Question for 914/6 oil tank/oil change, Does it need a supplemental way to drain? Options

[Krieger]

I have seen some of the members here adding ways to drain the oil tank. 911s have a tank drain, but their tanks are mounted fairly low in relation to the engine. The bottom of the 6 tank is close to being near the same height as the top of the engine caes. Won't the oil just run into the engine case?

[ArtechnikA]

911's and 914.6 have a drain plug in the bottom of the case for oil that has returned to the sump. There's always some. You always drain both places.

If the car has not been sitting long after shutdown, there probably won't be much oil in the sump. The oil pump kinda acts as a one-way check valve, and while a little oil may ooze back through a tight pump, it's not that much. As the pump wears and clearances increase, more gets back through.

In place of the tank drain, 914.6 has a separable fitting in the lower oil line. You use your BIG wrenches in a tight space to open the union, hoping you're prepared for the torrent of 9 quarts draining through a big hose.

[Krieger]

Thanks for this very helpful info One of the memers here posted this pic. I am doing a front cooler with AN lines and may do this to drain my oil.

[ArtechnikA]

Thanks for this very helpful info One of the memers here posted this pic. I am doing a front cooler with AN lines and may do this to drain my oil.

Traditionally the front cooler is in the scavenge circuit, while the tank drain line is in the pressure circuit (tank -> pressure pump).

Having a drain at the front for the cooler and the lines is sometimes done, but it's no substitute for the standard tank drain line (you'll never drain the tank through the scavenge side...).

Having a capped Tee is definitely convenient, although I doubt it's more so than just using a separable fitting with either two female hose ends and a union ( AN-815?) or a male and female hose end. Once you get into AN-16 (or larger) hose, all the ends and fittings are expensive...

That capped Tee scares me tho, without some kind of positive anti-rotation device. Maybe the cap is drilled for safety wire on the other side where we can't see... (As long as we're being picky, that Tee should be a bulkhead Tee with the bulkhead fitting on the Tee (they also come with the bulkhead on the run) and a proper bracket...)

[brant]

I chickened out on the T-drain idea when I built the race car
I like being able to split the hose, angle or point it where I want, and knowing that there are less fittings to come loose or create problems.

I actually saw a motor die once on a friend at the track... due to poorly designed oil line coming loose.

I put ALOT of money into the race motor and can't stand the idea of any unnecessary risk related to oil

(I do a full royal purple oil change every single weekend as an example of my "cheap insurance" thinking.... about 1 case on our system)

[Krieger]

I was planning on drilling the cap for a safety wire. I hadn't thought about a bulkhead T.

[Cap'n Krusty]

I have seen some of the members here adding ways to drain the oil tank. 911s have a tank drain, but their tanks are mounted fairly low in relation to the engine. The bottom of the 6 tank is close to being near the same height as the top of the engine caes. Won't the oil just run into the engine case?

Might want to look again. The bottom of the /6 tank is about the level of the lower cam cover. Plenty low for the oil to drain out of the divided lower hose. Besides, on a cold engine ta good percentage of the oil is in the case.

The Cap'n

[Krieger]

I will be using two metric to an adapters at the tank and below the oil cooler. If I run a single an 16 line between them why not disconnect the line below the cooler to drain the oil?

[ArtechnikA]

because there are two separate oil systems in a 911 engine - scavenge and pressure.

The line from the cooler to the tank is the scavenge line, and it dumps to the _top_ of the tank (it's the return line).

The pressure inlet line - from the _bottom_ of the tank to the pump - is the one you have to open to drain the tank.

[J P Stein]

because there are two separate oil systems in a 911 engine - scavenge and pressure.

The line from the cooler to the tank is the scavenge line, and it dumps to the _top_ of the tank (it's the return line).

The pressure inlet line - from the _bottom_ of the tank to the pump - is the one you have to open to drain the tank.

The scavenge line feeds into the lower part of the oil tank. (see pic) Internal passages feed it thru the filter then into the tank.....it also feeds the opposite way to the sump if left to sit for a week or 2.

Many feed lines ...tank the below oil cooler....have a steel joint that can be cracked to drain the tank if necessary. You wouldn't want to use an aluminum fitting here as they will wear out if disconnected repeatedly.

[rfuerst911sc]

It may not need to have it but having one makes it easier/cleaner to drain. I have a aftermarket oil tank installed where the OEM tank mounts and have plumbed it with -16AN to the engine case. I did install a tee and have used it twice in a year and so far no issues and very easy to do oil changes. I suppose the cap could vibrate off under the right conditions but when I look at my 911SC and see the " S " hose from the tank to the engine is just held with clamps I don't worry about it.