Last attempt to save the motor... (LONG STORY)

[Plays with cars]

Last year I bought an original 914-6 that had a 2.7 transplant in it and it has slowly, or quickly if you consider the miles driven, headed downhill. I spent this weekend trying to figure out why it wouldn't build oil pressure. I've scoured the archives, checked everything I can think of, but still no pressure. I'm praying it's not a dead oil pump because that means a rebuild, and that means the car will be parked. I'm hoping the collective wisdom on this board will point me down another path to resolving the problem w/o a rebuild. In the back of my mind I'm also worried that I'll pull the motor, rebuild it w/ no obvious problems found, put it back in the car, THEN discover the real problem external to the motor.

So, here's the scoop: when I first purchased the car there was no oil pressure gauge, and little did I know, the idiot light wasn't hooked up either. (I know, first sign of trouble, but after discovering this and tracing wires I found the previous owner had an aftermarket gauge mounted in the car and he used the original oil pressure wiring for it instead of the idiot light. Gauges were removed before I bought the car so the wire deadended by the glovebox). I had driven the car a number of times w/ no obvious problems (~50mi). When I discovered the idiot light was disconnected, I traced the wires and hooked it back up. Now, this is where it starts to get strange. The idiot light was on at idle when the car was cold, but never came on when the car was warm. Above idle, no problem. (note: no gauge yet so I have no idea what kind of oil pressure it was building only that it was over 6psi.) Checked the oil level after the car warmed up and all is good.

Jump ahead to the next club autocross: pulled the car off of the trailer, same thing oil pressure light on and off at idle, off above idle when cold, always off when warm. Drove the event, let's not dwell on how I did, let's just say there is set up to do on the car and I need to learn how to handle the additional power compared to my 914-4 2.0. Fun runs at the end of day turned out to be, well, not so much fun.

Coming through the lights at the end of the last run and I see smoke coming out of the back of the car. Shut it down and coast into the (empty) grid lanes near Timing in case I need a fire extinguisher. Oil dripping on the ground, pop the engine lid and notice the left side of the engine is sitting low. Broke a transmission mount and the ear off of the transmission case on the left side, so the engine is hanging off of the oil lines to the oil tank. The return line is clearly damaged and leaking oil. Pushed the car on to the trailer.

Fast forward a couple of weeks when I get a chance to work on it again. Had a new line made at the local hose shop and installed it. Changed the oil and fired it up. Same thing, oil light on at idle, but now it is hesitantly going off at higher RPM. As soon as it warms up though, no problems. Drive the car to work one day, 25 miles. At the end of the day start it up to go home and the oil press light is on. Raise the rpm, oil press light still on. Shut it down, scratch head, start it up, oil press light on. Repeat a couple of times all the while hoping it will build pressure. Finally get in one of those moods, you know you've all been there, and say F*&! it. Just got done working 12 hrs, it's too late to have my wife come pick me up, so, I drive the car home. 1.5 miles later oil pressure, no problems the rest of the way home. At this point there should be problems, right? 1.5 miles w/o oil pressure? (I know, dumb decision, but at this point I'm ready to just get rid of the damn car. There have been multiple other issues)

Jump ahead a couple of weeks (did I mention I was studying for Professional Engineering Exam during all of this?). So, now I decide to get into this more and figure out what is going on. Put an oil pressure gauge on the car, spin the motor with the starter, no pressure. SPIN it longer, no pressure. Check the oil in the tank, its empty. Hmmm. All of the oil is in the case. Added 2qts of oil to the tank to see if there was oil would it build pressure. Well, it tried. You could see the oil making its way up the tubing to the gauge. Okay, figure I'd start it and let the scavenge pump empty the case. Built 25psi almost immediately, then dropped to zero just as quickly. I have not started it since, but not been able to get any indication whatsoever that it was attempting to build pressure when turning it over with the starter. I've gone to the extent of pulling the oil pressure gauge plumbing off of the engine and looked down the passage while cranking the engine, no oil.

The car has been sitting again for a while and all of the oil is back in the case. Drained the case to start over w/ oil level and get the oil back into the tank. Cranked against the starter, no oil pressure. Drained the case again, pulled the oil pressure relief valves and checked for sticking. Seemed fine. Cleaned them up w/ 400 grit wet and dry and reinstalled. Pulled the sump plate and checked the screen, checked the pick up tube to the scavenge pump to make sure it wasn't falling out. All is good. Put 8 qts of oil in the tank and crank the starter, no oil pressure. Pulled spark plugs so it could crank faster, no oil pressure. At this point I'm really hesitant to start the motor, I really doubt it will build pressure.

Does this sound like a dying oil pump? It's totally opposite of any previous experiences I've had with worn out motors or oil pumps. Usually if clearances are too high you loose oil pressure when the motor is warm and the oil gets thinner. So far this has been the exact opposite.

So, before I park the car for an extended hibernation while I beg and plead with my wife to let me spend money on a rebuild, did I miss anything? Anything else I should check before pronouncing this a dead oil pump?

[techweenie]

Is there any sort of external oil cooler in your car?

[Plays with cars]

No, no external cooler, only the engine mounted one.

[HarryD]

Hard to say what is going on.

Are you measuring the oil pressure at the point where the pressure switch is installed?

If you remove the oil pressure switch, can you get oil to squirt out of the hole?

Here is a schematic of hte oil system on your car to help you figure out what is going on. Where is your gauge?


(thanks grady)

[Walter_Middie]

Is the sump plate on correctly? It can be put on upside down, making the oil pickup tube really close to the sump plate. Or maybe someone did this in the past, damaging your pickup tube, and the pickup tube has come loose from the oil pump - or you just aren't measuring the oil pressure in the correct place. Although, finding all the oil in the engine and not in the tank is very strange.

[Rich Lambert]

Is the pressure sender working? I had a low pressure reading and found it was the sending unit...after I replaced the pressure relief springs.

[moneymanager]

I have no answer to your problem. But normal, on the two Porsches I own, is very high pressure when cold.. 50-60 lbs at cold idle, dropping slowly to the proper range of 10-15 lbs per thousand revs when warm. Also, when warm, its not unusual to see the oil pressure light at low idle.

[Plays with cars]

Hi Harry, this is where I tapped in to check the pressure:



Walter - yes, sump plate was installed correctly and the pick up tube on the pump is secure.

Harry / Rich - I put a second gauge on the car w/ no change, so I pulled it off entirely and no oil came out of the hole.


Don't you just love trouble shooting a "new to you" car? Makes me appreciate the ones that have been in the stable for a while. I know their quirks, what works, what doesn't, and what the priorities are for correcting. This new one though, it's been a challenge.

[techweenie]

Years ago, there were some infamous engine builders that used excessive amounts of RTV to seal cases, and wads of it would break loose and get stuck in the oil system. Hate to say it, but your symptoms seem to me to be consistent with this sort of random blockages of oil passages.

[tctnd]

Pull out the oil pressure relief valves and look for contamination (RTV as techweenie mentioned or metal bits, shop rag shreds etc). These can also be assembled incorrectly or with the wrong springs or pistons. Don't know what case you have, but if the oil bypass mod was done without updating the valve bits it will not work properly.
regards,
Phil

[Rusty 356]

Mark, hope your tests went well and you are on your way to bigger and better things. Looking at the lube scheme it appears the cams are the last to get oil. You might pull one of the upper cam covers and see what things look like in there. Are they getting oil or wearing themselves out. Rocker arm bushing would be easy to check as well.
If you pull it down now and find the problem it shouldn't be too costly if you do the work. If you wait parts expense will surely be much higher. You might try that argument on your wife.
As you can also see there are two pressure valves, one controls operating pressure the other max pressure should one stick. Make sure you check both.
Good luck, by the way I have to pull my 914-6 motor back out. Word based on experience, don't have your case vatted unless It is someone familiar with the magnesium cases. Bought a replacement 2.7 case two weeks ago.

[Plays with cars]

Thanks for the input. No contamination found when I pulled the pressure relief valves.

Phil - it is a 7R case from 1976 911S. Not sure how to tell if its has the oil mod done or not. The pistons are the old style, not updated. Is there a way to look in the pressure relief piston bore and see if the oil passage has been drilled for the update? If it has, then we've definitely found the problem, but I doubt this is it. The motor isn't a recent rebuild, if at all, and would have disintegrated long ago if it had never built pressure. this is something that changed recently.

[porsche930dude]

what oil are you using?

[tctnd]

Well, I can only think of one more "external" test. Intermittent pressure is unusual but would cause me to suspect the scavenge side of the system. I would drain any oil in the sump then fill the tank and start the engine immediately. If you have good pressure for a while (til the tank empties) the pressure side is good but the scavenge side is not. If there's no pressure from the start, the pressure side (and possibly both) is non functional.
regards,
Phil

[J P Stein]

When you drained the oil how many quarts did you put back in?....BTW, how much came out?

[Plays with cars]

Hey, Phil I had the same thought so I probed the tank to see if there was any oil in it to prime the pressure side. The car had been sitting for a couple of weeks and all of the oil was in the case. Cracked the line from the tank to the engine and confirmed all oil was in the case. Okay, made sense it wouldn't build pressure. I added 2 qts to the tank and cranked the engine again; started to build pressure (up to 25psi) then went to zero again.

Since this try I've drained the tank and case (J.P. ~9 qts removed), refilled the tank, and began cranking immediately; no pressure. Cracked the line from the tank to the engine and confirmed there was oil.

Do oil pumps just die?

Edit: The amount of oil removed has be scratching my head also and can't be 100% certain of the order of events and oil added/removed over time. I've been chasing this off and on since October. But if you do the math 9qts removed doesn't sound right, especially after having added 2qts. That means it only had 7 qts in it when it was running, warm, had oil pressure, and was inidicating full on the dipstick. Somewhere I think I've lost track of an oil add or delete, or forgot the carry the one when doing the math :-)

[J P Stein]

It is conceivable that the pump could "just die".....or, more accurately, cease to function. There is a splined coupler on the intermediate shaft. Concievably this may have stripped and it may cause the condition you have described...internmittent oil pressure...tho I've never heard if it happening. There should be a fair amount of steel attached to your magnetic drain plug along with this. I suppose the keepers that hold the coupler may have come adrift and allowed the coupler to move off the splines.....I'm reaching here.....

It appears that you have tried a mechanical gauge and that being the case, you've confirmed the oil pressure problem & 9 quarts is what should be in there....
Assuming the external oil line routing is correct and there are no blockages therein, it's time for surgery, me thinks.

[KlaasyT]

Hi, When I acquired my 72 911 it wouldn't build pressure either. Tried the things you have tried. In the end I pulled the sump plate and was able to see that the pumps drive tube was not turning when the engine crank was turned. I pulled the engine apart to find that the end of the intermediate shaft had sheared cleanly at the spline. I then pulled the oil pump apart (would not turn) and found a cracked tooth that locked it up. I'm not sure what caused the cracked tooth as I did not find any foreign material in the pump or oil, or on the magnet.
I hope your problem is not this big. If you drain the oil again, pull the sump cover and see if you can see the drive tube.

Hope things work out

Clarence

[tctnd]

I agree with JP Stein about the possibility of spline failure; unlikely as that would be, we're running out of options. It might also be possible that there is an intermittent blockage (a piece of rubber, rag, etc) at the pump pickup in the sump or at the tank outlet.
regards,
Phil

[regency]

Hi Mark: From where, did you purchase this car? Have you any info on the engine builder? I had an engine that made no OP, I tried everything and finally pulled the engine / took it apart to find an oil pump seals missing / not installed. Sounds bad but my particular "builder" did such a crappy job, I needed to start over anyway.

Sad / funny additional note: Recently sent my cylinders to EBS in Reno as cores on a 85mm exchange............a day later, EBS called, they said, "have bad news - the cylinders you sent are Chinese and are now usable"