Wheel Lock and Happy 4th!

[lash]

Happy 4th of July to all US people out there! Was grilling at my mothers today and tried to take my sisters car for a drive. She has been away for about 3 months and has a 2010 Gen 2.0T coupe. The car starts fine, goes into gear, but the rear passenger tire spins, rear driver seems locked. Put in neutral and tried to push....nothing. Tried reverse, 1st, and second...nothing. anyone heard of this before?

 

[mikec]

Sounds like the brake on that wheel has rusted in place. Try this:
Chock the opposite front wheel.
Release the parking brake.
Transmission in neutral.
Use the jack that came with the car and jack that wheel up.

You should be able to rotate it by hand. If it rotates just a teeny bit either way, it's probably not brakes but something jammed in the drive line (differential most likely, or wheel/hub bearings). If it won't budge at all, the brake caliper is probably jammed in place. That can happen from:

a: interior damage to one of the rubber brake lines going to the caliper. Imagine a "hangnail" of rubber on the inside of the hose... that flap of rubber can act like a one-way gate allowing brake fluid pressure to go to the caliper (applying the brake) and then preventing the fluid from back-flowing when releasing the brake. This typically happens when the brake hoses are many years old; it's not something that typically happens on fairly new cars.

b: water in the brake fluid... that leads to rust between the caliper piston and the caliper body which then jams the piston inside the caliper body. Fairly common. Tears in the rubber bellows/boot between the piston and the brake pad are another source of water getting onto the piston surface.

c: rust on the parking brake linkage... jamming that caliper. Also common especially if a rubber boot, typically on the backside (towards center of car) of the caliper is damaged.

d: on most disk brake setups, there is one, sometimes two, pistons on one side of the caliper... the caliper has arms that reach around to the other side of the brake rotor for the second pad. These arms are supposed to slide in/out freely... damaged boots, missing grease, etc. can jam them to the "slide bolts" that support them which makes one of the two brake pads stay firmly against the brake rotor. Cars with multiple caliper pistons - i.e. pistons on each side of the rotor (high performance, more expensive, harder to fit inside the wheel rim, etc) don't have these slide parts. I don't know what style the 2.0T coupe uses on the rear brakes...

e: if a brake pad was dragging (due to other brake problems or leaving the parking brake on while driving), or the pads were really worn out, eventually the pad material will wear away completely which then allows the metal backing of the pad to rub against the brake rotor. VERY VERY NOT GOOD! This metal-on-metal creates a ton of heat - destroying the rotor quickly - and often results in molten metal blobs that jam/weld the rotor and pad backing together. If this has happened, many times you'll see grooves cut into the disk. Imagine taking a screwdriver to a record as it plays... pretty much the same thing. (yeah, I know - "what's a record?")

mike c.

 

[lash]

Thank a lot for the detailed response, appreciated. I will return to my mothers this weekend and jack the car up!