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Hello:
A couple of questions for everybody regarding diesel engines.....
- What effects does overfilling your engine oil have on your engine?

- Is it good practice to run the engine when the oil is only at the full mark on the dipstick or can it be run when oil is anywhere between the full and add marks?

- How much oil is too much, how far above the full mark on the dipstick can the oil be before problems start?
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Well, it depends alot on the particular engine. In general, as long as the oil stays below the crank throws in the pan, there is no downside to overfilling. If the crank-throws get into the oil, it is whipped into foam, with a vareity of bad consequences (lack of lubrication, seal damage from crankcase pressure, etc.)

Having said that, a lot of engines can be filled over the limit somewhat(most GM)...and a handful are considered to do better slightly underfilled (Northstar's). What engine do you have? You might check

I like keeping the oil topped up, mainly for the additive boosting value...and for a little insurance in case I have to take a long trip or something similar. The downside is keeping partially full oil bottles around...I keep a full spare in the car typically and keep the partial top-off bottle at home.
I can strongly recommend not to overfill Diesel engines with oil. "Engine oil" and "Diesel oil" are chemically rather similar. If the oil is sucked through your blowby system in a sharp curve due to overfilling, you may not be in a position to shut off your engine until the oil is finished and your engine is broken. It runs at full RPM's and the pistons are melting.

I have seen such engines, it is an ugly sight. Besides it is very dangerous for the driver, because he may loose control of the vehicle in the middle of a curve.
Very interesting comment Callisa. I never thought of that aspect of overfilling. So you are saying it will suck the oil out of the engine and cause oil starvation? Not to mention the sliding wheels on the oil slick!

Another thought springs from your comment. Is it possible to have an over filled crankcase somehow get sucked into the blowby, then around to the intake, and hydrolock a cylinder or two? Pretty ugly scenario also, eh?

But I think this would not happen in a gasoline engine as the blowby (or PCV) hooks to the top of the valve cover. Diesels must have it mounted much lower?
Wait...I'm confused. How would the PCV system run the crankcase dry? It might do some nasty things with the oil that it burned as far as deposits, but it couldn't burn more oil than was present at the breather locations?


Some diesels, notably ford powerstrokes are EXTREMELY sensitive to oil quality in general, to anti-foam characteristics...and I would imagine that overfilling to the point of foaming would make one VERY unhappy.

I have seen engines, overfilled, turn the oil into foam and suffer bearing damage from the foam's inablility to lube well, but that has nothing to do with a diesel versus a gas engine.

I still stand by my comments that there are some engines that are well known to be happy with a bit extra, and a smaller number happier with underfilling. I honestly can think of very few engines where the full line is that close to catastrophic problems.
quote:
Originally posted by TallPaul:
Very interesting comment Callisa. I never thought of that aspect of overfilling. So you are saying it will suck the oil out of the engine and cause oil starvation? Not to mention the sliding wheels on the oil slick!

Another thought springs from your comment. Is it possible to have an over filled crankcase somehow get sucked into the blowby, then around to the intake, and hydrolock a cylinder or two? Pretty ugly scenario also, eh?

But I think this would not happen in a gasoline engine as the blowby (or PCV) hooks to the top of the valve cover. Diesels must have it mounted much lower?


I had an 84 GM diesel van. Used to get the oil changed at a stop-n-steer. Impatient new employee on the end of the oil gun had the air turned to max pressure so the 5 liters were dispersed in several seconds.
The oil spout is directly on the intake manifold. The PCV is plumbed into the oil spout. Some of the oil got into the pcv "t" on the spout.
Once the engine was full, they go through their procedures to comission the oil change and I start the van up.

...Well holy s$%^ the engine went into orbit and I never heard a diesel rev that high other than watching modified tractor pulls. I turned the key off and holding in my hand staring at the key the engine still doing several thousand rpms. The shop filled with white smoke, the shop owner's 84 yr old dad never ran in 50 yrs but believe me he ran that day. I just sat there "what do I do", the engine eventually stopped.

Only thing I could think of was "oil" was the culprit as I've had two experiences with GM 8V92 detroit diesel's doing the same thing after a "wet stack" ...thaz another story.

We figured out the problem down to the young feller and the air gun.

Months later, I go for another oil change. This time the owner did my change, however when he was adding the oil slowly he put an elastic band around the trigger and walked away for a moment to grab a coffee. Another new employee grabbed the gun and cranked the air up, the oil was put in the engine in seconds. I heard this and came running. *sigh* Now what do I do?

Once the change was done I thought back to the Detroit Diesel incident. I put my van in neutral and got ready to start the engine. The owner opened up both doors for fear of the smoke show. Started the van and as I let go of the ign key, I dropped the tranny into 1st gear and mashed my foot into the brake pedal. Well the engine labored very hard away at a few thousand rpms and I did a brake stance right where the van sat. The passenger side rear tire incinerated and squeeled like crazy before the engine labored to a halt.

...the owner give me a free oil change for the trouble. heh heh...

Oil substituted for fuel in diesel engine makes great power. hahaha
Here is another problem associated with engine oil overfilling:


One severe problem would be creating what is called a “RUN-A-WAY” diesel.

This occurs when the oil level would be high enough that the crank and connecting rods would splash in the oil in the oilpan.
This splashing can create an oil mist or vapor that can be drawn into the cylinders on the intake stroke, around the piston rings or other paths, creating an unregulated fuel source for the engine.
A diesel engine’s speed is regulated by the amount of fuel injected into the combustion chamber, with the unregulated supply, the engine will rev out of control until it blows up from centrifugal forces.
The safest thing to do is, "RUN-A-WAY".
@tallpaul's question: Hmm....interesting question. I used to drive a 74 Intl. tandem dumptruck with a 290 cummins that had a Hi/Lo Jacobs brake. The [on/off] microswitch on the fuel pedal was rotted off from road salt, owner too cheap to fix it. He told me not to use the Jake brake because of the switch being broke. Bah...used it anyway. I was gearing down for a turn using the jake, just to see what would happen, I depressed the fuel pedal and it certainly diminished the retarding power, white smoke come chugging out of the pipe and i'm sure choked the innocent drivers behind me.

The intake valve opens and air is forced into the cylinder by turbo boost.
Air is compressed by the piston with force produced by the vehicle's driving wheels. Near top dead center, the Jake gives the exhaust valves a little tap to open the valves slightly and vent the high pressure air as the piston dwells through t.d.c. thus dissipating the stored energy out the exh pipe.

I think the engine would still run and rev up however with diminished power if the jake is on. So much energy would be lost after the jake gives the exh. valve a little blip to let the compressed charge out.

@cccous: runaway diesel...
http://bangernomics.tripod.com/diesel.htm
And finally, a word about 'runaway diesels'. This is a nasty little problem which can affect any diesel where the crankcase breather pipe feeds direct into the air intake. Land Rover turbodiesels are notorious for it, and I have seen it on 1.9 Peugeot/Citroen diesels as well. What happens is that on a worn engine, gases blow past the sides of the pistons and into the crankcase. They emerge from the crankcase breather laden with oil mist from the crankcase, which feeds into the air intake. Now a diesel will run quite happily on oil mist, and so the revs will increase as this extra 'fuel' is taken in. The higher revs result in greater crankcase pressure, more oil mist is forced out of the crankcase and sucked in to the engine, and a vicious circle is created.

Eventually the point is reached where the engine is generating enough oil mist that shutting off the supply of diesel by switching off the ignition will not stop it. The engine runs faster and faster, generating huge clouds of grey or black smoke, until it blows up. If your engine starts to run away, you can sometimes stop it by selecting top gear, jamming your right foot hard on the brake and letting the clutch out to try and stall the engine. But diesels generate a lot of torque, and if the clutch is weak, it will just slip. In this case there is nothing you can do other than abandon the car, retire to a safe distance and wait for the engine to explode. Do not under any circumstances open the bonnet - it isn't worth the risk.
If I just caught the problem that I have the engine overfilled by 1.5 quart. Will just draining the oil and refilling to the proper level clear things with no problems? I took the car to a station a half mile from my home and they drained and put new oil in at the proper level. It did make the engine smoke from the overfill.
quote:
Originally posted by VWnMD:
If I just caught the problem that I have the engine overfilled by 1.5 quart. Will just draining the oil and refilling to the proper level clear things with no problems? I took the car to a station a half mile from my home and they drained and put new oil in at the proper level. It did make the engine smoke from the overfill.
I'd assume you will be fine now if it is running normally now that the oil level was corrected. By the way, I assume it is a gasoline engine as a diesel presumably would not have survived that treatment?
greetings! a noob here, so please pardon my ignorance.

we have a diesel nissan power pickup circa 1992. it has a whole lot of miles on it. recently a triad of problems popped up:

1. the engine oil leaks thru the hole where you put the dipstick

2. the smoke emitted by the exhaust suddenly worsened (we just had the engine calibrated to lessen said smoke)

3. when i step on the accelerator pedal, i feel that there is no power being transmitted by the engine to the wheels. this problem disappears when i run the engine for a relatively long period of time.

what do i do?

thanks!

olrayt@gmail.com
Run the engine when oil is anywhere between the full and add marks! Comparing overfilling and "underfilling" effects tells that for engine is more dangerous overfilling than "counterpart". Foaming and hydrodynamics shocks are principal reasons for that.
It's quite opposite thing with transmissions. You can overfill it as much as you can. It is not recommended though, but it is not dangerous as much as "underfilling".

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