You're overthinking by a lot. Just get a brand new Pierburg pump that has the sealed bearing, a new gasket from the MB dealer and you're done.

End of story

 

While you're right, I could simply R&R it, that pump is twice the price of either of the alternative pumps I am considering. If the trans doesn't demand a range of vacuum for shift strategy I can buy a relay, fuse, pump, gasket, and a piece of aluminum for half the price of that pump (in fact I already have all that except the pump and gasket). Reroute a vacuum line, and never worry about the VP damaging the engine.

If the electric pump ever dies I don't have to worry about availability, it costs less than half of the OE option, and it's less than 10 minutes to replace being as it's a single connector and two bolts.

From what I've read folks say to replace those pumps every 100k-200k miles, which is fine, that's a solid service life. But, I'd rather that be an $80 part and 10 minutes of my time than a $230 part and an hour or two. Even still perhaps the electric rotary vane pump will last 300k miles without a hiccup. Personally I'll spend the hour or two retrofitting it once just to never worry about it fragging the engine again. If I saw the merit to installing a replacement pump I would, but I don't when there are potentially identically functional, more serviceable, and cheaper options.

 

Sounds like it's just about cost, in which case these are the worst cars.

Keep in mind that you have a mechanical diesel with a vacuum driven shutoff valve inside the injection pump. Vacuum is being generated by the vacuum pump until the engine stops rotating. Similarly, fuel is being pressurized and injected as long as the engine is rotating. That is why both are sandwiched on top of each at the same place on the engine. The timing is critical.

With a electric vacuum pump, your vacuum instantly goes to zero as soon as you turn the key vs. when the engine physically stops rotating.

 

Sounds like it's just about cost, in which case these are the worst cars.

Keep in mind that you have a mechanical diesel with a vacuum driven shutoff valve inside the injection pump. Vacuum is being generated by the vacuum pump until the engine stops rotating. Similarly, fuel is being pressurized and injected as long as the engine is rotating. That is why both are sandwiched on top of each at the same place on the engine. The timing is critical.

With a electric vacuum pump, your vacuum instantly goes to zero as soon as you turn the key vs. when the engine physically stops rotating.

I have no qualm spending the money for the OEM part. But of course if I can save money I will, especially if it makes the car more reliable, serviceable, and the part will be available for much longer. I'm not really sure what I did to trigger you attacking me like this but I'd appreciate if you wouldn't. Perhaps you are always this crabby when folks consider modifying their own possessions?

From what Kent Bergsma at Mercedes Source says you can't even get new VPs or rebuilt kits for certain models so I'm not really sure what other options some folks have sbaert...

However, you do have a good point with the vacuum timing. I may have to make a small timer to keep the VP running for another 2 seconds after keyed ignition goes off. Might be fine without it, but it's certainly a consideration.

I found this thread on a failure; (71) 1995 E300D Vacuum Pump Failure - Oil Leak | Mercedes-Benz Forum (benzworld.org)

On my year and model (84 300D) the Timer front bushing wear causing too much end play seems to be the main reason for the VP to fail. I don't know if there is a similar reason you the later models.

Heck yes! Thank you! I was reading through a transmission shift tuning guide for the 722.3 and 722.4 and saw that the VP should make about 20-23" of vacuum at idle and no other references to total vacuum. So what you found verifies that this works as a replacement. Pretty sure my VP is either bad or I have leaks somewhere because my trans is hard shifting for sure.

 

I found this thread on a failure; (71) 1995 E300D Vacuum Pump Failure - Oil Leak | Mercedes-Benz Forum (benzworld.org)

On my year and model (84 300D) the Timer front bushing wear causing too much end play seems to be the main reason for the VP to fail. I don't know if there is a similar reason you the later models.

 

I'm not attacking anything/anyone. It is you that kept mentioning the $ part. When it comes to MB, $ is the last thing I consider within reason.

Hard shifting transmission is usually caused by bad trans vacuum modulator, modulator not adjusted properly, pressure control cable adjustment, bad transmission mount, etc, etc, etc.

If your vacuum pump was on its last legs, you'd have virtually no brake boost assist.

Why not do the $0 diagnosis other than a new gasket? Take off the pump, clean up the pump, check the condition of the bearing, check the condition of the injection pump timer ramp gear and go from there. If everything looks kosher and the pump has the sealed bearing type, I'd just put it back. No reason to fix what ain't broken.

The vacuum pump is not the Achilles heel of the OM606. Fuel leaks and the CCV on the other hand, but that is a separate conversation

And for the record, Kent is just plain wrong that vacuum pumps are not available for the W124 (see link below). He is not the messiah when it comes to MBs and he is regularly wrong Besides, if you order with Mercedessource you may not get what they advertise. Example:. I ordered a Bosch voltage regulator, they sent a Meyle. When I called them up about it, they merely said"it's all good" and they wouldn't take it back since it was electrical part.

If it aint OE or OEM, it ain't going on my car.

Fwiw, you should replace your regulator too based on the mileage. Cheap insurance

Pierburg 0002303165, 720607740 Vacuum Pump - Mercedes | 0002302865 0002302965 0002303065 98056

Find Pierburg, 720607740 Vacuum Pump 0002303165 at discount prices in our extensive Mercedes auto parts catalog. AutohausAZ offers a large selection of Pierburg parts online. The installation guide supplied with the pump must be followed for correct installation procedures in order to be...

www.autohausaz.com

 

I performed an inspection today, as well as replaced the leaky fuel lines. The VP was produced in 94, so it's likely original as the car was produced in 94. I listened to the VP with a stethoscope and determined that I can hear the ball bearing rolling with no ticking. That said, I'm going to let the car sit until I have serviced the pump. Also, my #4 injector needs some attention (realistically all of them probably need attention).

While I respect your intention to keep the car original, I am going to follow my own path. The price is just a piece of the puzzle. All things considered, everything aspect (aside from originality) is beneficial to performing this modification. Okay, okay, I know I will invest a couple hours into making this a reality, I've accepted that. I have determined the vacuum pump from a 2016 Cadillac CTS will fit the bill. Yes, it's $40 more expensive than the $70 pump I was looking at originally, but it's a purpose built factory item for brake boosters. I have already ordered the basics to perform the modification.

Here's my next steps:

- Determine the load for the pump so I can select the correct relay, fuse, and wire gauge.
- Determine if there is space for another relay and fuse in the factory location (unless there is a factory keyed relay with enough overhead for the pump).
- Determine a proper location to tap into the factory vacuum harness.
- Visit a GM dealership and get the factory pigtail so that the installation is plug and play for future serviceability.
- Find or design a vacuum canister to store ample vacuum to turn off the engine.
- Once I have everything on hand, model and print a bending jig to fabricate a mount for all the accessories for a proper installation.

In my opinion, the best part of this is future serviceability is easy as dirt, and the replacements will be available for a long time. As you pointed out, the regulator probably needs to be changed which I will likely have to do anyway once I put a non-OEM VP in the car. Heck, I might even gain an eigth horsepower from this .

 

In my opinion, the best part of this is future serviceability is easy as dirt, and the replacements will be available for a long time.

GM/Ford/Chrysler (or whatever they're called this month) does not make anything 10 years after the last model rolls off the line, so if futureproofing is your goal you're better off with Toyota, Honda or . . . MB for long term parts availability.

Try finding a new in box original GM fender or a fuel tank for a 80s-90s era car at a dealership. It's just down to the bare essentials like filters and some brake stuff (mainly pads & rotors)

 

You didn't mentioning anything about doing a diesel purge. I'd do that and run LiquiMoly SDA (super diesel additive) with every other fillup to restore sulfur to pre-ULSD levels before anything else.

 

The Japanese manufacturers aren't much better than the others. No matter what industry you look at, they tend to not support their products longer than 10 years, and they try to find reasons to cut that down.

As for Kent and MercedesSource, I know a few folks value what he does but I think he just likes to hear himself talk.

 

They don't want to support their products, they want you to buy a new car. If they could avoid selling all replacement parts just to force you into a new car they would. It's a much better financial model for them.

Oh I tend to agree about Kent. Any of his stuff I watch at 2x speed because it's painfully drawn out. He has also figured out a way to monetize all of this stuff. Like you have to buy his instructions instead of just including them with what ever you're buying... Poppycock. That said he has a bunch of stuff that is free and useful.

 

I didn't mention anything about servicing the injectors because this thread is about modifying the vacuum system. Thank you for the advice, I run redline cetane booster, it also adds lubricity to the fuel. I will certainly give the engine a diesel purge session, but I suspect new injector nozzles will be necessary.

Back on topic, I highly doubt GM will pull this item. If anything it will end up in more vehicles as forced induction is becoming more common. AC Delco is GMs brand, and I can still find many items for cars from years past. On top of that, there's already other manufacturers selling the same pump, I just wanted to stick with an OE manufacturer as my life depends on the brakes.

 

So, the end goal is to make a stand alone vacuum pump module. Part of my reasoning for doing this is the system could be used on any diesel, cammed gasser, or boosted application.

You're right that I will invest hours into doing it, but I'm fine with that. I'm also not attached to things being OEM. Once I've done the R&D installing a kit like this should take about an hour. Replacing the pump should it ever fail should take about 5-10 minutes, cost less, and be one less wear item in the engine. While it's not quite as important for this vehicle since VPs are still available, there are plenty of older and modified vehicles that would benefit from having access to a kit like this. Also, one day replacement VPs will no longer be available. If someone wants one for their application I can design a mount for their application and it will be a clean bolt on kit with parts intended for the task.

 

Looking forward to the project. Let us know the final "bill of materials" needed to other's can replicate.

Time: Spending time working on these old cars is satisfying, so I understand your willingness to put in the time.

Testing: When you're done, please do some severe operational testing, in a safe manner, to make sure your brake system still has the factory performance and some safety margin. I'm thinking a track day or some such, closed course, wearing a helmet etc. etc. Stop with full braking from 100+ mph, multiple panic stops from 70 mph, that sort of stuff.

 

Looking forward to the project. Let us know the final "bill of materials" needed to other's can replicate.

Time: Spending time working on these old cars is satisfying, so I understand your willingness to put in the time.

Testing: When you're done, please do some severe operational testing, in a safe manner, to make sure your brake system still has the factory performance and some safety margin. I'm thinking a track day or some such, closed course, wearing a helmet etc. etc. Stop with full braking from 100+ mph, multiple panic stops from 70 mph, that sort of stuff.

I will both include everything I did, and also will be considering offering it as a kit if it's worthwhile, or at least the block off plate. I've decided I'm going to make the first block off plate by hand due to time constraints, and if anyone else wants one I will model it in CAD and have them cut by my machinist. Sadly modeling something like this will take about as much time as making it and I want to get the car daily drivable. Plus then I'd have to wait for an already busy machinist to make the part.

Spending the time doesn't bother me. I just hope the results are meaningful, and I'm not just wasting time. I was hoping someone would chime in earlier and say something like tjts1.

I will of course test the system. So long as the brake booster sees the same vacuum then it will behave just as before. Taking it to a track day wouldn't be a terrible idea, but the closest track is about 2 hours from me, and the performance of this car on track would be laughable to me.

The problem the problem with using an electric vac pump on these engines is that the vacuum system is very leaky especially for the pods under the dash. So your pump will be running almost continuously. Electric vac pump makes sense when you can turn it off most of the time.

Very leaky as in over time they commonly develop leaks, or it was designed to be inherently leaky? I tried suck/blow testing a couple lines by mouth and it seems like I have many leaks. Going to hook up my friend's smoke tester in a couple days here and start patching the vacuum system before I put the pump on. I agree with you that the ideal vacuum system for an electric pump is a well sealed one, which makes me consider that this project might not be fruitful. That said, if it can be made less lossy I don't mind tearing into the dash to fix things... I already want to refinish the wood in the center and the center vents don't blow air at all.

I've been looking over the vacuum diagram and it seems like the EGR and the air resonance flaps are tied to the same vacuum line. If I want to disable the EGR can I throw a BB in the EGR line and call it a day? PO already pulled the linkage connected to the throttle. How important are the air resonance flaps? When I draw on the secondary side of my vacuum system it's for sure pulling atmosphere in more than one place. I take it that means my intake cross over and many other things are not working as they should. Probably also explains my hard shifting.

 

Or let my wife drive it for the day!
She is heavy on the brakes and discs.

 

The problem the problem with using an electric vac pump on these engines is that the vacuum system is very leaky especially for the pods under the dash. So your pump will be running almost continuously. Electric vac pump makes sense when you can turn it off most of the time.

 

Your intake runner flaps are also vacuum driven. Truth be told, if electric was the way to go the factory would have done so before the car left the assembly line.

In other words, you're trying to create a solution for which there was never a problem

 

You say that they would have used them if it was the way to go, but they didn't have pumps like this at the time. Did you work for Mercedes designing this car? If not then you don't get to say what they would and wouldn't have done.

Thanks for your opinion. I'm going to politely ask you to refrain from making any more non productive comments. I'm already aware of your opinion on the matter. It's written in your signature.

I'm aware the runner flaps utilize vacuum. That doesn't mean that when they actuate they leak. You think I haven't looked over the vacuum diagrams?

 

They used a electric vacuum pump for the locks, so electric vacuum pumps were available during W124 production and even before.

As I said, if they could have saved a buck by running a couple lines to that pump they would have.

End of story

 

Yeah, they used an electric pump for the door locks. You know what, that electric pump is probably twice the size and moves half the volume. As I said, pumps like this weren't available, not that they weren't available at all.

Mercedes used Takata air bags. I hope you don't still have those installed in your car because they were OEM. Just because it's OEM doesn't mean it's 100% the best answer.

Maybe I'll try it again with another set of words. If you have nothing relevant to moving this project forward, don't contribute to the thread. There's got to be something better to do with your time than be obnoxious to others for conducting their own experiments... Don't you think?

 

So, I just watched a whole video on dash teardown and pod replacement... Looks not terrible, but it's definitely a job. From what I can tell, these are supposed to be well sealed with minimal leak down. Likely there is supposed to be no leak down, but nature hates a vacuum.

Some of the pods are not available anymore, but you can use the membrane from others to swap into the original pods. I will end up doing this because I already know my pods are bad, the center vents no longer work in my car. When I do it, I will likely soak the rubbers in something like armor all to help the membranes last longer. I will probably also put them back in using a tiny bit of RTV to fully seal the pods and avoid further leaking. Unfortunately that will make them harder to replace in the future, but my hope is that they will last longer.

My alternative is recasting the membranes in silicone, which would also be cool, and I'm sure there's a handful of folks who would want those. But, that would be another large undertaking and would leave me with the dashboard in pieces for a couple days. I might however make them and then later on down the line install them if they ever fail again... Or if somebody wants replacement membranes.

 

Alrighty, I bought a hand vacuum pump after work and checked a couple of things... Basically the only thing that holds vacuum is the brake booster line and the engine off circuit, no surprise. I was however surprised that the vacuum shift modulator is holding vacuum. That's nice.

I have a couple dilemmas that perhaps others can help with. I am going to redo all the vacuum lines in the engine bay because I'd rather do it once correctly than wrong three times.

First, are the air resonance flaps useful? I am going to do the off road conversion as folks call it.

Second, I have my own idea on how to do this, but I would like other ideas on this. I want to set up the vacuum pump to prioritize the brake booster (BB). I am half debating using two vacuum pumps and just making one dedicated to the BB. While this adds cost, it also adds safety and redundancy.

Third, does anyone know of a good reference for vacuum canisters? Has someone made an excel sheet of requisit vacuum canisters? If not, I will do this, but does anyone know of a good resource to look over? I still need to get an FSM. I have been using a html based version that I found, but it would be nice to one day have a paper manual... I will print it and bind it if I have to. No way I am going to pay that much for an old book. My buddy threw away a whole stack of AllData CDs a couple years back and I wish I had known, would have been real nice to have. I digress, let me know if you can help with that. If not, no worries, I will figure it out. Enjoy your weekend!

 

First, are the air resonance flaps useful? I am going to do the off road conversion as folks call it.

Yes. They create three different intake manifold lengths, which means there are three different engine speeds where the pressure wave front produces high pressure directly on the intake valves, so you basically get a 'poor man's' turbo-charger effect. Effectively, there are three torque peaks.

Think about this as if it was a pipe organ. The flow of air into the pipe creates a sound (a pressure wave). Different pipe lengths make different pitches (different frequency pressure waves).

If your intake manifold was fixed in length, it would only be capable of making one note, and it so happens that the torque peak RPM for the engine is found at the speed where that standing wave of pressure puts the pressure peak at the intake valves. Higher pressure at the intake valves = more air going into the engine, equals more power.

 

Are Y127, Y128, 102, and the VCV all EGR related? Does any of it have power/running benefit? Thinking about just completely switching mine to the without cat diagram. Looks like all I'd need is a vac cap for the passenger side (a) line, a Y line after 61, and to remove the junction at 62 to run a single line to 106. Just want to question folks with more experience than myself.

 

So, I drew up a basic supplemental vacuum diagram for installing this system while I am thinking about it. That way other folks can consult it if they want to do what I'm about to. Here's what I have picked up to get it done.

Vacuum Pump - GM 178-0884
Vacuum Switch - MULTICOMP PSF109S-81-330
Bosch 20/30A relay
Vacuum Accumulator -YC2Z-19A566-AA
Various vacuum fittings and check valves

Just a warning - I am not advocating for anyone to do this. It is potentially a safety risk if it fails and could lead to bodily injury or death of the operator, occupants, or others. I am not a trained professional, nor am I seeking DOT approval. In no way do I assume any liability for what you do with what I have shared here.

This is the first revision, and I may add a second pump that applies vacuum to the 61 line, with a check valve so it can draw on the brake booster line as well (but not the other way around). This would add a layer of redundancy so that if one pump fails the other will maintain vacuum of the BB regardless. I suspect this will be just fine, which is why I'm not opting to buy another pump, pressure switch, and relay. Time will tell. Just about have everything to get started on this. I ordered an intanke manifold gasket

 

Been real busy lately, going to be busy for a while, but I wanted to give an update. I tested the pump plugged into just battery power and it made 27 inHg. I expeditedly installed the pump and it works... I made the terrible decsion to start the install the day before I had to go drive to a wedding in Vegas at my buddy's shop where I couldn't leave the car for a couple days. It's fine, I only had to drive 5 hours to Vegas on 2 hours of sleep to catch my friends wedding the day after haha... I'm back now, and I'll tinker with it some more tomorrow. I didn't install the Vacuum accumulator and there's not enough residual vacuum to turn off the engine. Either that or the the 23 inHg that I set the switch to needs to be adjusted. I wanted to see the system would work without it, and it might, but I'll have to do some more testing. It's probably also a good idea to run the accumulator anyway to help shut off if there is every a leak in the system.

The brakes work the same, the trans shifts great now that my shift modulator has vacuum, it has a little more pep in the bottom end now that the manifold flappers are flapping. I also had to get this all installed and sorted in a day. Wish I had just installed it and only hooked up the brake booster and shut off for the time being. Redoing the vacuum lines was more time consuming than I intended but everything is sorted up to the A, B, and C terminals now... Every one of my interior lines is leaking, which will be a blast to fix, but that's outside of the purpose of this discussion.

As for the OEM vacuum pump, it was fully intact. The bearing were however stiff, and there is a discernable wear mark on the wobble plate. I ran into a snag when installing the block off plate, I noticed that there are what appear to be oil returns under the vacuum pump cover. I ended up just gutting and capping off the vacuum pump for the time being instead of potentially blocking oil returns. If anyone can verify whether or not it's okay to block off the holes then I'll install it. In the mean time I'll see if I can find an oiling diagram for the engine. If I had thought about it I would have just scalloped the plate I made with a carbide, but I was in a rush and gutting the pump was the first thing that came to mind. Two of the ports look like simple through hole drains, but one of them might be something important and I don't want to make the naive decision to frag something.

All in all I would say that it was a success, everything works correctly aside from the shut off and I will get that resolved. It feels like it almost shuts off. The idle drops, but I can't say how much since the gauge cluster shuts off when you key off. I can set up a circuit for a delayed off on the pump if I really need to, but I doubt that it needs that. I need to revise the install a little as I made the decision to bite off more than I had in time. But, it does work, I can hear the vacuum pump kick on briefly when I hit the brakes (this is normal as the booster loses volume the pressure in the system goes up). The pump took less than a second to depressurize the system (after I realized I left a hose disconnected that is ). I suspect that will probably go up a little when the interior lines are hooked up. I'll report back tomorrow after I get the engine off working correctly.

 

Okay dumb move on my part. The system works perfect. I had the line from the ignition switch capped off. No vacuum accumulator required.

When I installed the system, I had tested all the cabin lines and determined they were all leaking... Well, one of them was leaking because the ignition circuit was passing air and another line was open. I also didn't realize "other consumers" (on the vacuum diagram) meant ignition switch 😅. Hooked it up, keyed off immediately. Works great! Now I just need to permatize the system a little more. Mostly cable sleeves and make a new mount for the pump and alarm horn. The factory tab for the alarm is where I mounted the pump. I also need about 5 inches more soft hose as the 5 feet I ordered was just a little short.

 

Sone pics of your setup would be interesting.

 

Sure, the setup is function over form right now. I haven't put any time into making it truly proper and pretty. I'll reroute the wires in the tunnel behind the engine bay and organize the vacuum lines a little better. I just wanted to get it all working and was in a time crunch. I kinda did the wiring the lazy way. I used the vacuum switch for the ground on the relay so I only had to run two wires from the battery to the pump/switch. I'll probably revise this so it's on the positive terminal and run three wires. If anyone knows a good place to grab keyed power I'd appreciate it. It was the end of the night and where it ended up was the easiest place I found. I still need to mount the switch to the vacuum pump bracket as well.

Here's some pics. Sadly I didn't take any of the stock VP before I gutted it.

My wobble plate. I'm still curious if I can block off the holes in here without harm.

The block off plate I cut and drilled by hand which I didn't install because I don't want to block returns.

Here's the relay vampired into keyed power for what I believe is the oil cooler solenoid. I'm still pretty green to all of the spicifics in this engine bay, but I'm learning. I need to install an inline fuse for the power from the battery to the VP.

The T to the IP/Key off/vacuum switch

General overview

 

Also, I lied. It takes about 5 seconds for the pump to initially pull vacuum when everything has been disconnected. When I first turn the car on it usually takes 1-3 seconds to pull vacuum. When I hit the brakes it takes less than a second for the pump to recover the vacuum.

My biggest concern is that the vacuum system will develop a leak somewhere. I'll be keeping a couple vacuum caps and golf tees on hand just in case. If it does develop a leak it will be easy to tell, as the pump is audible. Not extremely, but it's definitely there, which I think is actually good. Otherwise I'd probably set up a dummy light or something to know if the pump is running constantly.

 

Mine just failed theres a small piece of metal from the booster line ring i didn’t recover

 

Mine just failed theres a small piece of metal from the booster line ring i didn’t recover

Ouch! How many miles on that pump?

I bought my first '95 E300 with about 200k miles on it, with a failed vacuum pump that had sidelined the car, and a whole host of other issues. Had to install a new vacuum pump and new wobbly drive face / gear for the injection pump, and 200k miles later all is good.