "all in" this was probably a $270 fix. Definitely one of those rare repairs where the cost came in substantially lower than what I was expecting.Did you buy OEM master cylinder or…. Figure I should get one now and avoid the pain in the future…
Awesome, I will be making the purchase from Rockauto...
I got a good deal on a used 2002 Camaro SS at an online auction because I used Live Video Streaming, so I can see the condition of the car. For now everything is perfect, but I am already preparing for the future issues. Information about fluid is very useful, thanks
Good information here. Before I parked my car, I had noticed the brake pedal slowly creeping towards the floor at prolonged stops.
I have planned to replace the brake lines and flush the system, but I guess it couldn't hurt to include a new MC. My car has very high miles.
Did you have any subsequent ABS issues after bleeding the brakes?
I have planned to replace the brake lines and flush the system, but I guess it couldn't hurt to include a new MC. My car has very high miles.
Did you have any subsequent ABS issues after bleeding the brakes?
Awesome! If you aren't already on LS1Tech, it's a great place to tackle any issues that arise on the F-body. The 10-bolt rears are a huge weak link so limit the sticky tires unless you plan to upgrade it or deal with the regular rebuilds. I fought with it for years and never dumped the clutch at high RPM at the track for fear of shredding another one -- finally bit the bullet on a Dana S60 and it's been a complete gamechanger in the enjoyment I get from the car. Aside from the rear, the issues they have are relatively minor and typically cheap to fix. My 02 SS feels like a tin can compared to the CTS-V. It's lightweight, irreverently loud and you smell like fuel when you get out, but it sure is fun on the track. Enjoy yours!!I got a good deal on a used 2002 Camaro SS at an online auction because I used Live Video Streaming, so I can see the condition of the car. For now everything is perfect, but I am already preparing for the future issues. Information about fluid is very useful, thanks
None at all so far. As I would expect most on this site would do, once the brakes were "fixed" I felt obligated to confirm there were no lingering issues. Passed on all tests. The weather around here hasn't been great so I haven't had the car out long enough to brake from higher speeds and really get some heat in the system, however that will come soon enough.Good information here. Before I parked my car, I had noticed the brake pedal slowly creeping towards the floor at prolonged stops.
I have planned to replace the brake lines and flush the system, but I guess it couldn't hurt to include a new MC. My car has very high miles.
Did you have any subsequent ABS issues after bleeding the brakes?
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