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Nov 04, 2019 3:08 pm
Peter S30 Offline
Global Moderator
Registered since: Nov 27, 2007
Location: Germany

Subject: 2ltr oil pump and pressure
Finally I take the time to post some experience with the oil pressure and pump on my 2ltr.

On our last continental rally I used my 2ltr (summer 2018) I first had a broken oil pipe driving to the meeting (repaired on the way), so check the soldering of your oil pipe if it is soldered.

During the rally and on the way back it was very hot and oil pressure reading dropped to something like 0-5psi in idle. Back home I was adviced by John Batt (sadly missed) to check especially the axial play of the oil pump. It was huge and I introduced 2 thin shimps to adjust it. Also the rotor circumference and static part of the pump is quite worn. Nevertheless when putting it back with reduced axial play, the oil pressure was back in normal range.

Then after a winter of not using the car, this spring when I started the car again, oil pressure was absolutely 0. Priming the oil pump did not help. So I started investigations using an external (peristaltic) pump. In the image you see it attached to the feeding point at the oil distributor part. And I cleaned the little pipe conecting the gauge with the point where the pressure is measured (camshaft). When I now pumped in 40ml/min of the 20/50 oil at 10C I had 20psi directly after my external oil pump and 15psi on the gauge of the car.
I also measured the pumping capacity of the oil pump of the car: 1.6ml per revolution. That means it would deliver the same 40ml/min at 25 rpm. Rpm of the oil pump is the same as rpm of the engine. That means the oil pump of the car is delivering much much more than needed (as confirmed by John)

Putting the cars oil pump back and starting the car: plenty of oil pressure. Even with the pressure relief valve screwed out as far as possible I have 40psi. I also have put a second gauge at the inlet point to the main bearings, it reads about the same as the gauge on the dashboard now.

So my conclusions:
1. A bad oil pressure can be a faulty gauge. Check the gauge first and clean the pipe to the gauge (oil is not flowing through but only pressure is transmitted, so it will block with deposits over the years). This may avoid time consuming or expensive and unnecessary engine overhaul.
2. A worn oil pump will be impoved a lot simply by reducing axial play

Thumbnails of attached images:

Filename: external oil pump.jpg
Filetype: File Type Information for: jpg jpg
Downloads: 15
Filesize: 61.11 KB
Image size: 640 x 853 Pixels


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