How to replace aneroid compensator or ALDA? 300sd

The ALDA (aneroid compensator) consists of two small metal aneroid capsules (like small inverted pie pans) which expand and contract with the car's altitude and its turbo's boost pressure. As you can imagine their expansion and contraction is very very small. A series of levers inside the injection pump accentuates their minute movement and slides the fuel rack to add some fuel during acceleration.

I've never seen these aneroid capsules for sale but understand they are available from Bosch.

There's no reason for an ALDA to simply break so to exclude all other possibilities, have you:

Cleaned the banjo fitting and hollow bolt at the aft end of the intake manifold? Checked the plastic line from the banjo fitting to the switchover valve (on the fire wall), including its rubber hoses? The switchover valve gets dirty and may be stuck open (pressure relief) in which case the ALDA won't get the pressure it needs to operate. Finally, if the ALDA has been screwed IN, it may just be mis adjusted to add NO fuel.

The ALDA is adjusted OUT to INCREASE fueling and IN to DECREASE engine fueling (and smoke from excess fuel). There's a balance between power and relatively clean, smoke free exhaust. The factory setting is optimum.

Whoever told you that there are shims doesn't know what he's talking about - and if your ALDA still retains the bench set factory setting leave it alone and explore why it's not getting the pressure it needs to operate.

Thanks to the group for helping me and thanks to T. G. Lambach Who is frequently giving out the info I find in the group,

I bought this car 3 years ago it seems to run good with little power. I discovered just a couple of weeks ago that the screw is not supposed to be exposed on the ALDA, mine is so the assumption is made, and it has been screwed with, just not by me.

I look on the groups and all I can find is info on don't touch alda!! combined with info on touching the alda and getting increased power. I buy the first tip. I also see several comments on "you will break it if you touch it and then will have to get a new one" well, I have good one and I think my old one is broke.

I have an Alda that I bought from an internet sight it comes with 3 different shim washers that are of different thicknesses and the seller says that the choice of shim you use will determine the setting and that the screw on top is not touched. Well I don't know but in thinking it all out there is some credibility to the thought that how thick the seal washer is would affect the richness as this vessel is an acting force against another opposing force. My problem is I have this good and tested part that seems to work you can see it react by using a squeeze bulb. My old one dose not seem to work. My test of the one ALDA in place is as fallows, my car has less power then a 300sd I drove recently witch is what set me off on this adventure. I am quite familiar with my cars functions and wonder why I have less power so I started to investigate. All timing, turbo, waste gate, vacuum lines are all ok, banjo fitting is open and valves are set correct. I placed a tee into the hose at the ALDA and ran a hose into the cabin a 0-30 pound gage is attached to the hose. I am able to see the boost pressure as I drive. I get about 10 pounds when I step on the fuel and it tapers off as I accelerate. 10 pounds is obtained at 3000 rpm and peddel most pushed to the floor. This is not an official test I know but it tells me I am getting a pressure to the Alda. The second part of the test is I take the gage off the hose and stomp on the gas and time 0-60 in 34 seconds, now returning to the start point I repeat the same test with my thumb on the end of the hose and get 0-60 in 34 seconds, no difference. I have also played with just putting my thumb off and on the hose as I drive inder power to see if any power is gained or lost. I find that the car could car less if there is torbo boost or not. I have gone as far as I can to if my alda is bad short of unscrewing it and testing it on the bench so this is why I am looking for first hand experience. I don't want just unscrew it and let big lesson I did not want. Comment is available about replacement so logic is, instructions are too. What's your thoughts?

Thanks, Bruce Buchanan

Yes, you adjust it by shims. You need a 27mm wrench. A short one! The nut is part of the top of the pump. It is captive. The threads are part of the Alda unit. They are right hand thread. Remember that as you figure out which way to turn the nut. Even though it is right hand thread, you unscrew it backwards of what you think. You are uncrewing it off the treads from underneath.

Start with the thickest one. The thick one should be about half the thickness of the copper drain plug seal washer, correct?

I eat crow - about there being no shims inside the ALDA. None are shown in my supplemental turbo manual but it doesn't address the IP's insides.

Follow Karl's advise, for he knows, professionally, whereas we armatures think we know.

After the ALDA is fixed your car should accelerate 0 - 60 in about 13 -

Yeper do I will get on it and report how all this works, Thanks for the help guys. Bruce Buchanan