June 19

2017 Mercedes Benz B250 Engine Overheating



Mark: Hi, it's Mark from Remarkable Speaking. I'm here with Bernie Pawlik, Pawlik Automotive in Vancouver, BC Canada, Vancouver's best auto service location, and 24 time winners of best auto repair in Vancouver. We're talking cars. How you doing Bernie? 

Bernie: Doing very well today. 

Mark: Today's victim is a 2017 Mercedes-Benz B250. This is a funny looking for Mercedes little car that you don't see a lot of what was going on with this car?

Bernie: Yeah. These cars are actually only sold in Canada, well, they're available in Europe, but not in the US in, at least around here, the US is kind of the big market, so yeah, they're not too common.

So the owner's complained, he was driving down the highway and the engine was overheating. So pretty serious concern. That's why it came to our shop. 

Mark: So just to throw a curve here, was there any kind of engine lamps on? 

Bernie: Not as far as I know. I didn't actually do the work in this. My technician, Ed did it and he didn't mention anything about lights. It has a temperature gauge, so I believe the gauge was reading high. 

Mark: How do you go about testing and diagnosing engine overheating? 

Bernie: Well first thing of course with any modern car, we plug a scan tool in to see if there's any trouble codes. That's the first thing before we even start it up. We do a visual inspection. Look for fluid leaks, cuz of course, if you're low on coolant, that can make a difference. But usually Mercedes will have a warning light if your coolant level is low and there was nothing on like that. Found the coolant level was full. We do a pressure test on the cooling system to see if there's any leaks. There were no leaks. 

There was one trouble code stored in the computer. I don't have it handy, but Ed said it was a thermostat code. So the thermostat of course regulates the temperature of the engine coolant. And so after doing some more diagnosis, we found that the water pump was defective. 

Not leaking or broken, but there's a vacuum operated valve in the water pump. And it seemed it was stuck in one position and causing the engine to overheat. So we figured the best repair would be to replace the water pump, obviously, and to replace the thermostat as well, which is a good thing to do. Every once in a while on a vehicle anyways but especially when you have a major cooling concern, like an overheating problem. 

The vehicle is about 150,000 kilometres. That's almost a hundred thousand miles for people to think that in those terms, so you know, it's getting up there in age. Time to do some work. 

Mark: So a vacuum valve, vacuum operated valve in the water pump. Is that something unique to a Mercedes? 

Bernie: Well, I don't say unique to Mercedes, but unique to this engine. That's the first time I've seen anything like this. And there might be other cars that use them. Just look at some pictures right now and I can show it to you. But it's definitely something we've not seen on another car.

So here's our B250. Nice little compact. I guess you'd call this an SUV or it's just a larger size car. 

2017 Mercedes Benz B250 Engine Overheating

There's the water pump. So there's a, I'm moving my mouse pointer around, that's the drive pulley for the water pump. It's kind of unusual shape for water pump too. They're usually sort of short and stubby, but this one's very long. There's outlets for hoses here. You can see I'm just moving the mouse pointer, inlets, outlets, and then here's our vacuum operated valve. I didn't tear everything apart and look at it, but it's definitely a bypass valve of some sort or a flow restriction.

2017 Mercedes Benz B250 Engine Overheating

It would increase or decrease flow under certain conditions. And this is the vacuum pod up here for the unit. So when Ed found it, he said this valve was stuck in place and once he freed it up and moved it, then the overheating issue stopped. So that was a pretty clear indication that that was definitely a problem. 

There's the thermostat assembly. Lots of hoses in and out. The thermostat is located somewhere here where I'm moving my mouse pointer, and this is one of these electric thermostats. So it's got like a electric heater inside the thermostat.

2017 Mercedes Benz B250 Engine Overheating

Mark: Why would it have an electric heater inside the thermostat? 

Bernie: I don't know exactly why they do it, but it might just be to keep the temperature at a certain range or to sense the temperature of the thermostat. Maybe it allows it to open and close if the computer says, Hey, you know we need to open this thermostat. We need to get more coolant flow through the engine. This might also be a sensor as well, not a heater, but some of them are heated electrically. Some of them have a sensor. So yeah, modern technology on cars, it's like to control everything.

It used to be things were mechanical. So the thermostat would just mechanically open at the right temperature and then close and open and close. Now it's like, well let's get a little more control over this. So then they add electronics to it. And that's why things like oil pumps just used to pump oil at certain pressures you know, and they just run all the time. Now, it's like, well, we don't actually need that much oil flow at this speed, so let's make things more efficient and cut the flow down and get an extra mile a gallon outta the car. So it's all about efficiency.

There's a picture looking at the top of the engine. The arrow in this picture points to where the water pump is located, which is buried way down here. Turbochargers up here. This is sort of the front of the engine that the drive belt is down here somewhere.

2017 Mercedes Benz B250 Engine Overheating

So maybe I should have taken a picture a little further back, but the top of the engine's up here. So this is the water pump. It's buried down here. The thermostat's at the backside of the engine. So kind of complicated for a little four cylinder. 

Mark: So fairly extensive, time consuming repair.

Bernie: Yeah, it's quite labour intensive work to replace both these parts. There's a lot to be removed. And the interesting thing we've found, this is some new Mercedes thing, it's 2017. So, you know, as time goes by, we're always working on newer and newer cars. Of course, this is five, six years old now, this car, but some of the clamps that we had to remove to take off coolant hoses are actually disposable.

They're one off use plastic clamps that we had to get from Mercedes. So it's a little delay in the job and it's kind of annoying where you can't just clip things together like you used to at one time. Now it's like you have to dispose of clamps. They're a one time use piece.

Mark: So once everything was buttoned back up again, what did you do to retest the vehicle to make sure it was working properly? 

Bernie: Well, of course we refilled the cooling system. We have a vacuum filler which helps remove any air right in the cooling system right away. So it warms up quickly and kind of almost like there was never any coolant removed. If you have air pockets in a cooling system, it can often be a nightmare to say, bleed the cooling system out. So we fill the cooling system up, warm it up, make sure that everything's flowing properly. The thermostat's good. 

Take it out for a bit of a road test. And on this one, because the client's concern happened only at highway speeds, we took it out for an extra long highway drive. So about an extra half an hour drive on the highway, just to verify it was all good. So always best to do those kind of things before handing it back, saying, Hey, yeah, it's fixed. And then having it towed back or having a phone call, Hey, by the way, I drove it for 15 miles and it overheated. 

So we took care of that before verified the temperature stayed rock solid at the right operating temperature. 

Mark: Part of the service. So how are these part of the service? Yeah. How are these B250s for reliability?

Bernie: Well, this is probably the newest one we've worked on. And I have to say some of the older ones were a little quirky and problematic and strange to work on. And I guess this thing's no different, but it's newer and I think it's a little better than previous models, but I guess time will tell how they are overall. This is so far so good. I mean, this is probably the first major repair that's been done on the vehicle. 155 Ks. That's pretty good. So I think overall they're probably pretty decent vehicles. 

Mark: If you're looking for service for your Mercedes-Benz in Vancouver, the guys to see are Pawlik Automotive. They're experts in all European makes and models, all makes and models of cars, actually. Even electric cars. Pawlik Automotive. You can book online at pawlikautomotive.com or you can give them a call to book (604) 327-7112. They'll discuss it with you. They'll find out what's going on. They'll get ready for your appointment. Pawlik Automotive in Vancouver. Thanks for watching and listening. Thanks Bernie. 

Bernie: Thanks, Mark. Thanks for watching.

About the author 

Bernie Pawlik

You may also like

2013 BMW X3 Timing Chain

2013 BMW X3 Timing Chain

BMW 323i Clutch

BMW 323i Clutch
{"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}

You might also like