Hi All

I was getting lifter tick and low oil pressure, sometimes less than a bar at idle on the gauge as well as on a calibrated mechanical test gauge. So I decided I would go for a full strip down as I was planning a supercharger project in the near future and want to make sure the bottom end is tip top. I have just had the Head rebuilt with new guides etc.
I was wondering if any experienced members know what are the usual suspects that cause low oil pressure? As you can see in the pictures the bearings show evidence that suggests the low oil pressure issue, being less worn in the center and more worn at the outer edges where oil pressure diminishes.
The rod bearings were quite frightening, especially no 2, the previous owner had replaced the bearings approx 15k ago apparently and while it is often driven hard it is a street car so the wear seems harsh to my inexperienced eyes.
I have attached pictures of the oil pump also, its condition does not appear bad enough to be a cause for such low pressure, I have seen worse on other cars with no problem, what do other do with the oil pump, replace at $900 each time?
There is 258k Kilometers or 160k miles on the car, so the mains show this and are worn accordingly and may also be a contributing factor.
The car still has the old 3 piece OPRV and has been run on 20w 50 valvoline predominantly.



Thanks for any input guys

cheers

 

To clarify, the crank bolt was tight, and there was no evidence of any spinning on the drive gear or any parts

 

No input here from anyone? Can I provide more information?

 

Hi Will , what year type & engine type ?

 

Are you sure the OPRV wasn't getting stuck?

Was the oil pump well sealed to the block with the required Locktite?

You may want to have a peak at the cylinder walls. I ran my old S2 engine with the same condition for a little while knowing that I was building another engine and when I pulled it apart the cylinder walls were a mess.

good luck

Mark

 

was the o-ring for the oil pickup tube installed?
is the pickup in good shape?
OPRV in good shape?

the pump should almost never need to be replaced.

 

is it possible that the PO drove it milkshake too long before the crank bearings where replaced and the mains suffered also? he installed new rod bearings but the excess clearance on the mains remained...thus low pressure even with new rod bearings.

 

Cheers guys
To answer, yes the pick up tube appeared in perfect condition and had the O-ring in place and appeared to be in good condition. The oil pump appeared to be well sealed with what looked like the correct locktite flange sealant type stuff, so was the main girdle around the oil pick up gallery too.
It is a pre 85.5 NA model, with the three piece ORRV. The OPRV does show some surface pitting as pictured which may have allowed some bypassing. I dont think it was getting stuck, the plunger moves freely in the bore and it all fell out when I removed the end cap of the assembly.
I have looked at the cylinder bores, there are some minor scratch marks on two of the bores probably from the piston rings, the upper ones on 3 pistons had cracked. I will hone and use new rings after I confirm the bores are within wear tolerances.

Yes I am hoping the wear on the mains was the largest contributor to the low pressure condition, just the visible wear did not appear significant enough to warrant it. The milk shake condition could indeed have been a major issue in the past, I have in the service history a receipt from a porsche specialist carrying out the repairs after this happened, no bearings replaced.

Thanks all

 

I would see if lart or plyhammer would have some of the wear parts on the oil pump. It would probably prime on start up quicker.

Just wrapping up a rod shell job. Measuring with improper tools show about 0.0007 wear in 94k miles. It has been hot once but never mixed. Pressure was at the 2.5 bar minimum hot but would drop to 2.2 or so after 30 minutes of sustained thrashing, for lack of a better word.

 

Just a long shot but take a peek at your power steering crank pulley and confirm that there is no off center cut around the hole which is a telltale symptom of a past assembly problem....Bruce