Oil pressure gauge

1995 Blazer s10, enging has 70k miles.

The oil pressure on the gauge drops down close to the red only when braking. It will drop and then go back up to normall idle pressure (20psi) after the can sits for a second.

The weird thing is it drops down when braking even if the engine is in nutrual. The Engine seems fine, no drop in idle. The oil level is fine.

Could it be the oil sending unit going bad? I don’t have a manual gauge. Anyone have any suggestions? Thanks

Have you checked your oil level lately? It sounds like maybe the oil in the pan could be sloshing away from the pick-up when you’re braking.

I know you said the oil level was fine but, did you check the oil level correctly?

No offense meant, but as I don’t know your level of mechanical knowledge I feel I must mention the following:
Like when the engine is cold before starting and shutting off.

Pull stick out, wipe it off, stick it back in, pull out and check. Do it twice as sometimes oil in the tube will throw off the actual level reading on the dipstick.

It is possible the oil pressure sending unit is faulty (perhaps just a bad wiring connection) or the oil pump has a fault.

The more I think of it the more I think the oil pan screen fell off the oil pump. If this is the case this would be a big job. Someone please TELL ME DIFFERANT!

You mean off the pickup tube? If it did it would not cause your pressure to drop.

What’s your RPM doing when you brake? When you apply the brakes, the vacuum from the decelerating engine assists by pulling on a diaphragm (called a booster) that’s in line in your brake linkage. It’s inside the frying pan shaped thing that your master cylinder is attached to. I’m wondering of you have a vacuum leak in the booster and it’s cauing your engine to falter due to a temporary lean condition.

If the pick up tube/screen fell off it would not be submerged as deep in the oil. I’m thinking when braking the inlet on the oil pump is not submerged it the oil due to a differance in oil inlet height. Although I would hope your right about the vacuum loss. The thing is the engine sounds good and I dont hear the enging idle go down. I guess I should pull out the scanner and check the rpm’s. I’ll go check it.

Buy a new sender and install it or else get a pressure gauge. Anything else is just guessing. You can find an inexpensive 100psi gauge at a farm supply store or check Home Depot etc in their plumbing department. You might also need to buy an adaptor fitting. Remove the sender and install the gauge there. Be aware that the pressure will be greater when the engine is cold. The oil pump’s blowoff valve is affected by oil viscosity.

You say, “…it [oil pressure] drops …, when braking, even if the [transmission] is in neutral”. Right?
Does the oil pressure indication drop if the truck isn’t moving, and you press the brake pedal? I suspect a wiring problem between the oil pressure indication circuit and another circuit…maybe, a wire the brake pedal is moving against?

install a gage that uses a metal line from sending unit and run it in cab so you can watch it like we did in 1950 . no wires just pressure

I see your point. Is the pickup tube in the rear of the pan?