Oil pressure drops as jeep warms up
01-14-2011, 10:40 AM
#17
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Year: 2000
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Oil or any liquid foams when it is aerated. Just like a water out a hose, if you try and force too much oil through too small an opening the flow becomes turbulent and fluid begins to aerate. The more viscous the liquid the more likely this is to happen. Now Im not saying that running 10w-40 over 10w-30 with cause your oil to foam, cuz it most likely wont. If you do increase the viscosity enough the oil can aerate.
Im an Engineer, I studied oiling in college. There are a reasons manufacturers recommend a certain weight of oil.
01-14-2011, 11:14 AM
#18
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Year: 1992
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The oil foaming your refering to is when the crankshaft spins in the oil sitting in the pan, this however is not the only cause of foaming.
Oil or any liquid foams when it is aerated. Just like a water out a hose, if you try and force too much oil through too small an opening the flow becomes turbulent and fluid begins to aerate. The more viscous the liquid the more likely this is to happen. Now Im not saying that running 10w-40 over 10w-30 with cause your oil to foam, cuz it most likely wont. If you do increase the viscosity enough the oil can aerate.
Im an Engineer, I studied oiling in college. There are a reasons manufacturers recommend a certain weight of oil.
Oil or any liquid foams when it is aerated. Just like a water out a hose, if you try and force too much oil through too small an opening the flow becomes turbulent and fluid begins to aerate. The more viscous the liquid the more likely this is to happen. Now Im not saying that running 10w-40 over 10w-30 with cause your oil to foam, cuz it most likely wont. If you do increase the viscosity enough the oil can aerate.
Im an Engineer, I studied oiling in college. There are a reasons manufacturers recommend a certain weight of oil.
I build racing engines, and have been around high performance engines my whole life, I know from experience. You can use google just like everyone else. The fact is you said that by increasing your oils viscosity to much you will cause the oil to foam. That is false. AND what the heck are you talking about the water foaming?!? The only thing I know of that makes your coolant bubble or be aerated is if your head gasket is blown or your engine is over heating, causing boiling.
The poor guys engine is running the way it was ENGINEERED to run. If he is uncomfortable with his engine ideling at 5-10psi on a hot day or when oil temp is all the way up, 20w-50 will let him sleep at night without causing a lick of harm to anything, PLUS it will help with his lifter tick, unless he has a sticking lifter.... Its a push rod engine its going to make some noise...
I didnt go to college. I am a lesser person than you and I dont have a paper saying that I can use big words I found on the internet to try and out smart the next guy BUT I know from my own research and knowledge that I have picked up over the years of being around very smart engine builders and years of racing...
Last edited by Tomxj48; 01-14-2011 at 11:40 AM.
01-14-2011, 12:42 PM
#19
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I build racing engines, and have been around high performance engines my whole life, I know from experience. You can use google just like everyone else. The fact is you said that by increasing your oils viscosity to much you will cause the oil to foam. That is false. AND what the heck are you talking about the water foaming?!? The only thing I know of that makes your coolant bubble or be aerated is if your head gasket is blown or your engine is over heating, causing boiling.
The poor guys engine is running the way it was ENGINEERED to run. If he is uncomfortable with his engine ideling at 5-10psi on a hot day or when oil temp is all the way up, 20w-50 will let him sleep at night without causing a lick of harm to anything, PLUS it will help with his lifter tick, unless he has a sticking lifter.... Its a push rod engine its going to make some noise...
I didnt go to college. I am a lesser person than you and I dont have a paper saying that I can use big words I found on the internet to try and out smart the next guy BUT I know from my own research and knowledge that I have picked up over the years of being around very smart engine builders and years of racing...
The poor guys engine is running the way it was ENGINEERED to run. If he is uncomfortable with his engine ideling at 5-10psi on a hot day or when oil temp is all the way up, 20w-50 will let him sleep at night without causing a lick of harm to anything, PLUS it will help with his lifter tick, unless he has a sticking lifter.... Its a push rod engine its going to make some noise...
I didnt go to college. I am a lesser person than you and I dont have a paper saying that I can use big words I found on the internet to try and out smart the next guy BUT I know from my own research and knowledge that I have picked up over the years of being around very smart engine builders and years of racing...
As for my reference to water I wasnt speaking of coolant. I was merely using it a reference to a common liquid. Ever fill up a glass of water real fast and have bubble in it? The surface tension of water is fairly low so it doesnt hold the bubbles long. Do the same thing with a thicker fluid and you'll have the same effect, only it wont just disappear.
Im a lil worried that you, an experienced engine builder, would recommend 20w-50. Chances are it wont be an issue but the temp rating for 20w is around 0 degrees. Depending where the OP lives that could be an issue.
I dont know the Cherokee oil system much at all but There is a reason manufactures recommend certain oils and 20w-50 is getting pretty thick. The Cherokee is pretty old so the clearances shouldnt be that tight but it could cause issues if they are.
01-14-2011, 02:53 PM
#20
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Year: 1992
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Im not trying to say Im better than you or talk down to you with "big" words. Im just using the terms I've learned and discussing my knowledge of the subject.
As for my reference to water I wasnt speaking of coolant. I was merely using it a reference to a common liquid. Ever fill up a glass of water real fast and have bubble in it? The surface tension of water is fairly low so it doesnt hold the bubbles long. Do the same thing with a thicker fluid and you'll have the same effect, only it wont just disappear.
Im a lil worried that you, an experienced engine builder, would recommend 20w-50. Chances are it wont be an issue but the temp rating for 20w is around 0 degrees. Depending where the OP lives that could be an issue.
I dont know the Cherokee oil system much at all but There is a reason manufactures recommend certain oils and 20w-50 is getting pretty thick. The Cherokee is pretty old so the clearances shouldnt be that tight but it could cause issues if they are.
As for my reference to water I wasnt speaking of coolant. I was merely using it a reference to a common liquid. Ever fill up a glass of water real fast and have bubble in it? The surface tension of water is fairly low so it doesnt hold the bubbles long. Do the same thing with a thicker fluid and you'll have the same effect, only it wont just disappear.
Im a lil worried that you, an experienced engine builder, would recommend 20w-50. Chances are it wont be an issue but the temp rating for 20w is around 0 degrees. Depending where the OP lives that could be an issue.
I dont know the Cherokee oil system much at all but There is a reason manufactures recommend certain oils and 20w-50 is getting pretty thick. The Cherokee is pretty old so the clearances shouldnt be that tight but it could cause issues if they are.
Worry as much as you want, like you just said, I recommended an oil that will give the guy the result he is looking for with no harm to anything on the AMC 4.0 engine. We are not talking about an 8,000rpm engine. And as great as this debate is, its turning into a thread jack so my apologys to the OP. I completely understand your theory behind the water bubbling however oil is COMPLETELY different while its working in the engine. Thicker oil would simply result in a fraction less of a horse power. I would never run 20w-50 in my race engine.
Now this statement made by "textherex"
"
Quote:
Originally Posted by Tomxj48
that is not true. the only thing that "foams" oil is over filling the engine.
Erra, the thing that foams oil is water/air. Doesn't really matter how much oil you have, over filling the oil will cause it to leak into your cylinders. "
is completely false and overfilling your engine with oil can result in catastrophic engine failure.
01-14-2011, 03:41 PM
#21
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Straight 30w oil is the same thickness at operating tempa as 10-30 and 0-30...so with thicker oils you are killing your engine at startup...startup is the most critical time.
http://www.alfabb.com/bb/forums/anyt...rari-chat.html
01-14-2011, 03:46 PM
#22
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Worry as much as you want, like you just said, I recommended an oil that will give the guy the result he is looking for with no harm to anything on the AMC 4.0 engine. We are not talking about an 8,000rpm engine. And as great as this debate is, its turning into a thread jack so my apologys to the OP. I completely understand your theory behind the water bubbling however oil is COMPLETELY different while its working in the engine. Thicker oil would simply result in a fraction less of a horse power. I would never run 20w-50 in my race engine.
Now this statement made by "textherex"
"
Quote:
Originally Posted by Tomxj48
that is not true. the only thing that "foams" oil is over filling the engine.
Erra, the thing that foams oil is water/air. Doesn't really matter how much oil you have, over filling the oil will cause it to leak into your cylinders. "
is completely false and overfilling your engine with oil can result in catastrophic engine failure.
Now this statement made by "textherex"
"
Quote:
Originally Posted by Tomxj48
that is not true. the only thing that "foams" oil is over filling the engine.
Erra, the thing that foams oil is water/air. Doesn't really matter how much oil you have, over filling the oil will cause it to leak into your cylinders. "
is completely false and overfilling your engine with oil can result in catastrophic engine failure.
01-14-2011, 06:01 PM
#24
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X2!!!
The 4.0 at idle runs at 10psi. That is where it is suppost to run with say a 10w-30 oil. I run 10w-30 in winter and 20w-50 in the summer and that will keep your oil a little thicker on those hot days just to make you feel better... You dont have to do all that pointless work. You might have some noise, make sure its not just lifter tick man, all these old jeeps get that... its the nature of the engine.
The 4.0 at idle runs at 10psi. That is where it is suppost to run with say a 10w-30 oil. I run 10w-30 in winter and 20w-50 in the summer and that will keep your oil a little thicker on those hot days just to make you feel better... You dont have to do all that pointless work. You might have some noise, make sure its not just lifter tick man, all these old jeeps get that... its the nature of the engine.
01-14-2011, 06:03 PM
#25
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Running oil that is to heavy can be just as bad, or even worse that running to light a weight oil. Oil thats too heavy can foam due to the added restriction and take the oiling of your engine to basically zero.
Def get the pressure check with a mechanical gauge. It should however drop as the engine heats up, oil flows more easily as it warms up.
Def get the pressure check with a mechanical gauge. It should however drop as the engine heats up, oil flows more easily as it warms up.
01-14-2011, 06:05 PM
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01-14-2011, 06:08 PM
#28
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Mine has been doing the same thing since I bought it 3.5 years and 30,000 miles ago. With 369,000 miles on the clock, I'm just going to keep running it the way I have been until it quits, which, hopefully isn't the middle of nowhere and after I already have a spare engine. 
01-14-2011, 06:15 PM
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I build racing engines, and have been around high performance engines my whole life, I know from experience. You can use google just like everyone else. The fact is you said that by increasing your oils viscosity to much you will cause the oil to foam. That is false. AND what the heck are you talking about the water foaming?!? The only thing I know of that makes your coolant bubble or be aerated is if your head gasket is blown or your engine is over heating, causing boiling.
The poor guys engine is running the way it was ENGINEERED to run. If he is uncomfortable with his engine ideling at 5-10psi on a hot day or when oil temp is all the way up, 20w-50 will let him sleep at night without causing a lick of harm to anything, PLUS it will help with his lifter tick, unless he has a sticking lifter.... Its a push rod engine its going to make some noise...
I didnt go to college. I am a lesser person than you and I dont have a paper saying that I can use big words I found on the internet to try and out smart the next guy BUT I know from my own research and knowledge that I have picked up over the years of being around very smart engine builders and years of racing...
The poor guys engine is running the way it was ENGINEERED to run. If he is uncomfortable with his engine ideling at 5-10psi on a hot day or when oil temp is all the way up, 20w-50 will let him sleep at night without causing a lick of harm to anything, PLUS it will help with his lifter tick, unless he has a sticking lifter.... Its a push rod engine its going to make some noise...
I didnt go to college. I am a lesser person than you and I dont have a paper saying that I can use big words I found on the internet to try and out smart the next guy BUT I know from my own research and knowledge that I have picked up over the years of being around very smart engine builders and years of racing...