No oil pressure at operating temp?

[AJPTHNG]

Not sure if this is the right area, and I'm sure I know the one who will have an answer for this question :D

99 Dodge Ram 1500 360 with just over 100,000 miles. When its cold the oil pressure is fine 60-80 PSI. When its warm and your driving the oil PSI sits around 30 and when the engine RPM's are at idle there is NO oil PSI. The oil sending unit has been replaced, manifold gasket has been replaced (it was doing this prior to replacement) and seems to be fine other then the pressure gauge hitting the bottom when its at operating temp. I think that the pump is going but we are looking into other options before we replace it.

[naturalbornmudder]

I thought once the oil warmed up and thinned out, the pressure lowered as well. The oil pump should be mechanical, i.e. doesn't it run faster with higher RPM's? So RPM's low equals low oil pressure. Cold start equals thicker oil equals higher pressure. Kind of like blood pressure, IMO.

[arcticmutt]

I had this happen on an f150 I had so I just turned up the idle :D

[The Bronze]

No quick easy answer for this one :cool:

The chrysler V8 are a known sludge builder, especially in the oil pan and the pickup screen. If the screen is clear, then check the rod/main bearings for clearance, install a new oil pump and give it a shot. You can (should) also check crankshaft thrust as a worn thrust washer will drop the pressure as well. If all that checks out, the new *high volume, high pressure* pump is installed and it isn't any better, than you are going to be checking cam bearings and such. If you have lots of sludge build-up in the pan, expect certain bearing wear that will require a rebuild.

This one doesn't cost you McDs :D

[wayne_l]

also before you drop the oil pan run a quart of marvil mystery oil thru it with engine warm and running drive it for few hours then change it cleans the engine amazingly well and gets rid of alot of sludge build up ..i have done few tear downs of before and after using it ..its amazing stuff ..because it works so well i would be afraid to use it in the oil for long periods of time loosing oils viscosity ...

i have done this to alot older motors with good results then when you clean out the oil pump it should have good oil pressure long as your main bearings aint shot or pump bad ..

[AJPTHNG]

We will try the marvil mystery oil on the next oil change and pull the pan. Thanks for the input on this and I will try to keep you up to date on what it looks like when we get into it.