Massive oil consumption from towing a trailer

[Clevy]

Originally Posted By: zray
Originally Posted By: Shannow
Originally Posted By: zray

There won't be much oil or anything else being sucked out of the crankcase during the situation described by the OP. WHY ? Because the PCV system depends on engine vacuum to do sucking. And there isn't much engine vacuum at any rpm when the throttle is wide open. Put a manifold vacuum gauge on the car and you will see little to no vacuum when the throttle is open wide at any rpm.

. That's why race cars just an exhaust crankcase evacuation system and not a traditional PCV system, the exhaust driven system works all the time, not just when there is a high engine vacuum.

Z


PCV closes on high vacuum to limit the flow...at no vacuum, it is wide open, and crankcase pressure pushes the blowby into the manifold, just like the old walking stick breathers used to do.


Correct, but those old vent tube breathers were notoriously ineffective at letting the crankcase do the "push". H ha. I should know, I ran one on my 289 HiPo for years recently. The sound you hear is me coughing.

And a PCV system without the vacuum pulling the crankcase clean is just as bad.(ineffective).the orafice of the PCV is designed for a vacuum, the pressurized crankcase is not goiing to be doing any amount of effect venting without a vacuum pulling it. Proof: check out those leaking valve cover gaskets and crankcase seals after a hard run around the track or highway. That's were the excess crankcase pressure is going, not much in comparison is making it thru the PCV. The very same (unchanged) gaskets and seals are dry under normal circumstances when there is a vacuum.

Z







How is a carb'd 289's pcv similar to a fuel injected 3.3.

I'm seriously asking how they are similar to the point a direct comparison being made,and how does a race engine compare to a minivan towing a trailer.

I'm seriously asking. Not being facetious.

 

[Shannow]

If the crankcase pressure is causing gaskets weeps, then there's a whole bunch of flow going into the inlet manifold...period.

 

[440Magnum]

Originally Posted By: zray
. Proof: check out those leaking valve cover gaskets and crankcase seals after a hard run around the track or highway. That's were the excess crankcase pressure is going, not much in comparison is making it thru the PCV. The very same (unchanged) gaskets and seals are later dry under normal circumstances when there is a vacuum.

Z







No, the proof that PCV systems flow more oil mist under hard running is the fact that PCV catch-cans fill with oil much faster under hard use than cruising. End of story.

 

[zray]

Originally Posted By: 440Magnum
Originally Posted By: zray
. Proof: check out those leaking valve cover gaskets and crankcase seals after a hard run around the track or highway. That's were the excess crankcase pressure is going, not much in comparison is making it thru the PCV. The very same (unchanged) gaskets and seals are later dry under normal circumstances when there is a vacuum.

Z







No, the proof that PCV systems flow more oil mist under hard running is the fact that PCV catch-cans fill with oil much faster under hard use than cruising. End of story.



Actually, they don't. I've used a catch can on my cars for the last 6 years. They fill up faster when the engine vacuum is highest, not during full throttle action.

Z

 

[zray]

Originally Posted By: Shannow
If the crankcase pressure is causing gaskets weeps, then there's a whole bunch of flow going into the inlet manifold...period.


The flow of oil into the intake manifold, if any, has nothing to do with the valve cover gaskets leaking. The valve cover gasket and main seal leaking are a product of the increased crankcase pressure during full throttle operation, and nothing else.

I had expected a better reasoned response from you

Z

 

[zray]

Originally Posted By: Clevy
Originally Posted By: zray
Originally Posted By: Shannow
Originally Posted By: zray

There won't be much oil or anything else being sucked out of the crankcase during the situation described by the OP. WHY ? Because the PCV system depends on engine vacuum to do sucking. And there isn't much engine vacuum at any rpm when the throttle is wide open. Put a manifold vacuum gauge on the car and you will see little to no vacuum when the throttle is open wide at any rpm.

. That's why race cars just an exhaust crankcase evacuation system and not a traditional PCV system, the exhaust driven system works all the time, not just when there is a high engine vacuum.

Z


PCV closes on high vacuum to limit the flow...at no vacuum, it is wide open, and crankcase pressure pushes the blowby into the manifold, just like the old walking stick breathers used to do.


Correct, but those old vent tube breathers were notoriously ineffective at letting the crankcase do the "push". H ha. I should know, I ran one on my 289 HiPo for years recently. The sound you hear is me coughing.

And a PCV system without the vacuum pulling the crankcase clean is just as bad.(ineffective).the orafice of the PCV is designed for a vacuum, the pressurized crankcase is not goiing to be doing any amount of effect venting without a vacuum pulling it. Proof: check out those leaking valve cover gaskets and crankcase seals after a hard run around the track or highway. That's were the excess crankcase pressure is going, not much in comparison is making it thru the PCV. The very same (unchanged) gaskets and seals are dry under normal circumstances when there is a vacuum.

Z







How is a carb'd 289's pcv similar to a fuel injected 3.3.

I'm seriously asking how they are similar to the point a direct comparison being made,and how does a race engine compare to a minivan towing a trailer.

I'm seriously asking. Not being facetious.


Both types engines have little or no engine vacuum under full throttle conditions. That is the similarity. Every internal combustion engine has more similarities than differences once the induction systems are stripped off.

Z

 

[OVERKILL]

Originally Posted By: zray
Originally Posted By: Shannow
If the crankcase pressure is causing gaskets weeps, then there's a whole bunch of flow going into the inlet manifold...period.


The flow of oil into the intake manifold, if any, has nothing to do with the valve cover gaskets leaking. The valve cover gasket and main seal leaking are a product of the increased crankcase pressure during full throttle operation, and nothing else.

I had expected a better reasoned response from you

Z


I believe Shannow was speaking as to flow in general, not oil flow (note he didn't say oil flow). He's saying that if there's enough pressure in the crankcase to cause gasket weeps then there's a whole bunch of flow going through the plumbing into the intake manifold as well, which is correct.

That is of course assuming the PCV and breather system is not blocked.

 

[Gokhan]

Originally Posted By: Oldtom
Good Afternoon - I have a 2004 Dodge Caravan 3.3 liter v6 automatic. I run Mobil one EP and a Mopar filter. I had 3000 miles and 5 months on the oil change when I towed a 1300 pound trailer into the North Carolina mountains. The roads were so steep my tach was at 5000 RPM to maintain any speed at all. On the way back, I checked the oil and found it one quart low. I added a quart of oil ( Thanks Walmart ! )

Does it sound like the oil is sheared down and needs changing? The car has never used oil before.

I do a pan drop and change the ATF in the pan and filter once a year when I tow. I also vac another 4 quarts of ATF out and replace it once a year.

THANKS IN ADVANCE FOR ANY ADVICE

You have an eleven-year-old vehicle. Likely, what happened was that you ground away whatever material that was left on your valve-stem oil seals when you did 5000 RPM for extended periods. Chances are that from now on, you will experience similar or higher oil consumption.

Use 0W-40 to reduce oil consumption -- thicker oils is sucked less through the valve guides.

See this thread on the valve-stem oil seals:

Wonders of valve-stem oil seal replacement

 

[Shannow]

Originally Posted By: zray

There won't be much oil or anything else being sucked out of the crankcase during the situation described by the OP. WHY ? Because the PCV system depends on engine vacuum to do sucking. And there isn't much engine vacuum at any rpm when the throttle is wide open. Put a manifold vacuum gauge on the car and you will see little to no vacuum when the throttle is open wide at any rpm.


Here's another article... http://mewagner.com/?page_id=434

Yes, I've had a poorly sealing (poor ring seal, as a dpistick prior owner ditched the thermostat) V-8 that overwhelmed the PCV at 130km/h, and spat oil out the breather...engine problem not proof of your (incorrect) assertion.

 

[440Magnum]

Originally Posted By: 440Magnum
Originally Posted By: zray
.

No, the proof that PCV systems flow more oil mist under hard running is the fact that PCV catch-cans fill with oil much faster under hard use than cruising. End of story.



Actually, they don't. I've used a catch can on my cars for the last 6 years. They fill up faster when the engine vacuum is highest, not during full throttle action.

Z


Not mine, nor any of my friends who have them. Its always during hard driving with sustained higher revs flinging the oil to a mist.

 

[zray]

I think the correct engineering of the baffle arrangement in the valve cover has more to do with how much oil gets thru the PCV valve and into the catch can or intake manifold, than how much high rpm driving is done. Some cars never pass oil into the intake manifold and do quite nicely without a catch can regardless of the rpm of the engine. Others are not so fortunate.

I drive 50 year old cars that often have poor or unsophisticated baffles in the valve covers. They will pass more oil when the flow thru the PCV is the greatest, ie at highest vacuum. While there is flow thru the PCV when engine vacuum is low or at zero, it is substantially less than during the high vacuum periods of engine operation. The PCV valve is a poor pressure relief for crankcase pressure that is present during low engine vacuum operation. Yes, some pressure escapes thru the wide open PCV valve , but not nearly enough to lower the crankcase pressure to the degree needed to eliminate the excess pressure on the seals and gaskets that is causing them to leak, if only temporarily.

Z

 

[Shannow]

Originally Posted By: zray
They will pass more oil when the flow thru the PCV is the greatest, ie at highest vacuum. While there is flow thru the PCV when engine vacuum is low or at zero, it is substantially less than during the high vacuum periods of engine operation. The PCV valve is a poor pressure relief for crankcase pressure that is present during low engine vacuum operation. Yes, some pressure escapes thru the wide open PCV valve , but not nearly enough to lower the crankcase pressure to the degree needed to eliminate the excess pressure on the seals and gaskets that is causing them to leak, if only temporarily.

Z


Again...nope...

http://www.autocarepro.com/pcv-system-sometimes-things-just-have-to-suck-to-be-right/

 

[Merkava_4]

- Under a severe load like towing a trailer, the piston is forced hard against one side of the cylinder wall.

- The oil flows past the rings on the side of the cylinder wall that's under the lightest pressure.

- Thicker oil can remedy the above situation.

 

[zray]

L
Originally Posted By: Shannow
Originally Posted By: zray
They will pass more oil when the flow thru the PCV is the greatest, ie at highest vacuum. While there is flow thru the PCV when engine vacuum is low or at zero, it is substantially less than during the high vacuum periods of engine operation. The PCV valve is a poor pressure relief for crankcase pressure that is present during low engine vacuum operation. Yes, some pressure escapes thru the wide open PCV valve , but not nearly enough to lower the crankcase pressure to the degree needed to eliminate the excess pressure on the seals and gaskets that is causing them to leak, if only temporarily.

Z


Again...nope...

http://www.autocarepro.com/pcv-system-sometimes-things-just-have-to-suck-to-be-right/


Once again, real world experience is trumped by internet bull sh*t. Actually your diagram proves my point . It shows At full load, the PCV is flowing very little, which is the point I've asserted from the beginning. At high rpm, which is usually a full,load in top gear, the PCV is passing very little despite the higher crankcase pressure.

Z.

 

[camrydriver111]

Originally Posted By: Shannow
Originally Posted By: zray
They will pass more oil when the flow thru the PCV is the greatest, ie at highest vacuum. While there is flow thru the PCV when engine vacuum is low or at zero, it is substantially less than during the high vacuum periods of engine operation. The PCV valve is a poor pressure relief for crankcase pressure that is present during low engine vacuum operation. Yes, some pressure escapes thru the wide open PCV valve , but not nearly enough to lower the crankcase pressure to the degree needed to eliminate the excess pressure on the seals and gaskets that is causing them to leak, if only temporarily.

Z


Again...nope...

http://www.autocarepro.com/pcv-system-sometimes-things-just-have-to-suck-to-be-right/


At the highest RPM why does the PCV flow drop?

 

[zray]

It closes, but not 100%, when the vacuum is very low, or very high.

So at high load, or at idle, at PCV is flowing much less than it does at cruising load & moderate rpm. If you take one apart you can see the cone shape that rises up, and that seals off more flow as the vacuum rises above a set level. Conversely, under little or no vacuum the shuttle valve is primarily at rest and seals off at the bottom.

Z

 

[TFB1]

Originally Posted By: zray
It closes, but not 100%, when the vacuum is very low, or very high.

So at high load, or at idle, at PCV is flowing much less than it does at cruising load & moderate rpm.

Z


Most of the ones I've seen use a spring that holds it slightly open without vacuum and probably 95% closed(metering mode) with high vacuum, includes idle, cruse, closed throttle decelleration etc... At high throttle opening there is no or little vacuum to hold valve in it's full metering position, so it begins to open allowing additional crankcase flow(blowby) through valve... This is mode that generally allows blowby to push oil into the PCV system or into a catch can if used... As already stated configuration is much of the reason some engines blow out oil and others don't...

BTW in the event of a backfire in the intake(or boosted application), any reverse pressure forces the valve fully shut so pressure does not enter the crankcase... Any flame in the crankcase could possibly ignite oil vapor, especially in a high fuel dilution situation...

 

[mjoekingz28]

Originally Posted By: camrydriver111
Originally Posted By: Shannow
Originally Posted By: zray
They will pass more oil when the flow thru the PCV is the greatest, ie at highest vacuum. While there is flow thru the PCV when engine vacuum is low or at zero, it is substantially less than during the high vacuum periods of engine operation. The PCV valve is a poor pressure relief for crankcase pressure that is present during low engine vacuum operation. Yes, some pressure escapes thru the wide open PCV valve , but not nearly enough to lower the crankcase pressure to the degree needed to eliminate the excess pressure on the seals and gaskets that is causing them to leak, if only temporarily.

Z





Again...nope...

http://www.autocarepro.com/pcv-system-sometimes-things-just-have-to-suck-to-be-right/


At the highest RPM why does the PCV flow drop?


A family member tried to explain something similar to me once upon a time. I asked why is there SO much exhaust exiting the pipes at around idling, but it almost seems to be pulling air into the exhaust pipes.

I figure it is acoustics. Feel the port on a subwoofer at varying frequencies to learn more!

 

[Shannow]

Originally Posted By: zray
Once again, real world experience is trumped by internet bull sh*t. Actually your diagram proves my point . It shows At full load, the PCV is flowing very little, which is the point I've asserted from the beginning. At high rpm, which is usually a full,load in top gear, the PCV is passing very little despite the higher crankcase pressure.

Z.


You stated that there was maximum flow at idle, and nearly none at full load...clearly...wrong (nicer term than you used BTW)

to quote the Simpsons..."start digging up !!!"

 

[zray]

Originally Posted By: Shannow
Originally Posted By: zray
Once again, real world experience is trumped by internet bull sh*t. Actually your diagram proves my point . It shows At full load, the PCV is flowing very little, which is the point I've asserted from the beginning. At high rpm, which is usually a full,load in top gear, the PCV is passing very little despite the higher crankcase pressure.

Z.


You stated that there was maximum flow at idle, and nearly none at full load...clearly...wrong (nicer term than you used BTW)

to quote the Simpsons..."start digging up !!!"


Shannow, you're such a sweetheart to be so kind to me. Yes, the flow thru the pcv valve is greatest during the mid-range vacuum numbers and not at idle, nor at the high rpm / high load / no vacuum situations, which is where this thread was originally concerned. However, under the full load condition, flow is minimal because the crankcase pressure does not move a significant volume thru the pcv system in comparison to the flow generated by a vacuum. That may be too simple for some to accept, so don't.

Z.