Oil pressure electrical

[skidrew32]

At idle, in park, when I apply the brake my oil pressure drops to 0. It seems to be an electrical maybe ground issue. I also have a left brake light with no power not sure if they are related. There is no RPM change when I apply brake in park so I'm guessing its electric. I did put a new sending unit. no difference

 

[chengny]

At idle, in park,

Only happens under those conditions?

What if the engine RPM is raised above idle (while still in PARK) and the brake pedal is depressed? Still a huge drop in indicated oil pressure?

No other gauges are acting this way (e.g. coolant temp or gas gauge)

How about if the gear selector is in N (instead of P) - same reaction?

Do you have a tilt steering column by any chance?
If you do, try moving it all the way up or down - see if that changes anything.

 

[skidrew32]

At idle, in park,

Only happens under those conditions?

What if the engine RPM is raised above idle (while still in PARK) and the brake pedal is depressed? Still a huge drop in indicated oil pressure?

No other gauges are acting this way (e.g. coolant temp or gas gauge)

How about if the gear selector is in N (instead of P) - same reaction?

Do you have a tilt steering column by any chance?
If you do, try moving it all the way up or down - see if that changes anything.

Only happens at idle with brake in any gear position. If I raise above Idle it goes up a bit.

Before I realized it was related to the brake pedal, I replaced sending unit (didn't help), dropped pan cleaned it and new oil pump and pickup as well as new oil and filter all of those didn't change it. No smoke or noises from engine.

No tilt column although I am in the process of putting 1 in now. No other gauges have been affected.

 

[89Suburban]

I notice my oil pressure gauge fluctuates slightly when at a stop light, foot on the brake and turn signal on.

 

[chengny]

Only happens at idle with brake in any gear position. If I raise above Idle it goes up a bit.

It would probably be worth the time and effort to (at least temporarily) install a mechanical gauge. That will allow you to compare the actual oil pressure - as indicated by the gauge - to what the dash indication shows.

There is a 1/4' pipe plug in the block about an inch above the oil filter flange. The passage behind it is the outlet from the oil filter. It is a bit of a pain in the ass but, you can replace the plug with a nipple and a 90. Then you'll always have a port to measure actual oil system pressure.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

As engines accumulate miles, the bearing clearances increase and even a new oil pump in unable to develop the pressure it did when the engine was new. A lot of people freak out if their oil pressure isn't 45-60 psi, but truth is - the actual GM spec for a SBC is really quite low. Ready....only 10 psi at idle - well not really idle, that's at 500 RPM:

You must be registered for see images attach

Understand that the pump is still operating at capacity - (actually it's moving more oil as the bearing clearances increase) - and the bearings are still getting an adequate supply of oil for lubrication. The bearings generate their own pressure (the pressure in the oil wedge of a automotive journal bearing is well over 1000 psi). All the really need is a steady supply of fresh cool oil.