How to verify Oil spray bar is spraying correclty

[blockerb]

1986 528e unmodified. everything runs fine no over heating or other issues. Some ticking but i think that's normal. and Getting oil pressure light flickering here's what happens, pretty much like clock work...

currently running 15- 50 oil i think can't recall...

start car cold, oil pressure light is off...
car warms up a bit...oil pressure light starts to flicker a bit....at idle
once operating temp. oil pressure light is on pretty consistently...at idle
when at idle, if rev RPM to at least 1000 and hold, (idles currently at about 700-800)...oil pressure light pretty much disappears
at road/hwy speed, obviously higher RPM, oil pressure light is fully off until stopped in traffic or idling, then the oil pressure light reappears

so...was thinking tired oil pump/clogged pump screen, maybe loose oil pan bolts or loosed oil pump bolts. will check these and change oil to 20-50 Valvoline as has been recommended here. I've got a used oil pump to possibly replace.

I have read that a oil spray bar that isn't "spraying" correctly can be cause for oil pressure light.

Question is, is there a way to test or verify that the oil spray bar is spraying oil. maybe can run with the valve cover off, but sounds like a bad idea and seems vacuum loss would prevent anyway???

[Blue Shadow]

if the cam lobes are not damaged, the bar is spraying. Usually #1.
but check to see that the spray bar bolts are at proper torque. Too much crushes the oil passage and too little will allow the bolt to back out. New bolts have a locking material on them to prevent backing out when properly torqued. It ain't much but the Bentley should have the number.

Proper weight oil, 20W-50 unless you have 10°F temps regularly will help build pressure as will fresh oil. Most would swap out the pressure switch to verify it is not the problem as it is cheaper than swapping the pump.

I was off a bit on temp range for oil choice.

Here is the list from the manual of the temp range for different weight oils.
20W-50 15°F to 122°F
15W-50 -4°F to 105°F
15W-40 -4°F to 85°F
10W-50 -20°F to 68°F
10W-40 -20°F to 50°F
10W-30 -20°F to 40°F
5W-30 -40°F to 22°F
5W-20 -40°F to 15°F

[turbodan]

The oil spray bar will not affect oil pressure. It just distributes a spritz of oil along the cam if there is sufficient pressure available.

Have you replaced the pressure sensor? This is a pretty common failure mode. They falsely indicate low pressure.

[Blue Shadow]

The oil spray bar will not affect oil pressure.
Have you replaced the pressure sensor?

won't the oil pressure drop if the bolts holding the spray bar are removed and oil can freely flow through the channel to the top of the head? I don't know if I have experienced this drop in pressure in my ride. The pressure gauge reads over 45 at temp at speed.

The pressure switch is a switch to turn on the light. A sensor is used to provide a signal to a gauge. But you are right, it is a common replacement before going further.

[Mike W.]

Have you replaced the pressure sensor? This is a pretty common failure mode. They falsely indicate low pressure.

YMMV, but IMO they mostly leak as a failure mode. Sometimes weeping, occasionally gushing. But I agree with your premise, replace the cheap, failure prone part first, then go in deeper. And cross your fingers first.

[turbodan]

The oil spray bar will not affect oil pressure.
Have you replaced the pressure sensor?

won't the oil pressure drop if the bolts holding the spray bar are removed and oil can freely flow through the channel to the top of the head? I don't know if I have experienced this drop in pressure in my ride. The pressure gauge reads over 45 at temp at speed.

The pressure switch is a switch to turn on the light. A sensor is used to provide a signal to a gauge. But you are right, it is a common replacement before going further.

The spray bar on the M20 is fed by slots in the front and rear cam journals. As soon as these slots open to the spray bar, oil is fed into the bar which of course has several holes in it and immediately distributes the oil along the cam. The bar offers no resistance to flow and builds no pressure but it is only open for a certain period. The spray bar could be removed and it would still only be open for this certain period.

One thing I have done in the past is actually grind and lengthen these slots to increase the duration of feed through the spray bar. The M20 routinely experiences valvetrain wear and although I think proper oil is the cure, more oil certainly couldn't hurt.

Have you replaced the pressure sensor? This is a pretty common failure mode. They falsely indicate low pressure.

YMMV, but IMO they mostly leak as a failure mode. Sometimes weeping, occasionally gushing. But I agree with your premise, replace the cheap, failure prone part first, then go in deeper. And cross your fingers first.

When I sold them during my stint at the dealer that was usually the customer complaint. Not specifically to the e28 but I think the sensor is similar if not the same on a lot of these motors.

[gadget73]

OP's symptoms to me line up with worn bottom end bearings based on my experience with other engines. I suppose a tired oil pump might do the same thing though.

verify with a mechanical gauge, hopefully its just a lying sensor.

[Blue Shadow]

The spray bar on the M20 is fed by slots in the front and rear cam journals.

Different from the M30. Thanks.