300TD catastrophic vacuum pump repair adventures - Page 2 - PeachParts Mercedes-Benz Forum

dkr · #16 05-29-2016, 07:10 PM

I see. So, if you pull the vacuum pump regularly and check for play in the bearings, it should not surprise you with sudden failure?

It looks like the rebuild kits were mostly to replace old rubber so that would seem to make sense here...

Dkr.

BWhitmore · #17 05-29-2016, 07:39 PM

Checking the bearings may yield some warning but I would not go over 130k miles without changing the pump.

rasper · #18 05-29-2016, 08:24 PM

Quote:

You can buy a new pump from the classic center for around $340. Once again, cheap insurance.

Owning one of these old Benzes is like being in love with a no-good woman. If I were to replace all of the things that should be replaced every so often as insurance, such as flex disks, vacuum pump, etc., etc., I would have more money in just the new parts than the entire car is worth. Forget the labor to have them installed.

Richard

Diesel911 · #19 05-29-2016, 09:35 PM

Quote:

Originally Posted by dkr

I was wondering that as well as I've heard about this a few times. If anyone knows, I would really appreciate knowing:

- What causes the vacuum pump to fail?
- I've heard the vacuum pump rebuild kits don't always work right. Why is that?
- Are there warning signs before the vacuum pump fails? Is it enough to drive home and fix later or will it just die and spit it's guts into the engine?
- Can inspecting the existing vacuum pump help to determine it's condition and longevity?

Dkr.

This is for the Piston Type Vacuum Pumps on the W123s.

The older Piston type Vacuum Pumps had Bearing that has a plastic bearing cage and the cage would eventually desinigrate. when that happend it was possible for the related parts that got tore up to fall into the timing Chain and or Gears.

It has been a long while back but at one time the Vacuum Pump kits came with O-rings that did not have a fat enough cross section to seal. Resulting in the pump not working well after the rebuild kit was installed.
I don't know if the O-ring issue was fixed or people just do not rebuild the Pumps as they did in the past.

My question What in particular causes vacuum pump failure?
http://www.peachparts.com/shopforum/diesel-discussion/204187-what-particular-causes-vacuum-pump-failure.html

2 Vacuum Pumps destroyed timer Bushing Identified as the problem
http://www.mbca.org/forum/2013-12-29/why-are-these-vacuum-pumps-being-destroyed

dkr · #20 05-30-2016, 01:50 AM

Quote:

Checking the bearings may yield some warning but I would not go over 130k miles without changing the pump.

That's pretty crazy. There are tons of people who have hit 400,000 or more miles on the original vacuum pump. This story is the exception not the rule.

How do you know the issue is not age-related more than number of miles? Where do you get 130K as some type of "common-sense" metric?

I wonder if it would help to just install a vacuum gauge and look at it from time to time. I would presume if the pump was going downhill, the vacuum would drop over time like if the bearings were to go out.

Dkr.

t walgamuth · #21 05-30-2016, 07:24 AM

The vac pump on my 82 wagon failed at about 120K miles fifteen or more years ago....so its not age related.

ROLLGUY · #22 05-30-2016, 10:37 AM

Quote:

Originally Posted by dkr

That's pretty crazy. There are tons of people who have hit 400,000 or more miles on the original vacuum pump. This story is the exception not the rule.

How do you know the issue is not age-related more than number of miles? Where do you get 130K as some type of "common-sense" metric?

I wonder if it would help to just install a vacuum gauge and look at it from time to time. I would presume if the pump was going downhill, the vacuum would drop over time like if the bearings were to go out.

Dkr.

The mechanical part of the pump can fail at any time, regardless of its ability to make vacuum. That means that it could still be making vacuum up until the time the bearing goes away, and causes damage. On the other hand, it could mechanically be just fine, but have a worn out piston ring or diaphragm, and not make vacuum. Replacing it at a certain mileage will (should) head off the potential for catastrophic damage, such as I am dealing with now. Even after inspecting a pump, the "roller coaster", and timer shaft bushing, a pump can fail without warning. I believe the pump on the engine I am working on, was the original pump, and the car had over 200,000 miles on it. Although I can't put a specific mileage when a pump should be changed, it would seem as some have said, to be "cheap insurance". I totally agree with this statement. I will be replacing the broken pump with a new one, or at least with a completely rebuilt unit (seals, valves, piston, arm and roller).

BWhitmore · #23 05-30-2016, 11:53 AM

There is no magic miles number. 130K miles is a number thst I set, but I will also admit that I am sometimes over the top when it comes to maintenance on my cars. I just know what is costs (parts alone) to repair a Mercedes engine especially when some fairly low to moderate maintenance items will help prevent a catastrophic engine failure. While our engines are well engineered they do require regular maintenance.

dkr · #24 05-30-2016, 12:11 PM

How difficult is it to R&R the pump for replacement. It looks like fairly easy access, but it would be nice to know before attempting to pull it off. Do you have oil coming out after removing it or risk damaging the rubber by inspecting?

Dkr.

BWhitmore · #25 05-30-2016, 12:50 PM

The vacuum pump is fairly easy to remove and replace. Begin by rotating the engine to Top Dead Center. Remove the power steering belt. Spray the vac pump retaining bolts with penetrating oil and let soak for about 1/2 hour. Unscrew the vacuum tube (metal) from the vac pump using two wrenches. Using the proper size allen head socket remove the retaining bolts in a criss cross fashion. Once the retaining bolts are temoved pull the vac pump forward to remove it.

Clean all gasket residue from the engine block. Apply gasket sealer and a new gasket onto the new pump. Install the new pump keeping in mind that you will need to apply some rearward pressure to the pump as it is being installed. Some people have purchased two longer bolts used to get the pump started and draw it in close enough to get the stock bolts started and then when the stock bolts are tight, remove the two longer bolts and replace with the stock bolts. Tighten the bolts in a criss cross pattern. Re-attach the metal vacuum tube using two wrenches, replace the powrr steering belt and you are done.

You may get some slight oil seepage when the vac pump is removed. Check for oil leaks when finished.

oldmako · #26 05-30-2016, 01:02 PM

Interesting discussion.

Please educate my FNG self as this is my first diesel. I have an 85 300CD with 160,000 miles.

1. Does my engine have the grenade pump? And if so,
2. Is replacement of this pump considered essential at my age/mileage?
3. Who is the best source for a replacement pump?

My car is pristine and there is no sense in not keeping it that way if I can spend $300 or so and head off a catastrophic failure.

Thanks

Diesel911 · #27 05-30-2016, 01:06 PM

Quote:

Originally Posted by dkr

That's pretty crazy. There are tons of people who have hit 400,000 or more miles on the original vacuum pump. This story is the exception not the rule.

How do you know the issue is not age-related more than number of miles? Where do you get 130K as some type of "common-sense" metric?

I wonder if it would help to just install a vacuum gauge and look at it from time to time. I would presume if the pump was going downhill, the vacuum would drop over time like if the bearings were to go out.

Dkr.

I have noticed from reading the various mercedes fourms that people with similar milage often have different degrees of timing chain stretch. My best guress is that the forumer owners that changed their oil regularly helped keep the wear on the timin chain and gears down. The same may apply to wear on the timer bushing.

Vauum Pumps seem to gernade suddenly. Some times you get some warning in the form of a metalic ticking sound. If you hear that sound pull over and determine where the sound is coming from.

The people who have had engines that survived serious damage from a gernading vacuum pump have usually be people that started the Engine and started moving at low speed and had the vacuum pump go out.

Who has or knows someone that has experienced a timing chain breakage/failure?
Who has or knows someone that has experienced a timing chain breakage/failure?

dkr · #28 05-30-2016, 01:15 PM

I see. I think it was uberwasser who mentioned checking his pump every year. It seems like a lot of work and possible risk just to pull it every year, especially with having to replace the gasket each time.

I suppose if I'm going to pull it, I might as well replace it at least initially knowing that I'm still on my 30+ year old pump.

Are there timing marks for the engine so you know you are at TDC? I've marked TDC by the valve springs, but you have to pull the valve cover to see them.

On another thread, I had heard the argument that the vacuum pump was aluminum and these issues could be prevented if the parts were re-machined into steel. Did that ever go anywhere?

Dkr.

Clemson88 · #29 05-30-2016, 01:15 PM

Quote:

Originally Posted by rasper

Owning one of these old Benzes is like being in love with a no-good woman. If I were to replace all of the things that should be replaced every so often as insurance, such as flex disks, vacuum pump, etc., etc., I would have more money in just the new parts than the entire car is worth. Forget the labor to have them installed.

Richard

TLC seems to help but the constant attention is tough for an old man to produce. Seems the car is more worthy of the effort. At least it will bring scrap price someday.

Disclaimer:

Sorry if you're an old no-good woman, nothing personal.

ROLLGUY · #30 05-30-2016, 03:07 PM

Quote:

Originally Posted by BWhitmore

The vacuum pump is fairly easy to remove and replace. Begin by rotating the engine to Top Dead Center. Remove the power steering belt. Spray the vac pump retaining bolts with penetrating oil and let soak for about 1/2 hour. Unscrew the vacuum tube (metal) from the vac pump using two wrenches. Using the proper size allen head socket remove the retaining bolts in a criss cross fashion. Once the retaining bolts are temoved pull the vac pump forward to remove it.

Clean all gasket residue from the engine block. Apply gasket sealer and a new gasket onto the new pump. Install the new pump keeping in mind that you will need to apply some rearward pressure to the pump as it is being installed. Some people have purschased two longer bolts used to get the pump started and draw it in close enough to get the stock bolts started and then when the stock bolts are tight, remove the two longer bolts and replace with the stock bolts. Tighten the bolts in a criss cross pattern. Re-attach the metal vacuum tube using two wrenches, replace the powrr steering belt and you are done.

You may get some slight oil seepage when the vac pump is removed. Check for oil leaks when finished.

I would add that removing the PS pump helps a great deal. Also, clean the engine around the vac pump before doing the job, and use a pointed object to clean out the heads of each bolt so the 5mm allen bolts do not strip.