should I replace engine vacuum pumps? - PeachParts Mercedes-Benz Forum

James L · #1 07-30-2002, 11:33 PM

I have read the horror stories of a blown diesel engine vacuum pump breaking timming chains, cam shafts and worse! Should I replace this $300.00 part on my 1993, W124, 150K miles (5 cyl, 602 engine) and W126 , 220K miles (5 cyl, 617 engine)?

No oil is seeping out of the gaskets but I am still worried. The 1995, w124 (606 engine) was notorious for the blown vacuum pump.

I hear that MB went with a mesh screen to keep blown vacuum pump parts from entering the oil pump. Can I get this upgrade for my cars? Is there any tech bulletins on the vacuum pumps on my MB service CDs?

Thanks

#2 07-31-2002, 07:47 AM

The original vac pump on my 616 engine went a half million miles with no problems. I heard a noise from the vac pump area one day and posted here. That's when Benzmac told me that the roller could possibly come loose and destroy the motor, so I should remove and investigate. Sure enough the roller was worn out but still intact. I replace the pump.

The good news is that it will give you warning, but you have to listen to the warning and take action. I fully expect that most of the situations where the roller did indeed destroy an engine was because the driver did not heed the warning. When you here noises, investigate before they become bigger problems.

My $0.02,

#3 07-31-2002, 03:36 PM

well.... Larry has forgotten more than I know but my approach is to use preventive maintenance in this case.

I replaced my vacuum pump recently without much difficulty. Also am replacing timing chain/tensioner and did water pump last Spring. The only aggravation I had with the vacuum pump was getting at the allen head fasteners that are used to attach it and having a strong enough allen tool to loosen them.

I don't think there are other potentially destructive components to worry about. I know the oil pump could fail but apparently that is extremely rare. The oil cooler lines can blow but are supposed to weep first as a warning.

Different folks take different approaches to this type stuff but at 150k intervals, this type spending seems ok.

I'll let the A/C compressor, power steering pump, and generator go out on their own.

Nic
'85 300CD @ 151k miles

GregS · #4 07-31-2002, 05:30 PM

Do the vaccum pumps on w123 bodied diesels have a similar engine-destructing capability? How common is it for them to fail? I have an '84 300D with 164k miles and would be interested to know what the "warning signs" of a bad pump are on these engines.

Thanks,

Greg

#5 08-01-2002, 08:49 AM

Greg,

I don't know the statistical probabilities but it is clear that they can and do fail and the result can be serious damage to the engine. Apparently, some of the internal parts of the pump can break off and get down in the engine, causing bad things to happen. Also, a vacuum pump failure can lead to oil getting into the car's various vacuum lines which must then be cleaned out at considerable effort/expense.

The Mercedes Club of America has a "maintenance" frenquency discussion that suggests replacement by 150k, but Larry notes in his comments that they make a certain sound when they are starting to break, so he is comfortable waiting for that indicator.

All 123 series (617 moters) have this issue and, I suppose, some of the other vacuum oriented diesel motors.

There are repair kits available as well, but I don't know how reliable they are. Probably depends on skill of re-builder.

Nic

#6 08-01-2002, 10:23 AM

The pump is actuated by a roller that rides on an axial eccentric on the front of the fuel injection sprocket. The roller bearing can wear to a point where it eats up the shaft it is on and falls into the motor. If that happens, anything can happen. It might just go to the bottom of the pan without hurting anything on the way, but with something metal and about an inch and a half in diameter is rattling around inside the crankcase of an engine, all bets are off as to what the result will be.

If you heed the audible warning and replace the pump, all will be well. To replace it your best bet is a set of metric allens in 3/8 drive. On the 616/617 you will probably have to pull the power steering belt to ease the job, but it's pretty quick and easy.

Good luck,

lrg · #7 08-01-2002, 02:30 PM

I replaced the vacuum pump on my 124 (603 engine) when it started to leak oil at 110,000 miles. The pump itself looked OK but it seemed foolish to take the chance. On the 124 the pump itself protrudes well into the front of the engine block and resides about an inch from the cam chain pretty much guaranteeing a catastrophic failure if the pump falls apart. On the 123 the pump is actually in a housing that attaches to the front of the block so at least you have a chance that the parts may fall in without taking the rest of the engine with it. Personally I'd replace it if you think it's showing any sign of problem but on the 124 I'd replace it as a regular maintenance item.

gsxr · #8 08-01-2002, 07:24 PM

Like LRG said, the OM60x engines are totally different than the OM61x. Larry's 500kmi vac pump is just great. When they fail, they mostly just stop working, or induce oil into the vacuum system. But attempting that on an OM60x is Russian roulette. Change the OM60x pump every 150-200kmi as a preventive maintenance item, whether or not it's making noise. Your car cost $35-75k new, would cost ~$10k-25k to replace used, a new engine is ~$8-$12k (plus labor), used is $3-4k. You want to risk that for a lousy $300 every 150,000 miles? That's .2 cents (two tenths of a cent) per mile. It's your choice...

(Both of my 124's with OM603.960's have new vac pumps.)

Regards,