Howdy -

Looking to measure the boost pressure from the switchover valve on the firewall to ALDA... Could someone point me to the right link or give me a hint on how to measure it?! Mainly, what type guage should I buy and how do I splice the connection to the line?

Can I get a boost/vacuum guage (0 - 30psi) from NAPA with a plastic T-connector to splice into the lines?! Or do I need some other type of guage for that?!

I'm assuming I should measure the pressure BEFORE the valve and AFTER it - from what I've been reading I should see about 9-13 psi going into the ALDA. Please confirm...

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1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
1995 Toyota Land Cruiser - 3X locked; 182K

Yes, you could do it that way. Typical pressure gauges work. If you are thinking of putting it in the car permenantly, there are 15 PSI gauges that look nice. If you just want to check, adjust, then remove the gauge, I would think about getting one of those pressure/vacuum gauges so that you can check the transmission vacuum too.

There is also a hole on the side of the intake manifold. There is a plug in it right now, but it can be taken out. From what I hear, that is the proper place to test the intake manifold pressure. Sorry, don't know the thread size.

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1982 300CD Petrol/Black Leather

It is 10 x 1.0 mm. Go to an auto parts store and get a 10 x 1.0mm brake bleeder valve - it already has a handy place to ayttach the pressure tubing.

MercFan,
I just went through checking boost pressure, ALDA, and other parts. Look for recent thread "Perplexed-Sudden loss of power-Please Help. This shoud give you lots of ideas. As for checking boost pressure.
I bought a Harvard brand 0-30 PSI pool pump guage at a local hardware store for only $4.99. I also bought a brass adapter that screwed on to the guage and with a 1/4" female compression fitting on the other end. ($.89). Get some 1/4" clear poly tubing used for ice maker hookup. ($.10/ft). Get the little meet ferral insert and plastic ferral used for ice make compression fitting to hook the tubing to the guage.

Remove the plastic vacuum line (actually pressure line) from the out bound side of the overboost valve located on the firewall just next to your brake booster. This is the tube other than than the one connected directly to the ALDA (I unscrewed the overboost valve from the firewall so it was easy to work with)

Use a plastic "T" to connect the tube you disconneced, the guage hose, and on to the overboost valve. I ran the pressure guage tubing out the corner of the hood and through the window and hung it across my visor. Take the car out and see what you get. If you don't get any boost pressure when pushing the car, check the hoses for leaks, and check the overboost valve and transmission transducer (also connected to the ALDA) for leaking diaphrams using a hand held vacuum pump with a guage. (ie. might vac or equiv.)

If you send me your e-mail address I will send you pics of how I hooked this up. I can't seem to attach pictures to these forum responses.
Gene