[Campbell203]

Specs: 2000 Dodge Dakota 3.9L V6 4x4 SLT Club Cab with 137,000 miles.
Also I use 10w-30. It has had 5w-30 when this started (Walmart oil change)

Issue: Low or no oil pressure

I changed my water pump, thermostat, and return hose. After completion I started the truck only to have low oil pressure. Once I put the vehicle in drive oil pressure was 0. Checked the oil and it looked like chocolate milk. I have done 6 oil changes with 2 new filters. The oil currently looks good, no milk look, but my oil pressure is low and once it warms up in drops to 0. I keep being told head gasket but vehicle is not burning antifreeze and no antifreeze or water in new oil.

Really need help with this, I've had the truck for 10 years and want to keep it for as long as possible.

Thank you

 

[niebs]

well water had to have gotten in there some how. if the whole oil system was contaminated then its possible that the sludge have clogged an oil passage or you may have got lucky and only fouled the oil pressure sensor. i wold take it out and look at it to see if its fouled or not.

 

[Campbell203]

Update

So I have changed my oil and filter and few times now. Oil looks good no water or antifreeze in it. I'm still having problem with oil pressure. The pressure is good (40-60psi) when the engine is cold but as soon as it gets to normal operating temp it goes down (2-7psi). I installed a mechanical oil pressure gauge and I know it is accurate.
Once the vehicle is warmed up, if I raise the RPM's the pressure drops, I let off and it goes up slightly and then starts dropping until I have less then 5 psi according to the gauge.

Any thoughts as to why once the oil is hot and presumed thinner then when it's cold that I'm loosing all my oil pressure.

Thanks

 

[RXT]

A quick question, before you replaced the water pump, did the engine happen to overheat?

Ok every engine has it's oil system and cooling system isolated from each other. The closest point where they meet is at the heads and gasket. If the gasket is blown or there is a cracked head, you can get mixing between oil and coolant. Sometimes only the oil gets mixed and sometimes only the coolant gets mixed and sometimes both get mixed, but if any of these things happen, you have to suspect either a blown head gasket or a cracked head. Low oil pressure can indicate worn main bearings or a worn oil pump. Since Dodge engines are known to last well beyond 200k I'm inclined to believe that the issue is the oil pump, however we can't simply dismiss the bearings because they could wear out prematurely if the engine wasn't well maintained, or badly overheated or overworked at some point.

Unfortunately my only suggestion is you may have to consider a replacement or rebuild.

Ed

 

[Campbell203]

There was no overheating issue before I replaced the water pump. Only thing was I went to Walmart for an oil change and they put 5w-30 instead of 10w-30 which is what I always put in.

 

[niebs]

well 5w-30 is thinner then 10w-30 when its cold but the same when its heated.

 

[RXT]

There are only a few options left you can try, but anything you do now is delay the inevitable of having to rebuild or replace your engine. The easiest thing to do is dump out the thin oil for thicker oil. There are high mileage brands which will maintain pressure a little better, but I would have to suggest running thicker oil and perhaps a can of STP oil treatment. You could also replace the oil pump with a high volume/pressure oil pump. This replacement would address both a worn pump and worn main bearings at the same time. The higher pressure would give you back what pressure you lose to the greater clearances that worn bearings have. But it only buys you time, because the best fix is to have the engine rebuilt or replaced.

Ed