2011 Mercedes GLK 350 Brakes
Mark: Hi, it’s Mark from Top Local, we’re here with Bernie Pawlik, Pawlik Automotive in Vancouver, Vancouver’s best auto service experience, 18 time winners of Best Auto Repair in Vancouver. How’re you doing Bernie?
Bernie: I’m doing very well.
Mark: So we’re going to talk about a 2011 Mercedes 350 GLK, there was a brake problem. What was going on with this SUV?
Bernie: Well, the client brought it in for some brake concerns, it was just brakes didn’t feel quite right and we did a brake inspection on it and found a few issues. The brake fluid was discoloured and dirty and old which is not untypical, the front pads and rotors were worn out, not metal on metal, but worn out, also the brake calliper, they were sticking and wouldn’t retract properly. The rear brakes were in pretty good shape for the time being so they didn’t any service but that’s basically what we found. It needed new front brake pads, rotors and callipers.
Mark: So are callipers a pretty frequent replacement on this car?
Bernie: No they’re not, actually for Mercedes and a lot of European vehicles, we don’t do callipers very often. They tend to be quite durable. I’d say, if you know, for all the Mercedes we work on, maybe 95% of the brake jobs don’t require callipers. It’s really once you get into the older models, you know 15, 20 years old, even some of those don’t require any calliper replacements and it’s not an often replaced item anyways. Usually once you do a set of callipers, they last for a long time.
Mark: So this vehicle wasn’t in that age category, is it, was it a really high mileage vehicle?
Bernie: No it wasn’t and it was kind of surprising that the callipers were actually sticking but you know, sometimes it does happen. It had only about 135,000 kilometres, that’s pretty young but not too many of them need callipers at that age but nonetheless, it’s just something that needs to be done.
Mark: So what does a brake calliper actually do?
Bernie: Well, let’s have a look at some pictures and I’ll explain that. Here’s out nice GLK350 2011, nice looking car, nice compact little sport utility vehicle. The brake calliper you can actually see through the wheel here, each wheel has a calliper and basically the function of the calliper is to squeeze the brake pad against the brake rotor. So there’s a picture of the brakes with a nice new brake rotor, the rotor turns with the wheel, the brake pad sits in here. Now those two pads, one on each side, you could only see the outboard pad and this is the calliper and this is actually the bracket of the calliper. So it’s not a full picture of the calliper, well actually this part here, this darker part is actually the calliper bracket, it bolts to the steering knuckle and the pads ride inside this bracket and the calliper, this is the sort of outer part, the ear squeezes the brake pads against the rotor when you apply the brake and inside this area here, there are I’m pretty certain, there are two pistons and the pistons, once you press it, brake fluid forces the pistons against the pad and that forces this part to compress and causes the pads to squeeze. So that’s basically how a calliper works. As soon as you let the brake off, the pressures released and then the wheels are free to turn again. What goes wrong with callipers is the pistons will stick, moisture will get inside, the pistons will stick, there is also a slider pieces inside this area here on top and bottom and these pins will stick. Again it’s usually moisture gets in and attacks it and ruins it, but also dirty brake fluid can cause the pistons to seize from the inside. So that’s basically the brake calliper explained.
Mark: So what would cause the brake fluid to get dirty?
Bernie: Brake fluid is what’s called a hydroscopic fluid, it actually absorbs water and it absorbs water right out of the air. I thought at first that’s kind of a bad thing but actually there’s a reason why it does that, that is because if water wasn’t absorbed into the fluid, it would accumulate in certain areas of the brakes. So it would accumulate, say if it was petroleum based fluid, water would separate and it would accumulate in certain areas and cause rusting and corrosion. So the fact that the water is absorbed into the fluid is actually a good thing and when you flush the fluid out it gets rid of the water. The brake fluid, I mean, there’s heat that takes place, there are lubricants that are put in at the factory, inside the master cylinder and the calliper pistons and these lubricants, I won’t say they break down, but they contaminate the fluid and it’s basically heat from the brakes that really contaminates the fluid and moisture that just gets absorbed out of the air in the fluid. So it’s good to flush the brake fluid every two to three years on any car, unless I guess if you live in you know, the Arizona desert or something and the car never leaves there it can last longer. But as a general rule if you own a car, flush the brake fluid every two to three years.
Mark: And I’m sure that that fluid running in the vehicle, it’s hydraulic, so it’s going to get pretty hot.
Bernie: It does get very hot. It can get up to, I think the boiling point for .4 brake fluid is somewhere around 450 degrees Fahrenheit, so I mean the other brake parts, you can’t even touch a brake rotor, you can fry an egg on a brake rotor after stopping a few times, it’s that hot. But it transfers into the fluid, it gets really hot, it’ll be a few hundred degrees Fahrenheit for sure, two, three hundred. If you’re going down some steep hills for a long period of time, you can see it approaching 400 degrees for sure. So that’s pretty hot.
Mark: And how are these vehicles for reliability?
Bernie: They’re good vehicles, you know they’re not the most common Mercedes. We don’t work on a ton of them compared to the ML’s which just seems to be a lot more common around this part of the world, but it’s a nice little vehicle. It’s a more compact sport utility vehicle than an ML or a GL, the K’s in a Mercedes usually indicates a smaller version of a larger vehicle, like a SLK is a smaller SL car and a GLK is a smaller GL vehicle. But it’s a nice sized vehicle and reliability, they’re pretty good, we don’t really find much in the way of unusual problems with them.
Mark: So there you go. If you are looking for a service for your Mercedes GL class vehicle in Vancouver, the guys to see are Pawlik Automotive. You can reach them at 604-327-7112 to book your appointment, they’re busy, you have to book ahead or check out our website pawlikautomotive.com or our YouTube channel, search for Pawlik Automotive, got hundreds of vides on there. Thanks Bernie
Bernie: Thanks Mark