What in particular causes vacuum pump failure? - PeachParts Mercedes-Benz Forum

Nate Stanley · #1 03-20-2008, 08:15 PM

Here's another possible failure mode:

On 2 pumps in a 617 engine, I've had the piston shatter. They are cast aluminum and have often wondered if anyone would be interested in a run of machined pistons from 6061 alloy.

Diesel911 · #2 08-01-2008, 10:48 PM

Quote:

Originally Posted by Nate Stanley

Here's another possible failure mode:

On 2 pumps in a 617 engine, I've had the piston shatter. They are cast aluminum and have often wondered if anyone would be interested in a run of machined pistons from 6061 alloy.

None of the regular part places (internet included) sell the pistons.The kit to rebuid the valve end is $45 on up to aroud $70 depending on who you buy it from. The few companies that sell the kit that replaces the arm and other drive parts; one wanted $265.00 for that kit. If you were to add the cost of a new piston it would be better to buy a new vacuum pump with a warranty.
I think the engine driven vacuum pump nees to be gotton rid of and replaced with some sort of electric on or at least a mechanical one that the parts of which will not fall into the timing chain when it fails.

Stevo · #3 08-02-2008, 07:08 PM

On one of the "later" engines I went back to the "diaphragm" type pumps found in the early W123. The top of the air cleaner had to be swapped out for one with a vacuum fitting. The rebuild kits for those pumps are considerably cheaper also. They can, of course, lose their ball bearings too

One cause of a vacuum pump going south with catastrophic results is "for and aft (laterel?) play in the timing device due to a worn bushing on the intermediate shaft. If the timing device can be pushed back and forth more that 1mm, beware

Diesel911 · #4 08-03-2008, 12:20 AM

Quote:

Originally Posted by Stevo

On one of the "later" engines I went back to the "diaphragm" type pumps found in the early W123. The top of the air cleaner had to be swapped out for one with a vacuum fitting. The rebuild kits for those pumps are considerably cheaper also. They can, of course, lose their ball bearings too

One cause of a vacuum pump going south with catastrophic results is "for and aft (laterel?) play in the timing device due to a worn bushing on the intermediate shaft. If the timing device can be pushed back and forth more that 1mm, beware

After reading this thread I went looking and found as you say the diaphragm pump is cheaper to rebuild but I could find no one that sold the rebuild parts for the arm and bearing.
I also found there are 12 volt electric vacuum pumps made to power the Power Brake Boosters on gassers that have special camshafts or Blowers/turbos on the engines. But, new one are in the $270-$300 range.

Stevo · #5 08-03-2008, 01:17 AM

Humm, I wonder if one couldn't take the guts out of a VP (to cover the hole) and hook up and 12v one. At least with the diaphragm type there is no piston to come apart just the ball bearings.