Oil filter replacement

Question - are the aftermarket oil filters as good as the oem?

The pressure on my 78 911 SC Targa 3.0 pegs the needle on start up - the gauge for the tank level is in the red. As the engine warms up, the pressure drops ( use 10W30 synthetic oil) After the engine is warm, the pressure is about 1.2 bar above the engine rpm - it does take a while for this to happen however. I am presently using a puralator L30260.

I am concerned about the high pressure because it may cause a blowout somewhere in the engine or with one of the hoses.

Is this a problem. I just rebuilt the engnine and it has about 1000 miles on it. The engine had 81,100 miles on it when I rebuilt it. Any concerns?

Regards

Steve

Why would you use an aftermarket oil filter?

Brian

The question was not weather I use aftermarket or oem oil filters, but how they compare.

Is it possible for a oil filter to cause the pressure in the engine to become higher than normal. Or, is there another problem?

Regards

Steve

The oil filter is not on the pressure circuit of the 911 oil system. It is at the end of the scavenge circuit just before the oil returns to the tank. If the filter plugs up and the pressure becomes too great in the scavenge circuit, the OEM filter will bypass oil into the tank. An aftermarket filter may not have the bypass. If the filter clogs and cannot be bypassed, then the pressure may blow the filter's innards into the tank, where it will be sucked into the engine.

The oil lines are also not part of the pressure circuit. They would only see higher pressures if the filter clogs.

Panorama has had several articles on filters, and the conclusion was to not use aftermarket filters.

[This message has been edited by Brian K. Haggard (edited 01-16-2000).]

I also have a '78 3.0L, but I don't run synthetic oil due to my driving habbits. The gage always pegs on startup and settles down to around 10lb/1000RPM when warm. The gage has been checked and the car runs perfectly. It takes a while to warm up all that oil. If your filter is plugged you would have a lot more trouble than just high pressure. Oil filters don't do all that much - if they did you would never have to change your expensive synthetic oil - it would stay clean. Any crap in your engine that would plug a filter would surely cause or indicate damage.

I appreciate the information. I'm going to change to a Bosche filter within the next few days. My only concern is if this is a problem, I surely don't want to blow out a hose or possibly the filter if pressure is too great for it to handl while the engine is running. As a rule, I change the oil every 3,000 miles on both the engine and the holding tank. The filter is also changed. I may be overdoing it, but I had a toyota that my wife drove with over 200,000 miles on it and the oil always looked like it was just changed. Never had a problem with the engine, and it had maintained its power. So, I think this does help.

Regards,

Steve

I don't think the oil filter is part of the equation here ... if you are really worried about crud inside the filter, take it off and cut it open with a sharp chisel and tin snips!!! I don't think you will find anything of significance trapped in the filter, but cut the paper out anyway and rinse it in gasoline ... carefully outdoors!

Did you disassemble the bypass and regulating spring/plunger assemblies in the crankcase while the engine was apart? One or both of those plungers could be stuck in the 'up' position, but my best guess from a distance is gauge problems ... corroded connections, bad/flaky sender, who knows. It is possible to rig up a test jig with compressed air hose, a mechanical regulator w/ built-in gauge, to adjust air pressure, a hose approx. 3/8 - 1/2" i.d. to the sender, removed from engine block but still wired to harness (DON'T FORGET a temporary ground strap/ test clip lead from engine ground to sender body!!!) to test gauge and sender in the car with ignition switch on, but engine NOT running. I would check the pressure at 10 lb. increments from 0 to 100 psi.

Also, the oil level indicator is easy to check, just compare the dipstick reading after the engine has warmed up ten minutes! If I remember reading the owner's manual, the dipstick is ALWAYS the ABSOLUTE test of a proper oil level!

I am assuming, of course, that the engine is NOT making ANY abnormal sounds at all!!!

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Warren Hall
1973 911S Targa