Jacob on the Lake

Thanks @DaveT. I guess I should clarify that I'm driving the vehicle up to 60 MPH while warming up. When all warmed up, I can rev to 5000 RPM and the oil pressure needle moves a little, but settles right back at zero. Are you referring to the gauge inside the dash? I have an 87 Brat for parts, maybe I'll swap in that gauge. It was working properly 4 months ago.

Hi, this is my first post to USMB. My current project is an 83 Brat, 131k miles, sat for the last 10-15 years in Texas, probably in the direct sun. The oil pressure gauge shows nominal pressure when the engine is cold. Over the first 10 minutes of running, the oil pressure eventually drops to zero as the temperature comes up. Here's what I have tried: - drain the oil looking for sludge; fill with oil and sludge remover and run 10 minutes; fill again with new filter - switch to 20W-50 Didn't find any sludge. The heavier oil helps a little (I think), but still the pressure goes all the way down to zero. I'm convinced that the oil pump is working, else I should see zero pressure when the engine is cold. I could replace the oil pressure sending unit, but why would the sending unit malfunction only when warm? Has anyone else had this problem?