MarkItZero

The seller suggested it needed new pads, I guess I got a little giddy and caught up in the whole buying experience that I didnt really notice. However when driving it home I did find that it was lacking in stopping power. Could that be rectified simply by pads? This almost seems like it could be some issue related to the power brake system. I would just hate to spend all the time to take the wheels off and open the calipers just to find that, it didnt need pads in the first place.

Anyone have any tips on how to diagnose this? and anything common I should check for?

aklim

Hard to say. If you said it was spongy, I'd definitely suggest a brake flush. In fact, I would suggest you do one every couple of years per MB spec. I have a flusher so I do it every year.

Without knowing what you have on the car, it is going to be hard to suggest anything other than see what is commonly liked and try that before we go anywhere.

MarkItZero

I really can't remember having ever done this (or paid anyone else to) to any cars I've owned prior. Tomorrow in the light I will inspect the fluid, it seems like from what I read online if it's not dark it's probably ok.

mrodoc

Brake fluid usually doesn't change color. It just stays in the reservoir and goes down slowly as the pads wear. You should be able to check for pad wear by just removing your tire/wheel. Flushing is cheap and simple. Just get a friend(free beer helps) to depress the pedal as you drain the fluid. Work your way from the wheel farthest from the master cylinder(passenger rear) to the one closest to the master cylinder (driver front). Google is your friend. If that doesn't solve it, I'd be thinking master cylinder. Good luck.

aklim

MB, Audi, Porsche, BMW standard is every 2 years for brake fluid and 3 for coolant, IIRC. US vehicles don't do as much PM as they do probably because they know:

1. They have created the perfect sealed system
2. It sells better than to say you need more regular service
3. It will be out of warranty by the time any issues come up
4. US Owners are too lazy to do it.

When you are looking at it with a fleshlite, look for the blue water molecules that the hygroscopic fluid has absorbed if you can.

davekp78

Mine required heavy pedal pressure when I first got it (used). Changed to Hawks pads and now it is much better. May have had some "high performance" pads when I got it.

s carter

First question you say it's lacking braking, is the pedal rock hard with very little travel can a vacuum hiss be heard with foot resting on brake. If so start looking at the booster, and like Aklim said a good flush wouldn't hurt

MarkItZero

The pedal is hard and can only be depressed a very short distance, but there is no hissing sound. I did once have a lexus es300 with a bad booster and it certainly felt much different than this does. Looking at it closer, it looks like I do need pads and probably rotors. Hopefully that fixes it.

Is there anyway to determine if your rotors can be turned vs replaced, without using a micrometer? I dont have one and it doesnt seem worth it to purchase one, do they loan them at autozone?

s carter

The Machine Shop That will cut your Rotors Should Measure them Before and After.

Make sure you have Vac. to the Booster the Hiss is Just the Icing on the Cake.

OK next Booster test WITH CAR OFF pump up Brake Pedal get it to the Top of it's Travel with Foot on Brake start car if pedal Drops a Fair distance odd's are it's Working. If it stays were it was You will need a Booster.

Also Give a good look around the Booster for Cracks. I have had 2 Split by the Vac. Port on me and a 3rd crack between the Master Mounting Studs but that was My Bad for Drawing the Mast on with the Bolts instead of a Push with hand.

Mr. Peabody

Welcome to the world of C4

I remember back when I first bought my 95.. I felt that it took an inordinate amount of pedal pressure compared to the other cars I had owned previously. It took a while to get used to.

I understand that you don't want to spend money unnecessarily but routine maintenance on your C4 really needs to be kept up for the car to be reliable.

The C4 is fantastic bargain but it's not inexpensive to maintain.

aklim

If you have more than one car, I'd buy one.

Here is the issue. Without a micrometer, you have to bring both the rotors to the shop and have it checked. With it, you can do it on the car and decide to toss them or not.

Local2Ed

Verify that each caliper is working by spinning wheel by hand as someone presses the brake pedal.

You may have one or more calipers that are seized.

Gibbles

Big difference in brakes, but my 84s brakes sucked.

I could put my weight into the pedal and i could hardly get a screech.
stopped ok, but nothing like a modern car.

I ended up doing the C5 front brake conversion, but that really brought out the weak rear brakes.

To resolve i installed the "DRM brake bias spring", and while i was at it, i rebuilt the rear calipers (new seals and dust boots), and replaced the brake hoses.

Result was a drastic improvement in overall braking.

If i were to do it over again, i would start by replacing the hoses first, and installing that bias spring.

​​​​​​​that said, i love the look of the C5 calipers, i got my set quite cheap, and i got a real good deal on a set of C5 wheels to go with it.

Skidmark1

Skidmark1

aklim

https://www.autozone.com/clamps-and-...ils/186492_0_0

I'd get the digital brake micrometers which are designed for brake rotors.

aklim

What's worse than expensive? Unobtainium made parts. IDK about the rest of the system but the sensors are made of unobtanium at this time. I haven't dared to pull my ABS sensors yet for fear of breaking them so I'm putting up with it having the ABS check light once in a while and the light flickering on certain maneuvers when I can't see a reason.

I would if they are old or I am uncertain of the age. Most car owners are "penny wise, pound foolish" when it comes to maintenance and I'd hate for brakes to fail. You don't have to drive but if you do, stopping when necessary is MANDATORY.

True. I'm not sure about 911 parts but while GM parts are usually cheaper than MB, I can assure you that I hear far less "NLA" or "Obsolete" at my MB counter than GM counter. My GM parts guy used to say "It's obsolete. Now what was it that you wanted?" every time he saw me.

Purple92

OK - so you know you need pads - but before you open your wallet - run two tests.

First off - when driving the car and do you feel any pulsation in the brake pedal when braking ??? If so - the rotors are likely warped, and significantly more metal will need to be removed from them to make them true again than if they are not warped.


Second test - with the car idling depress the brake pedal a couple of times and get an idea how it feels and how far it travels. Then turn the car off - and using your other foot - hit the brake pedal a couple of times to dump any vacuum from the booster. Now - hit the pedal again and see how it feels. It should feel significantly different than it did with the engine running. If it feels pretty similar or the same - there is a good chance your power brake booster is trashed.

Anyway - assuming that the booster is OK - jack the car up - pull the wheels, and pull the front calipers off. Look at the old pads - is the wear even - or is the material left on the pad tapered (this will tell you if your calipers are in good shape or if they may need rebuilding or replacing.) Assuming the pad wear is uniform - things are probably good. Check the brake hoses (remember the newest C4 is over 20 years old) - and like most things in life - brake hoses don't last forever - if they are deteriorating - now Is the time to change them. Remove the rotors and bring them to a machine shop that machines rotors - and see if they can be machined - the operator will generally measure them for you for free. This is where it helps to know if they were warped or not - typically new rotors can lose about 0.060" before they are too thin (the wear limit number is typically cast into the rotor). Cutting rotors typically involves two passes - one roughing *** to get out any imperfections, and a slower - lighter finishing pass to get a nice surface finish on the rotor. If the operator knows that the rotors are close to the limit, he can try to take VERY light cuts to try to keep the rotors within the usable range. But - if they're warped and close to the limit - they are most likely going to need to be replaced.

Get yourself a good set of pads (brake pads rank right up there as one area in life where cheaping out is NOT a good idea - you don't have to go crazy - but buying "economy brake pads" is probably about as good an idea as looking for a cut rate cardiac surgeon. Pick up a can or two of bake fluid while you're at the parts store. Before putting the machined rotors (or new rotors - if the old ones were not salvageable) back in place - spend a few minutes with a wire brush removing any surface rust around the hub flange or on the back of the rotor - I normally apply a bit of anti-seize compound to the front of the hub so the rotors don't rust in place - then reassemble. I would STRONGLY recommend doing a brake fluid flush while you're at it - who knows how old or moisture laden the old fluid is. When the fluid coming out of the caliper bleed valve looks like new fluid - you're done. Repeat on the other wheel, put the wheels back on - lower the car, clean up, and take her fir a nice test drive.

Then consider doing the back brakes...

aklim

If you have any doubts about the pads and rotors, replacing all 4 would be better than 2.