A friend borrowed my truck and left it with the brake pedal stuck in the down position! Is this bound to be a brake vacuum issue or is there a return spring in the cab to bring the pedal back to the 'rest' position?

Thank you.
Flickit

 

A brake booster issue. There is no external return spring for the pedal.

 

Thank you!

Flickit

 

So we replaced the brake assist drum and the master cylinder and still the pedal stays down. My friend mentioned some electronic device that needs to be replaced that has something to do with the ABS.

Any idea what this is called and where to find it?

Thank you,
Flickit

 

Nope. Won't matter. You have a mechanical issue, not an electronic issue. Check the pivot for the brake pedal.

 

What HeyYou said. The pedal should "float" freely. Either the pushrod is getting stuck in the booster/firewall and/or the pivot has issues.

 

Was your friend towing without trailer brakes, maybe? That could cause someone to stand on the brakes hard. You might be leaking brake fluid somewhere. Check the lines going everywhere and fluid level. Check up by the ABS unit too. Pull the wheels off and check the calipers. Spin the wheels while on stands, see if anything is locking up.