Hello,

My 99 dodge ram 1500 5.9L is losing an insane amount of oil. I just did an oil change and filled it up with 5 quarts and have probably gone 120 miles and it is all gone. The truck has 158k on it and does not seem to have any apparent issues (loss of power, excessive smoking etc)
I would expect their to be excessive smoke with this amount of oil loss which I have no seen which leads me to believe it is the plenum. So I checked hughes website, here is an excerpt I used to confirm my plenum is indeed bad
"Clues to help diagnose the problem:
1. With the engine shut off open the throttle body wide open. Look down into the manifold with a flashlight. This area should be clean aluminum - no oil or black soot. If there is oil (usually dirty black) the plenum gasket is leaking.
2. With the engine running, remove the PCV from the valve cover. There should be air pressure coming out of the valve cover. If there is a vacuum, this indicates the plenum gasket is leaking."

Both of these tests proved that the plenum is indeed leaking (massive amount of fresh oil pooled up in the bottom of the plenum and removing the PCV from the valve cover created a very powerful vacuum)

I am planning on changing the plenum with the hughes kit but I am a bit concerned there isn't more at play here since the oil consumption is outrageous.

Any thoughts?

thanks

 

What weight oil did you put in? Thinner oil will burn faster. Since you confirmed the gasket is bad change it.

 

What is "all gone"? No reading on the dipstick just means you're down maybe 1.5 qts (which would still be a lot in 120 miles)

If it was truly "all gone" it would be knocking horribly and you've toasted your engine. You will know if it's all gone if you pull the drain plug and nothing comes out.

Anyway, if there's just no reading on the dipstick, we have to at least ask the obvious questions like when you changed the oil how much did you put in (edit: I see OP says 5 qts) and what filter are you using? I ask because the larger Ford *8A or FL-1A adds about 1/2 qt capacity. Secondly, how do spark plugs appear and have you run a compression check?

Basically I'm sure your plenum ain't great but we should consider ALL things that could contribute to oil consumption because 120 miles is nothing. At that rate you'd be burning ~10 qts every thousand miles which is ludicrous

 

Yeah, think I would do a compression test on that motor before investing a dime into it.

 

Yep, @HeyYou stated it more succinctly. This is exactly what I was trying to get at: you could invest time and money into the plenum only to find that it helps the problem only a little. Basically, you might be trying to treat a leg for sciatica when really the lower back has a herniated disc.

OTOH, 158k would be low mileage for a Magnum to have catastrophic failure....but anything is possible and we don't know the history of the truck.

 

My 96 with the 5.9 had a pretty healthy appetite for oil as well. I had close to 200K on mine though. Even after doing the plenum fix, it would still eat a quart about every 100 miles..... and it wasn't leaking either... Would sometimes get a blue cloud at startup, but, that was fairly rare. On hard acceleration, it was a REAL smoker though..... Tested compression, and after finding two cylinders with about 65 PSI.... I stopped.

 

I used SAE 10x30W and the mopar filter from walymart. And to clarify, the oil gauge started acting funny - dropping to 0 here and there which prompted me to check the oil levels to find out there was no reading on the dipstick. I will be performing a compression test later today but if it is bad, I am kind of f***ed since the wife and I were suppose to be moving out of state with this rig and it leaves me only two options: replace motor at my buddies shop myself, or replace plenum at house and keep adding oil. And now, I am committed to this vehicle since we just got a canopy for it last night and ordered the replacement tranny parts I previously posted about which should arrive on monday - lol


I have been looking out to see how it could possibly burn so much damn oil (combustion chamber) but I am not seeing it. Anyway, only way to know for sure if its the internal engine components is with the compression test



Update:

Completed compression test and the numbers looked decent:
1:120
2:125
3:125
4:120
5:120
6:118
7:125
8:120

 

^^^^those numbers are good. Are you sure it read full on dipstick after oil change? I'd fill it up again and see if you can repeat the results, being sure it reads full before you start recording mileage.

Go ahead and plan on plenum I guess, and I personally wouldn't be the least bit concerned about using 20W-50 in these motors. They're old tech and you've got enough mileage clearances have surely opened up at least a little. 15W-40 HDEO would be fine, too, and can often be cheap by the gallon at farm supply stores like TSC etc

 

Try a wet test as well. Just add a teaspoon or two of oil the the cylinder, then retest. See what the numbers do.

Those do look really consistent though, if a bit low. Did you have the throttle wide open?

 

I’ll go ahead and do a wet test and see if the numbers change. What would be normal numbers when conducting the wet test?

also, Keith, I did duplicate the issue. We drove about 1.5 hours to get the canopy, then the oil pressure was acting funny, so I stopped and checked and the dip stick did not have any oil on it, so I filled it up then drove back home and it got low again about 5 minutes from the house. Checked when we got home and again, the dip stick was not reading anything.