Help understanding the 5.3

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cjmcglaughlin

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You need to understand how oil pressure in an engine is created.

The oil pump, which is driven by the engine and is speed-dependent, generates oil flow, not oil pressure.

This flow of oil is forced through the filter and transported through the oil channels to the bearings. This becomes oil pressure, because at the end of the oil channels in an engine there are usually plain bearings, for example on the camshaft and crankshaft.

The oil is pressed into these plain bearings and can only escape again with difficulty.

This nozzle effect creates back pressure and thus oil pressure.

Now there are several factors that ensure that the oil pressure is no longer the same as with a new engine.

Firstly, if your bearings in the engine are already very worn out, they can no longer hold back the oil, so the oil pressure drops.

As the oil becomes more liquid when it is hot, the oil pressure drops.

When the revolution is low in idle, the pump does not deliver as much flow, so the oil pressure drops.

If you drive for a long time, the oil is of course really hot and everything is really flushed through, so your oil pressure drops to its lowest value when idling then.

But as long as your oil light doesn't come on when idling and the engine has an oil pressure that is close to the middle (40psi) of the instrument display under normal load, everything is fine.
Right, I understand what you mean. I was inquiring if others oil pressures seem to warm up faster than mine, or if it might be a guage issue if it seems to be going down a bit even after I would think it’s fully warmed up. I might be just overthinking it though
 

nonickatall

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Right, I understand what you mean. I was inquiring if others oil pressures seem to warm up faster than mine, or if it might be a guage issue if it seems to be going down a bit even after I would think it’s fully warmed up. I might be just overthinking it though
You never can take too much care on oil pressure... :)
 

Doubeleive

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Right, I understand what you mean. I was inquiring if others oil pressures seem to warm up faster than mine, or if it might be a guage issue if it seems to be going down a bit even after I would think it’s fully warmed up. I might be just overthinking it though
sometimes the sensor goes bad but generally they either read 0 or peg at 80+
 

Doubeleive

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Just did the sensor w/ a genuine GM just to rule that out.
the bottom line is if there is metal in the motor from whatever source then the damage is already done, send out a oil sample and see what it say's cost's about $30 and takes a couple weeks. if you get the all clear then you know it's likely just the pump or pickup tube o-ring
 

cjmcglaughlin

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the bottom line is if there is metal in the motor from whatever source then the damage is already done, send out a oil sample and see what it say's cost's about $30 and takes a couple weeks. if you get the all clear then you know it's likely just the pump or pickup tube o-ring
Sorry I kinda hijacked this thread, I believe the OP had metal in oil but I did not
 
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TheEnder53

TheEnder53

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If you are dropping the pan for other work, that would be the perfect time to check a main bearing as well as a rod bearing.
If the bearing caps aren’t torque to yield i’d like to do that. Maybe throw a new set of bearings in.

After doing the (final) oil change before i drop the pan, no metal shavings or metal in oil at all. I will still do a test.
 

nonickatall

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Without having seen the chips myself and having my own opinion, I wouldn't be too worried if the engine itself is running, doesn't make any noise, has oil pressure and this didn't happen during the last oil change.

But I would take the oil pan down and replace the O-ring and the pressure relief valve.

And of course look at the general condition.

Are there any chips, what about oil carbon? And then I would remove the valve covers and take a look inside the valve train.

Fortunately, this can be done in an hour with our cars. And if you have the opportunity, I would do another compression test and maybe look into the cylinders with an endoscope camera to validate the condition.
 

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