Brake problems

[wiski]

First things first. This is not regarding a mustang, but brakes are brakes, so here goes ... I've got this 90's Nissan Sentra and its got messed up brakes. I just replaced the pads (which weren't that bad) but the pedal still sinks down most of the way to the floor when I press on it. When it does engage, it does so decently but I don't find it satisfactory. I thought about bleeding the lines, but I didn't think that there could be THAT much air in the lines. I did add about a half of a can of brake fluid to the MC (it was below the min level by a just a bit)



Thanks!

 

[b1gp1mp1n247]

id bleed the brakes and if that doesnt solve the problem then its probably a bad caliper. is there fluid under ur car after u park it?? if you havent checked for it, then i would check for fluid. cause there may be a leak. good luck

 

[wiski]

I did check around the pistons, the calipers and the lines leading into them. I didn't see any signs of fluid leaking from the pistons, nor did I see any signs of recent fluid leakage on the lines going into the calipers.

 

[HISSIN50]

bleed them anyhow. the fluid is hygroscopic (has an affinity for water). flush them to clean up fluid and remove any air. a mitivac is great for doin this.

also, have you noticed any fluid under the master cylinder (like a trail goin down the brake booster). normally, with a good closed brake system, new brakes are on, and the fluid level is full. brakes wear, level goes down. if you dont add anything, when you do the brakes, as you just did, the level goes back up near full (minus a little amount for rear pad/shoe wear, which is normally minimal). do you have to add fluid to it ever? if so, really check the lines and calipers (as mentioned), and esp the master cylinder. a bad MC seal can lead to loss of fluid and spongey, slow brakes. also, if braking improves when you pump the brakes a couple of times, look further. in any case, fix it. you dont want to operate with barely marginal brakes. one more iota of diminishment could be very bad. good luck.

 

[wiski]

I didn't notice any fluid going down the back of the MC, but to be honest, I didn't even think to look that hard. I understand that if my brakes wear, the fluid level in the MC will fall a bit. When I pressed the pistons back into the calipers I expected to see the fluid level rise, but I didn't see nearly the change I hoped. I did have to add about a half of a bottle of fluid to the MC. (it acutally surprised me how much I had to add since its just a little MC and the fluid level was just below min when I started) I didn't notice the braking improve at all when I pumped the pedal (which was a huge surprise for me)

 

[PRO50SC]

If you pump the brakes and the pedal doesn't get any higher than there is no air in the system. If you pump them and they come up, they need to be bled. Also check the condition of the rear brakes. Are they adjusted properly? Rear brakes that are out of adjustment will cause a low brake pedal.