Why to have your top end looked at!

[merle&louise]

There has been a lot said about draining the oil when the bus is going to sit up for a long while.

What actually happens inside the engine if the oil stays in the oil pan for say 6 months or so?

Does it rust? Corrode? Cause pitting?

I read that diesel produces sulfuric acid when an engine runs. Assuming this is correct (and I am not sure that it is) is that the reason for changing the oil?

Could someone explain this?

[James]

There has been a lot said about draining the oil when the bus is going to sit up for a long while.

What actually happens inside the engine if the oil stays in the oil pan for say 6 months or so?

I'm not sure what happens to the oil. The Series 60 manual does state however that if you're going to not operate the engine for more than 30 days to:

"Fill the crankcase to the proper level with Tectyl® 930A preservative lubricating oil or an equivalent 30–weight preservative lubricating oil
meeting Mil-L-21260C, Grade 2 Specification."

[travelite]

Tuga,

From what I gather engine oil has a buffering characteristic that neutralizes the acids that you talk about, predominantly sulfuric and nitric. As the engine oil ages, the buffer/neutralizing capability diminishes. These acids, if left unchecked, attack the metals in the engine, damage surfaces and possibly lead to early engine failure. As the engine sits, the thin layer of oil covering vital surfaces becomes ever thinner until virtually nothing is left to buffer against the acids that may form due to condensation. This situation is made worse if the oil is worn out; i.e., it's buffering/neutralizing capability is down by 50%. Get some fresh stuff in there and you stand a better chance of guarding those precious surfaces. This is my layman's understanding.


David Brady
'02 Blue Bird Wanderlodge LXi,
Series 60 Equipped,
Asheville, NC

[flyu2there]

One thing I forgot, the Valley Detroit guy did stress that you need to follow the manual on changing the oil if you're going to let the engine sit for awhile.

Seems you want to drain the old oil out when the engine is cold to make sure you get all of the condensation that is in the old oil, fill with new oil and only run the engine for a couple of minutes with the new oil so it lubricates everything but doesn't get hot enough to cause condensation when you shut down.

There is no condensation in oil, any water would float on top but that would be a sign of a major problem...head gasket and so on. The moisture that is a by product of combustion will condense on the valve cover, fill tubes and other hidden places, and may eventuallly cause rust.... the chances of it dripping back onto the oil...slim to none! Changing the oil when cold would only aggravate the problem as the hot oil has the ability of carrying moisture out with it when it drains and venting thru the fill.

Should this really be a concern why not take the oil filler cap off the engine when you shut it down....it allows the system to vent and the moisture will evaporate. Really want to get down to the nitty gritty, buy a Tanis System for around 700.00 http://www.aircraftspruce.com/catalo...Dehydrator.php

[flyu2there]

Tuga,

From what I gather engine oil has a buffering characteristic that neutralizes the acids that you talk about, predominantly sulfuric and nitric. As the engine oil ages, the buffer/neutralizing capability diminishes. These acids, if left unchecked, attack the metals in the engine, damage surfaces and possibly lead to early engine failure. As the engine sits, the thin layer of oil covering vital surfaces becomes ever thinner until virtually nothing is left to buffer against the acids that may form due to condensation. This situation is made worse if the oil is worn out; i.e., it's buffering/neutralizing capability is down by 50%. Get some fresh stuff in there and you stand a better chance of guarding those precious surfaces. This is my layman's understanding.


David Brady
'02 Blue Bird Wanderlodge LXi,
Series 60 Equipped,
Asheville, NC

Close, no cigar! The stuff in the oil, commonly known as detergent, hold the not so pleasant effluent in suspension within the oil. There is no expiration date on a can, gallon or drum of oil...the "stuff" is still there after years. True, the detergents dissipate after use however the oil change intervals are set to the conservative and most folks drain oil that still has all the necessary properties.

A non running engine will produce very little, if any condensation, that is all a result of combustion, blow by and the like. Starting an engine and not allowing it to reach full operating temperature when there is a moducum of hope that the moisture will evaporate, is perhaps the most lethal thing one can do.

[flyu2there]

I'm not sure what happens to the oil. The Series 60 manual does state however that if you're going to not operate the engine for more than 30 days to:

"Fill the crankcase to the proper level with Tectyl® 930A preservative lubricating oil or an equivalent 30–weight preservative lubricating oil
meeting Mil-L-21260C, Grade 2 Specification."

Don't! That stuff is the first cousin of cosmoline, a waxy rust preventative used by the military. You have to get it out of there once you put it in...not so easy!

[James]

I found this prelub system that Cummins installes. See https://quickserve.cummins.com/info/...ts/prelub.html .

The maker, RPM Industries indicates that it is also installed on CAT and Detroit engines. It replaces the starter.

http://www.rpmindustries.org/cms/

[dale farley]

If DD shops are using a drill connected to the generator line, why couldn't a small pump be connected in that line to do the same. A normally open solenoid could be in parallel to allow oil to always flow straight through except when the pump is engaged. This would only require a pump, switch, solenoid and connectors for a manual system. I don't see why a simple pump such as this one wouldn't work. http://cgi.ebay.com/ebaymotors/Biodi...ssoriesQ5fGear

[travelite]

Close, no cigar! The stuff in the oil, commonly known as detergent, hold the not so pleasant effluent in suspension within the oil. There is no expiration date on a can, gallon or drum of oil...the "stuff" is still there after years. True, the detergents dissipate after use however the oil change intervals are set to the conservative and most folks drain oil that still has all the necessary properties.

A non running engine will produce very little, if any condensation, that is all a result of combustion, blow by and the like. Starting an engine and not allowing it to reach full operating temperature when there is a moducum of hope that the moisture will evaporate, is perhaps the most lethal thing one can do.

Well, not quite the full story. There are 2 types of contaminants in used oil, soluble and insoluble. What you are referring to are the insoluble components. These are the particulates and abrasives that need to be lifted, emulsified, and filtered. The soluble components include acids: sulfuric, nitric, and others. These components need to be buffered and neutralized. The TBN, total base number, is the measurement of an oil's ability to neutralize the acids, and yes, TBN degrades. At some point the acids can do real harm to engine surfaces.

David Brady
'02 Blue Bird Wanderlodge LXi,
Series 60 Equipped,
Asheville, NC

[Kevin Erion]

This is good reading, what a pandora's box I opened up! Maybe I can help to close it. Today I spoke to one of the engine rebuilders at United Engines, OKC. From looking around the shop I think we can all agree that they might know Detroit Engines as good as we do, maybe a little better! This is what a very seasoned technician told me. I might get it off a little so it's not a quote, just my interpretation of our conversation.
1) Do not put the motor on high idle until after it has run at low idle for at a minimum of 3 minutes. I am guessing this is when it is cold and the first start up after sitting, but not a bad thing all the time.
2) use the Detroit recommended oil.
3) If the engine has not been run for 3 or more weeks, turn engine over without starting for 15-20 seconds to prime oil to top end. This is done with the start button in the engine bay without turning the run switch to on. After cranking over for 15-20 seconds, then allow engine to start.
He did say that the damage is done at start up both by sitting to long and also # 1 cause is by going to high idle to soon!

I have to say that I would agree with all he said, lots of common sense.