Air in brake line

This depends on how low it got and if you have air in the system.

Do you have a pedal that goes to the floor or a soft pedal? Here is a guide that helps with this:

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

If there was still fluid in the reservoir then you should be fine. However, if you are concerned then here is a guide that will help with bleeding the system:

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

However, the reason the fluid gets low is due to a leak or brake pads are low, so we need to check the pads and find out if they are worn out. It is not a good idea to just add fluid as that is an indicator or a possible issue.

https://www.2carpros.com/articles/how-to-replace-front-brake-pads-and-rotors-fwd

https://www.2carpros.com/articles/how-to-replace-rear-brake-pads-and-rotors

Please run through this info and let us know if there are questions. Thanks

Okay. Just trying to confirm the progression. You replaced the pads and calipers and the fluid was low at that point? Then you bled the brakes and it was still soft. Then you start the engine and it still feels soft but it will be firm when the engine is off?

If this is the case, you may still have air in them. I would suggest starting over and bleeding the master in the vehicle. You do this by taking the lines off and routing lines back into the mater and then pump the brakes. If you get a bleeding kit then it will have clear lines so you can see if there are any bubbles coming out but you just pump it until you see two or three in a row where it is solid fluid. Then reconnect the lines and bleed all of them again. Starting with the right rear, left rear, passenger front, driver front.

Also, when you have the lines off and after you bleed the master if you want to confirm it is ok and there are no leaks internal to it, just cap the lines with bolts and press the brakes. You should have a hard pedal. If not then you need to replace the master. Just make sure you use bolts that are the same length or shorter then the threads on the brake line nuts. Otherwise you could crack the master then it needs to be replaced.

Let me know if you have questions on this. Thanks

You cannot 100% bleed a master unless you take the brake lines and route them back to the master because you have no way of closing a bleeder screw to release the pedal.

So if you crack the lines loose and push the pedal, you will have brake fluid everywhere, and then tighten them again before you release the pedal, there is no guarantee that the air came out and didn't just go into the line.

I think this could cause more issues if we try to find other ways to do this. They may work but if the issue is not fixed, then we can't truly cross it off the list.

Next when you bleed the master and then remove the bleed kit to reinstall the lines then yes. There is a chance that air is back in the lines. It will not get into the master as long as you don't press the brake with the lines off. So once you install the brake lines again, you must bleed each wheel again to ensure there is no air in them.

You are welcome. Please let us know what you find with this and we can go from there. Thanks

Not a problem. Please just keep this link that gets emailed to you and whenever you get back to it, just updated us with the good news that you got it resolved. We will be here when you get back to it. Thanks for the update.

That is progress. Thanks for the update. Please let us know after you get the booster.