Drain interval??

[OneQuartLow]

Ray,

quote:

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Originally posted by Ray H:
With the oil pickup no longer immersed, would it be possible the oil pump would lose its prime during an extended drain?

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With warm oil a pump will quickly drain most of its oil past internal clearances but those clearances aren't enough to prevent pumping once the engine starts. (unless the pump is completely shot) Oil pumps are positive displacement and residual oil is enough to make a pretty good prime.

With very cold new oil the draining might delay the time it takes to bring up pressure, but it's just a matter of a moment to fill the passages again. There's maybe ~1-3oz capacity between the sump oil level and the pump outlet vs ~1-2GPM pump volume at idle. Compare this to an empty filter capacity of ~12-20oz. I've never run into visible pressure delays from extended drains but delays are obvious every time I neglect to pre-fill a filter, however it's mounted.

Engine builders and people bringing vehicles out of storage do pre-prime before starting, and there will be differences between engines, but in general it isn't something you need to worry about. As others have said before, if any of this were critical there'd be lots of carcasses on the sides of our roads, clustered heavily around the lube shops.

David

 

[Patman]

quote:

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Originally posted by ryansride2017:
buster,

A few years ago I conducted an interesting experiment. I use to work in a quick lube shop where they told us to only have the drain plug out for 2 or so minutes so they can get cars in and out faster. I used my own vehicle (with a 4 quart capacity) and took the drain plug out for 2 minutes and then replaced it (with the engine hot). Then I waited several HOURS and drained the rest of the oil that was in the pan. It turned out to be a 1/2 quart. That means if you go to the quick lube places (at least the one I worked at) 13% of the oil in your engine would be "old oil" (based upon my engine). While 13% might not be a huge percentage, it probably is a significant amount to the oil nuts on this website. For best results, change your own oil and DRAIN IT UNTIL IT STOPS DRIPPING!

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I did a similar test in my 98 Firebird, I let the oil drain for 10-15min, then put an empty bottle of oil under the dripping oil to see how much oil collected from that point until 90min was up. In that time, 4oz more oil came out. So even after 10-15min not all of the oil is out. And even when it stops dripping not all of it is out either. At least 1/4 to 1/2 quart gets stuck in the engine, with no way out unless you use compressed air. If you're really worried about getting all of it out, say if you overextended your last interval, then run 3 or 4 quarts of new oil in there, run the engine, then drain it again.

 

[Mike_dup1]

Refer to TSB 93-1 of the Filter Manf. Concil. It has some information on this topic that may be of interest. Here's the jist of the TSB, I highlited in bold the revelent info. if you want to see more, then go HERE

quote:

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Immediately after an oil change, one of the most confusing issues to face the typical do-it-yourselfer or professional mechanic is lack of oil pressure on engine start-up.

Although not a common occurrence, it is very possible that the oil pump may lose its prime during the oil change.

When the used motor oil is drained from the engine, the oil may also drain from the oil pump pickup tube and possibly from the oil pump itself. When new motor oil is added, the pump's pickup tube inlet again becomes submerged, trapping air in the tube on the suction side of the oil pump. The trapped air will cause cavitation of the pump and prevent it from producing oil flow and subsequent oil pressure. The low oil pressure light will remain on or the oil pressure gauge will register little or no pressure when the engine is started.

Many installers tend to blame this on the oil filter and assume that the filter is blocking the flow of oil. Since the filter is now suspect, the installer will install a second filter. Sometimes this solves the problem because the trapped air was released when the first filter was removed. Of course, the installer's suspicion that the filter was at fault has increased.

The point is, the oil filter was not the problem and, in most cases, there is a simple solution.

If the low oil pressure light remains on or the oil pressure gauge reads little or no pressure within 30 seconds of engine start-up, stop the engine. Loosen the oil filter until the sealing gasket barely touches the filter mounting base. Disable the ignition system so the engine will not start. Turn the engine over with the starter until oil appears at the sealing gasket. DO NOT CRANK THE ENGINE FOR MORE THAN 30 SECONDS. After oil appears at the gasket, tighten the filter and wipe off the excess oil. Start the engine. Oil pressure should return to normal within ten seconds.

If the above procedure fails, it may be necessary to remove the filter and use an oil squirt can, with clean motor oil, to squirt oil into the oil filter's mounting base inlet hole, which is adjacent to the threaded mounting stud. This will prime the pump.

Next, fill the filter with oil, reinstall and tighten. Oil pressure should return to normal within ten seconds after starting the engine.

Replacing the oil in the crankcase immediately after draining will prevent the oil pump from losing it's prime.

Also, make sure the spin-on oil filter is installed correctly. Printed installation instructions will be found either on the filter itself or on the filter box.

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[Ken2]

So...if the oil is allowed to drain from the sump so long that the oil pump loses it's prime, and the oil filter is filled with oil (usually a good idea), then does this thick, cold oil in the filter make it harder for that air bubble in the oil pump to pass into the oil system?...the oil pump can't pick up a prime until the air passes down the line.


Ken

[ February 18, 2003, 04:05 PM: Message edited by: Ken2 ]