low oil pressure

[jgorden]

I recently bought a 93 k 2500 4x4 pickup that had broke a oil cooler line and run low of oil had spun rod bearing. Replaced crank with reground crank and new rod and main bearings new oil pump (even tried second and third oil pump to elimnate that got bad pump) and plastic gauge everthing and all was within spec replaced cam bearings also has john deere 15w40 oil at start up it will run 50 to 60 psi and after the motor runs about 20 to 30 min it will drop to where has only about 10 psi oil pressure all data says this is fine but I'm not comfortable with this. We have looped the oil cooler lines and bypassed the cooler and also the turbo try to isolate the problem with no change. I think i have stumped every machine shop guy in 200 miles of me they all say there is no reason for this thing to do this. I have found a lot of interesting things about this engine such as the y could have many diferent size of rod and main bearing from the factory just to get them within spec direct from factory would it not be easier to just grind the crank right the first time? Has anyone ever run into this problem before and what was cure for it

[sixnickel]

Is this at idle or at higher RPM? And what are you using for a guage the truck guage or a shop guage? 10 lbs at idle I would not worry. Also I would not trust the truck guage!

[jgorden]

The 10 psi is at idle appros 850 to 900 and ihave put manual gauges on and changed sending unit both show the same

[Chevylover]

10 PSI is minimum at idle.
45 PSI at 2000 rpm.

I think you should do an oil change and change the oil filter to a Fram HP4 :

OILFILTER @ SS Diesel Supply (http://www.ssdieselsupply.com/product_104_HiPerformance_6.5_Oil_Filter.html)

Than your oil pressure should be higher, if not i would think, that your engine is worn.


After I changed oil and filter the oil pressure und my truck rised about 1/4.
I use Liqui Moly 15W-40 HD Diesel special oil and the Fram HP4 oilfilter.

Cu,
Sven

[sixnickel]

You won't like this I have heard of blocks cracking at the main bearing journals. You could have a crack in a oil galley leaking back into the pan. Sorry for the bad thought but this could be the cause.