1971 300SEL 3.5: what is the check valve next to the cold start injector?

[werminghausen]

I am about to install the cold start injector: I could open it up yesterday after I have put it in carb cleaner for a week.
So now I see this check valve and the valve seat is hanging down low leaving a gap and air can enter. There seems to be a spring underneath but it is not strong enough to close the valve seat.
Does this valve supposed to be closed?
Who has advise here?

[Tomguy]

I think you're talking about the PCV valve. Is it connected to the left side valve cover?

[Gurunutkins]

Hi Martin
I'm home again for a few days - glad you got your cold start valve sorted out. Do you mean the auxilliary air valve? looks like the picture below
its supposed to be open when cold to allow in more air for the extra fuel the cold start valve is injecting. As the engine gets warmer the copper bulb on the bottom sits in the water stream and slowly closes the valve so all of the idle air eventually comes in past the idle air screw next to the AAV. both sit next to the cold start valve.

[werminghausen]

Originally Posted by Tomguy

I think you're talking about the PCV valve. Is it connected to the left side valve cover?

Yes, not sure about the name but the valve is mounted slightly left to the cold start injector (same aluminum housing the cold start valve is mounted). It is connected to the valve cover with a rubber hose. Is it normal that the valve seat is not closing?

[werminghausen]

Originally Posted by Gurunutkins

Hi Martin
I'm home again for a few days - glad you got your cold start valve sorted out. Do you mean the auxilliary air valve? looks like the picture below
its supposed to be open when cold to allow in more air for the extra fuel the cold start valve is injecting. As the engine gets warmer the copper bulb on the bottom sits in the water stream and slowly closes the valve so all of the idle air eventually comes in past the idle air screw next to the AAV. both sit next to the cold start valve.

Hi Barri, it is the other valve a bit left of the cold start valve (if you stand in front of the engine it is a bit to the right) connected to the valve cover with a formed hose.
Yes I am happy that the cold start injector is working now!
I am almost there to start the engine again.... just the trigger points in the distributor are missing.

[bwostosh]

the auxiliary air valve,

It flows air when cold and shuts when hot, take it off test in boiling water, Hold with tongs, dip the bulb in the hot water, blow thru the top to test These go bad and operate similar to the radiater water thermostat.

[werminghausen]

Originally Posted by bwostosh

the auxiliary air valve,

It flows air when cold and shuts when hot, take it off test in boiling water, Hold with tongs, dip the bulb in the hot water, blow thru the top to test These go bad and operate similar to the radiater water thermostat.

Hi Brian, no, it is the other check valve connected to the valve housing.
The valve seat is not closing properly

[Tomguy]

weminghausen: There doesn't sound like there's anything wrong with your PCV. A rattling / non-seating valve is typical. You can ask to look at a generic in-line PCV similar to the one in your Benz (like a 1999 300M) if you want to compare. It will only close if there is a sudden pressure change where the manifold pressure is higher than the crankcase pressure.

[werminghausen]

Thanks Tomguy
This is all I need to know and I will move on.