longevity of vacuum pump diaphragm

Hello all-

Does anyone have any idea what the "average" lifespan of a diaphragm is? I was just curious if a person should change the diaphragm (as preventive maintenance) after a certain amount of miles or years of service since the last one had been changed. I know that a ruptured diaphragm can cause many different problems in a Mercedes.

Also, I replaced all the fuel lines in the engine compartment recently and I would like some help identifying the numbers for two of the lines that are left. I want to keep the car all original....so that is why I need help in identifying these numbers. The first line comes off the main fuel filter and is black. It is the one that looks like it has "expanded" as is about to burst. I have seen this same line on other mercedes engines and it looks the same way----skinny where you put the host clamps and bloated in the middle. The other number I need is for the clear lines (what used to be clear) that come off the injection pump. Can a person order these clear lines with the fittings on the ends? Mine are brown-black and I would like to replace them too. So, if you happen to have the numbers for these two types of fuel hoses, I would greatly appreciate it.

Thanks,
mike

The original vacuum pump on my 240D made it past 500,000 miles. The diaphragm was still in good shape. It started making a noise, the noise was the roller, so I pulled it off and replaced it. If the roller comes loose it can fall in the engine and destroy it. I would be much more worried about the roller than the diaphragm. I would NOT replace the diaphragm on a preventive maintenance basis. If it does happen to go out, the consequences are minor and you will know right away.

As to when it will fail, it is impossible to know at what mileage ANY part will fail. This is why you need to wear out the hood hinges before everything else. If your raising the hood a lot and checking things, you can catch things early before other problems, or being stranded beside the road happens.

Good luck,

[Nate Stanley]

Mike,

unless the cigar-shaped fuel hose is leaking, don't replace it. The Mercedes engineers designed it that way.

The reason is that the vibrations from the Injection Pump can send shock waves backwards thru the fuel lines, causing them to resonate under the car body.

The solution was to design the fat-in-the-middle hose to absorb the pulsations and thus cancel the vibrations.

One more piece of evidence why these 123 bodied cars and their engines were designed for the long haul.

Ditto Larry's comment about the vacuum diaphragm. If you later experience low brake boost assist, rough shifting in the auto trans, or the engine not shutting off with the key, then check out the vacuum pump, it may be starting to have a failed diaphragm.

[JimSmith]

mrwith,

I had the diaphragm fail in my Mother's 1971 220D before the car had 30,000 miles or so on it and have never had one fail since (on that car or any other Diesel I have owned). I changed one on my 1975 240D because I suspected it was leaking but it turned out to be fine when I removed it. I put the new one in, just because it made no sense to put the old one back.

I agree with Larry, these things fail randomly, and the result of a diaphragm failure is to draw engine oil into the intake manifold in quantities you cannot ignore - if it didn't scare you seeing that much bluish white smoke coming out of the tailpipe at idle it would be kind of interesting. The rate it uses oil is highest at idle, but you can always make it home by just stopping and adding a quart when it gets low. Makes a mess of the line going to the intake manifold, but in general it is a spectacular but benign event.

Hope this helps, Jim

Is this "roller" easy to replace? Has anyone done it on their car? My 240D almost has 250,000 on it and I don't know if the pump has ever been taken apart. I don't mean to sound like a worry wort. I am just a big believer in preventive maintenance and have read several posts on this forum about vacuum pump failures.

If anyone has the number to that "bloated" hose coming out of the main fuel filter, I would appreciate it. Someone (previous owner) took that hose off my car and they have some "other" type of hose on there. It is not original the way it is right now.

thanks,
mike

[sixto]

FastLane lists the bloated return hose as the cigar hose.

Sixto
91 300SE
87 300SDL
81 300SD

[Kyle Blackmore]

Hi Mike,I just went through this with my vacuum pump.The roller bearing and it's carrier(?)were like new,as was the bearing race that is mounted to the engine.My car has 366,000km(225,000+miles) and hasn't had the engine replaced.After all the money I spent on the pump, if it needed anything else I would have fixed it.Like you I'm a firm believer in MB original parts,most of the time they are cheaper than the aftermarket ones.BTW have you tried the dealer for those hoses,nothing ever seems to be obsolete just superseded Try that with a 67 Mustang.Good luck.

You don't need to worry about the roller until you hear it. When it starts to fail it will be NOISY! You will hear a distinct tapping sound coming from the vac pump. Not to worry. Just pay attention to your car. Keep those hood hinges oiled well so you can open it and check things alot.

Good luck,

[Billybob]

MB number 000-997-51-52 Cigar Hose