Missing Plug on '72 Oil Tank

Jeff Higgins · 06:10 PM

Here is a photo of what I gather is the standard '72 oil tank, showing the bottom:

Here is a photo of my oil tank. Notice it is missing the plug just forward of the drain. I thought it might be an aftermarket tank, and it may very well be, but you can see the copper plating where I scraped the dirt off:

From what I understand, the return line from the front cooler is plumbed into that hole. What can I do since my tank does not have that hole? I just received one of Chuck Moreland's complete cooler set-ups (great looking stuff by the way) and was looking forward to installing it this weekend. Am I dead in the water, or are there other oil return options?

Oh, I almost forgot. I'm not sure if this will make a difference, but I plan on machining out the stock filter console and installing the thermostat in there.

real550A · real550A's Garage

Jeff-
I'll look at mine when I get home tonight and let you know, if no one has answered your question by then.

Shuie · 05-19-2006, 07:32 PM

I think I have the same problem. Its things like this that tend to interrupt the flow of my day

real550A · real550A's Garage

Jeff-
Here's the bottom of both of my '72 tanks.

They both have the extra opening.

Shuie · 05:15 AM

I had to go look at mine to make sure. Thankfully, its there.

Jeff Higgins · 05-20-2006, 09:22 PM

I wonder why it is missing on mine. Just my luck, I guess.

I can use the single return inlet at the top of the tank if I forego the '72 thermostat set-up. So here is my preliminary plan: Use one of the Mocal 16AN thermostats. It is my impression from reading through the archives that the 30mm metric flex lines are essentially the same as the 16AN flex lines. I think Will Ferch or some one has pointed that out.

I would need to make four new hoses. They would each have a 16AN female fitting on one side to screw onto the Mocal thermostat, and a 30mm female on the other end. One hose from the filter console to the thermostat. One hose from the thermostat outlet to the top of the oil tank, so I'm essentially splicing the thermostat into the existing filter to tank return line. The other two ports on the thermostat (the thermostatically "switched" ports) would then be plumbed to the Elephant finned lines. That should work, shouldn't it?

Jeff Higgins · 05-30-2006, 12:19 PM

I have arrived at what seems like way too simple of a solution for my oil cooler return line woes. With a simple 22/30mm adapter, I can route it to the drain plug hole in the tank instead of the stock location that is missing on mine. I figure draining the oil would then be as easy as cracking the fitting at the end of the hard line, up just behind the jack socket. That would drain the tank and the front cooler at the same time.

Am I missing something obvious? I am worried about the close proximity of the return line to the supply line that feeds the crank case, possibly feeding aerated oil from the cooler right back to the crank case without "settling" a bit in the tank first. Looking at the angle of the supply line as it enters the back of the tank, though, looks like it actually comes closer to the stock return line location than it does to the drain plug.

Does anyone know if there is a "bubbler" tube of some kind above the stock return line location? I looked inside another '72 tank with a flashlight the other day and just couldn't see anything like that. If there is one, it must be very short so that it is covered by the oil even when cold. I really suspect it just feeds into the wide open floor of the tank.

Did Porsche employ two bottom fittings just for convenience? That seems logical with hard lines, but with about a foot between the end of the finned hard line and the oil drain, the flex line between is very easy to pull out of the way to drain oil.

Anyway, thoughts on this hair-brained plan would be appreciated. Am I on to something, or is it back to the drawing board?

Wangrande · 05-30-2006, 03:49 PM

There IS a tube that is shaped like a candy cane that is fixed to the bottom oil line opening. It sends the cooled oil to the top of the tank. I cut an old tank in half to use that part in a custom replacement tank for my 72.

Jon

Jeff Higgins · 05-30-2006, 04:46 PM

Thanks, Jon. I was affraid there was something like that in there that I just wasn't seeing. So even if I brazed a fitting on the proper place in front of the darin plug, I would still need that "candy cane". I was wondering how they would do that without making it so hot oil would spray in your face every time you checked the level.

So now you have me thinking. I wonder if I could make the same kind of set-up and have the pipe brazed onto the adapter that I will screw into the bottom of the tank. Sounds simple enough...

wm711 · 05-30-2006, 06:13 PM

i have been working with my machinist on a similar problem...as related to the thermostat, we decided to turn down the thermostat, instead of opening the oil console.BTW, I saw a 72 oil console FS on the classifieds page today. I am watching this thread closely. Bill Woods

Jeff Higgins · 05-30-2006, 07:16 PM

I have the console machined to accept the thermostat already; that part turned out to be pretty easy. I also thought about chucking up the thermostat in a lathe and turning it down. I thought the wall thickness was a little marginal already, so decided against that. Future replacement was also a consideration.

This whole tank/return line problem has me scratching my head, though. I thought I could mimic the factory "candy cane", but through the drain plug hole. Alas, the pick-up tube to the engine passes too close over the top of it.

It looks like I'm stuck either getting a new tank or brazing on the fitting in the stock location. I have been very hesitant to braze or weld on my almost irreplaceable '72 tank, much less to hole saw through it. I'm just worried about messing up the plating. Not so much the outside, but rather the inside, and having it flake off because it got re-heated after so many years of being under hot oil.

My other thought was to attempt to get a nut on the inside. Because of the depth of the tank, and the location of the cap being kind of back over the wheel arch contour, it would be very difficult to snake a series of socket extensions down to the bottom. That, and that pair of internal screens really get in the way.

I'll have to give this some more thought. I'm not up for much risk involving my tank, and I'm certainly not up for its $1K new replacement value. Anyone have a spare, with the return line provision?

Shuie · 07:30 PM

What about piping into the drain plug hole and finding somewhere else to drain the oil from during an oil change? Maybe use a flex line to connect the cooler line to the bottom of the tank and then just unhook that line from the cooler line whenever you do an oil change. Or maybe find an inline valve to open and use as a drain between the tank and the cooler. I've never tried it with oil, but I know you can use gravity to siphon gas out of a tank from the filler pretty easily as long as you get the drain end of the line lower than the tank. You could also pump it out from the filler. Nothing suggested above would be real elegant, but youre in a weird situation here.

Shuie · 05-30-2006, 08:09 PM

still thinking.....

If you could find a T fitting that you could thread into the existing drain plug I think you would be fine.

Jeff Higgins · 05-30-2006, 08:16 PM

Great minds (or '72 T owners anyway) think alike, Shuie. Here is a photo of what I have right now. The flex line disconnects from the tank very easily, so draining oil will only be a little messier than it was before.

My remaining concern is where the oil is being fed back into the tank. Without the "candy cane", it is obviously just going to feed into the bottom of the tank.

Save for finding another tank with the required fitting and internal features, this might have to do for now. Maybe it will even work. I'll let you know when I get it all buttoned back up and get a chance to drive it. It will be a week or two; I'm waiting for one more connector to the back of the filter console so I can finish this. If this doesn't work, what the hell; I tried. I'll be shopping for a tank if it doesn't.

Shuie · 05-30-2006, 09:07 PM

I think that will work for now, but I would change it whenever you can. Talk to Chuck. I think the the threads on the oil lines are going to eventually gall or deform since they are brass and the fitting is steel. they may not hold up to repeated loosening & tightening.

I've been looking through a tube fitting catalogs, and while I don't know the thread pitch of the drain plug, the right T off of the old drain plug should work fine for a permanent and clean solution.

You could also find a ball valve to thread into the T for draining. I may do this for my car so I don't splash hot oil on my hands and drop the damned drain plug every time I change the oil.

Jeff Higgins · 05-31-2006, 06:22 AM

I've been looking through my Granger and McMaster Carr catalogs for similar "T" fittings. They all have standard, rather than metric threads. I'll probably wind up making one myself. I'm a little concerned with oil flow around such an abrupt 90 degreee corner, though. I think I can splice the "T" into that short section of flex hose instead. That way the oil flow would still be straight through. I'm picturing a drain valve that looks a lot like the brass ball valve you have picured, with the drain being where the red plastic handle is. That should work fairly well.

Shuie · 05-31-2006, 06:30 AM

there is an instrumentation company somewhere that makes a fitting the will work for this. We have a bunch of instrumentation supply shops around here and Id be happy to look for a fitting that would work for you. I will be looking for a ball valve to use as a drain for my own car anyway as a result of this thread. Do you know the thread pitch on the drain plug? Is it the same as the oil lines?

Jeff Higgins · 05-31-2006, 08:44 AM

The drain plug hole is M22-1.5 and the oil lines are M30-1.5. If you can find something that matches this, or even if it requires adapters on either end, that would be great. I see BAT (MOCAL) shows metric to AN adapters in their catalog, and Elephant looks like they may have some as well. That might open up the selection on valves a bit. I'll keep looking too.

Jeff Higgins · 06-01-2006, 08:51 PM

Well, it's all back together and running. I took it out for about an hour test drive and everything seems to be working just fine. When looking in the top of the tank with the car idling and warm enough for the thermostat to be open, it does not appear that the oil is bubbling, frothing, or anything unusual in the tank. It looks just like it did before, with no big geyser shooting up from my cheesy drain plug return. This is admittedly very un-scientific, but I'll continue to drive it and see how it goes. Watching pressure and temp like a hawk the whole time...

I have a D.E. at the end of the month, so I will see how it does there. I should have enough time on it by then to have a feel for whether or not I should even attempt the D.E. We'll see.