Hello 

First of all greetings to all the fans of the Scotty Kilmer  community!

My questions are the following:

1.Is there a relation between oil level and the amount of vacuum the engine makes to the brake booster (considering all the hoses are intact and the check valve is functioning properly) on a v6 petrol engine? 

2. I have performed tests on my brake booster (pumping the pedal while engine off, keep depressed and start engine - pedal drops)

(run the engine, turn off, press the pedal several times, every time the pedal stops higher than the previous)

(run the engine, press the pedal, switch off the engine, keep the pedal depressed, the pedal doesn't drop after 30 sec)

All passed. The only issue is engine misfiring when I press the pedal. If I clamp the vacuum hose between the check valve and the brake booster and press the pedal, no misfiring.

It turns out I drove the car with this issue a couple of months, no problems. Changed the old brake pads with new, no problems. And suddenly after I changed the oil and filters a couple a days ago, my front brake calipers seized up both the next day (I filled in the oil between the max/min on the dipstick, before that it was slightly over the max level).

After performing the tests on the brake booster, now the callipers are ok. I haven't driven the car since then (I checked by jacking up the car and rotating the wheels, it's a rear wheel drive).

What could be the issue?

Thank you!