do antidrainback valves really do anything?

[edwardh1]

my question, after the engine is shut off-
for the filters installed with open end up, the filter stays full of oil - right ?

and it seems to me for the filters installed with open end sideways, or down that the oil would drain thru the element and into the outlet holes and slowly drain into the engine ???.
so what good is an antidrain back valve?

what am I missing - help

 

[Donald]

But the faster there is oil pressure to the bearings the better. Do you really want to wait for the filter to fill with oil each start of the engine? I don't. The filters are made for many applications and in some cases (as you point out) its not really needed.

They sell or use to sell an electric oil pump that would turn on when you turned the car to on and there was no oil pressure. (But not yet started the engine). You wait until the gauge or idiot light shows oil pressure and start the engine. The wear is mostly at cold starts.

 

[SteveSRT8]

Yep, had a pre luber on many cars up until about 1990. Still have one on a mega bucks motor in my boat.

Dirt simple system, small powerful pump connects to the sump, and it pumps into the oil pressure sender fitting via a T fitting. Turn it on for 10 seconds and the engine is pressurized to 30 psi.

With a screwdriver and a little hose it quickly becomes a drain pump to change the oil!

 

[wrcsixeight]

Even if the oil filter is vertical, there is oil in the passages above the filter. Without an antidrainback valve, sure the filter will stay full, but the passages above will be empty.


My service manual states that the oil capacity is 4 quarts, but 5 if I change the filter. There is no way the oil filter listed in the parts catalogs even holds half a quart, so some percentage of a quart of oil remains in the passages above the filter.

 

[JOD]

Originally Posted By: wrcsixeight
Even if the oil filter is vertical, there is oil in the passages above the filter. Without an antidrainback valve, sure the filter will stay full, but the passages above will be empty.


My service manual states that the oil capacity is 4 quarts, but 5 if I change the filter. There is no way the oil filter listed in the parts catalogs even holds half a quart, so some percentage of a quart of oil remains in the passages above the filter.


?

How is this possible? The oil filter is continually full of oil. So, it's not going to become 'more full', except possibly for a tiny amount due to the oil contracting as it cools. So, where does this oil go when it leaves the oil passages...and what does the ADBV have to do with it? I've heard this repeated before and it's never made any sense to me--and no one was ever adequately explained it?

I've also heard the reverse, and that vacuum formed in the engine could result in oil being sucked out of the filter. Give the weight of oil in an oil filter, I'm having a really, really tough time believing that one, either.

 

[CATERHAM]

Originally Posted By: SteveSRT8
Yep, had a pre luber on many cars up until about 1990. Still have one on a mega bucks motor in my boat.
Dirt simple system, small powerful pump connects to the sump, and it pumps into the oil pressure sender fitting via a T fitting. Turn it on for 10 seconds and the engine is pressurized to 30 psi.
With a screwdriver and a little hose it quickly becomes a drain pump to change the oil!

Yes prelubers or pressurizers are great particularly in engines that are not driven daily. ADBVs are good, but any engine sitting for a few days or weeks will be "dry" on start-up. I hate the bearing rattle on starting an engine that's been sitting for a stretch of time.
Having said that I don't actually know if it reduces wear measureably. If the anti-wear oil additives like ZDDP and moly that are their for boundary lubrication do their job you should still not have actual metal to metal contact while the engine rotates for a couple of seconds without oil filled bearings since the engine not under load.

 

[wrcsixeight]

Without an ADBV, the oil in the passages above the filter will drain down into the filter, displacing an equal amount of oil that was in the filter, but is now back in the oil pan. Now the passages above the filter are empty and must be refilled after start up before oil makes it to the top of the engine.

My filter is close to vertical, and I prefill the filter with oil upon installation, and it still takes a few seconds for oil pressure to register on start up, all the while the lifters are tapping away, along with other noises that make me cringe.

 

[JOD]

Originally Posted By: wrcsixeight
Without an ADBV, the oil in the passages above the filter will drain down into the filter, displacing an equal amount of oil that was in the filter, but is now back in the oil pan. Now the passages above the filter are empty and must be refilled after start up before oil makes it to the top of the engine.


OK, here's the part I don't understand; if the car is turned off, and the oil pump isn't pumping, how does the oil in the passages displace the oil in the filter? the total weight of the oil in the passages would have to be heavier than the oil in the filter to exert enough pressure for the oil in the filter to be displaced. "How much heavier" would depend on the path the expelled oil would have to take. But considering the oil would have to be pushed through the filter's media and up a tube of (almost certainly) greater diameter than the oil passage tubes, I simply don't see this happening.

In practical terms, I notice absolutely no difference in startup noise in a Subaru Legacy with a filter with or without an ADBV.

 

[wrcsixeight]

Well perhaps in your engine it makes no difference. Many years ago, before I was aware of BITOG, I was getting start up noises that lasted nearly as long as after a fresh oil change, and a replacement filter cured the issue.

How can an ADBV be detremental? I can see how it can be of no benefit in some engine designs, but not how it can be detremental?

 

[cchase]

The real question is, what is the volume of all oil passages downstream (uphill) from the oil filter on any given vehicle, and how long does it take, if empty, for them to refill again?

If the oil volume of passages is insubstantial it would seem to me that just the cranking action would be sufficient to pump oil into those passages.

 

[ZeeOSix]

Q: "Do antidrainback valves really do anything?"

A: Apparently they do ... see test details in this thread. Note that the oil did NOT all drain out through the center tube in this test, even though the filter sat for a week with the base down.

http://www.bobistheoilguy.com/forums/ubb...807#Post2042807

 

[SteveSRT8]

I agree that is impressive, but I don't think that it's conclusive.

How hot was it? How much head pressure? What kind/viscosity of oil?

I mean there are tons of variables. Not that your test was bad.

 

[ZeeOSix]

Originally Posted By: wrcsixeight
Without an ADBV, the oil in the passages above the filter will drain down into the filter, displacing an equal amount of oil that was in the filter, but is now back in the oil pan. Now the passages above the filter are empty and must be refilled after start up before oil makes it to the top of the engine.


That will only happen if the head pressure of the oil volume above the filter is enough to actually displace the oil down into the sump. If the ADBV works well, the head pressure may not be enough and oil will stay in the galleries. Every engine is different.

Originally Posted By: wrcsixeight
My filter is close to vertical, and I prefill the filter with oil upon installation, and it still takes a few seconds for oil pressure to register on start up, all the while the lifters are tapping away, along with other noises that make me cringe.


When you remove the oil filter for an oil change the oil galleries above the filter will surely drain. But like I mentioned above, if the filter is in place the galleries may or may not drain, depending on the exact engine design and filter used.

 

[ZeeOSix]

Originally Posted By: SteveSRT8
I agree that is impressive, but I don't think that it's conclusive.

How hot was it? How much head pressure? What kind/viscosity of oil?

I mean there are tons of variables. Not that your test was bad.


Like I said in the thread describing the test. I removed the filter when the oil (5w30 Mobil Clean 5000) was still pretty warm in the filter, then instantly put the filter base down in a large funnel to drain for a week. If the ADBV was leaky, or the oil was to drain through the media and down the center tube then it would have been empty after a week.

Instead, the filter was almost completely full of oil when I propped open the ADBV a week later and let the trapped oil in the filter drain out into a new clean container over night for volume measurement.

If a filter in this orientation can hold oil in for a week it tells me the ADBV was not leaking, and the oil does not seep out of the media and drain down the center tube.

Other people should conduct their own test to see how their filter(s) do in the same test scenario.

 

[ltslimjim]

I've had an Amsoil EaO off for a week and it hasn't drain any out while being base down(after some small amount did come out when initially removed from the block).

Either the adbv works great on it or it's empty. I pulled the filter suspecting it to be 'filtered' to capacity OR a faulty replacement Oil Pressure Switch(the original was leaking internally though worked fine) causing the dummy oil light to 'almost' come on during operation a week ago.

Not sure IF it's built-in bypass is triggered, whether that would keep oil in the filter more so or not once removed from the engine?

 

[Sayjac]

I've done similar to ZO but without the pics or measuring to prove it. Let the filters drain base down for a ~week after removal. Later, I've either punctured a hole in the dome or held the adbv open with a thin nail or qtip and a substantial amount of oil drains out.

I think a good/functional adbv helps keep the filter full (or close) of oil on the inlet side, and helps keep oil in the oil galleries.

I also think some vehicles are more susceptible to start up rattle without a good adbv. Example, son owned 4.6L Explorer, once had a quick lube oil filter with nitrile adbv installed. Got a regular start up rattle for that oci. Switched back to the Motorcraft FL-820S with silicone adbv next oci, start up rattle gone.

 

[ltslimjim]

^I agree with this.