Oil pressure indicitave of engine mechanical fitness?
- Thread starter JonS
- Start date
The absolute number isn't of much value per se, the benefit is being able to spot a change in pressure over time (engine running obviously), which is an indication of trouble.
going down fast or slow is of no use alone as it depends on numerous things. If it always goes down slow and suddenly starts dropping fast, or vis-versa; well, ok, something is wrong. Again, it's the change from the norm that should be noticed.
BTW, 275 kPa = 39.9 psi. What year is the Celica?
The Celica is an 88, with 208000 kms. The wagon is a 90, with 249000 kms. I notice when I start the Celica I hear some clatter for a second or so after I start it, then the motor tends to be a bit noisy for the first minute or so when I'm driving it. The 3300 in the wagon doesn't make a sound, and isn't noisy during the first few minutes when I start driving it like the Celica is.
Factory gauges are notorious for low-quality. An aftermarket piece (FARIA, AUTOMETER) is a much better hand-holder.
That said, a low pressure reading at idle and at speed is worrisome and needs investigation. Sometimes a fairly simple fix (oil pump; dead-easy on an old Chrysler B/RB), or it may be indicative of further, more serious problems (crankshaft bearings, etc)
If the rod big ends are loose your oil pressure should drop as RPMs go up because of increased throw off of oil. If the main bearings are loose, well OffOrWFO gave an excellent test for that in this thread on oil pressure, which post I will quote below:
quote:
The way to tell if the bottom end needs rebuilt is to: Get an accurate mechanical OP guage. Then run the engine full throttle for 20sec (at highway speeds)then let completely off and watch the guage. When you let off the crank will center its self in the main bearing because there is no longer a down load on the crank. When the crank is centered, less pressure escapes from around the main bearing. If the OP increases more than about 2-3 psi then the main bearings are getting loose.
Is having good oil pressure a way to tell if the engine mechanicals are in good shape? The wagon has an oil pressure gauge that's marked in Kilopascals. On a cold start, the engine will run about 1300-1500 rpm, and the gauge will be a bit above 275 kpa. Is that good? On a cold start with the Celica, the gauge is slow to rise, about 2-3 seconds before it settles right about the middle, the Celica's gauge isn't marked with any numbers. I believe if the main bearings are worn, then pressure would be low, but if pressure is good, that at least indicates the bearings are in decent shape, right?
quote:What oil filters are you using? What oil weight are you using?
Originally posted by 55: The Celica is an 88, with 208000 kms. The wagon is a 90, with 249000 kms. I notice when I start the Celica I hear some clatter for a second or so after I start it, then the motor tends to be a bit noisy for the first minute or so when I'm driving it. The 3300 in the wagon doesn't make a sound, and isn't noisy during the first few minutes when I start driving it like the Celica is.
Is that Celica engine a chain or belt camshaft driven engine?
Some Toyota engines with chain drives have plastic chain guides that wear, allowing the chain to make contact with the block.
And, with accumulated mileage and wear, slop can form in the chain resulting in various levels of noise.
Not sure about your engine but it's sumpthin' to consider.
It's got a 3SFE, which is belt and gear driven. Timing belt goes around the intake cam sprocket, and there's a gear on the intake cam that drives the exhaust cam. The Celica has an oil leak somewhere, not sure where it is. I was using GC, but I imagine most of it's leaked out by now. Since I last changed the oil on the Celica, I've put 1 quart Castrol GTX 10w30, and 2 quarts Zellers housebrand Autoprix 10w30. It's got a Valvoline Maxlife oil filter. I'm just using cheap stuff on the wagon. 4.4 quarts Autoprix 10w30 and a Honeywell Defense oil filter.
quote:Jon, unless it's a mechanical gauge (and few are), the power to the gauge is shut off, and the residual oil pressure has nothing to do with the fall of the needle. Also, with no accumulator in the system, as soon as the pump stops turning, pressure should be zero. I beleive that most electrical gauges fitted to cars are so heavily damped that the slow rise/fall is due to gauge design, and to stop people worrying about spikes/dips.
Originally posted by JonS: I've heard that when you shut down an engine, the pressure on the gauge show go down really slow. If it goes down fast, this mean worn bearings.
