Oil Tank Leak Repair Update - Useful Info.

[Sunroof]

Several months ago I reported an oil leak in my oil tank located in the right rear wheel well on my 1973.5T. The leak appeared to have come from the oil filter housing. My first attempt at repair was to replace the oil filter thinking I had grit on the seal. That did not work as the oil leak continued. Next, I drained the oil and replaced the cork gasket for the oil level unit, tightened up all hoses and lines and refilled. The oil still leaked.

It was apparent that the oil came somewhere for the top of the tank, so I removed and inspected it. I noticed nothing abnormal, so I decided to have it pressure tested.

I took the tank to a local radiator shop here (Simms Radiator in Atlanta, GA). They cleaned it with a mild caustic solution, pressure tested it in a water tank (I wasted a new oil filter for that purpose) and no leaks were noted! All seams were sound.

I reinstalled and the leak continued!!!!!!!!!!!!!!!!!!!!!!!!!!

Here's the deal...............

There are two bolt flanges that are welded at the top of the tank to support it in the wheelwell into the engine compartment. CAUTION. Do not overtighten these two retaining nuts located on either side of the oil filter. If you do you will force the flange tighter to the body and a crack in the weld might happen.

Although the presure testing showed nothing (I question how much pressure was applied when testing in a vat of water), it turned out that there was a small hairline crack in the weld that held the flange to the tank! Apparently age and overtightening the retaining nut were against me. As the oil heated up it rose to the upper level of the tank and leaked out the crack therefore dripping down past the filter. It would have been difficult to access the flange area with the tank attached to to the car because the space is to small for a mirror.

I had both flanges re-welded, cleaned up the tank, gave it a couple of POR 15 coatings and re-installed. The repair was successful. No more mes on the garage floor.

Another Porsche 911 Oil Tank mystery solved............

Bob
1973.5T

[RWebb]

very useful info

any pics?

& is that the flange that is supposed to mount to those rubber isolation buffers, not directly to the body?

[Jim Sims]

"There are two bolt flanges that are welded at the top of the tank to support it in the wheel well into the engine compartment. CAUTION. Do not over tighten these two retaining nuts located on either side of the oil filter. If you do you will force the flange tighter to the body and a crack in the weld might happen."

There are two soft plastic/rubber washers (2 washers per bolt - one on each side of the body/inner wheel well) in the grip of both of these bolts to give these joints some flexibility so the tank is not excessive stressed by body flex and vibration and differential thermal expansion. There is also a plastic spacer in the grip of the lower attaching bolt that secures the bottom of the tank to the right rear fender support strut. If these rubber washers and plastic spacer are missing or are original ("rock hard" due to aging) these attachment points put more stress and vibration into the oil tank structure than probably intended - it appears the oil tank and oil filter console should be "floating" on these rubber/plastic suspension points and the rubber collar around the base of the oil filter.

Regards, Jim

[Sunroof]

Thanks Jim..

Your correct on the rubber bushings. Mine were worn well under the brass support plates and I must have overtightened to create the crack. It weakened the weld, which is the obvious weak point on the tank. The tank otherwise held up like new.

What a headache all that was!

Sorry no photos.

Bob
73.5T

[Zack S.]

EXACT thing happened to me, 69 s racecar, drove me nuts!

[Evans, Marv]

A good reminder of a solution for another potential mystery. Thanks.