Hi. I have a 2000 blazer. It sat for a year. I had to replace the brake lines. Put new calipers all around. After I got the lines bled I thought maybe the pedal was more stiff than I remember but wasn’t sure. Drove around for about 5 miles and got a non flashing P0300 code. Never got that before. Noticed front brakes were warm. I erased the code thinking old gas would cause it to get that code. On my way to get wheel alignment the engine light started flashing P0300 code and my brakes were smoking only on the front wheels and pedal super stiff. I think it’s a vaccume related issue and hopefully something stupid and easy. The engine runs great. Thanks for the help in advance.

 

The only way I could see the P0300 being related to the brakes is if you had a vacuum leak through your brake booster, or the vacuum line itself was cracked/disconnected. Your engine wouldn't run great, though.

I have seen the dragging brake problem caused by the MC piston not being allowed to fully retract for one reason or another (pedal or booster pushrod too long), or from using the wrong "brake fluid" (ATF in a couple of cases), which caused the rubber parts to swell and not allow the calipers to retract.

 

I used brand new dot 3 fluid. But even if my calipers were causing it to lock up then why would my pedal be extremely stiff?

 

A lack of vacuum at the booster (bad hose or diaphragm) would definitely cause your pedal to be stiff, but it should make your engine run like crap. It sounds like pressure is building up in your front brake system and partially applying the brakes. Try cracking the brake line at the master cylinder and see if it's holding pressure when it shouldn't be. Also, your reservoir isn't overfilled, is it?

 

It is slightly above the max and I noticed when I i took off cap the rubber was like sucked inside out. I’ll take some fluid out.

 

It's probably not your problem unless it was so full that it built up pressure in the reservoir when it warmed up, but it's still a good idea to not have too much.

If you crack the brake line and pressure escapes, and the brakes stop dragging, the next step would be to make it build up pressure again, then loosen the nuts holding the master cylinder to the booster so the master cylinder can be pulled away from the booster 1/4" or so. Don't try to drive it like that! If that causes the pressure to release, then either your brake pedal isn't returning all the way or the pushrod on the booster is too long. But pushrods don't suddenly grow longer so, unless you've recently changed something, I don't see how that would be the problem. I would definitely make sure the pedal isn't hanging up on something.

 

Pedal for sure isn’t hanging up and the only thing i did brake wise was brake lines, calipers, discs and pads

 

Well, I'm stumped. I assume everything fit together easily? You didn't have to force the caliper over the rotor or anything?

 

Would pressure building up in the brake system from to much fluid cause the vaccume to not be right and cause the p0300 code?

 

I go back out there and the brakes seem fine again and the code isn’t flashing just on