Oil leak from ALDA - PeachParts Mercedes-Benz Forum

Yuros · #1 11-21-2013, 12:26 PM

I removed the ALDA unit on my '87 300TD a few weeks ago as it was not working properly and caused lethargic acceleration. Removing the ALDA made all the difference and I noticed drastic improvement in performance and smoother shifting.

However, I have now developed an oil leak from the opening where the ALDA unit was mounted.

The instructions for ALDA removal on this and other forums are quite straight forward; Remove ALDA, drive.
Should I have capped the hole, or is it self-sealed? Is oil coming out of that opening normal, or indication of some other problem?

My mechanic tells me that if ALDA is working properly the car would actually accelerate better than with ALDA removed and recommends that I repair the ALDA and install it back. However the improvement in performance and shifting was so significant that I'm very reluctant to put the ALDA back on. But I can't have the oil leaking from that hole either....

vstech · #2 11-21-2013, 01:14 PM

Pics? Oil should not be present.

sixto · #3 11-21-2013, 01:21 PM

Many ALDA problems are actually a clogged signal line between the manifold and ALDA. The line goes through an overboost switchover valve. Cleaning a dirty line wakes up the engine.

You should be able to use any MB ALDA through '95 since the ALDA can't be repaired. At least I don't know the MB repair shop that will repair an aneroid capsule. The ALDA is adjusted when assembled onto the IP at the factory so a a used ALDA joined to a used IP probably needs adjustment. It's not worth the cost to do this on a bench. You can do it by the seat of your pants through the adjustment screw atop the ALDA or with shims between the IP and ALDA.

The ALDA is an inhibiting device. I don't see how the car can accelerate faster with an ALDA. Conversely, the car should run well enough with the ALDA to have been worth $50K in 1987.

The plugner the ALDA sits over is open to the inside of the IP. There is an oil seal that keeps things dry when the plunger is relaxed; i.e., the ALDA isn't pressing on it. If oil leaks when the ALDA is off the IP, the plunger seal is bad or something's propping the plunger open. Unfortunately you have to get inside the IP to replace the seal or do anything with the plunger. Even if you decide to go ALDA-less, slip a couple of washers between the IP and ALDA so there's no pressure on the plunger yet everything is sealed.

Sixto
87 300D

shertex · #4 11-21-2013, 01:44 PM

By turning the set screw all the way counterclockwise it will be effectively the same as having no ALDA....but with no oil leak.

I think there are some folks that have devised caps for the top of the IP when ALDA is removed....but don't know if it would stop an oil leak.

Yuros · #5 11-21-2013, 03:06 PM

Quote:

Originally Posted by sixto

The plugner the ALDA sits over is open to the inside of the IP. There is an oil seal that keeps things dry when the plunger is relaxed; i.e., the ALDA isn't pressing on it. If oil leaks when the ALDA is off the IP, the plunger seal is bad or something's propping the plunger open. Unfortunately you have to get inside the IP to replace the seal or do anything with the plunger. Even if you decide to go ALDA-less, slip a couple of washers between the IP and ALDA so there's no pressure on the plunger yet everything is sealed.

Sixto
87 300D

Thanks for all this information. If I understood you correctly, if the oil seal on IP is broken or plunger is not relaxing, then even if I get a new ALDA I'll still have oil leaking into it. So the best course of action would be to cap off the alda port and continue to drive without ALDA?
Disassembling the IP and fixing the seal seems like a lot of work, especially for ALDA that seems redundant.

Alternatively, as SHERTEX suggested, I could install the old ALDA unit back with adjustment screw turned all the way in, effectively making ALDA nothing more than a cap for that port. Correct?

shertex · #6 11-21-2013, 03:46 PM

Quote:

Originally Posted by Yuros

Thanks for all this information. If I understood you correctly, if the oil seal on IP is broken or plunger is not relaxing, then even if I get a new ALDA I'll still have oil leaking into it. So the best course of action would be to cap off the alda port and continue to drive without ALDA?
Disassembling the IP and fixing the seal seems like a lot of work, especially for ALDA that seems redundant.

Alternatively, as SHERTEX suggested, I could install the old ALDA unit back with adjustment screw turned all the way in, effectively making ALDA nothing more than a cap for that port. Correct?

You mean adjustment screw all the way OUT. Made sure you loosen the nut first. Then turn CCW till you meet resistance.