Low oil pressure getting lower

[kangaboy]

Ok well I'm going to hook up a stick idiot light and see what happens at operating temps.
I don't know for sure that the oil pickup tube is loose either, I just assumed after I had checked everything else on the out side that the loose pick up tube may have been the problem cause I couldn't check it. Ima go to harbor freight and get a cheapo mechanical gauge too. I need to figure this crap out so I can drive the bastard!!

Edit: if I do want to check the relief valves again...do I need to drain the oil again? I just put 5 new quarts in less than 30 miles ago. And is it acceptable to reuse that oil if I do need to drain it?

[FJCamper]

Hi KangaBoy,

You can recheck the pressure reliefs without draining all the oil. Just catch what spillage there is and pour it back in.

FJC

[Clatter]

IF everything checks out OK, and there's no swarf in the oil,
i might be inclined to use it as the first oil that gets changed out after the re-assembly.
a.k.a. save it into a clean container,
and use it as the 'first run-in' oil.

If the case is Brazilian, or other non-German variety,
the surface of the bottom of the oil piston bore,
(where the piston seats when hot and idling),
can be less than smooth and flat.
Ac.net used to (still does?) rent an end-mill and positive stop to re-surface this.

Those swedged-in pickup tubes worry me too!
Especially after wiggling/pushing/pulling/twisting that goes along with pickup tube extensions.
Another reason to love the type 4...

Worn lifter bores can contribute to low oil pressure.
Was this case ever home to a hot cam with fast ramps?

Very common is bearings that were manufactured with wrong tolerances.
Thus, automotive machinists have to set their cutters to non-standard specs.
If the guy running your line-boring equipment is an old-timer,
he just sets them to the number everybody used when bearings measured correctly.
Now, cases are line-bored, and cranks are turned to match what the bearings measure.
If the guy tells you that you don't need to so all that, find another machinist or buy a boring bar.

Triple-check that your case isn't spread at the center main.
BTDT...

Have also seen a (Brazilian) case with the cam bearing bore cut all wrong at the factory.

My experience testing a ball to replace the relief piston was less than successful, too.

Here's to hoping you have a slipping fan belt, or some other external problem..!

Report back to us what it was.
Always love to learn more...

[kangaboy]

WOW!! I think i figured it out. VDO=TRASH!!
I switched out the dual post VDO sender for the stock oil pressure switch and guess what? Things work normally again!
The light is on before i start it, and besides coming on with a hard stop from hiway speeds, or coming off the interstate after a long drive, it doesnt come on again till i turn the car off.
Thats a win in my book. Sucks when you pay $75 to have something that is supposed to be better, just to have it fail and cause all sorts of issues.
STOCK FOR THE WIN!

[Chris V]

The range on a stock oil pressure switch is pretty wide - .15-.45 bar (~2¼ to 6 3/4 psi)

As Bruce alluded to, typically gauges are most accurate in the middle of the sweep...keep in mind a difference of a couple PSI is not much considering the graduations on the gauge...