Recently, my 2004 Disco's oil light would intermittently come on when stopped at a traffic light or stop sign. If I increased the RPMs, it would go away. After some searching on this forum, I bought an oil pressure gauge and have taken the following readings:


cold idle: 46 psi
cold 2000 rpm: 48 psi
hot idle: 7 psi
hot 2000 rpm: 30 psi


It is now obvious why the oil light is coming on when the engine is hot and at an idle. it also rules out a bad pressure switch.


I have been using Rotella 15w40 with Mobil 301 filters. About 3 months ago, I took the Disco into a shop for a oil leak fix. When I got it out, I noticed the filter had been changed. I don't know if the oil was changed or not. I am not sure if the pressure issue is related or not to the change in filter and possibly the change of oil, but I wanted to bring it up as a data point.


So what is the next step?


1 - do an oil change with 15w40 and a 301 filter?
2 - drop the oil pan and look for sludge at the pickup?
3 - remove the front cover and examine the oil pump?


Current mileage is at 73k.


Thanks for your input.

 

Thicker oil brings higher pressure. If the oil was changed back to a thinner grade when the leak was fixed and it brought the pressure down this low, then I would say the pump is at the limit of being able to provide adequate pressure.

Mine did that, just before the light stayed on permanently. Turns out the outer gear in the oil pump had broken in three pieces, just like so many others did before.

Anyway given the history of those oil pumps, I'd look there first. It's not that hard to remove the front cover. Just follow the rave.

 

even if they did put in 5-30 wt oil, you were having a problem long before that is why your OPL was coming on at idle.

 

Failing oil pump. Replace it before permanent damage is done. Even with thin oil, it should make more than 7psi.

 

It sounds like the oil pump is 'cream crackered'. Even if the tickover was far too slow the pressure should remain sufficient to not activate the low oil pressure switch and light. You don't mention tickover rpm so I guess it's within spec range. IMO don't use the truck until you positively sort the problem as if the oil pump fails totally your engine will be toast and even the intermittent oil light coming on at tickover is not doing the engine components any favours whatsoever.

 

Nah, throw the engine into the boonies and fit a decent engine, a TD5



Only pulling your leg eh

 

you will probably find the outer oil pump ring broken in several places

 

Thanks for all the feedback. I figured it was probably the pump. I'm going to start tearing into it tonight.

 

Yep -- it is a cracked outer ring...


Thanks for everyone's help with this.

 

Was your engine making any ticking or knocking sounds while you were dealing with this ? Mine is and I am hearing that could either be lifters or the oil pump.