Brake Pad Replacement Question

[lipmana]

Hello,

This may be a somewhat naive question but I appreciate your info:

I own a 1986 190e. I have noticed that it is becoming more difficult to stop the car--that is, when I depress the brake pedal, it takes the car longer to come to a full stop.

Is this more likely to be due to worn front brake pads or rear brake pads? I understand that it may be both, but is there a way to predict with a relaible probability which of these it likely is, without removing the wheel, based on the manner in which the ability to stop is diminishing?

Any idea how much replacing front pads should be, (as well as front and rear)? Auto Parts Warehouse has the pads themselves for about 25.00 US for the front set, same for rear. Don't know what labor would be however.

I would like to avoid replacing the rotors--is there a way of knowing whether this will be necessary, and if so, approximate cost?

Many thanks for any informatioin that you can provide.

Best,

Alan

Dr. Alan J. Lipman

 

[Myros]

hie yourself off to a good mechanic

and pronto Alan. Your problem could be caused by any of the things you mention, as well as brake fluid going off. As you are in the US, I don't know how well your prices compare, but 25 bucks for pads isn't bad. Labour shouldn't be much as they ought not to take an hour to replace. First step is get to a reputable honest garage, or dealer and get them to give the brakes and the fluid a once over. It is a safety issue after all.

 

[TimN]

Your car should be fitted with brake pad wear sensors. These will bring on the warning light with a ! on your instrument cluster. As will a low level of brake fluid. That is of course assuming that they have been refitted last time the brakes were done.

Any manual will give you the rudiments of replacing the brake pads. It does sound as though you could be heading for a major brake overhaul given the age of the vehicle and the apparent lack of maintenance. Sticking brake caliper pistons, warn disks and pads, corroded brake pipes and brake fluid level and contamination are all the usual suspects.

Are you sure that the servo is working properly. Depress the brake peddle when starting the car. The peddle should go down a bit more as the servo cuts in. You can test the servo further but it is easier and safer to do it on a rolling road.

 

[Bobby Dazzler]

Alan

Brake fluid does sound as though it may be the cause based upon your description. Braking efficiency will reduce steadily as the fluid ages, and becomes contaminated (air, moisture, etc).

Pads & discs (rotors) will in relative terms maintain their braking efficiency until worn to a critcial level, at which time there will be a step change in braking performance and a whole lot of scraping noises!!

With regards to your question about front or rear - front brakes take most of the load most of the time - but that doesn't necessarily mean that they'll need replacing before the rears - just depends when each were replaced.

Do service records suggest when pads, rotors and fluids were last replaced?

Having just replaced the pads on my M-Class on Sunday, and being naturally aversive to getting my hands dirty, I couldn't believe how easy they were to replace. I can't imagine that they'll be more complex on your 190, but best have someone alongside to help if you're not confident alone - best if that person has tackled a similar job on another car, even if a different make.

I found this really useful when doing mine, but only relevant if you have four-pot fixed calipers: http://www.mercedesshop.com/Wikka/W124BrakePads. However there may be similar guides on the web, that another 190 owner may be able to suggest.

Safety is important though, so if in doubt consult a local specialist.

Hope this is useful.

 

[turnipsock]

Are the pads wearing evenly?

 

[turnipsock]

I ask the question as it sounds like a caliper is sticking somewhere. Check the pads for even wear. Also check the disks (rotors), they are easy and cheap to replace anyway.

 

[paulcallender]

Everyone else has listed most of the parts to check. I'd add only a couple more:

Flexible lines - check for tiny 'balooning' which appears on hard application of the brakes.
Mounting security of brake pedal/servo, master cylinder, calipers

Also, it won't affect brake performance, but could cause abnormal wear:
security and missing components, of rigid-flexible brake line couplings and security of the rigid brake hose supports.

Many "Kwik-fit" style centres do a free brake check - which should look at all the above. However, I've had mixed success here. They missed items, which although didn't cause danger, subsequently failed the MoT (which they did too!). But its an independent opinion and if they are friendly, could also advise on the work required, eg giving you guidance on how its done.

A top tip is to buy 2 'one-man' kits and bleed both rear brakes simultaneously. There is a T piece in the system and a bunch of air hangs around this, during bleeding, so you can struggle to get it out unless you do both rears at once.

 

[190D]

Does the brake pedal feel very hard when you are applying the brakes

If so I would check the brake servo unit to do this turn the engine of

And press the pedal about 5 times to exhaust it. Then with your foot on the brake pedal start the engine you should feel the pedal moving and becoming easier to press

If it is still hard check vacuum pipes. As to the brake pads they are very easy to fit
Hope this helps