losiglow

iTrader: (1)

So my brakes have been getting a little spongy over the last 6 months for so. A full bleeding helped a bit but not much. I decided to replace the master cylinder but didn't want to fork out the $180 for OEM, so I purchased a Raybestos from Rockauto. I installed it last night without much of a hiccup. After install however, the brakes were sticking pretty badly after heating up. It got eventually so bad that the car would barely move in 1st gear at full throttle. I pulled over and my passenger side front rotor was glowing red. I had to call an Uber to get home and get some tools. Once I got back to the car, I took the tire off and released some of the fluid from one of the bleed valves. It squirted out pretty fast, so apparently there was a lot of pressure in the lines. After that, I was able to get home, trying my best not to use the brakes more than absolutely needed since they were starting to stick again. It was nearly 1:00am by then since we had gone to see Solo last night and I didn't have time to dick around, so I just reinstalled the old MC and called it a night. It worked fine - still spongy but no caliper sticking.

My first assumption is that the new MC is defective. However, I'm not ruling out that I may have installed it incorrectly. I bench bled it before install but didn't hold the piston very long like some tutorials recommend. However, I bled the whole system really well so I don't think air is an issue. The pedal was super stiff after install so it's as if there's just a ton of pressure buildup both in the lines and cylinder. Possibly a sticking piston or something? Any ideas? Oh, and any ideas on how to eliminate the sponginess of the original MC? Maybe I'll just go that route. It's not so spongy that it goes to the floor. I can still lock up the brakes. But I have to push it down at least halfway before it really grabs.

Oh, the silver lining is that the front passenger side rotor was either warped or the pad material wasn't distributed correctly when I bedded them. Apparently it was pad material because after torturing it last night, I no longer have brake pulsing But it's still spongy which is super annoying.

justnspace

iTrader: (1)

because of noob reasons, I had to replace my master cylinder..
then because of other noob reasons, that master cylinder failed...
when taking off the first one i installed...I noticed two gaskets...on the shaft...that's wrong! lol
make sure you only have one gasket! it kinda sticks to the firewall, that's why I didnt notice it the first time.

losiglow

iTrader: (1)

I had the opposite problem. I remove the old gasket off the brake booster and didn't put the new one on so I ended up with a vacuum leak and had no power brakes. But once I took it back off and installed the gasket it worked fine. A little too fine is the problem though. I can't figure out what the heck would have caused it to build up pressure. It's almost as if the master cylinder would only allow fluid to be pumped out instead of sucked back in.

I'm going to try to bench bleed it again and then reinstall it sometime, maybe on Monday.

Rancher2005

Did you bleed the calipers in the order Acura suggests? I think it's not the conventional method where you start nearest the MC instead of farthest away first. Please check me on this. I thought it was odd.

losiglow

iTrader: (1)

No, I bled from the front driver, passenger then rear driver, passenger. That's the way I've always done it, but not with a new MC. I'll have to look it up in the tech manual.

losiglow

iTrader: (1)

I narrowed the problem down. It's the brake booster. Not the MC. I thought I had solved the problem after dinking around for 5 hours with the MC yesterday, which included installing and reinstalling the old and new MC, bleeding the system several times, even tearing apart each MC and using different components in each to try to narrow down what internal part was bad. On my way to work, sure enough, the brakes started binding again. I stopped at the side of the road and tried to figure it out. I knew it wasn't the calipers because all of them were sticking, and only when the brake fluid started heating up. I knew it wasn't clogged or kinked brake lines because all of them bled with no problems. And I couldn't imagine how it would be the MC since I tried every combination of both the old and the new with no change. The only component left was the brake booster. But from what I understand, when a brake booster goes bad, the opposite effect takes place: spongy brakes, pedal not returning after pressing brakes, etc. However, it was the last thing to try. So I disconnected the vacuum from the intake manifold and got back on the road. Sure enough, No binding! Granted, I had to press on the brakes pretty hard to stop without having any assist, but absolutely no binding. I confirmed this by monitoring MPG, which totally sucked when the brakes were sticking, but was perfectly normal once the vacuum was disconnected from the brake booster.

Anyway, I guess I have a bit of work cut out for me. I'm going to check the gasket on the booster as well as the check valve (if it has one). If that's all good and it's still doing it, I'll probably have to get a new booster.

losiglow

iTrader: (1)

Just wanted to update to confirm the problem. I Replaced the brake booster and voila, problem fixed. I purchased a used one on eBay from a scrapped 2013 TL that had 50K miles on it. Way cheaper than dealer prices. It was a pain to get the old one out but once it was installed and the system bled, the pedal is nice and firm. Hopefully this is helpful if anyone has a similar problem. It may not be your master cylinder but your brake booster instead. Logic would point to your master cylinder first, but if that doesn't work, try the brake booster.