Brake rotor removal question; should I use a heat gun?
 

You can use heat gun. not sure how much good it will do though. No big deal if you strip it, just drill head off and then knock rotor off (if you are replacing rotors).

Using eye protection! Take a punch and strike the center of the bolt inside the six sided hole, not on the face of the bolt, rather hard several times. Then take a pointed punch on the face of the bolt outside of the six sided hole on the flat part in the direction that you want the bolt to turn. If you can, have a helper wearing EYE PROTECTION apply moderate torque using the bit in the six sided hole while you strike it around in the loosening direction. It will come out.

Good luck!!!

HM:

Are you working on the rears? You have not said so.

Are you replacing the rotors? Do you have new ones?
If you have new rotors, place a block of wood thru the caliper opening on the inside face of the rotor. Hit the wood with a hammer to knock the rotor to the outside. Turn the rotor a few degrees, hit again. Turn, hit, turn, hit.

Put PB Blaster around the hub flange...wait a few minutes and do what Frank R said.

First, detergent with fine ScotchBrite, then brake cleaner. Do not use anything that contains oily components.

It depends on what type of coating is on the rotors. The rotors we used to get had some sort of light oil coating that needed to be washed off. But, some rotors these days have a rust preventing zinc coating. The ones I last installed said to leave it on.

Brembo says:
Huskyman, you should find out and advise just what type of coating you have.

If it is zinc, this link has some good info. If plain steel with oily surface coating, Frank's advice is good.

Use the brake cleaner on the rotors. Use a wire brush, preferably a wire wheel and drill, on the hub to get the rust off. Then use a light coat of grease on the hub to keep the rust off and to keep the rotor from rusting on the hub in the future. This trick works amazing. I even apply a very thin coat of white lithium grease to the hat of the rotor to keep it from rusting. It works amazing, just dont get any on the part of the rotor where the pads rest.

Install both pads, and one of the pins. Then slide first end of spring under the pin. The 2 short ends of the spring rest on top of the low part of the pads so that the top of the spring is flush with the edge of caliper. Next, press down on the other end of the spring and slide the other pin through the caliper hole and brake pad hole and over the other end of the pin.

HuskyMan, the gray primer on the rotors should be left as-is. Braking will remove the primer from the brake pad contact surface only, and the other surfaces will not rust.

When hammering on rotors to loosen them, it's best to install one lug bolt a few turns to prevent the rotor from flying off.

Use blue thread locking compound on the caliper bolts.

Sounds like you have uncoated rotors - follow Frank's and Brembo's advice to remove the light oil film.

You need a dial indicator to check run-out. Not a dial caliper ;)

Lot's of links on net on how to use and you can buy a cheap and adequate one at HF. You also need the magnetic base that they sell separately.

https://www.youtube.com/watch?v=6SbWB2CNqio

If you buy high quality rotors you shouldn't need to check the run out with a dial indicator. Out of the box they should be true and straight. If they are not, return them immediately and buy genuine MB rotors.

Typically you get what you pay for. You cannot purchase a MB vehicle for the cost of a VW.

Hopefully the Brembos he has are of good quality.

They should be! Besides, run out is not only to do with rotor quality. It is also affected by installation. Cleaning up the hub surfaces, properly torqueing stud bolts, wheel bearings, etc.

Shops don't often check runout, but it is so cheap and easy to do, why not!

How do I remove front disc retainer springs?
 

With the 2 pins punched out the spring clip has to come out by itself, might just need a light tap due to the rust.

Manually spread the top end of the calipers or pry up on the spring. It's loose already.

"How do I remove front disc retainer springs?" That is the pad retainer.

It is stuck between the pads, because the pads are completely worn out, and the tops of the backing plates have been forced against the retainer spring by the pistons, which are stuck in the caliper bores, preventing their retraction.
Get a prying tool under the spring, use excessive force, and pop it out.

Yes.

And it is the pistons that are against the pads.

They have threadlocker on them. A little heat will help soften that. I used one of those small pencil butane torches to heat the bolt head and that helped. Can't really recall, but I think I have used a piece of pipe to get extra leverage on some brake jobs. (maybe impact gun on others - but is there access)