Vac line from ALDA

[sjh]

w124 '90 300D 2.5L Turbo - Automatic.

I believe this is present on most 123, 124 & 126s but I know it is on my car.

There is a black plastic vacuum (or could be pressure) line from the ALDA that goes through the firewall. Where does this line end up? What's it do?

Thanks.

[jt20]

it should go to the vacuum amplifier for the transmission.

a blue or a black disk with 4 vac lines running onto it.

[sjh]

Originally Posted by jt20

it should go to the vacuum amplifier for the transmission.

a blue or a black disk with 4 vac lines running onto to.

The BFS does get a line from the ALDA but I'm asking about the line that goes THROUGH the firewall into the dash.

Thanks.

[jt20]

Have you compared your system to a stock diagram recently?


http://w124-zone.com/downloads/MB%20CD/W124/w124CD1/Program/Engine/602_603/07.1-0500.pdf

[sjh]

Originally Posted by jt20

Have you compared your system to a stock diagram recently?


http://w124-zone.com/downloads/MB%20CD/W124/w124CD1/Program/Engine/602_603/07.1-0500.pdf

Yes and I find nothing on diagram that corresponds.

Originally Posted by Jeremy5848

Are you sure it's ALDA? Might it be the transmission's VCV. It draws air as needed from behind the dash because (in theory) it's cleaner than air under the hood.

Hi Jeremy,

Sure seems like it to me. I find the vent line off of the VCV but this is a different one.

Originally Posted by Jeremy5848

With this type of question the OP is advised to include a photograph, for example, this one showing the VCV:

Ask it shall be given.

I thought this was a stupid question and everyone would say it is such-and-such and I would go, "Gee I can't believe I had to ask."

So here are 3 pictures.

The first shows a "T" off the ALDA with the lower line heading over to the vacuum amplifier. The upper line runs behind the CC bracket.

The second pic shows the continuing path of the upper line and the third pic shows the line and a larger bundle heading into the middle of the firewall.

Of course the real reason I did not put up any pictures is because they are so crummy compared to the excellent shots done by others!

[Jeremy5848]

Are you sure it's ALDA? Might it be the transmission's VCV. It draws air as needed from behind the dash because (in theory) it's cleaner than air under the hood.

Could it be the line from the shut-off valve on the IP to the ignition switch?

There are also one or two vacuum vent lines from the EGR solenoids. They also draw clean air from behind the dash.

With this type of question the OP is advised to include a photograph, for example, this one showing the VCV:

[jt20]

That is not a stock connection. Make sure there is a clamp on the ALDA fitting for that 'Y'.

Regardless, find the switchover valves like the ones in the diagram and you should have your answer. Pull a vacuum on the lines at the switchover valves to see which one corresponds.

If the line was routed properly, it does not go into the cabin.

[sjh]

Originally Posted by jt20

That is not a stock connection. Make sure there is a clamp on the ALDA fitting for that 'Y'.

Regardless, find the switchover valves like the ones in the diagram and you should have your answer. Pull a vacuum on the lines at the switchover valves to see which one corresponds.

If the line was routed properly, it does not go into the cabin.

There were three metal clamps but one fell off while taking the photo. I'll use a small nylon wire wrap as a replacement unless someone advises against it.

On my car the switchover valve is mounted next to the vacuum amplifier and gets it connections from the vac amp.

Looking at the vac lines in the FSM everything is properly connected on my car except that additional line that I've asked about.

I guess I'll put the mighty-vac on it and see what I find.

[jt20]

In that link, did you scroll down to the correct diagram for your model?

Believe the diagram, not whats on car. Start from scratch, and re-install the lines according to the diagram.


Also, what is with the open port on your intake manifold? Isn't that where the ALDA gets its boost signal from?

[sjh]

Originally Posted by jt20

In that link, did you scroll down to the correct diagram for your model?

Yes.

Originally Posted by jt20

Also, what is with the open port on your intake manifold? Isn't that where the ALDA gets its boost signal from?

Moved out of way for photo.

[jt20]

Maybe a previous owner had a boost gauge?

Hope it holds vacuum.

Good luck.

[jt20]

ps

scroll down to page 15 on that link, just to be certain that does not work for you.

[sjh]

Originally Posted by jt20

ps

scroll down to page 15 on that link, just to be certain that does not work for you.

That's the diagram I'm using.

Line holds vacuum but, following your comments (which make sense) I have removed the line from the ALDA and capped it.

You may be correct that it once went to a boost gauge.

Thanks.

[babymog]

There should be a vacuum line from the manifold where your photo has an open fitting, to the bottom of the switchover valve. The electrical connection on the sensor just above the vacuum fitting on the manifold, is for the overboost protection that actuates the switchover valve.

The middle line from the switchover valve, goes to the ALDA. Top is a vent and not connected.

[sjh]

Originally Posted by babymog

There should be a vacuum line from the manifold where your photo has an open fitting, to the bottom of the switchover valve. The electrical connection on the sensor just above the vacuum fitting on the manifold, is for the overboost protection that actuates the switchover valve.

The middle line from the switchover valve, goes to the ALDA. Top is a vent and not connected.

It was removed for photo but is in place.

I understand the switch on manifold drives switchover unit.

I have factory vac diagram. I performed gsxr's boost-gate mod. All vac lines on passenger side are removed. System holds great vacuum. It's the 1/8" OB black with a thin white stripe line that holds vac and was connected to ALDA that I do not understand.

As someone else suggested it may have gone to a boost gauge.

Thanks.