[todde702]

Sounds more like a power brake booster issue than the master cylinder. The booster should retain enough vacuum with the engine off, for power assited stops, for like 2-3 presses of the brake pedal. The noise you're hearing is probably a vacuum leak.

 

[todde702]

I'm not sure where the diesel is concerned, you may even have an electric or mechanical vacuum pump to drive it or it could use power steering fluid as a hydraulic booster. But the symptoms sound like a vacuum booster that has a leak.

 

[todde702]

Could still be air in the lines. So long as the abs hasn't cycled just more bleeding should fix it. I flushed my old fluid out myself initially using a gravity bleeding, then using an bottle with hose in some new fluid to solo pump bleed it. But i had to get the wife to pump the pedal while I bled the calipers to get a firm pedal.

 

[todde702]

You could try bleeding it at the master by having an assistant pump up and hold the pedal, then crack the line loose to see if any air comes out.

 

[todde702]

The brake light switch is an oddity. The first time I replaced mine I took the oem one apart to figure out why and found you probably could reassemble it back into it's factory setup to auto-adjust, but it's finnicky to do it. Thankfully they are a cheap enough part. I'm on my third one now and can confirm that it can cause a lightning bolt light too depending on how it fails internally.

 

[todde702]

Give the contacts a little emery or fine sandpaper love and you'll have a spare on hand!