This was my first time so a read some stuff and watched a youtube video then gave it a try.

I used a 12mm socket to remove the lower bolt and I merely loosened the upper bolt because I had read that the caliper could then be made to pivot up using the upper bolt. This worked well. (I did not mess with those 10mm allen type bolts). I tied the caliper up with string. after this I have a bit of uncertainty and hope I didn't screw up anything.

On inspection I could see that each pad had only one clip - an upper clip. Yet my renewal kit provided two per pad. So: should I have used an upper and lower clip?
Hope so cause that's what I did.

The guy at the store said not to use any anti-squeal goo because these pads don't need it (a recent innovation?). I did not add goo to the new pads.

Now the worrisome part. In order to push the piston back I used a 2 by 2 piece of soft wood to sort of lever it back. There must be a better way! Is there a tool for this?

Then I cut the string to allow the caliper to pivot back and here I had a bit of difficulty. I ended up lightly taping the pads inward so that (finally) the caliper would swing back over them. However, I could barely hear the soft rubber from the piston dragging against metal (or maybe the pads) and I was worried I might damage the rubber. I don't think I did but would this cause a fluid leak if I did?

Finally, I could not quite get the lower bolt alligned to go back in until I first loosened the upper one. Does this mean that I should have instead merely removed both of those bolts. I believe the Haynes manual says to just remove the lower one.

One more thing: do most folks extract some brake fluid from the reservoir to prevent overflow when the piston is pushed back? I did not but I can see how this might be needed. Just wondering about that.

I am going to do the other side tomorrow.

I did a quick scan of the comments and did not see anyone addressing the issue of pushing the pistons back on an ABS car. I am under the impression that with ABS cars you do not want to force brake fluid back towards the reservoir as in doing so risks damaging the ABS.

Opening the bleeder (and perhaps clamping the brake hose closed) will allow the fluid to exit the bleeder rather than being forced back toward the master cylinder.

Thanks for posting this. I can't believe I forgot that... ABS is the real reason NOT to push fluid back into the hose.

hi sages- never heard this item about abs brakes, but would like to hear it expanded on and explained from the voice of experience . did front pads on a 92 245 and a 01 merc marquis; pushed piston back in and have seen no problem or loss of function or red warning lights requiring a $500+ job at the shyster shop. im all ears. thanks tons oldduke

Have been wrenching for many years, 40+, always squeeze/push the caliper piston back, ABS or not, the fluid backs up, never any issue afterwards!

So where does this fear of old fluid backing into the ABS and MC come from?

While I am unable to cite any real authority that warns against damaging the ABS equipped cars by pushing the pistons back without opening a bleeder valve it is mentioned in our own FAQ's and I have read it other places on the Internet. It is not a bad practice.

If you were to open a bleeder while pushing the pistons back you might notice the fluid is usually dark (perhaps contaminated?). Why would you want to keep that fluid in the system?

Randy

hi stark- very good point. so far i have found no one who can explain to me why or how mechanically pushing the caliper piston in on a pad install damages the health of the abs system. could be a shyster's canard. should we file this under cheap tricks? thanks tons oldduke

Dear oldduke,

Hope you're well. I'll hazard a guess. When the piston is compressed, it creates back-pressure in the brake system, presuming neither the bleeder valve or the brake fluid reservoir cap have been loosened. Something has to give, i.e., the backpressure has to be relieved, or the piston simply will not move. My practice is to loosen the brake fluid reservoir cap, before compressing a piston.

If the brake fluid reservoir cap has been loosened slightly, the backpressure is relieved. The fluid level rises ever so slightly and almost certainly not noticeably.

If neither the brake fluid reservoir cap nor the bleeder valve is loosened, then the backpressure could feed through to the ABS unit. I've never dissected an ABS unit, so do not know if there's anything inside, that could be damaged by backpressure.

A brake system engineer or technician likely would know if ABS units have parts vulnerable to backpressure.

Hope this helps.

Yours faithfully,

Spook

hi sages- pete , ted and bisco are likely correct. no problems from my experience. old myth may be part of fear of creeping communism in the 50s. thanks tons oldduke

I have done my 94 940 and 95 940 and squeezed the pistons back into place, then motive power bled after reinstallation. No issues. I don't think there is sufficient volume for contaminated shite to be squeezed all the way back into the ABS unit. Just my rookie two cents.

Retracting pads can be as sophisticated or simple as you want but leaving in the old pad and using a large c-clamp is the most common.

The clips have nothing to do with braking itself so if the pads fit, you are good. They are for anti-squeal/rattle and to keep the pads in place while you are working.

You could have possibly damaged the DUST boots but it is unlikely. Unless the pads are over sized like what we use for racing, if the pistons were retracted enough, this would not have been an issue.

As long as both bolts are in and torqued, no worries.

If the fluid is over the full line when you are done, feel free to remove some. I never do unless I am flushing the brake fluid.

Hi,

Anti-squeal paste shouldn't be needed if you see some kind of rubber padding behind the new brake pads. Some new pads come with it, some don't. Even if you apply a bit of anti-squeal it doesn't hurt.

You should lubricate the sides of the metal backing plate of the new pads (without touching the pad's friction material) i.e. the part that rides on the brake bracket.

About pushing-in the brake piston you could use a C-clamp or a pair of big pliers. Never leverage a tool against the brake disc in order to push-in the piston as you could warp the disc.

Yes you could open the bleeder valve to throw some fluid out for the piston to move in. I used this method before but now no more. With the bleeder still open some air could get sucked in behind the piston as soon as you release it as the piston moves out a bit when the inner rubber sealing ring recovers.

I would just use a C-clamp to push-in the piston without opening the bleeder and the fluid would return back to the reservoir. Empty out the reservoir a bit before using this method.

One more useful tip I discovered - put some red rubber grease (RRG) into the piston's boot and massage it around well. It helps to lubricate the piston, preserve the boot and inner rubber sealing ring. Braking performance is much better with quicker response. RRG is fully compatible with brake fluid. Only caveat is you can't do this to old boots. You might tear it apart in trying to slip in some grease.

Lastly don't forget to lubricate or renew the grease at the sliding pins. A synthetic high-temp grease is recommended here. Old grease could have caked up, lubricates poorly and causes uneven pads wear miles later.

Regards,
Amarin.

hi sages- good advice from coachs nabisco and amarin. have done this job on my92 245. always risky to loosen the bleeder screw. could break or round the flats even when using a flare nut wrench. only do that when absolutely necessary due to corrosion. better to let fluid push back into resevoir. may have to empty some with a suction bulb- i have separate ones for battery fluid and oils. best to use c clamp and wood or better yet a worn out rigid flat lawn edger blade to move back the calipers piston. regards oldduke

I open the bleeder valve when doing pads as I usually bleed the system at that point anyway to rotate fresh fluid in.

I feel the bleeder valve should always be able to be opened. If it is rusted shut it is time to change it or the caliper.

And I have read several posts commenting against sending fluid back into the master cylinder due to the risk of running contaminated/dirty fluid through the MC. ??? As I commented before, some mechanics even clamp the brake line to prevent this.

Amarin, those are some good lubrication suggestion. I'll do that on my next brake job.

Good points there Mr Nabisco regd preventing old contaminated fluid going back to the MC. I must qualify my method that I change brake fluids religiously. Previously every 2 years with Volvo Dot 4+ and now yearly as I'm using a Dot 4 fluid from a local oil company. As I'm now living far away from any Volvo parts store I must adapt to my situation.

Regd the piston boot lubrication it started when I longed for that gripping brake feel of a new car. Previously had driven a friend's new compact Hyundai with gripping brakes. I've rebuilt my front calipers about 5 years ago with rubber kit from TRW yet none of that gripping feel. So how could I make my 20+ years old calipers perform almost like new? Thus comes in that red rubber grease...

Yes I must watch my rearview mirror nowadays just in case I'm stopping too fast ; )

Regards,
Amarin.

Amarin, FYI I did install stainless steel brake lines in my 945 and the feel is "tighter". That might get you closer to that grippy new car feel.

You do not mention if you opened the bleeder valve when pushing back the pads.

Some people will clamp off the rubber brake line to prevent fluid going back into the MC reservoir.

Channel locks can work as a means to press in the pads.