Used 7 quarts oil in less than 200 miles!

[Monkey Run]

Oil level exactly as marked prior to running



Cycled lift pump twice after tightening no leaks yet

[Monkey Run]

Going to start it once done in barn, can't take the fumes again today.

[Crasher]

Did you run it at highway speed or just let it run?

[Rob_M]

Sorry I tried to read the whole thread but wow….

Anyway, I keep seeing 24 quarts mentioned. Both the 8.3 in my coach and 8.9 in my work Peterbuilt take 5 gallons of oil including the filter. If you’re over filling by 4 quarts that would account for 4 quarts disappearing pretty quickly.

Also as mentioned, coach dipstick assemblies are often mis-marked and CAN slip out of the block causing oil level confusion.

[Monkey Run]

Was always filled with 24 quarts to answer that question.



I used the rpm boost feature and had it cranked up but not on road. Also manually revved and at no time was smoke detected in exhaust.

[Rob_M]

Originally Posted by Monkey Run

Was always filled with 24 quarts to answer that question.



I used the rpm boost feature and had it cranked up but not on road. Also manually revved and at no time was smoke detected in exhaust.

So possibly been over filled by 1 gallon every time because the dipstick was mis-marked. In the scale of the massive quantity of oil capacity these large engines have, 1 gallon off is not beyond possible.

I work for caterpillar and we speak and gallons not quarts.

[jacwjames]

My ISC manual says 21 quarts. I fill the oil filter before installing and then put the rest of that gallon in plus 4 other gallons for a total of 20 quarts. It shows that it is a little low on the dip stick.

In past I'd add a quart and after a couple thousand miles it goes down a little and then didn't use any more oil.
The last time I changed oil I only put in 20 quarts and I didn't use any in +5K miles. Seems like it's happy with the 20 quarts.

[jimbull34]

I didn't do anything to the lift pump. On my coach, 04 Monaco dynasty, the pump is almost impossible to get to. To change it out the dually have to be removed and the work is done from underneath. Just can't get at irom above. So, now the fuel runs thru it...if yours is leaking, then yes I would bypass it if you can get to it. Still use the existing fuel line just have to use a adapter between the two lines you remove from the pump.. I can't imagine the "pump" itself leaking but rather the fuel line connections...

[Crasher]

Apparently, Cummins puts different capacity oil pans on the same engine. My 8.9 450 hp ISL takes 28 qts for a complete change including filters. It has not used enough to add a qt between 10,000 mile annual changes. I've also seen where a 5.9 ISB in a pickup might take less than the same engine in a 36' motorhome. As thorough as the OP has been in his search for the reason of volume loss, I suspect 24 qts is the correct amount for his engine.

[Monkey Run]

Originally Posted by jimbull34

I didn't do anything to the lift pump. On my coach, 04 Monaco dynasty, the pump is almost impossible to get to. To change it out the dually have to be removed and the work is done from underneath. Just can't get at irom above. So, now the fuel runs thru it...if yours is leaking, then yes I would bypass it if you can get to it. Still use the existing fuel line just have to use a adapter between the two lines you remove from the pump.. I can't imagine the "pump" itself leaking but rather the fuel line connections...

Monaco has side radiator plus top access does it not? I'm looking at a 40' Beaver but with a CAT engine. Always loved those Monaco coaches.

The gasket at the top where it meets the fuel block is leaking but easy to get bolts from under the bed hatch. I believe it's completely stopped now as one of the three bolts was not nearly tight.

[jacwjames]

Here is the TSB on the fuel pump gasket. Cummins doesn't sell the gasket but there is an EBAY seller that does. If you are not going to replace the lift pump I'd suggest at minimum to carry a spare gasket.

I was anticipating the lift pump leak and actually bought spare gasket but after mine started to leak I just decided to install a FASS system and bypass the lift pump.

[Monkey Run]

Originally Posted by jacwjames

Here is the TSB on the fuel pump gasket. Cummins doesn't sell the gasket but there is an EBAY seller that does. If you are not going to replace the lift pump I'd suggest at minimum to carry a spare gasket.

I was anticipating the lift pump leak and actually bought spare gasket but after mine started to leak I just decided to install a FASS system and bypass the lift pump.

Will be replaced just can't get the new system before trials. Good idea re gasket though

[Monkey Run]

My mistake:

I accidentally checked the oil via the transmission tube due to having both sticks out at the same time. Thus the negative readings on the stick after changing the oil and filling with 24 quarts.

The process:

With the assistance of the folks here and my friend the X Cummins mechanic, I was able to verify all of the potential areas in which motor oil might end up other than in the pan.

Result:

Nothing found in any of the systems, including fuel, which would explains the disappearance of 7 quarts, other than an unseen leak or a thief. Hoping to run it out later this week as the weather is going to be decent. I'll check the oil at regular intervals.

Thanks to everyone for the assistance!

[Monkey Run]

Originally Posted by THenne1713

I have seen three cases of water leaks from spider-web string size sprays, that would land 5-10-feet from origin, which was confusing until the web-spray found. This MIGHT also occur with pressurized oil, spraying directly to the ground? Maybe ONLY at highways speeds? I too had a "about to spin-off and blow" oil filter, but it was on my GEN found shortly after purchase.

This is something I cannot disprove until a road trip. If it drops again, I may backtrack on foot just to check the road surface for oil.