oil pressure question
 

I have a 2004 Discovery with 150k. I have had issues with the oil pressure light coming on. I took it to a local garage and they said cold start was only at 20psi and idle was at 3psi and said my crank shaft bearings must be bad. The engine does not knock but does have the rear and front main seals leak and the oil pan gasket leaks. Tonight I installed a gauge to check it myself. I got 40psi at start up and once warmed up I had a constant 28psi at 2500rpm while at idle it does drop down to just a couple of pounds of pressure. I let it cool for a couple hours and replicated it again with the same pressures happening. I let it run at 2500 for about 10 minutes both times to make sure pressure did not bleed down. Does this sound like bad crank bearings, or the pump? I have not been driving it since the light issue. I am trying to determine if I need to replace the engine, or if it is something like the pump. Like I said previously, the engine runs smooth with no knocking sounds or smoke being emitted from the exhaust. Thanks for any guidance.

Most likely oil pump, they are a known weak point... However I've no experience with a warn crank, though I've had cracked oil pump gears and possibly a faulty bypass valve in the front cover, both can contribute to low oil pressure on start up, though I never had the light come on.

Sounds like you are catching it just in the nick of time. I can't imagine you would need a new engine by your description.

Possibly your new oil pump gears were installed incorrectly? Was it done at a land rover specific indy shop?

No the pump was not. In my area there are no Indy shops, etc.


I have a new oil pump gear and gasket set laying around that I bought for another project so I might as well try and install them and see what happens.

before you rip into it add a quart of Lucas engine treatment if your pressure goes up at idle you have a pressure problem.

You are referring to bearing issues?

i am referring to you're pump, if you bearing are bad it doesn't matter how thick the oil is it will just run out.

The oil pump gears have a front facing side and a back facing side and are not reversible...

I believe the chamfered side goes toward the front cover, the details are in many threads here and found in the search section, or someone with a better memory can chime in.

The causes of worn crank shaft bearings would be long term poor oil circulation due to a sludged up engine, long term use of inadequate oil (too thin,) or very long history of infrequent oil changes possibly in combination with the wrong oil. Have you had the truck long enough to rule out the above?

Low oil pressure due to broken pump gears typically start showing symptoms first in the valve train with ticking noises.

I have had the rig since 85,000 miles. I have used Rotella 15/40 in it since I have had it. It is my company truck and gets serviced every 3-4,000 miles.

My guess is that your local shop is probably wrong about it being the crank shaft bearings.

I should say that while the oil pump gears are not reversible they will go in backward, There are posts here about them being wrongly installed.

At least the oil pump/front cover would be the first place I'd look in your situation.

Plus the oil pump gears have a weak spot. They tend to crack in the skinny part of the gear. In between the teeth.