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The brake vacuum pump was replaced, but it does not seem to have solved the problem of the random brake pedal hardening and being high when the car sits overnight. Sometimes it can go for months without losing the vacuum.
I am trying to locate the one-way check valve along the brake vacuum line. However, I am not sure where to look for, if any. Anyone?
The brake vacuum pump was replaced, but it does not seem to have solved the problem of the random brake pedal hardening and being high when the car sits overnight. Sometimes it can go for months without losing the vacuum.
I am trying to locate the one-way check valve along the brake vacuum line. However, I am not sure where to l
ook for, if any. Anyone?
It could be the brake booster. The rubber diaphragm inside the booster can leak and cause a loss of vacuum. I had a similar experience and bought a replacement booster. However, since the problem was so intermittent, I put off replacing it until the next brake pad/rotor replacement. The car is off the road at the moment, so I may replace it now.
Unless there’s a check valve integral with the vacuum line, there isn’t one. In addition to the booster diaphragm, the plug where the vacuum line enters the booster can leak when it gets old. It’s a quick and inexpensive fix, so not much money wasted if it doesn’t help.
Unless there’s a check valve integral with the vacuum line, there isn’t one. In addition to the booster diaphragm, the plug where the vacuum line enters the booster can leak when it gets old. It’s a quick and inexpensive fix, so not much money wasted if it doesn’t help.
Thanks for this valuable information. I will have to get a replacement rubber grommet.
I am on the fence about getting a vacuum pump tester/gauge.
There are only 4-5 places where the vacuum can leak. The connection to the vacuum pump, the line connector about ⅔ of the way to the brake booster, the line connection to the booster, the booster diaphragm, and I think a grommet that holds the vacuum sensor to the booster.
You don’t need a dedicated gauge to read the vacuum. All you need is an OBDII scanner. Even some $30 hand held code readers that have a real time function can read it.
I'd like to replace the entire brake vacuum line from the vacuum pump to the brake booster on a 2013 W204 C250. Can anyone share the part number or link to where I can buy it? TIA
I'd like to replace the entire brake vacuum line from the vacuum pump to the brake booster on a 2013 W204 C250. Can anyone share the part number or link to where I can buy it? TIA
Vacuum pump to joint 204-430-55-29
Joint to brake booster 204-430-57-29-64
Brake booster grommet 000-998-14-54-64
Go to mbparts.mbusa.com. Put in your VIN and search Brake System->Brake Booster to make sure these numbers are proper for your exact car. Then use the numbers to search for the best prices at FCP Euro, Pelican Parts, etc, or one of the many online dealer sites that sell at a discount.
Vacuum pump to joint 204-430-55-29
Joint to brake booster 204-430-57-29-64
Brake booster grommet 000-998-14-54-64
Go to mbparts.mbusa.com. Put in your VIN and search Brake System->Brake Booster to make sure these numbers are proper for your exact car. Then use the numbers to search for the best prices at FCP Euro, Pelican Parts, etc, or one of the many online dealer sites that sell at a discount.
I used the vacuum gauge to troubleshoot the intermittent brake vacuum leak through elimination. On various occasions, the vacuum pump holds 28 in.Hg for days. The culprit is the vacuum line from the pump to the joint (A204 430 28 29). However, my search for a new A204 430 28 29 replacement turned negative. I replaced it with a pre-owned from eBay and the problem was solved. Good thing, I saved the stock vacuum pump.
I really don't think the line is supposed to have static vacuum if the booster check-valve is ok, vacuum stays contained within the booster.
According to some YouTube videos, the brake booster itself does not hold the vacuum but a check valve installed before the booster that allows vacuum flow in one direction while preventing backflow or leakage in the opposite direction.
I am not a mechanic but as mentioned in post# 3 above, there isn't a check valve in this car model.
The vacuum gauge has helped me diagnose the problem through the process of elimination starting from the vacuum pump. I can confirm that the vacuum pump on this car model holds the static vacuum pressure.
But I have been wrong many times so please correct me if my assumption fails again!
A short video clip of my diagnosis was uploaded on YouTube.
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