Brake pads squeak - PeachParts Mercedes-Benz Forum

milterino · #1 07-22-2003, 03:57 PM

76 450 SEL. I have installed new pads on all wheels and the brakes squeak. Bought something called disc brake quiet which is to be applied to the steel backing. Is this the way to control the squeak and is it normal for them to squeak? Milterino.

gmask · #2 07-22-2003, 05:02 PM

Quote:

Originally posted by milterino
76 450 SEL. I have installed new pads on all wheels and the brakes squeak. Bought something called disc brake quiet which is to be applied to the steel backing. Is this the way to control the squeak and is it normal for them to squeak? Milterino.

It is normal for new pads to squeak. Although I thought you were supposed to apply the anti-squeal paste to the sides of the pads so that it would slowly apply itself to the pads and the disks and lubricate them so that they didn't squeal.

milterino · #3 07-23-2003, 01:33 AM

Gmask: Thanks for your reply. You may be referring to another product. This stuff is called "Disc Brake Quite" and the instructions are. Apply liberally to the steel backing of each outboard pad. Spread evenly over entire surface. Disc brake quiet should not be applied to the brake lining. Then they say to apply a strip of it to the steel backing of each inboard pad. This stuff is sold by "Carquest". Perhaps someone has used it and can give me their results. Milterino.

gmask · #4 07-23-2003, 02:56 AM

Quote:

Originally posted by milterino
Gmask: Thanks for your reply. You may be referring to another product. This stuff is called "Disc Brake Quite" and the instructions are. Apply liberally to the steel backing of each outboard pad. Spread evenly over entire surface. Disc brake quiet should not be applied to the brake lining. Then they say to apply a strip of it to the steel backing of each inboard pad. This stuff is sold by "Carquest". Perhaps someone has used it and can give me their results. Milterino.

Huh... maybe it squeezes out the sides?? definatley follow the drections.

psfred · #5 07-23-2003, 09:59 PM

Pull pads. Toss if not OEM, nearly all the aftermarkets will scream forever. Textar are the best, according to Hans, for the rears, but Padgid will work too.

Clean the slots in the caliper where the pads ride. Must remove all the corrosion and rust, old pad dust, etc.

Clean backing plate carefully -- OEM pads already have a plastic coating (that's not paint on there!) to reduce squeal. Coat the back of the pad where the piston contacts it and the sides ONLY of the backing plate with antiseize (the sliver stuff). Never get anything on the surface of the pads -- lubricated brake pads are far too exciting for me!

Re-install pads. I also put a tiny dab on the antirattle spring/pin interface, also the points were the spring sits on the pads.

No squeal.

Avoid non-OEM brake pads for older cars, they almost always give you fits.

Peter

milterino · #6 07-24-2003, 01:03 AM

Thanks to psfred. I assume that Textar and Padgid are the brand name of brake pads and will investigate. On another subject a friend is going to change over my air conditioning fluid to the new cheaper variety. Any comments on that? Milt.

psfred · #7 07-24-2003, 01:27 AM

Textar and Padgid are brand names. Check the FastLane catalog for the correct ones.

Use only R12 or R134a for AC, the others are various mixture of the Freons and hydrocarbons, usually explosive if vented, and I've seen some information that indicates they aren't all that good for the internals.

Hydrocarbon base AC refrigerants are illiegal in some states, too, on top of the fire hazard.

Peter

Mark DiSilvestro · #8 07-25-2003, 05:50 PM

If you can't find Pagid or Textar brake pads, I've had good luck with ATE pads, availible from some import autoparts stores. Other aftermarket pads are a gamble.

As for the AC, the price of R12 is coming down in some areas. I'd stick with the R12, unless the cost to repair your AC leak is prohibitive. Even if done right, switching an old system to R134a may result in some loss of AC efficiency. Aside from your old AC components not being optimal for R134a, other issues include flushing out the old AC oil and selecting the correct replacement AC oil.
For R134a, there's PAG oil or Ester oil availible in different weights and some controversy as to which is best for retrofitting from R12 to R134a.

As for those other, cheaper 'drop-in' R12 replacements such as 'frigiCool', aside from flammability or legal issues, if you dump some of this stuff in your AC and later need to take your car to an AC shop, they may check it with a freon analyzer and then refuse to work on it.

Happy Motoring, Mark

milterino · #9 07-29-2003, 01:13 AM

Mark: the deed has been done, it now has 134a in it. I don't believe my "expert" did any flushing. What went in said it had some additive for the seals and some kind of oil which I suppose lubricates the cooling part of the system. The oil for the actual compressor is different i assume. Is this the oil that you were saying should be flushed? Is the old compressor oil not compatible with the r134a refrigerant? Well, thanks for your imput. Milt.

Mark DiSilvestro · #10 07-29-2003, 03:12 AM

There's no separate AC oil for lubrication of the 'cooling part'. Any oil in the AC system is there for lubrication of the compressor.
Typically, the AC oil circulates with the freon to lube the compressor although some older autmotive AC compressors will carry a few ounces as a reserve but that oil is still continuosly mixing with the freon.

There's been some controversy regarding flushing and types of oil to use with R134a.

Most original equipment manufacturers recommend to use PAG oil and not to flush. GM states that mineral oil (used with R12) and PAG oil are chemically compatible but that what mineral oil that remains after retrofit to R134a will park in the accumulator and evaporator and not circulate with the freon. GM recommends installing an in-line filter as an alternative to flushing.

The aftermarket manufacturers recommend to flush and drain the AC system as much as possible to remove mineral oil and contaminants, replace the accumulator or filter-drier and, if the system has one, the expansion tube.they recommend using Ester oil with the R134a, as it's less harsh on the compressor seals than PAG oil.

I recently repaired the AC on a '90 Ford Explorer, that had been previously repaired elsewhere twice with R134a and PAG oil. I don't know if the system had been flushed but the original compressor had seized and the first replacement had blown it's seal. The expansion tube was full of crud!

I opted to flush the system, install a NEW compressor (which cost less than the previous rebuilt compressor) new accumulator and new expansion tube and refill with Ester oil and R134a. The owner claims it's now been working longer and better than the previous 2 AC repairs.

Let us know how your retrofit works out.

Happy Motoring, Mark

milterino · #11 07-29-2003, 11:16 PM

Mark: Thanks a lot. That's all useful information that you took the time to pass on. The cooling works, or worked as long as I ran a wire from the battery to the clutch. Now I am trying to figure out where the trouble is between the clutch and the dash pushbutton. Also I got the blower apart and am going to get new brushes as they and the comutator? (rubbing surface) were all worn down causing intermittance. So the saga continues. Milt.