911SOUK

I found the discusion below when I did a cooler search. I too am running Castrol 20/50. And the symptoms are similar. High pressure when cold (50 to 60) and doesn't even register at idle when warm. My temp indicates less than 180F. The pressure does rise when the RPM's increases, but less than the rule of thumb, 10PSI/1000RPM. Could my motor be that worn or do I have a worn oil pump? I am using my '76S pressure transducer to match to the guage.

Engine history: It's a 3.0 from a 78 SC ("approx. 68K mile") that I bought from a well know Rennlister. He disassembled the motor and inspected it when he replaced the studs. According to him everything looked fine and he reassembled with new seals. The engine runs strong and doesn't seem to be burning oil. I made the swap from 2.7 to 3.0 in my '76S late fall and have not put a whole lot of hot miles on it yet.

Any thoughts guys???

........................................
I am running 20/50 castrol, oil pressure cold @ idle is 60
>>psi. Hot is as low as 7 psi (15 psi @ 3000 rpm ).
>
> I don't use Castrol motor oil. This info may be out of date now,
>but I have heard from one Porsche mechanic that motors that use Castrol GTX
>seem to show a lot more wear than ones that use other oils. He claimed that
>he could tell if an engine had used Castrol GTX just by looking at the
>cylinder walls or bearings. I tend to be paranoid about the motor internals
>(several thousand dollars worht of rebuild cuased the paranoia) so I have
>stayed away from Castrol motor oil. I use Kendall because it's what my own
>mechanic uses, plus it's widely available where I live. From the results
>of an oil study I saw a few years ago, there are better oils available than
>Kendall, but I've stuck with it through force of habit or some such.
> 15 PSI @ 3000 RPM is too low. You should be seeing at least 30 PSI
>at 3000 RPM when the engine is at operating temp. 10 PSI per 1000 RPM is
>the rule of thumb. 60 PSI at idle when cold is pretty normal. Either the
>engine is old and tired, or the oil really DOES get too darn hot. 8^(
> How long has it been running like this? If this is a fresh rebuild,
>it may be something as simple as the oil pressure control piston(s) being
>cocked and stuck in its (their) bore(s). If the motor has been run this way
>for a good number of miles, it may already have a whole lot of wear.
> Next time you change your oil, you might think about splitting open
>the oil filter and checking for debris. If you find much, you're gonna have
>to rebuild the motor REAL SOON. An oil analysis will catch smaller quanti-
>ties of metal and will probably give you more warning, but it costs a lot
>more than the other (which is essentially free).

Jeff Curtis

If you've double verified your oil pressure...I guess you really DO have low oil pressure? When I first started reading, I figured you had a faulty/inaccurate gauge/sender unit.

All things considered, it does sound like the oil pump isn't up to snuff in doing it's job. I had several MAJOR engine malfunctions with my SC motor, including breaking rings/pistons, etc. - when it was supercharged...but it never affected the oil pump operation. I had to disassemble the crankcase a couple of times just to get all the crap out of there!

To date, I find it hard to understand how these things wear out and don't provide ample pressure.

Using your second oil pressure gauge, was this measuring direct pressure through the oil passages or were you using the electrical output from the sender? If using the sender...I would definitely replace it and see what you get then.

911SOUK

Jeff,

I used the sender (transducer) and not a guage directly in the oil flow (next test). It is likely that the sender is out of calibration, but the pressure does register higher when cold.

I use to be a test engineering for a positive displacement meter company and with 0.003" clearance when new, the meters, when retested after some field testing/flowing, will show a shift in accuracy. I suppose the oil pump (a PD meter in reverse--a pump)can wear in such a manner that will allow more slippage, especially when the motor is warm and we see a lower viscosity in the oil as well as pump body expansion. Until I actually put a pressure guage that I have faith in, inline , I'm not going to believe this is happening.

Bottom line, the pressures I'm seeing are not normal, right?

Thanks,

ChrisB

Hope this isn't too off-topic but just wanted to put my two cents in regarding motor oil. I used to use Castrol GTX. I used to have a fair amount of particles stuck to my magnetic drain plugs when checking them during oil changes (every 3k). I then switched to Mobile 1 (5W30 in winter and 20W50 summer) and I now those magnets are clean - really clean. Now, I know how expensive this makes oil changes, especially with those front oil coolers, but the peace of mind is worth it.

jlkline

Chris,

Have you noticed any seepage of the Mobil 1 anywhere?

I have recently had my engine rebuilt, and been considering the switch to M1, but my previous experiences with it resulted in seepage at various places:case halves, cylinder bases, etc.

OK,OK, my 1st M1 experiences were with 2.7's,which were pretty leaky by definition but I also had a similar experiece with my 3.0. Since then, I have had the 3.0 rebuilt with 3.2 crank, rods, p'c's. All the parts now appear to be well seated, and nearly zero oil consumption,( even with my driving style ) The case is completely dry, but I do see a bit of "wear particles" on the tank and case plug magnets when I change the oil (every 3K) and I wouldn't at all mind NOT seeing these metal catchers cleaner upon removal, but not at the expense of oil on my garage floor after investing $8500 in this beautiful motor.

I have obviously seen more than a few threads on the subject of Mobil 1 here as well, but I'd be interested in your experience, as well as anyone else's who has switched.

ChrisB

JLKline,

I've been using Mobile 1 for 4 years now and I just now started noticing a drop starting to hang from the crankcase drain plug. It hits the garage floor about once every two weeks - I can live with that. Otherwise, everything else is clean and dry.

john d 81SC

At the risk of shifting this topic to one of engine oils - a few comments: 1. have heard the " P urban legends" re: Castrol GTX - can't scientifically document anything other than the anecdotal situations similar to what's posted here, but 2 local P specialists - one of whom races at Sebring, among other neat places, the other, who is a VERY respected P specialist both highly recommend Valvoline 20-50 motor oil for people choosing non-synth oil; 2. re: the use of Mobil 1 - if you check back to some VERY early threads, there may be an explanation as to why M 1 seems to "cause" leaks in the older engines. And if memory serves me (which it seems to be doing less and less these days *G*), one explanation I seem to recall is because of the "slicker" viscosity, it cleans out the "crud" that's built up over the years in the areas susceptible to leaks, so while the dino oil may not permeate these potential leak areas, M 1 does. Not sure if THIS explanation isn't another "P urban legend!" *G* FWIW, the PO of my 81 SC started using M 1 in 1984, and that's all that been in there since, and no drops yet on the garage floor. One benefit SEEMS to be keeping lower temps at DE events (which was pointed out to me by our own Bill Gregory, and that theory will be futher tested this summer at DE events..

Mike hachey

The best by far, bar none....Agip mineral 20-50W. My mechanic can't be wrong. It's a little pricey,if you can get it where you live.I've seen this go in everything from a T70 Lola to 1998 GT1 Leman car! And every racing Porsche that leaves his stable. Good luck. Mike. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Jeff Curtis

On that note, 911SOUK, I would certainly replace the sender unit before going any further. If you truly do have very low oil pressure, I would think the valvetrain would be nice and noisy by now.

The "spray bars" fitted inside your cam housings need some good pressure to lubricate the valve train. If they were clogged up, you would read higher pressure...if clear but not getting enough pressure, your rockers and cam would suffer.

You mentioned that your engine seems to run real well...but then you are the guy with the "rough" idle right? Hmmmmmm.

I have witnessed both problems...with the clogged spray bars surprising me the most! (not on my engine)

911SOUK

Jeff, the motor runs well and pulls strongly at larger throttle input. The idle is good, and it doesn't stumble and shake out of gear. When I'm driving, in any gear and at any RPM, the motor shakes and puts out the exhaust at a very specific throttle input range. That range is just baove idle to probably over 10% open.

I have checked the timing numerous times, and it seems to be as it should be, but if thins are wrong and I manage to create a condition that seems normal, then the correct vacuum might fix everything.

I could write on and on about the problems!! Anyone want my car? It's pocessed!! <img src="graemlins/icon107.gif" border="0" alt="[icon107]" />