Low(er) oil pressure after winter project

[Url]

This winter was the 1st time I dropped the engine of my 78 SC to (among others) resolve some oil leaks. I now have lower oil pressure than before (Startup 3.5 bar instead of +5 bar before) It also remains lower once engine is warmed up (Although due to Corona I've only been able to have it run in my driveway)

1. Do I need to worry?
2. Is this definitely due to the new oil pressure sender or do any of the below influence oil pressure directly? (I don't have another sender to test)
3. What I have tried so far is re-install the old (shorter) spring in the oil pressure relief valve but no change. Can the sump screen / oil pick-up explain low oil pressure?

For completeness, everything I worked on related to oil circulation:
- crankcase breather gasket
- oil pressure warning lamp switch
- Oil Thermostat O-Ring On Engine Case
- Oil cooler seals
- Oil pressure sender
- Oil pressure relief valve (Recall on 78 SC, hex nut with longer spring => as per http://forums.pelicanparts.com/911-engine-rebuilding-forum/712724-ultimate-oil-pressure-relief-valve-thread.html)
- Oil safety relief valve
- Updated Venturi sump screen (Oil pickup screen changed to this type:

[OSC911]

Do you have the turbo cam restrictions fitted? Probably isn’t going to help with the diagnosis of your original problem but might assist with oil pressure increase.
https://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=901-105-361-02-OEM&catalog_description=Restrictor%20Fitting%20for%20C amshaft%20Oil%20Line%20at%20Camshaft%20Housing,%20 Brand:%20Genuine%20Porsche%20Brand:%20Genuine%20Po rsche

[David Inc.]

What's the oil pressure when the engine is warmed up to temp, and what is the oil pressure at higher rpms with the engine warm?

[r lane]

I gather that you did not go into the motor, split the case. The gage and sender have to be matched as to whether they are 5 or 10 bar. I went through this on a track motor, drove me nuts and fixed it without a good ah ha on what at happened. It appears that you have a few extras of the venture screens, do you want to sell one. Bob

[Url]

Thanks for your input.

@OSC911 I didn't add the turbo cam restrictors

@David Inc. When warmed up oil pressure seems around +- 1 bar / 1k rpm although I notice it doesn't increase as much over 3k rpm (Seems to bottom out at 3.5-4 bar, similar to max oil pressure at cold start)


@r lane Picture was for reference, I don't have any other screens unfortunately. I didn't split the case and want to avoid having to buy another pressure sender to test.

[scottrx7tt]

I have the same exact issue. I just installed a new URO oil pressure sending unit. I believe the sending unit isn’t working correctly. I guess that’s what happens when you buy the least expensive option. Now I have to disassemble the AC compressor mount to swap it out with a genuine Porsche sender

Originally Posted by Url

Thanks for your input.

@OSC911 I didn't add the turbo cam restrictors

@David Inc. When warmed up oil pressure seems around +- 1 bar / 1k rpm although I notice it doesn't increase as much over 3k rpm (Seems to bottom out at 3.5-4 bar, similar to max oil pressure at cold start)


@r lane Picture was for reference, I don't have any other screens unfortunately. I didn't split the case and want to avoid having to buy another pressure sender to test.

[HaroldMHedge]

Try putting the old sensor back in if it's available.

[boyt911sc]

Compare your oil pressure reading between your old and new pressure sending units or install a mechanical oil pressure gauge.



The mechanical oil pressure above is use to test the oil pressure for newly rebuilt motor using the starter to run the oil pump. The gauge range is only 2 bar. In your case, you will need a 5 bar or 75 psi. gauge. Installing the restrictors will definitely raise the oil pressure readings.

BTW, the picture of the Venturi sump screens is an old picture I posted long time ago. The sump screen has no effect on the oil pressure readings because it is installed at the scavenger pump side. The oil pressure sending unit is installed at the pump pressure side and oil delivery coming from the oil tank.

Tony

[FrankM_]

Originally Posted by scottrx7tt

I have the same exact issue. I just installed a new URO oil pressure sending unit. I believe the sending unit isn’t working correctly. I guess that’s what happens when you buy the least expensive option. Now I have to disassemble the AC compressor mount to swap it out with a genuine Porsche sender

Can you do that without dropping the engine ? I am hesitating on doing this as most treads show replacing it on cars without A/C or on an engine out of the car.

[Url]

Originally Posted by boyt911sc

Compare your oil pressure reading between your old and new pressure sending units or install a mechanical oil pressure gauge.



The mechanical oil pressure above is use to test the oil pressure for newly rebuilt motor using the starter to run the oil pump. The gauge range is only 2 bar. In your case, you will need a 5 bar or 75 psi. gauge. Installing the restrictors will definitely raise the oil pressure readings.

BTW, the picture of the Venturi sump screens is an old picture I posted long time ago. The sump screen has no effect on the oil pressure readings because it is installed at the scavenger pump side. The oil pressure sending unit is installed at the pump pressure side and oil delivery coming from the oil tank.

Tony

I would have tested with the old pressure sender (heck I wouldn't even have replaced it) if the connector pin didn't break off during reassembly ...
What you are saying on the sump screen confirms my thoughts so thanks for that! It seems nothing I did, except the pressure sender, has a direct impact on oil pressure...
I'll order a new original one to test and make sure.

[scottrx7tt]

Absolutely! It took me about an hour or so from start to finish. You will most likely have to remove your muffler. I didn’t in my case because my turbo car does not have a muffler. But there are 2 bolts holding the compressor mount to the engine console. Pull. The compressor off, then the top fasteners for the mount. It pulls right out of the top. Undo your oil lines and pull the block out. Not that hard.

Originally Posted by FrankM_

Can you do that without dropping the engine ? I am hesitating on doing this as most treads show replacing it on cars without A/C or on an engine out of the car.

[r lane]

Apples to apples. Make sure the sensor and gauge are compatible. Take the reading at the same place. I was bit by an inaccurate mech gauge, so borrow a tried and true one if you can. URO pieces are vert consistent, but not in a good way.

[UROParts]

Hi Scott, we've sold about one hundred of 0-5 bar Oil Pressure Sender 911 606 111 01 / 911 606 111 03 over the last 12 months with only one returned, so it's odd that yours isn't working. Email your order confirmation / purchase details to "sales at uro parts dot com" and we'll get you a prepaid return label (so our engineers can check out that sensor) and ship you a replacement sender.

[Flat6pac]

Are you sure you’re not set with a 0-10 atm sender?
Bruce