HELP. I'm driving down the mountains on I-40, and when I get to the bottom, I realize that the power brake assist on my brand new (at least to me) 1995 E300D, with 51000 miles on it, is not power assisting any more. I then notice that the transmission now shifts with a pronounced klunk when it shifts, especially going into 4th gear. It seemed to me that both these things went all at once. Is there some sort of pump that provides the suck for these things, or does it pull a vacuum off the manifold? Does anyone have a clue what part failed to cause both these power assist functions to both go at once? Am I correct in assuming that the transmission gets a power assist in the first place? Maybe I just got carried away with things falling apart and assumed the worst. Otherwise the car is a real roadstar, but as I am a travelling salesman, it must work right. Any insights would be really appreciated. mkcos

One other thing that occurred at the same time. Now it won't cut off. I have to turn it off at the knob at the front of the engine. I assume this is somehow related, since all three things happened at once. mkcos

Yes, both systems use vacuum from the vacuum pump mounted on the front of the engine.

Since your car has so few miles I would guess that the pump has swallowed its check valve. The valve is available separately MB# 004 997 18 72 $21.50 list.

To check first determine if lack of source vacuum is your problem. Next shut-off motor and remove the hard plastic hose from the pump to booster. Remove at the pump only. Beneath the line is a removable fitting 19mm if I recall. This fitting is the check valve. Remove it and you shouldn't be able to see through it. The guts are inside the pump. You should get the rest of the pieces out by removing the front plate. Or, you could replace the whole pump MB# 000 230 30 65 for $410 list (partsshop could really help here I bet).

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Okay, Steve. Thanks for the quick reply. As near as I can tell, there is no vacuum in any of the lines. I am also assuming that this lack of vacuum is also responsible for the ignition failing to kill the engine. You mention the pump at the front of the engine. Where exactly is it? I find something of a juction for all the lines that is down and beside the exhaust manifold , on the passenger side, sort of underneath the air intake apparatus. Is that little gizmo mounted undeath there what I'm loking for? mkcos

The check valve is on top of the vacuum pump that is on the front of the engine. The large vacuum line could break as well. Just check it.

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Benzmac:
Donnie Drummonds
1992 500E (very soon I hope
1981 280GE SWB
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Follow the large vacuum line (as big around as a finger) from the power brake booster forward. It will take you to the fitting which is screwed into the top of the pump.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

First off, thanks for the quick help. Okay. I checked the main line at the check valve, and there is no sucking whatsoever. I then took of the valve, and it seemed okay (by the way, its 22mm). I started it up, and there still was no suction. I guess this means a new pump. Any insights into the widom of used/remanufactured parts? I've about busted the bank buying this car, so I need to explore the cheapest option. On the other hand, if the track record for this sort of thing is bad, then new may be the only option. Anyone?

Check with PartsShop. This is one of those items where the same part is available significantly cheaper in the aftermarket.

I gave a list price so that you could compare. I could supply a new pump for nearly half of that list price, I'm sure PartsShop could do similar.

I say this to save you from spending 50% of list on a used pump. Most salvage yards are going to be reluctant to sell that pump off a complete motor, as it will leave the insides open when removed. They also will sell the motor with a pump so they won't want to break it up.

Any used pump will probably come from a "core" motor (one that has failed and is being parted out). This is likely to have more miles and/or some of the failure left in it.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

A quick up-date to this nightmare. The entire vacuum pump innards disintegrated, sending metal throughout the engine; this caused the timing chain to break, which then torsion-sheared both camshafts in half, destroying the girdles that hold them in as well. As if that wasn't enough, at least one valve broke too. My question(s) are this: Is this car going to continue with catastrophe? My tech, who has held my hand throughout this says it's going to be a 300,000 mile car. I'm essentially getting a bottom rebuild. Any opinions on this? Anyone every seen this kind of a failure in a diesel engine before. Mercedes-Benz is utterly uninterested, even though the car has only 52,000 miles on it, hiding behind the fact that the repairs are not being done at an authorized repair center. They just sort of said, gee, too bad. That alone is enough to drive me back to BMW. Opinions?

I would have started at the dealer because of the miles. I'm sorry that you didn't. You might want to take it there now. I know my dealer would have tried to help.

Yes, I have heard of this before and so have they.!!

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Benzmac:
Donnie Drummonds
1992 500E (very soon I hope
1981 280GE SWB
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Donnie: Unfortunately, I bought the car in Chicago, and I live in North Carolina. The mechanic I use is terrific, and I trust him completely. I get the impression at the local Benz dealer here that they are completly uninterested in helping because the car was not bought from them. I have, however, previously bought 3 E-Classes from them ('87 260E, '91 300E 2.6, and a '91 300D). The truth of the matter is, I got such a deal on the '95 E300D from this place outside Chicago, it would take a rather large expenditure out of pocket for me to go in the hole on this deal. I paid $20,900 plus $500 shipping. All of the ads I have seen nationally show prices for a '95 E300D with this many miles (52,000) to be selling for a much higher price. I do have a 2 year bumper to bumper warranty on it, but I remain somewhat nervous about the long term prospects of the car. Someone please convince me that all will be well. As I said, my tech assures me that he has taken the engine apart and has found that it is fixable and the long term outlook is excellent. Anyway, I would still be curious to know if any one else has experienced a similar problem with this engine. I did notice in the forum that someone else had a vacuum pump failure, but it dosen't sound like the problem exploded like mine did. Let me know out there if any one else has heard of similar situations.