oil viscosity and overhauls - Performance Forum

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oil viscosity and overhauls
Tuesday, October 04, 2016 5:55 PM
So I have '00 2.2L and I recently did an overhaul. Nothing fancy, just a stock rebuild. I was losing a rod bearing at 350k so I yanked a crank and cam out of a low mileage block and went 30 over on the pistons and rings. Crank, cam, and old block checked out fine at the machine shop so I didn't bother machining any of them and just went with standard bearings. Otherwise it was "by the book"...New timing, pistons, oil pump, so on and so forth.
She runs great but I get a low oil pressure indication at operating temp when at idle. Changed sensor, done wire work... nothing. So I figure there may be more play than I realized in the bottom end after all... And that's what's confusing me.

Isn't my oil supposed to be thicker at operating temp due to the additives? If so, low pressure from "loose" bearings would show at ambient temp BEFORE operating temp, right?

Re: oil viscosity and overhauls
Thursday, October 06, 2016 2:19 PM
So, Just to get this straight, during warm up, the oil light is not on. correct?
It only comes on after some time during warm up?
Also, I believe as it heats up, the oil pressure goes down, which is by design. (I have an oil pressure gauge in my 2.2 for years, and after it's warmed up, at idle, it can be 15psi. But at a cold start, it's more like 50-60psi. )
However, I have the opposite problem as you. Because I teed the spot where the sensor goes into the block, it doesn't seem to get pressure exactly at startup, and it trips the light. From then, it will never go off. It doesn't continually check, but since I have the pressure gauge, i know what the pressure is, so I ignore my oil light.
If I was you, i'd double check that the oil isn't low somehow. Not sure why it would get low pressure all of a sudden after warm up.



Re: oil viscosity and overhauls
Friday, October 07, 2016 11:51 AM
Correct; Once warm, it kicks a low pressure light. I didn't know about the oil pressure change built into the system... that could definitely explain it. A pressure change like that could likely overcome the higher top end viscosity if my bearings aren't to spec, I imagine.

I'll get back into the service manual and see what it says, then physically check the pressures.

Thanks.
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