My daughter has a 2013 C250 which just turned 72K miles. The vacuum pump which provides vacuum for the brake booster failed completely the other night. Internals were completely shattered. What's worse is the brakes on the C250 are virtually useless without the vacuum assist. Worse still is there's NO indication whatsoever that you have lost brake booster vacuum... it's just the sudden surprise when you hit the pedal and realize you're in deep trouble!

I replaced the pump yesterday with a new one (overpriced from the dealer at $250) and have taken the original apart. In short, it's a poor design. I'm wondering if anyone else has had such a sudden and complete failure with this vacuum pump. My old 1993 190E 2.6 has never had a brake failure in 24 years... this leaves me to wonder about the reliability and safety of the newer Benzes... I also just picked up a 2014 C250 CPO car... hmmm... wondering more.

Regards, KM

 

This has happened to me! However, the even more annoying thing is that the replacement part seems to be failing after only a couple of weeks. The mechanic who fitted it has hinted - although he hasn't looked yet - that if it's not something like a broken pipe causing the problem, it could be something terminal in the engine, which has not pleased me!

If anyone has any advice, I'd be grateful.

 

Note that the vacuum pump is attached to the rear of the cylinder head and driven from the exhaust camshaft. The pump gets an oil supply from the rear of the cylinder head which circulates through the pump and back into the head and drains into the crankcase. If you have any clogs in the cylinder head oil feed, this might limit the oil supply to the pump and the result would be the pump burning up and the internals shattering. If you're not holding vacuum, then it's possible that you have a more classic vacuum leak in the line, one-way check valve or the brake booster itself.

One interesting thing I've noticed. When the car sits overnight, the first engine start of the day... with your foot pressing on the brake pedal, once the engine starts you will feel a pull down of the brake pedal as the vacuum builds up. If you use this as a simple test, you can check for a basic vacuum leak by repeating the start sequence after an hour, two hours, etc. (engine off for this time period of course) and see if you get the same effect of the pedal being pulled down. If you're loosing vacuum quickly then you should look for a leak elsewhere in the system, unless you have a defective pump.

One last thing, you can check for vacuum at the pump fitting directly by unclipping the vacuum line that feeds the brake booster. At the rear of the engine just to the left of center when standing in front of the vehicle. It should draw a strong vacuum quickly when placing your finger on the fitting, but don't hold it for long as it can create a very strong vacuum!

 

The chap who fitted my new pump had looked again and there is what he called swarf in the pump and there were fragments of metal in it, indicating something bad in the engine. Attached is the data from the engine. Does this sound as bad as he's making out? Thanks in advance.

 

Based on the report attached, you would have a solid engine check light when the car is running, is the indicator lit?? If not, then the report showing would not be from your car.

Also, based on the issues showing (the first two codes), you would notice a significant reduction in engine power, as the ECU would (should) put the engine into limp mode. Again, if this is not the case, then perhaps the codes are not from your car.

If your mechanic found metal fragments in the pump, then that's a pretty interesting mystery, as there's a fine filter screen on the oil feed to the pump. I would also suspect you would notice some metal bits in the engine oil via the dipstick. In short, metal fragments in the engine oil is not a good sign. Then again, every standard paper element oil filter does not filter 100% of the oil, as the flow rate is too high, so only a percentage goes through the actual filter.

If you are experiencing a power loss and the check engine light is on, then the error codes showing could indicate problems which would include:

- faulty exhaust camshaft sensor (or a more serious problem with the exhaust camshaft position, i.e., internal cylinder head issue)
- faulty knock sensor (or low grade fuel being used... or camshaft positions are off causing the ECU to be out of normal operating parameters)
- A bad thermostat assembly (I just had mine replaced under warranty a few months ago.... the engine never came up to normal temps in cold weather)

- note: with the above errors showing, you could also have a wiring harness problem, either part of the wire harness is pinched and shorted or some cut/broken wires or possibly some bad connectors. It's worth checking the physical harness connectors to the various sensors and at a minimum, re-seat them (in case of some corrosion or oxidation buildup).

In short, if your mechanic isn't a properly trained MB tech, you might want to go to the local dealer and have them run an ECU scan for you... which would also show your VIN number as part of the scan.

 

Many thanks for the comprehensive reply. The light comes on but not all the time. I haven't really noticed a dip in power, although I drive it daily so might not notice a gradual dip.

The guy's a German car specialist, but not an actual mb technician obviously. I'd rather sort it than ditch the car, but if it's a massive job I'll off load. I'll need to take it elsewhere for a second opinion I think.

 

Yet another technical innovation ... a pump to provide vacuum to the brake booster instead of using engine vacuum via the intake manifold ...

 

Not exactly new.... Diesel engines have had vacuum pumps for decades. The point here is that a boosted engine (turbocharged or supercharged) will not always have vacuum, as the intake manifold will have pressure during boost periods. Using a dedicated vacuum pump ensures constant vacuum for the brake system. Unfortunately if the pump fails, you loose the ability to stop the car in virtually all instances, which I consider to be very dangerous.

I have other cars which are turbocharged and supercharged and neither use a dedicated vacuum pump for brake assist. Both use a traditional intake manifold vacuum line with a one-way check valve (and the braking power is exceptional). Based on this, I suspect the MB system requires a higher vacuum to work normally, as the system also detects an excessive application (stomping on the pedal) and will instantly apply a higher braking force than would be normal. This would require a higher level of vacuum to implement, hence the dedicated vacuum pump.

So, I prefer to do that initial check as noted above for the initial start and feeling the brake pedal being pulled down once the engine starts and the vacuum builds up. Safety first.... as best you can.

 

I think I have the same problem.
For the last week I could hear an audible "shoosh" sound when pressing in the brakes. Today, out of the blue, the pedal went rock hard and I had virtually no ability to stop the car. Thankfully this happened in the driveway.

I did the pres pedal + engine start test to see if the pedal drops at all. It doesn't.
Interestingly I did also recently have a whine in the engine bay that I couldn't put my finger on but it went away.

 

So I was having this same issue. I pulled the vacuum pump and it was broken so I figured that was my problem. I put in a new one and it seemed to fix and car drove perfectly. I drove the car out of town (about two hours) and on my way home the same issue starting occurring again. I am wondering did the pump fail again or is it something else? Is the pump supposed to have vacuum at all times or just when pressing the brakes? Because I never tested it when I put in the new pump and now there is no vacuum at the nipple where the hard line attaches? Could it be the pcv valve or something else causing this issue? Could my pump still be good? I pulled it out and it is not broken like the original was. I would assume either way I would need to address whatever is causing the current issue/whatever caused the pumps to fail? Driving me insane and considering getting rid of but don't want to get rid of if this is an easy fix.

 

I just had this happen to me.. Brakes went out,, no warning,, on the HWY going 70mph. Luckily I avoided traffic and slowed to a atop. Mechanic is saying it is the brake vacuum pump. That there is no leak l, and can't find a reason for why it went out. MaxCare warranty will cover the replacement, but whats to say it won't go out again!? Is this a thing? Super dangerous. Did you ever find out why yours went out ?

 

Same thing happened to me highway speed and I make a quick stop fairly quick because it stopped traffic and then at the next time I want to use my brakes hard as a rock had to pull over and make sure I didn’t have a leaking brake line or something from debris in the road near Atlanta. Frustrating. Got the pump off yesterday unit is getting a oil but no vacuum through the line and checked the check valve off the master cylinder enable to blow air towards the vacuum part and unable to drawl air from the vacuum pump towards the booster. I only saw one small metal wire fragment on the screen of the pump. I can’t believe there is no fuse or relay or electrical connections going to this pump and it can fail and give me no warning. This is probably why they don’t make this pump anymore! So did replacing it fix your problem because it looks like it just happened last month? And did it last or did you have to replace it like the other thread? Thanks

 

Why a vacuum pump? Turbo charged. No vacuum when under boost.
Now, my question: How do you check for good oil flow out of/into the head? The pumps I have found have a warranty of only one year, so they must be leery of how they are being replaced.
Any more thoughts on how to improve the longevity of these pumps?
Thanks!

 

I had the same exact problem in January 2020. I was on the highway during rush hour in San Marcos Texas I was about to hit a car and I had to immediately exit and park in a hotel. I almost had a car accident while I was trying to find where to park to safety. I couldn't beak so I had to switch gears to Park so the car could stop once at the parking lot of the Hotel.

 

I was exactly in the same situation.

 

I found myself in the same situation last week. I pulled the line off of the vacuum pump that goes to the booster, started the car, and there was zero vacuum pressure coming from the pump. Rock Auto had a vacuum pump for $107 which took about 10 minutes to replace. I took the old pump apart, and it had totally come apart inside. I'd say I had MAYBE 30% braking capability when it occurred. It's definitely something you can do yourself and save money though.

 

I have replaced my vacuum pump for my W204, the brake work find on high speeds "actually high RPM" as long as I am driving the vehicle but on idle the brake pedal get so hard after 2 pressing, has anyone faced the same and what it could be, please?

 

The problem with poorly manufactured parts was the EU's wonderfull idea of the concept of "Outsourcing". Why is your MD tranny which is way more complicated than any outsourced part, like steering ignition motor etc, more reliable in comparison-?, makes one think. The problem with outsourcing is remuniration is guaranteed before parts are produced.