vac control valve - PeachParts Mercedes-Benz Forum

stayalert · #1 05-23-2005, 08:56 AM

To ease my replacement of the shut off valve I removed this little bugger from the rear of the injection pump.

Is there any PM or testing I can do whilst its on the bench?

There is a small nut and two phillips screws holding it togehter...Should I dissassemble and lube/clean or will it go "sproing" and fly apart in a million pieces?

crazy banana · #2 05-23-2005, 09:10 AM

not sure if you can rebuild it but it's worth the try. you can put a vacuum to the end and see if it holds the pressure..if it does.. it's good. the new one i recently replaced cost me $160 at bap-geon.

Pete Burton · #3 05-23-2005, 09:14 AM

as you move the actuator lever, the flow restriction should vary. Very little restriction at full throttle and quite a bit at the other end. Somewhere I read that there is an adjustment possible on that - have you checked out Steve Brotherton's site yet?

stayalert · #4 05-23-2005, 09:26 AM

Cool! I think I will get the car back togtehr and see if it runs (and stops) before I tinbker with the vac. control valve, I'm not sure if it works or not. I believe it was disconnected (as were many components) when I bought the car.

Kind Regards

hockeynut · #5 05-23-2005, 11:28 AM

If it was disconnected you would have major shifting problrms

I took mine off, took it apart and cleaned it all out with brake cleaner - it was dirty inside and had some crud in it. Regardless, it is working fine -that wound up not being the cause of my shifting problems, so I'm sitting on a brand new unit from the dealer.
There is an adjustment under the little plastic dome or cap that protrudes from the side of the unit that faces the driver's fender. It's a lot of fun trying to adjust it

There are threads about it. Good luck

stayalert · #6 05-23-2005, 11:52 AM

It was disconnected. as was the shut off valve. I drove the car home from where I bought it. It had shifting issues. I'm hoping in a couple of weeks when I get it back togtehr I will have solved a number of issues....

pawoSD · #7 05-23-2005, 03:27 PM

Its perfect timing that this thread came up, as my dad's 83 decided to no longer shut off with the key today, it used to shut off instantly, then it took longer this week, now it just doesn't at all. I suspect the valve....or a line....as the brakes/other vac items work fine. It also shifts fine.... We have to get a mity vac and get to work....

stayalert · #8 05-23-2005, 04:09 PM

If you determine that its the shut valve and pursue replacing it. observe and remember the orientation of the mounting flange with the 4 holes in it from the bolts. The directions I had were wrong regarding the orientation and I wasted 1/2 hour trying to make it fit improperly....

pawoSD · #9 05-23-2005, 04:30 PM

Question, I removed the brown striped vac line from the shutoff valve while the engine was running, put my finger over the end of the line and listened to it by my ear, but with the key in the "off" position there's no vacuum sound or suction on the line.....does this mean the problem lies elsewhere? Interesting tidbit....I was able to shut the car off by turning the key to "off" then breifly applying some throttle and letting off, and it would shut off, now it doesn't do it by that procedure either....I checked the vac pump....lots of suction, works fine.

I think there's something else wrong than the shutoff valve....a mityvac will prove that one, but till I get my hands on one where else can the problem come from? the valve on the ignition switch?

Also....is it a risky job to work on the IP/shutoff valve should I need to change it? I've read all the running away engine stories and now I fear working on any fuel things aside from filters/hoses.....

hockeynut · #10 05-23-2005, 04:55 PM

Quote:

Originally Posted by pawoSD

Question, I removed the brown striped vac line from the shutoff valve while the engine was running, put my finger over the end of the line and listened to it by my ear, but with the key in the "off" position there's no vacuum sound or suction on the line.....does this mean the problem lies elsewhere? Interesting tidbit....I was able to shut the car off by turning the key to "off" then breifly applying some throttle and letting off, and it would shut off, now it doesn't do it by that procedure either....I checked the vac pump....lots of suction, works fine.

I think there's something else wrong than the shutoff valve....a mityvac will prove that one, but till I get my hands on one where else can the problem come from? the valve on the ignition switch?

Also....is it a risky job to work on the IP/shutoff valve should I need to change it? I've read all the running away engine stories and now I fear working on any fuel things aside from filters/hoses.....

The problem may not be the shut off valve, but simply a vac leak somewhere else. If you have oil in your lines then you will need to replace the shutoff valve anyway. As I found out, that didn't get my engine to shut off. You can plug various lines that go to other comtrols and see if it shuts off. My issue was the HVAC control line for the AC. Mine AC does not work so I simply plugged that line and everything else now works great. I did need a vac shutoff valve anyway, as I had a lot of oil in my lines. I too was concerned about the runaway engine stories, so I had a phone book on hand and the air breatehr assembly removed just in case. All functioned fine however.

pawoSD · #11 05-23-2005, 11:19 PM

There doesn't appear to be any oil in the lines to the valve, and I tried plugging the lines to the climate control etc....all the lines that branch off before the brake booster (which does work just fine) and it made no difference/didn't shut down.....

I did notice that with the main tube to the vacuum pump disconnected, the tube to the pump had suction, but didn't feel thaaat strong when putting a finger over it, it was very easy to remove my finger from its suction, also, when revving the engine the vacuum actually became weaker....does this point to a pump problem? should there be more suction when the engine is throttled higher??? Just seemed strange to me....this car was taken very good care of by previous owners, even all the vacuum ruber Tee's and such under the hood have been replaced and it has a functioning egr as well....so I don't know where to look to fix it....we're probably just going to let the dealer fix it soon....

stayalert · #12 05-24-2005, 08:05 AM

Take my comments and reccomendations carefully as they come from a "newbie" If you want to reduce your need/desire to let the dealer fix it I think it will be helpful for you to get a vac. gauge/mityvac. These will help you diagnose problems more accurately than your finger. Could help you (or the dealer) focus on what the trouble is rather than hunt and peck.

- no oil in lines = good, a shut off valve that is "on the way out" or bad will allow oil to enter vac. tubing/lines and degrade rubber components of the vac. system.

- I'm in the process of reviewing the cirulation (lines) and organs (components) of my cars vac. system.....Sounds liek you mat have a leak soemwhere in your...good luck!

pawoSD · #13 05-24-2005, 12:22 PM

New developments today in this saga, now aside from the car not shutting off, more things have begun to happen, such as very hard shifting and somewhat increased braking force on the pedal (he drove it around this morning still)....so I now suspect that the vacuum pump is going bad, especially since with my finger on the tube the suction became less when revving it above idle....somehow I don't think thats normal.....the dealer is taking it tomorrow....so they should find/solve the culprit. I do try to avoid the dealer as much as possible....personally my SD hasn't been there in over a year because I have done everything since then myself (oil cooler lines/cooler, motor mounts....oil changes.....air cleaner mount......brakes/rotors/fluid flush....power steering flush......installed extra gauges......replaced an alternator on the 83......drained and replaced diff oil on both cars.....) I've done a loooot.

We usually bring it to the dealer for things like valve adjustments and issues like this vac problem. They are usually very quick about it and have fair pricing, so its not a big deal on occassion.

stayalert · #14 05-25-2005, 09:19 AM

Does anyone know if the plastic dome needs to be in place for the vac. control valve to function properly? Mine is missing....If I had it it would go over the adjustment nut visible in this picture:

Anyone got a spare dome lying around? I can't spring for a whole new vac. control valve right now....Particularly because I don't know if the one I have is functional or not.....

hockeynut · #15 05-25-2005, 10:24 AM

The dome is there to simply protect the adjusting shaft and lock nut. It will function properly without it.

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