300TD catastrophic vacuum pump repair adventures
 

A friend of mine bought a wonderful 300TD for cheap because of a catastrophic vacuum pump failure. He had a rebuilt engine ready to go in it (it will be the subject of another thread), but I suggested that I would try to repair the engine in the car before committing to install the rebuilt engine. He brought the car today, and I decided to start working on it. Upon removal of the cam cover, I found a broken timing chain, all but one of the cam towers broken, and the cam in three pieces. Upon further tear down, I found a two-piece vacuum pump. My iPad will only allow one photo upload, so I will just do the vac pump for now. I will try to post more photos with my laptop later. I was able to weave in a new timing chain only after removing the pan and oil pump. I had a challenge getting the old chain to move, as it was balled up between the lower guide rail and timing device sprocket. I was able to tie a wire on the end, and pull it through, and then turn the crank and pull the chain up and into position next to the upper guide rail. I wired the end up, and call d it a day. My next job is to put all the new parts on, crimp the timing chain, re-time the injection pump, and then hope to get it running again. I will post photos of the progress. Wish me luck!

A photo of the car
 

Beautiful car with a perfect dash, perfect wood, perfect carpet, better than average Palomino upholstery (notice I did not sat pink-omino) on the driver seat, the rest of the upholstery is perfect. The body is near perfect, with only the smallest dent just above the driver side corner light. The fairly new Michelin tires have 90 percent tread. The former owner just put a lot of money in rebuilding the front end as well.....Rich

¡Buena suerte! Pomaika`i. Bonne chance.

I guess the timing device which the vac pump rolls on is removable for the roller surface only? My later 95 606 engine is all one piece.

Just curious....

Sent from my SM-G920V using Tapatalk

Yes!

When all else fails, "Desenrascanço".:D

More photos
 

Broken parts

New timing chain installed (well at least routed around all the gears)

The underside with oil pump removed. I had to remove it to get to the broken chain to tie a wire on the end.

Another body photo

Shame it happened to such a nice wagon. Were there tell tale signs before the vac pump grenaded?

Did you check for bent valves before deciding to roll in a new chain?

I pushed on each valve, and none felt like they were sticking. I also turned each one, and they all had the same resistance. I am confident no valves are bent. Although I have not heard of too many people repairing this kind of damage without removing the head or entire engine, I have done one other repair of this kind, and the car is still running to this day. Both the owner and I thought it was worth the parts and labor to try to fix the existing engine before just replacing it with the rebuilt one. I will know for sure in a couple days after the parts arrive, and I get it back together.....Rich

Rich - a fellow I know recently bought a very nice 300CD in Colorado and felt confident to drive the car back to Southern California. Somewhere in Arizona the vacuum pump exploded taking with it the timing chain, breaking the cam in half and destroying several of the cam towers. He had the car flat bedded to Monterey Park where I saw the engine. He was able to get a good engine from a wreck but I cannot imagine the total cost for all of this. I now always replace the vacuum pump as a maintenance item every 130,000 miles and always use a new pump as opposed to rebuilding the vacuum pump. Cheap insurance.

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.

Generally the bearings in the vacuum pump fail and then it explodes. The pump will make some strange noise before failure but it is difficult to tell the difference between normal diesel sounds.

A total rebuild of the pump involves parts that equal the value of a new pump so why bother other than the feeling of rebuilding the pump yourself. You can buy a new pump from the classic center for around $340. Once again, cheap insurance.

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.

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

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

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

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

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).

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.

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.

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.

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

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?
http://www.peachparts.com/shopforum/diesel-discussion/203364-who-has-knows-someone-has-experienced-timing-chain-breakage-failure.html

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.

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.

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.

I just had one let go ,the bearings fell out of the housing giving the assembly a nice wear mark .The tick ,tick ,tick noise gave me concern that I had a lower bearing issue .The pump was actually still performing well up until last startup on friday when I noticed no vacuum during braking.Im now concerned about the 12 tiny bearings that have scattered amongst the engine,the pan will come off next weekend , 400K plus and pump looks orig.
On another note Ive owned some 190d cars and had much more issue with these vac pumps vs the 617 s .An example of durability concern was with the armature fingers ,weak spot and would break at this point.

Progress
 

I got the cam installed, timing chain crimped, and the oil pump bolted up. I got the head bolts, pan gasket, and other parts yesterday, so I will probably get the engine ready to run today with the exception of the vac pump (it has not arrived yet). I pulled the injection pump the other day, and will install and time it today, now that I have th gasket.

New chain crimped

New cam installed

Almost finished!
 

I had a couple hours available to work on the car today. I got it almost ready to start. I removed the motor mount arm to get the oil cooler hoses out, to replace them. The upper hos was available new, so I had to make a new lower hose using the old metal tubes, and replaced the rubber hose. I went to my local A/C shop and bought some #12 hose and some sleeves. I have a crimper, so I cut the hose to the proper length, and crimped it on. It turned out great.

I got both hoses installed, wow it is so easy with the arm and the injection pump removed!

Photo of both hoses. I also got the IP timed and the rest of the fuel system hooked up. All I have left to do is the rocker arms, oil pan, and vacuum pump (it has not arrived yet).

Just as a note for the DIY crowd ,Ive pulled several vac pumps over the yrs and it always pays to be patient with these allen headed bolts that are used on this unit.I eventually came to the understanding that pulling the radiator is the only sure fire bet to get easy access to these bolts.The oil and grim at this location is usually also very high so a trip to the car wash and to scrap out each bolt before getting a tool is a good idea.The last excerise in not having a stripped alllen bolt at the begiinning of this project is to use a socket allen wrench tool ,once youve got it in the bolt hit it with a hammer to make sure its set, an extension makes this easier to accomplish.Happy DIY EN.

Such a beautiful thing!
 

The vacuum pump arrived today, and it is nice! It was purchased from the Classic Center. I think by tomorrow afternoon, the car will be running. Woo-Hoo!

I found the vac pump cam to be bad, and that is what might have caused the pump to fail. It has divots in the surface where the roller has dug in. It is getting replaced with a good one. First photo is the bad one, the second is the good one.

THANX Rich for this informative thread chock full of good photos .

So I finally relented and ordered a new vacuum pump to replace the original in my 1983 300TD with 215,000 miles on it, even though I inspected it last year and did not see any signs of impending doom--the bearing looked fine as did the cam drive surface. But too many tales of woe and I spent money having the head rebuilt a few years ago and would hate to see that go away.

In looking for a new pump, I found one site that had a warning about installing the new pump, that it required a professional mechanic, without identifying any potential pitfalls. I have had mine off a few times and other than rotating the drive cam so the bearing mates with a low spot, inspecting the cam drive surface and replacing the gasket with a new one from MB, I am not sure what other pitfalls may exist. Can anyone offer any other advice?

Peter

Hell ide rather take the jeep trails up the side of the mountain for adventure!!

If you have had your pump off and on a few times you will not have a problem. A lot of people do it by simply removing the power steering pump belt, however, as Rich said, removing the power steering pump itself provides better access to the vac pump.

One step forward, two steps back
 

After installing the vac pump, I decided to adjust the valves (one of the last things to do before firing it up). I got #1&2 done, and was turning the crank to adjust #4, and it bound up tight. I assumed there was a piece of metal stuck on the crank gear. I also noticed that the chain was riding off the side of the upper guide rail, and it looked bent. While I was waiting for another guide rail to arrive, I pulled the crank pulleys so I could get to the guide rail pin. I removed the rail, and shined a light down the cavity. I saw a piece of metal stuck between the two rows of teeth on the crank gear, so I knew I found the problem with the bound up chain. I was able to get a magnet placed right next to the offending metal piece, and used the sharp end of a long rat tail file to dislodge the metal from the gear. It stuck to the magnet, and I was able to remove it without loosing it. I am sure it was a piece of the vac pump arm. Photo below. I will be getting the rail tomorrow. I will have to assemble a few more things now, but it is a small price to pay for actually being able to retrieve the metal shard....Rich

It's alive!
 

I got the chain guide today, and installed it. I assembled everything needed to fire it up, so a few things still need to be put back on to drive the car. After a little cranking, the injection lines filled up and it started to run smooth and quiet (well as quiet as a Diesel should be). There were no odd noises, and it revved up just fine. I would say that my efforts to bring this engine back to life were a success! I still have to put on the cooling system parts and all the belts and pulleys, as I did not want to put all those parts on if the engine would not run or if it still had another problem. The owner and I are happy to get this engine running, rather than to scrap it and put the rebuilt engine in. This way it is all original and has matching numbers.....Rich

SUCESS
 

Sweet ! :) .

Don't you just love it when a plan comes together ? :P .

I got it all put back together this morning, and fired it up. I noticed oil leaking from the new cam cover gasket, so I suspected the cover got bent from the timing chain or other parts trying to occupy the same space. Sure enough, the cover was bent, so I went to my parts stash and found another one. No more leak! Here is a photo of the parts that were bad, and replaced.

Make some junk art and create a purchase here ,IM thinking wind chime.

Very good Rich ;

Is there a How-To on removing the cam chain without cutting it ? .

I've never done a valve job in a OHC engine and I need to do my '82 240D .

I'm afraid to do some wrong thing and damage $pendy parts .

TIA ,