New calipers - bleeding tips? Also bleeder screw

[VW1300]

I know there is another thread about brake bleeding right now, but I have a slightly different issue -

I put rebuilt Ate calipers on the back end of my 300D. Also new hoses. I used a power bleeder to bleed them, but the pedal seems softer than it did with the old calipers. I haven't had the car fast enough to determine whether the braking performance is any better or worse.

Question - are new calipers difficult to bleed out, and are there any tricks I can try to get all the air out?

Question 2 - I just about stripped one of the bleeding nuts on the new calipers - I've seen new ones available for the front Ate, but not the rear - does anyone know if they are the same? The Bendix calipers I pulled off had nice meaty bleeder screws, the Ate ones are soft metal crap.

thanks in advance. Also thanks to the member who tipped me off to the O'Reilly rebuilt calipers a few weeks ago - you told me they were $49 - actual retail price was $42! I'm going to do the fronts soon before they stop carrying these things.

[dkveuro]

If you did not have the rotors turned, and you used new pads...pads need to bed in to rotors before pedal will feel right.

As long as each caliper was bleed through the bleeder, there should be no air in the system...BTW...in 45 years of doing this I have never used a power bleeder...seems they make more problems than they solve.

As a FYI. Never just pour fluid into the system when doing brakes...suck out the fluid in the reservoir.....remove the reservoir and clean it out...it can be pried out of the M/C carefully, or buy a new one....there is always dirt in the bottom of the reservoir that will flush down into the M/C and tear up the seals...besides screwing up the ABS if fitted.

.

[VW1300]

I did not have the rotors turned, I measured them and they were well within spec and looked OK. Yes, I used new pads, the old ones were shot.

How long does it take for the pads to wear in and the system feel OK?

What started my back brake rebuild was an inspection of the pads and hoses - hoses were scary, the rubber was very much cracked and I could see the inner tubing...now I'm wondering about my front hoses.

[dkveuro]

Rotors never wear parallel...pads will take 200 to 500 miles to conform to rotor swept surface.

Do not try to accelerate the bedding in....you'll hot spot the pads.

Hoses are relativly strong, taking 2700 psi pressure during hard braking.
However, the outer rubber covering is to stop the inner weave from rotting.
Normal to see cracks at the furrels where the hose bends the most.

If you think the hoses need renewing, do so.

Bleeding from the bleeder is only way to go on Mercedes. Allow the vehicle to sit for 12 hours so all the tiny bubbes in the lines have time to coagulate into large bubbles, then, without moving the vehicle, bleed system again.

Each caliper will require 4 to 6 full strokes of the brake pedal to move fluid from the M/C to the caliper.

Do not start the engine to get power to the servo...needs bleeding with a dead servo.

Use DOT3 fluid.


.

[jbaj007]

Are the calipers on the correct side, so that the bleeder screw is at the top. Won't let all the air out if they're at the bottom.

[t walgamuth]

you did bleed all four brakes after the job was complete?

if not you should since you have softness.

i am not discounting dkeurvos thoughts, just making sure about the bleeding.

tom w

[rbarnes]

Is there any tips about getting the flex hose unscrewed from the hard brake line? I was able to get the caliper off and the flex off of the caliper, but it looks like the hard line wants to turn when pressure is applied. How do you back up the hard line to keep it from turning?
Thanks,

[Stevo]

Originally Posted by dkveuro

Use DOT3 fluid.


.

Did you mean dot 4

[VW1300]

Yes, the calipers are on the correct sides. I know this because I discovered that the hose looks weird when you put the left caliper on the right by mistake...No, I didn't bleed the fronts. I'll try to bleed the backs again later this week, I drove the car around a little bit and it wasn't too bad, maybe the pads and calipers really do need to wear into the rotors.

On a different subject, I also adjusted the valves as part of my spring maintenance initiative. Holy cow! It starts better and runs so smooth now, I can't believe the difference.

Thanks to all for the advice and suggestions.

[dkveuro]

Originally Posted by Stevo

Did you mean dot 4

No.


Although most Mercedes have a DOT4 recommendation I stock and use DOT3 because most all have at one time or another been filled/topped off with 3.
The curse of the Quick Lub places.

It is cheaper too. I suck out the fluid in the resevior, remove it and clean it out.
Refit and bleed system...Do this on all customers vehicles that have 3 or 4 recommendations.

3 and 4 are totally miscable....DOT4 has borates in it...it flows better at low temperatures, which is better for vehicles in cold climates...( Oklahoma is mostly warm.)...especially now ABS etc has become common . Castrol LMA has better lubrication for these electronic controlled systems....or so the ad's say.

Use 3 or 4....either work well. Ford has a Heavy Duty DOT3 at good prices.
Do your homework...there's a lot of information about 3 and 4.
i might concider using 4 soon...I'm happy with performance of 3.

FYI......DOT 4 fluids are glycol ether based, but have a measure of borate esters thrown in for improved properties including increased dry and wet boiling points. A seldom talked about characteristic though is, that because of this chemistry, the DOT 4 fluid will have a more stable and higher boiling point during the early portion of its life, but ironically, once the fluid does actually begin to absorb water its boiling point will typically fall off more rapidly than a typical DOT 3.
.

.

[VW1300]

thanks for the info. Houston is always pretty warm, so I'll stick to Dot 3. I drove my car around tonight, got it up to 50 mph and hit the brakes...it seemed to stop OK so I'm going to drive it to work for a few days and then bleed it again...we'll see what happens.