Brake pads? or something else? Squeaking...
 

I'm wondering if squeaking brakes has to do with worn brake pads. They also seem to be less responsive than they should be.

It feels like you have to press harder to get the same stopping power. No brake light has come on, but to me that may only mean a bad sensor. The fluid level hasnt gone down and I recently replaced the MC with a brand new one.

My guess is the pads but are there other warning signs of worn pads? Or something else for that matter?

Thanks

Might be a leak developing in your vac system to the extent that it is affecting your power booster for your MC.....
That should not affect squeaking .. but will cause you to have to press harder and then when it goes out ( vacuum pump or diaphram) really really hard just to stop ... it happened quickly to me...and I almost rolled through a stop sign pushing as hard as I could...

Hmmm, not looking forward to a vacuum system inspection. Its been a bit of a headache in the past.

Is brake pad wear an unlikely reason for poor braking like that? They do sometimes feel soft. Its kinda hard to tell.

If I press it once slowly, it seems to go down far if I press hard. But if I press a few times quickly it becomes stiff with the pumping.

You might have air in the system.... given that last description..

but Really !!!

These are BRAKES ISSUES.... Sorta Important !!!

and your car is pretty easy to replace the pads on...
you need to get down and check it.. or just put new ones on..

yes, brake pad wear is not the likely cause of your problems unless something is not functioning properly..
I assume you have checked the level in your MC .. like front and back levels ?

pressing once causing the pedal to drop points to either fluid loss or MC failure.
pressing multiple times causing the pedal to get hard is likely just a slow to recover vacuum issue.

Could be slow vacuum issue.. but...
Isn't that the same situation encountered when bleeding brakes with a helper ?
Pressing several times ' pumps it up' then the fluid is released at the bleeder...
at the point where no air remains... pumping it does not cause it to get more firm...

yeah, but it's only getting firm from the previous bleed down situation. so air leak/lack of fluid could mimic the situation, but "hard pedal" is a different feel from "firm braking"

I'm guessing there's air in the system. Bleed your brakes again. You did bleed them when you installed the new master cylinder, right? While you're at it, inspect the brakes and see if you see anything amiss, leaks, old-looking hoses, uneven wear, etc.

I think I may do a thorough Bleed again. I did do one when I replaced the MC. I may get a new set of pads as well.

I see there are many different options for pads. With varying thicknesses. How do I know if I need a 15mm thickness or a 17.5 mm thickness for the front pads.
It seems there is only one thickness available for the rear.

I noticed I ave ATE rear calipers, but the front I couldnt make out anything but a mercedes star, so must be originals?

Does it matter if i get all one brand of brake pad or different brand pads than the calipers? (i.e. if I get ATE pads for the mercedes calipers?)

oh, can we know what kind of car, and what year please? it'll help with the diagnosis, and such...

Yes of course. Its a 1985 300TD Wagon. (its also written below my name on each post)

Thanks
Michael

Thanks!
it's ALWAYS best to ad in the post body or the title the make and model! (this site keeps threads for years, and you are likely to change cars and user text over them! even the sig line changes made are changed on EVERY post ever made by you, so info in the thread really helps!

not sure on the pad thickness, I've never measured mine. but the brand caliper is irrelevant to the pads! usual suspects are ate and bendix. if the spring clips match your rears, then they are the same brand, if the springs are different, then they would be bendix fronts.

Do you think it would matter what thickness I got? Would the thicker last longer because its thicker or is it simply the metal part attached to the pad that is thicker?
Thanks again

1985 300TD-T wagon

The distance the pistons will retreat... leaving a gap of a certain and limited size...will determine the thickest pad you can put in ..

but the more thickness may not mean longer lasting...
the hardness of the material they make the pad from will make a huge difference in that...

Would either thickness fit in the caliper? If not how do you determine which one is the right one?

In terms of thickness.... call/email / pm --- phil in this forum's parts department.... he will know...

click on ' buy parts' above on the diesel page..
click on ' fastlane' ..
phil's email address and phone are listed there....

An '85 model should use the thicker option.

DANGER DANGER, not a good suggestion, don't do this
suggestion withdrawn!

I'd get the thicker pad regardless, and if it won't fit, remove some of the pad material on a grinder... use a respirator or at least a dust mask, some pads have asbestos in them... or at least dust that is NOT good to breathe....

That is an incredibly poor recommendation. Fortunately, it is just as unnecessary as it is ill-advised.

yeah, I know... that's why I put in the respirator, and the other warnings...
but it is what I would do... :D

John does not miss often.. but he did this time..
Those pads need to be flat and even .... you can not do that with a grinder...and you do not need that dust in your shop AT ALL...

Thickness depends on the year/piston diameter of the caliper. 60 mm piston diameter = 17.5 mm pads

Based on an '85 with OEM brakes and not some odd retrofit you should use the 17.5 mm up front and 15.5 rear. If for some odd reason you've got pre-79 calipers, then you'd use the 15 mm. This is based on the FSM for pad replacement. There are several notes, cautions, footnotes etc in the book.

It sounds like you've got a few concerns: squeaking and pedal feel.

Squeaking - as long as it's not metal-on-metal "squealing" may be an installation issue. Not enough lube on the contact points between pad/caliper, an improperly installed or missing shim, etc.

Pedal feel or spongy brakes may be a bleeding issue.

Never "grind" a pad to fit. If it's too thick, then something's wrong: the piston isn't retracted, the caliper/disk/pad combo isn't correct, or something else.

Pads on the W123 are child's play to replace. Get a camera, take some before pics to show the whole setup on the caliper (retention springs, rust/crud build up etc). Post here are you'll get beaucoup opinions.

Squeak - did you spray blue stuff on the back of the brake pads and let it get tacky before you put the shims back on the new pads?

good rotors, good bedding in technique, and proper caliper piston setting, along with good cleaning of the pad backing slide surface and ground off pads can work just fine. (what, everybody doesn't have a mill?) it is NOT recommended for the average DIY.
I officially remove my recommendation of this practice. (now, can anyone get the Mcparts near me to stock the correct thickness pads for my range of cars?)

I ' have ' a Burke number 4 knee mill...
but would not put that kind of dust into my work area or even into a shop vac....
used to... but the results of those types of fibers hit like 20 years later... and they are very bad....glad you officially withdrew it.... LOL

So I took off the left front brake pads, they were in there very good (or bad I should say). I had to use a hammer to get them both out. the inboard one was completely seized up in the caliper.

In the Hanes manual I have, it says you should be able to push the caliper piston back into the caliper by hand. It doesn't appear I can do this on either piston. They dont budge. Ive pressed on the brakes and the outer piston pushes out but is not retreating back in, not even with a push using a flat part of a file with lots of force.

Is this a complete rebuild job or something I can do without a rebuild kit? (i.e. take apart, clean out put back together) Specifically, is there a different hydraulic fluid in the calipers? or does it simply use the brake fluid for the hydraulics?

Looks like it may not be as simple as changing the pads...

Whoa there....
Do not jump to worst conclusions first...

You have not been using the correct tool to press back those pistons..
so you can not know right now if they are seized up or not..
there are cheap ' scissor' type screw up presses which can be placed where you put that file to move them back..and you need to apply it evenly and square to the piston.. sometimes ' C " clamps can be used...
It is very dangerous to press on the brakes without taking some precautions.. like putting a wooden block to keep the piston from coming all the way out.. or even out too far and messing up the dust seal.. slow down a little and wear goggles when you are working on this stuff...
Until you do that.. which just takes more pressure than you could apply .. just relax...
Rebuilding calipers is not a DIY job except for the very experienced.. and sometimes not even them.... most FSM's say not to take them apart..
Since brakes are sorta important.... you need to be checking out finding rebuilt or new ones to install...

I am not saying they are not seized.. I am saying your test is not conclusive.

Thanks, thats a little reassuring. Is there anythign you can reccomend to use besides this scissor-like tool?
Im trying to do this tonight...
Not sure if Im being realistic. But it would be nice.

Is the fact that the pad was so difficult to take out a sign of a possible seized piston? Also it was my suspicion when I pressed on the brakes and only the outer piston came out and the inner one didnt budge.
(EDIT): I see you edited your post. A "C" clamp may work? Yes I did wonder weather should be putting something in between the rotor and the piston. I cant fit the new pads in as the old ones were considerably thinner.

Yes, it is certainly a possibility that it is seized...and I added some stuff in my last post..
The scissor tool.. if it is the correct type for your car is CHEAP...
C clamps if they will fit and you have them...

BUT..... really... rushing on BRAKES..... ???? Have to keep their relative importance in mind when working on them...

Im trying to figure out which calliper repair kit to order. Theres two types listed on the catalogue im ordering from. One is for ATE and the other is for Bendix.

As there are no visible marks on the front callipers with "ATE" on them like on the rear ones does this default them to Bendix?

They are likely the original callipers that came with the car.

Thanks for the support.

Maybe you could compare the pictures of the calipers on the Fastlane website. There are some very obvious differences between the ATE and Bendix models.

bendix calipers have wire springs, ate uses flat plate springs.

With no pads installed, it's reasonable to assume one piston will move and the other one won't since there's nothing holding either one back then the easier one will move. The sealing ring in the caliper may be "fighting" going backwards so it may be difficult to get it going in that direction. Once it starts it should be easier.

As stated above, pressing the pedal with no pads is probably asking for a piston to pop out too far, and then you've got trouble.

To push the piston back in, try a simple spring glue clamp like one of these: http://www.ronshomeandhardware.com/Spring-Clamps-s/2751.htm

Or one of those pistol grip clamps. http://www.ptreeusa.com/ratchetClamps.htm

Put one old pad back in (if you can) before you try to depress the piston on the other side or all you'll do is see-saw the pistons in and out. If you can't get the pad in since you've moved the pistons out with the pedal, then try to clamp the piston in place with the ratchet or C-clamp while you squeeze the other one back in.

You might want to remove the caliper and use the old pad(s) as backing plates on the piston so you get the clamping force "square" to the piston and don't make the piston go askew in the bore and jam up. You may need to do this in any case to make the C-clamp work.

The fact the pad was difficult to remove is inconclusive by itself. It may not have had any lube on the slide rails, it may have been crudded in there with caked on dust. But that may help explain the squeaking if the pad didn't easily move away from the rotor when pressure went off the piston.

That may contribute to your pedal feel as well (speculation) if the pad didn't track with the piston and you had to push a little extra to get the piston/pad/rotor into good contact.

I wouldn't jump into planning a caliper rebuild yet. Get the pistons fully retracted. Clean the old calipers, make sure your heat shields are in place and properly oriented (you do have heat shields, right?), properly lube the back and slide portions of the new pads and see what happens. Apply "brake grease" at the arrows (specific high-temp product, not regular grease) http://www.peachparts.com/shopforum/attachments/diesel-discussion/60623d1225870900-how-guide-replace-front-brake-pads-rotors-w123-pad-grease-point..jpg

Pics would be helpful.

You do know that you are breathing brake dust as you drive? It's coming from the cars in front of you when they step on the brakes.

That is a LITTLE different from what I ( and others ) used to do regularly... use the compressed air nozzle to clean the brakes while simply holding our breath... inside a garage...
and we are all breathing diesel particulate even when we are not driving our diesels in the same fashion... even when we are not near any roads or driving at all......

Az,

I just went through an episode of squealing brakes on my 85 300DT. What I found is the front pads were worn out. I also found the disc was worn to the point the disc could hold water ( looked like a bowl). The squealing noise was the backing plate coming in contact with the lip of the bowl on the disc. I didn't take any measurements, but I think my disc was below the minimum thickness for the disc. I could not remove either puck as the rim on the disc had the pucks caged in.

Pedal felt soft with the old pucks in. I sent the car to my mechanic to do the disc and pad replacement. Lifts and air tools are wonderful when dealing with 20 year old rusty bolts.

BTW, my car has Bendix on the front, and ATE on the rear.

Hammerwerfer

Thanks for that. The just heat sheilds are what again? I just ordered a new caliper repair kit, would they be included iun there?

Ill try some way of getting the pistons to push back in as suggested. I think Ill just take the callipers off to gte a good cleaning and might as well do a bleed while im there.

Ill try posting some pics today once I take everything apart again (I had to pack up for two weeks so had to put the wheels back on to move the car)

The link in post #1 in this thread: http://www.peachparts.com/shopforum/diesel-discussion/297468-bent-something-inside-front-right-caliper.html?highlight=shield

Notice how the shield (metal thing in the middle) has a crescent? That crescent fits into a cutout on the piston so the pad can sit nice and flat. If the shield is mis-installed, then the pad won't sit right.

If you end up doing a rebuild, you'll need to get the piston oriented correctly in the bore for the shields to fit and the pads to fit. It's all straightforward, but not necessarily simple or obvious.

With brakes, it's also important to know when you're in over your head. If it isn't working, ask for help; or go for a set of warranteed rebuilts and new hoses.

Heres some pics of the calliper on the drivers side. Looks like the heat sheilds are in place but not the best condition. I do have a rebuild kit. The boots look intact surprisingly.

As you can see the inner piston has not been able to retrac. I was ale to press th outer one all the way in usig my fingers wih a steady force. The other one wouldnt budge.

The other pic obviously is the pad, and its comparison to a new one. I measured and its rougly 7mm of pad-not including the metal of course.
I cant find what the recomended spec is for them. In the manual as well as in my repair manual they say "check for reccomended wear thickness"

Im going to go for taking it apart to see if I can get it moving again. I may try presing it in gently with a clamp first.

Do you think one seized up piston could cause poor braking - i.e. soft brakes or brakes that you need to push hard on to get to function?
My guess is that theyve been like this for some time, - the seized up piston, but I only started noticing strange behavior in the last month or two.

Pad wear is down to 2 mm, so the notch that's almost worn all the way through should be about the limit. Backing plate is supposed to 4.5, so 2 + 4.5 puts you really close to your measured 7 mm.

Compare the inboard pad to the outboard pad. Are they worn about the same, or was one side much thicker or thinner? If they were close, then the caliper was probably working okay and is less likely to be seized but only difficult to push back in.

Clamp the outboard piston in place. Expect it to retract/compress almost flush with the caliper. Once that is clamped, then squeeze the other side hard. Put an old pad in there and use a clamp. Try to compress from the center, not from the edges.

There's no evidence of grease on the slides and your pad is worn nearly to the limit. That may explain the squeaking. You've also got a LOT of crud in there and it'll be difficult to fit the new pads into the caliper until it's scraped out of the corners.

Pedal feel is subjective. If the piston is really seized, then yeah, it could explain a soft pedal and harder braking since you'd only be pushing on one side of the rotor, but for that to be the case I'd expect significant difference in pad wear between inboard and outboard so you'll need to compare them to help determine that.

Since the caliper is off, you might as well inspect the rotor for thickness, warping, etc. Consider replacing the hoses since they're undone as well.

OK so I got one of the pistons out using a bicycle pump like someone had suggested. I cleaned up the calipers and now Im wondering if I have heat sheilds in place or not. There are thin metal plates seemingly permanently riveted or bolted to the piston, but their shape is a little different from the new sheilds that came with the repair kit.

It looks to me like the new ones are actually supposed to sit in the ones that are built into the piston, am I right? The ones that are there, (the backing plate?) are a little bent here and there. Ill try and reshape them.

Ill try pushing in the piston with a c-clamp and a metal plate to see if I can get it to moe. Is it better to push it in rather than try and pull it out somehow?

Update: I managed to sueez the other piston down using a vice. It fit just right into the caliper but was pretty hard to push down. Now the chore is getting it out. How to do that now. I will have to plug the other side first obviously, but I wonder if its a sign of damage that it was significantly harder to push down than the inner calliper?
Off to bed

Ive been trying this morning to get the inboard piston to move out of the caliper without success. This is using a bicycle pump, with the other piston in place and
clamped down so as not to come out. Ive put all the force I can into the bicycle pump, (which ejected the other piston well) and it doesn't budge. Ive fully pushed it in with a vice but now cant get it out.

My only Idea is to reconnect the caliper to the brake line and bleed it and try using the brakes to push out the piston. I dont know how else I can get enough force to eject it.

Any Thoughts?

Update: I managed to get it to move out now that I hooked it back up and bled the line. Now I was thinking of pushing on the brakes till it popped out. my concern now is how to gte it back in if it was so difficult to come out.

Also I noticed the repair jit that I bougt for bndiz=x callipers have a heat sheild type ring which matches roughly th size and shape of the metal plate already on the piston, however there is no way for it to sit on there snuggly or at all it seems as there are some little parts bent a certain way that the original one doesnt have. Are you supposed to be able to remove the plate thats attached to the piston?

I saw the other thread. Do you have one or both pistons out now?

Its not looking good. Ill be looking for a new set of calipers..

That is probably the best thing to do... no use taking chances with brakes...

So waking this thread up again... I completely replaced the front calipers with a brand new set. The Mechanic i bought the car off in NC was nice enough to hook me up with a brand new pair for just over $100 each. He was even surprised as to why they were so cheap. He mailed them up to me and indeed they were brand spanking new Bendix calipers. They were pretty easy to install but they took a bit of work to bleed. I ended up needing to take a vacuum pump and suck it from the bleed valve in order to get the process going otherwise it seemed to be doing nothing with the pedal pushes.

Does anyone know approximately how many pedal pushed you need to press in order to do a good bleed of each brake both front and rear?

I seemed to get a good bleed as far as I can tell. I bled and i bled and I could quite tell if the little tiny cloud like bubbles were actually bubbles from the lines or if it was simply getting in to my clear vinyl hose because it didnt form a seal around the bleed valve properly (it wasnt super tight)

I still get a funny brake behavior now. If I havent pressed the brake while driving for a few minutes and press it the fisrt pressing will feel loose and go closer tot the floor. if I press it again immediately it is tighter and feels more responsive. Could this be due to air still or something else?

That sounds like symptoms of air in the lines. Vacuum bleeding is not preferred, although I use it like you seem to have in order to start the fluid flowing from the MC.

If you ever let the reservoir run dry while filling your calipers then you pulled air into the lines. That's one reason people recommend pressure bleeding.