Bummer. Time to check out some junkyards with your trusty Mityvac in hand?

Lukejt

My alda on my 87 300D leaked, and I got a used replacement off a 1982 617!

All the numbers on both alda's were the same..........it worked! BB

Looks like I need to find a benz boneyard. I did find an ALDA on a parts 123 in my uncles driveway, but he was unable to get it off in the cold and dark.

Can anyone point me toward a junkyard in or around NYC? Northern NJ is most convienent to my location. Thanks,

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-Mike
'87 300TD 304kmi (RIP)
'95 Toyota Camry Wagon 125kmi

Just for the fun of it, I took my old leaking alda apart last night to see if I could repair it. Not knowing what I'd find upon opening it up, I had to drill out one of the four screws, (they use thread lock) I was surprised at what is in there!

Basically there are two round, or disc, brass bodies, each probably filled with some form of gas. One disc (top) is firmly attatched to the adjust screw so it can be adjusted closer or away from the other brass disc (bottom) which connects through the alda body to the pin connecting into the IP and it moves up or down depending on atmosphric pressure and how much pressure is being exerted from the boost pressure from the intake manifold.

The bottom disc has a rubber seal, the alda body has also a rubber seal between the two halves. Water must have gotten inside my alda and corroded the alda's body seal and leaked past the rubber seal. The bottom rubber seal was just plane worn!

If you can find a similar rubber seal, for the bottom disc, and reasel with silicon the alda body seal, I believe one could have a rebuilt alda!

The only real pain was getting the 4 philips screws to break free without messing up the philips + slots! You need brace and large philips bit, a vise, and a lot of down force before turning the brace and bit!

Just a thought BB

BB, I was thinking about that too. Thanks for posting the results of your investigation.

Judging from Dave's pictures it looks like the device should hold preasure even when removed from the engine. By that I mean that the seal is sealing against the inside of the ALDA and not the IP.

Other than lack of power because of no fuel enrichment is there any reason I couldn't drive my car with the ALDA removed as long as I was careful to cover the opening in the IP? It might be even worse power than it is now if the ALDA adjustment is holding the spring down a bit. But I ought to be able to get it back and forth from my garage, eh?

Thanks,

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-Mike
'87 300TD 304kmi (RIP)
'95 Toyota Camry Wagon 125kmi

Somebody else recently reported driving without the ALDA and having no ill effects. You should get full fuel enrichment all the time, probably resulting in some smoke at low rpm.

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
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Thanks Rick.

We'll I've got some queries out to several salvage yards in NJ and Long Island. I'll see what I find. Still (not so) secretly hoping for Dave M. to pipe up with his ALDA rebuild kits or at least a lead on ordering one.

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-Mike
'87 300TD 304kmi (RIP)
'95 Toyota Camry Wagon 125kmi

Hi everone,

First, I'm not sure your ALDA is leaking. I tested them with a MityVac Silverline 4050 kit, which I highly recommend buying if you own any OM60x diesel. A bad ALDA won't let you pump the pressure over zero - pump as fast as you can, and it just stays at zero. A good one will pump up to 10-15psi pretty easily, and hold that pressure. If it will pump to 15psi and leak slowly at, say, 1psi per second (10 seconds to get from 15psi down to 5psi), that's probably fine and shouldn't affect performance any.

More likely, you just need to adjust the ALDA. I too wanted to retain the tamper seal and use shims, but that is not an optimum solution unless you have an assortment of shims to pick from. I think the usual stock shim is about 1.2mm thick which is approximately equal to two turns of the setscrew. Most cars with virgin ALDAs need about 1.0-1.5 turns CCW, or a 0.6-0.9mm thick shim (if my memory on the sizing is correct). Basically, you adjust it CCW (richer) until you can't feel any more power gain off idle. A small puff of smoke leaving a stop sign is normal. A big cloud is not (that's too rich). You can probably forget checking at WOT since the internal full-load stop is what limits fuel, not the ALDA. This may get your boost pressure back up to 10-12psi where it belongs.

Checking for a plugged catalyst is not a bad idea, but I'd adjust the ALDA first - it's easier.

If your ALDA is leaking and you need to fix it, you can't buy a new one from Mercedes, it has to come from Bosch ($200+, I think). They're all the same from about 1980-1987, so junkyard ALDAs are great donors. I don't have any rebuild kits, sorry. I think you got me mixed up with a different fellow on the MBZ.org email list, he sells the seals for about $5, and also sells "rebuilt" ALDAs with new seals for around $50, if you don't want to attempt it yourself.



HTH,

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Dave
Boise, ID
Check out my website photos, documents, and movies!

Dave,

That is indeed very helpful. Mine took 8sec to leak one psi. Now I have a little balloon pump that I tested with my preasure gage and it pumps up just great. (Will still need a mityvac to vacuum test.) Unfortunately my gage only goes up to 10psi, but I should be able preform a better test.

So unless it doesn't pump up at all my next move will be to open it up a bit and see what that does for me. The ADLA adjust seems to jive with my severe power problems at high altitude. Poor off idle performance at sea level = really really bad off idle performance in Denver.

As for the ALDA kit. I was refering to your day dreaming about ordering some parts from Bosch and making a "kit" in this year old thread:

http://www.peachparts.com/shopforum/diesel-discussion/76539-603-injector-pump-leaking-oil-post483780.html?highlight=kit#post483780

Obviously, still something you don't have time for.

Thanks for the feed back. Much appreciated. I should know on Sat. how my adjustment works out.

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-Mike
'87 300TD 304kmi (RIP)
'95 Toyota Camry Wagon 125kmi

Well, I was able to test my ALDA and timed to leak down from 10psi to 5psi in 5-6sec. Based on what Dave has said, I'm going to assume that there is enough volume generated by the turbo to old this open.

The disappoint thing was that I assumed I could get the 24mm thin head wrench I needed Sat. morning. Ooops! that turned out the be a bad plan. So I failed to remove and adjust my ALDA yesterday. I need to find a friend to share tools with in the NYC.

I did test my boost preasure with the line to ALDA disconnected. It gets up to about 3.5-4psi with no enrichment. I was getting 5.5 with (weak) enrichment. Looking forward to getting this back up to 12!

Thanks,

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-Mike
'87 300TD 304kmi (RIP)
'95 Toyota Camry Wagon 125kmi

I had a 24mm, and it was too long, wouldn't fit. I ended up using a large set of Visegrips and a quality adjustable wrench (goose neck notched for a nut Knipix I think, NOT cresent). It worked pretty good, and I didn't damage the hardware. The first time was a *****. Now that I've done it, it's easier. I did remove a bunch of the vacuum connections around the ALDA to prevent damage. Just be sure to remember where they go or mark them with a paint marker.

Lukejt

That's correct. While the leakdown isn't optimal, it's probably NOT affecting performance any. I wouldn't worry about it for now.


You shouldn't need a thin-head wrench. I just used a plain old Craftsman 24mm on the ALDA body, and whatever pliers fit on the gold-colored nut on the IP. I believe even local McParts stores (AutoZone, Pep Boys, Kragen/Schucks/Chief, etc) carry cheap 24mm "Taiwan" wrenches that will suffice for this application.

Ouch. On my white car, with the ALDA disconnected, I still got 12.5psi of boost, and a 14-second 0-60 time. With it connected, boost remained the same at 12.5psi, but the 0-60 time dropped to 11 seconds or faster. I'd say you're way lean on fuel delivery at the moment. I've wanted to repeat this test on my blue car, just to see if it acts the same way. That'll have to wait until the timing cover is fixed though (i.e., springtime).

Hmmm. Dave, your input here is very interesting. I'm sorry I didn't read your post while I was away in VA and had an opportunity to mess with the thing.

First, your quite right. I standard 24mm from Ace turned out to work just right. The first one I tried at my neighborhood part store was extra beefy and I didn't actually try the others that appeared to be the same size.

I was at my friends farm and we would have ground it down if needed, but didn't need to and was able to remove the ALDA with minor problems. Once I removed it I tried a couple of things.

First, I put in a shim (the large copper washer that comes with the oil filter had the perfect inside diameter, but I had to grind the outside down to get it yo fit. I think this was between .6 and .9 mm thick. It made a big difference off idle. The car jumped to attention as it has never done before, but the change was clearly more then needed based on the huge clouds of smoke visible in the rearview mirror on a sunny day. The boost preasure made it up to 7psi, but not enough to change my power problems.

Second, I tested the leak down with the ALDA removed and I can't get it hold anything. I called a Diesel Fuel Injection place in Harrisonburg, VA. They had part numbers for the two internal diaphrams $93 each. That tech's opinion was that the pressure leak was a problem. He wasn't familure with this specific IP, but in general when the anaroid doesn't hold preasure they fix that.

So I continued my search for a bone yard ALDA with no luck in the Shenendoah valley. So I removed the shim and drove home to NY with the system back in the original configuration. One thing I did find was the variablity in fuel. The stuff I got in NJ on the way home was noticably better then what I had purchased in VA.

But, I think the most interesting piece of information is the fact that the boost preasure builds up to the waste gate adjusted level of 12.5psi WITHOUT fuel enrichment via the ALDA. I was previously thinking that the feed back of the additional enrichment was required to build up the exhaust heat and preasure to reach maximum boost.

Wouldn't this mean that either my turbo is bad, my exhaust is blocked, or my waste gate is open?

Thanks,

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-Mike
'87 300TD 304kmi (RIP)
'95 Toyota Camry Wagon 125kmi

I was told the Alda is a pressure device and applying vacume may damage it....if that is true or not I don't know but I know it IS a pressure driven device adn not a vacume one.

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Proud owner of ....
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Hi Mike,

Good, I'm glad you got the ALDA removed and shimmed. If you're getting a decent smoke cloud at takeoff, you need to turn it down some, or install a thinner shim. Go leaner until you can feel a slight power loss off idle, then go back richer a bit to correct it, and that's about the perfect adjustment.

Testing the ALDA with vacuum won't hurt anything (well, shouldn't) but isn't a valid test. It needs to be pressure tested, but it's best to pressure test it while installed on the pump, not loose in your hand. It's hard to explain but the capsules inside move around and the pump's vertical shaft keeps it located (centered) in the seal. If it's not holding pressure while on the IP, you need a shaft seal. It's pretty rare to have one of the internal brass capsules fail. I think Jim on the MBZ email list sells used ALDA's with a new seal installed for ~$50.

Question: You said boost was 7psi with the ALDA shimmed, but I don't understand when you saw 12.5psi... did you drive the car with the ALDA removed, perhaps? When the ALDA is not installed, the pump is at full rich all the time. If the wastegate is stuck open you'd get zero PSI at all times, if stuck closed it would allow boost over 12.5psi. Not likely to be a bad turbo either if you saw 12.5psi.