5.3L Oil pressure does not increase....why

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Jan 16, 2015 | 08:34 AM

Chicago TDP

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5.3L Oil pressure does not increase....why

So, long story short....put a junk yard 2003 5.3L long block into my nova....started it up and it has 15PSI of oil pressure at idle. If I rev it up to 3K RPM, no change at all.

I went ahead and pulled the motor and saw copper on all of the cam bearings...mind you the motor has 200K on it. The cylinders all look like new, cross hatch in every single one.

I tore the motor down to nuts and bolts, put in new Dura-Bond cam bearings, inspected all of the crank and rod bearings (all looked good, no wear), cleaned all the pistons and crank and put on a new melling hi volume pump. I pulled the barbell in the back of the motor to make sure it was there, pulled the two allen head plugs for the main oil passage to check for "stuff" and put on a new cam retainer plate. Also, I put a new o-ring on the pick-up tube and made sure it was not pinched or popping out one side.

Put the motor back in the car, new 5W-30 oil and oil filter....fired it up....15 PSI of oil pressure at idle and it still does not jump up with an RPM increase.

I am at wits end here....If I did not have a $1,600 turbo to feed oil to, I would not worry but I do not want to burn up my new turbo...

I am reading the oil pressure at the oil filter location with a braided steel line to an Autometer ultra-lite mechanical gauge that was reading 30 PSI on the old 4.8L I had in the car so I mostly trust the gauge

Any thoughts, experiences, etc...

Jan 16, 2015 | 08:54 AM

thunderstruck507

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From: Northwest AR

try a different gauge and/or sending unit?

where is the sending unit?

Jan 16, 2015 | 09:37 AM

Chicago TDP

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I will get a different gauge on there.

The gauge is being fed off of the port above the oil filter.
I also tried to read the pressure at the turbo feed line which is off the old oil pressure port on the top of the block.

Jan 18, 2015 | 05:41 AM

RonSSNova

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From: Portland, OR

First question, what happened to your previous engine?

You replaced everything but the gauge and line.

Have you tried the new gauge yet?

I suppose there could be a crack in the main oil passage in the block...

Ron

Jan 18, 2015 | 07:47 PM

VandykeT/A

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From: Hurley, VA

What about the little freeze plug behind the timing cover?

Jan 19, 2015 | 08:12 AM

Chicago TDP

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Quote:

Originally Posted by RonSSNova

The old 4.8 that I beat on was also having oil pressure problems but I knew that it has a bad cam bearing when I put the motor in the car...basically the old motor had one bad cam bearing and it would make the oil pressure jump a little...the needle on the oil pressure gauge sat at 40ish psi but the needle bounced and fluttered.

I am going to try a new gauge. I have replaced lots of others things along with the gauge. I have a new braided steel line feeding the gauge because I do not trust copper or plastic line.

Jan 19, 2015 | 08:13 AM

Chicago TDP

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Quote:

Originally Posted by VandykeT/A

What about the little freeze plug behind the timing cover?

I did check that and it is there and holding tight.
I took out the threaded plug that is next to it on the outside of the block to make sure the passage was clear as well.