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4020 low oil pressure

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Red Whiskers

01-18-2023 14:01:18

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Friend has a early (round manifold) 4020 diesel with low oil pressure, like 10 lbs.
Supposedly have gone through the oil pump. Put a new gauge and oil line to the gauge.
Been years since I've worked on 4020s. Do they have a way do adjust the pressure? What could cause this?

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Glen D Anderson

01-19-2023 04:51:33

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 Re: 4020 low oil pressure in reply to Red Whiskers, 01-18-2023 14:01:18  
Assuming that the cause isn't simply significant engine wear or a result of the viscosity of the oil being used as already mentioned, the o-ring that seals the oil filter canister to the oil pump housing may have failed.

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01-19-2023 04:56:23

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 Re: 4020 low oil pressure in reply to Glen D Anderson, 01-19-2023 04:51:33  
Good possibility since he would have had that off to replace the pump. Or maybe something in the oil cooler bypass or broken spring.

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01-18-2023 17:51:36

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 Re: 4020 low oil pressure in reply to Red Whiskers, 01-18-2023 14:01:18  
To adjust the pressure, look at the tachometer drive, you will see a longer nut that goes through the side shield(if it has one), behind the long nut is a jam nut. Loosen the longer nut and remove it, loosen the jam nut and turn the stud in(takes a flat screwdriver) until desired pressure is achieved. Tighten jam nut and the long nut. done.

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Cliff Nelson

01-18-2023 18:35:52

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 Re: 4020 low oil pressure in reply to matthies, 01-18-2023 17:51:36  
If you can't adjust pressure as described, remove and inspect the tach drive and regulator housing. There is a steel sleeve/seat in the regulator housing that the pressure regulating spring seals against to regulate the pressure. The steel sleeve sometimes moves in the aluminum housing causing the regulator spring to not close off the passage properly, resulting in low oil pressure.

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01-18-2023 16:19:27

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 Re: 4020 low oil pressure in reply to Red Whiskers, 01-18-2023 14:01:18  
what causes that, as the engine brgs, wear you have more clearance in the rods and mains and camshaft. pretty soon at idle the oil pump cant keep up the pressure. and when the oil gets hot you have even less pressure. and the other thing is oil pump wear also. this means you are getting time for an engine rebuild. but with no info on this engine like hrs. to date, oil usage between oil changes that is the deal. what u can do... dont idle it slow keep it over 900 rpm, use a thicker oil . plus dont know what oil u have in there now.

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