What is the function of the vacuum line which attaches the vacuum pump to the air intake?

That line is the one where air goes that is evacuated from the vacuum system by the vacuum pump. The vacuum pump has two one-way check valves controlling the flow of air so that vacuum is created by the vacuum pump's diaphragm or a piston instead of a diaphragm if you have that kind of vacuum pump. If you have the diaphragm type of vacuum pump and the diaphragm begins leaking you will find oil in the air filter cannister and air filter. This has happened to me. I put a small metal can that nuts come in (6 oz. size with a bit of trimming so it fits into the cannister) right below the line from the vacuum line from the pump so that if the diaphragm begins leaking the oil goes into the can instead of the air filter. The last time my vacuum diaphragm began leaking all of the oil went into the can and not the air filter - I found the problem during my weekly once over.

Tom

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America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
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Hey Tom, thanks. The line from the VP to the intake was not sealed, so I took care of it with some silicone. Now the intake should be sealed. Eliminated the loud turbo whistle.

How did you
1.) secure the can, and
2.) allow oil to escape vacuum line so that it ended up in the can?

I've also used silicone to seal some of the grommets and other components until I got around to replacing the part - provided the part was non-critical and no damage could result from a part in less than perfect condition (usually only M-B had it, so I waited till I had several M-B only items that I needed and made one trip to the dealership to buy them).

The can just rests in my air filter cannister between a metal grid/support for the inner part of the air filter and the connection to the intake manifold. As I wrote, I trimmed the can a bit so it would fit into the air cleaner cannister and I trimmed it just enough so there is a very small amount of contact with the air cleaner cannister cover - not much contact, just enough to keep the can in position right below where the vacuum pump evacuation line connects to the top of the air cleaner cannister - the top of the air cleaner fits in place without forcing it, so the can does not interfere with the sealing of the air cleaner cannister.

My vacuum pump evacuation line connects to the top of the air cleaner cannister cover. My engine is the non-turbo 300D and your evacuation line may connect at a different place because you own the turbo 300D. If this is the case, then my can in the air cleaner to catch vacuum pump oil trick may not work for you.

Hope this helps!
Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.

Mine is the 79 SD (116 body, 617 motor) which does include the turbo. The vacuum pump evac. line connects to the intake chamber connecting the air filter housing to the turbo.

i have the same configuration, air cleaner to VP... the problem is that i dont know what connects to the valve cover gasket for air intake...
i bought the car recently and am not familiar with this configuration.

does anyone know what gets connected to the valve cover if no the air filter??

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1985 300D - "Desi"
1981 300D - "Pepi"
1984 240D - "Sticky"
1985 300TD - "Flitstone"
1984 300TD - "Frenchie"
1987 300TD - "4481"

which vehicle is this for? I'm guessing pepi... as only the non turbo motors should have the older style vacuum pump... but I thought they did away with that in 80...
there should not be oil in the line, only air. if there is oil, the vacuum pump is damaged, and needs rebuilding.

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