[Z06] Question about low oil pressure?
12-14-2006, 01:04 PM
#1
Burning Brakes
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Question about low oil pressure?
Anyone know how the oil is pumped back into the dry sump canister? I had heard problems with spun crank bearings and have been wondering how it happens.
Some people have reported just before their engine had to go into the shop because of spun crank bearings their oil pressure dropped below 25psi.
Yesterday, as I was washing my Z I took the engine valve covers off and I noticed that one of the lines from the canister connects directly to the intake right before the throttle body.
It then occured to me that they must be using vacuum generated by the intake to provide the suction to remove the oil out of the oil pan and put it into the canister??
It then occured to me,,, what if this line got lose, or got a leak?? Wouldn't the canister stay empty and thus the oil pump would be at a loss for oil?
Having not purchases the shop manual and read on this yet, I wondered if this is how it works, and perhaps this is what is causing the low oil pressure and blown crank bearings.
By the way, for some background, I have built three of the engines in my cars and have been working as a hobby with mechanics for 20 years.
Does anyone know for sure?? If it is the case this may be the weak link in the system.
What do you think??
Some people have reported just before their engine had to go into the shop because of spun crank bearings their oil pressure dropped below 25psi.
Yesterday, as I was washing my Z I took the engine valve covers off and I noticed that one of the lines from the canister connects directly to the intake right before the throttle body.
It then occured to me that they must be using vacuum generated by the intake to provide the suction to remove the oil out of the oil pan and put it into the canister??
It then occured to me,,, what if this line got lose, or got a leak?? Wouldn't the canister stay empty and thus the oil pump would be at a loss for oil?
Having not purchases the shop manual and read on this yet, I wondered if this is how it works, and perhaps this is what is causing the low oil pressure and blown crank bearings.
By the way, for some background, I have built three of the engines in my cars and have been working as a hobby with mechanics for 20 years.
Does anyone know for sure?? If it is the case this may be the weak link in the system.
What do you think??
12-14-2006, 02:42 PM
#2
Burning Brakes
You are off. The dry sump system does not use vacuum to draw oil.
If the vacuum line were to be disconnected, oil would still be circulating through the engine. This vacuum line is generally used to draw oil vapors into the combustion chamber rather than passively vent to the environment.
After the oil is drawn from the bottom of the sump via gerotor oil pump, it is pumped through the motor, it's a purely mechanical means of circulating oil in the system as a whole.
Low oil pressure can be caused by a failing oil pump, too much clearance in the oil pump area, lack of oil in the sump, air bubbles in the oil, miss-assembly of oil pump and pickup lines and or bearings, obstruction in an oil passage, worn or excessive clearance in the main/rod bearing, damage main/rod bearings, coolant/water in the oil, etc.
Eg. Severe detonation can lead to abnormal wear on a rod bearing(s) which can cause a loss in oil pressure which can lead to accelerated engine wear and subsequent decrease in oil pressure and if at high rpm load can lead to a failure and spun crank/rod bearings.
The dry sump on the C6Z06 is a hybridized dry sump system that is different from the traditional race-type dry sump where there is/are dedicated mechanical "scavange" pumps located throughout the motor and is typically belt-driven and located as an external unit.
As seen here on my motor:
If the vacuum line were to be disconnected, oil would still be circulating through the engine. This vacuum line is generally used to draw oil vapors into the combustion chamber rather than passively vent to the environment.
After the oil is drawn from the bottom of the sump via gerotor oil pump, it is pumped through the motor, it's a purely mechanical means of circulating oil in the system as a whole.
Low oil pressure can be caused by a failing oil pump, too much clearance in the oil pump area, lack of oil in the sump, air bubbles in the oil, miss-assembly of oil pump and pickup lines and or bearings, obstruction in an oil passage, worn or excessive clearance in the main/rod bearing, damage main/rod bearings, coolant/water in the oil, etc.
Eg. Severe detonation can lead to abnormal wear on a rod bearing(s) which can cause a loss in oil pressure which can lead to accelerated engine wear and subsequent decrease in oil pressure and if at high rpm load can lead to a failure and spun crank/rod bearings.
The dry sump on the C6Z06 is a hybridized dry sump system that is different from the traditional race-type dry sump where there is/are dedicated mechanical "scavange" pumps located throughout the motor and is typically belt-driven and located as an external unit.
As seen here on my motor:
Anyone know how the oil is pumped back into the dry sump canister? I had heard problems with spun crank bearings and have been wondering how it happens.
Some people have reported just before their engine had to go into the shop because of spun crank bearings their oil pressure dropped below 25psi.
Yesterday, as I was washing my Z I took the engine valve covers off and I noticed that one of the lines from the canister connects directly to the intake right before the throttle body.
It then occured to me that they must be using vacuum generated by the intake to provide the suction to remove the oil out of the oil pan and put it into the canister??
It then occured to me,,, what if this line got lose, or got a leak?? Wouldn't the canister stay empty and thus the oil pump would be at a loss for oil?
Having not purchases the shop manual and read on this yet, I wondered if this is how it works, and perhaps this is what is causing the low oil pressure and blown crank bearings.
By the way, for some background, I have built three of the engines in my cars and have been working as a hobby with mechanics for 20 years.
Does anyone know for sure?? If it is the case this may be the weak link in the system.
What do you think??
Some people have reported just before their engine had to go into the shop because of spun crank bearings their oil pressure dropped below 25psi.
Yesterday, as I was washing my Z I took the engine valve covers off and I noticed that one of the lines from the canister connects directly to the intake right before the throttle body.
It then occured to me that they must be using vacuum generated by the intake to provide the suction to remove the oil out of the oil pan and put it into the canister??
It then occured to me,,, what if this line got lose, or got a leak?? Wouldn't the canister stay empty and thus the oil pump would be at a loss for oil?
Having not purchases the shop manual and read on this yet, I wondered if this is how it works, and perhaps this is what is causing the low oil pressure and blown crank bearings.
By the way, for some background, I have built three of the engines in my cars and have been working as a hobby with mechanics for 20 years.
Does anyone know for sure?? If it is the case this may be the weak link in the system.
What do you think??
12-14-2006, 03:19 PM
#3
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If you want a really good guess on what leads to low oil pressure check out this post:
http://forums.corvetteforum.com/show...0&postcount=53
It has nothing to do with that vapor line. The oil is actually moved by dual gear pumps at the front of the crank. One (high volume) pump moves the oil into the separator tank where the air is removed by a series of baffles, and the second (high pressure) pump moves it form the tank to the engine oil galleries.
If you notice a drop in oil pressure take it very seriously.
http://forums.corvetteforum.com/show...0&postcount=53
It has nothing to do with that vapor line. The oil is actually moved by dual gear pumps at the front of the crank. One (high volume) pump moves the oil into the separator tank where the air is removed by a series of baffles, and the second (high pressure) pump moves it form the tank to the engine oil galleries.
If you notice a drop in oil pressure take it very seriously.
12-14-2006, 04:03 PM
#4
Burning Brakes
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If you want a really good guess on what leads to low oil pressure check out this post:
http://forums.corvetteforum.com/show...0&postcount=53
It has nothing to do with that vapor line. The oil is actually moved by dual gear pumps at the front of the crank. One (high volume) pump moves the oil into the separator tank where the air is removed by a series of baffles, and the second (high pressure) pump moves it form the tank to the engine oil galleries.
If you notice a drop in oil pressure take it very seriously.
http://forums.corvetteforum.com/show...0&postcount=53
It has nothing to do with that vapor line. The oil is actually moved by dual gear pumps at the front of the crank. One (high volume) pump moves the oil into the separator tank where the air is removed by a series of baffles, and the second (high pressure) pump moves it form the tank to the engine oil galleries.
If you notice a drop in oil pressure take it very seriously.
The more I read it sounds like this LS7 is not as reliable as the LS2 has been so far.
12-14-2006, 05:41 PM
#5
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The LS7 Dry Sump System uses a 2 stage mechanical Gearotor Oil Pump mounted on the crank snout (vs. a single stage on the wet sump LS6).
1st Stage (Scavage) pumps oil from the engine dry sump pan to the reservoir cannister.
2nd stage (Pressure) pumps oil from the reservoir cannister to the engine priority main oil gallery
Both oil lines are located on the Right side of the oil pan and enter the reservoir tank at the bottom.
The LS7 also uses the reservoir tank as a "catch can" for the revised PCV system. The 2 small lines entering/exiting the reservoir tank on the top are the PCV lines.
Note that the LS7 2 stage OEM oil pump can be blueprinted and ported just like the LS6 single stage pump. The LS7 pump(s) can also be shimmed and a heavier pressure relief spring added to produce a higher system pressure.
The caveat is that the 2 stages must be equalized in flow if modified.
1st Stage (Scavage) pumps oil from the engine dry sump pan to the reservoir cannister.
2nd stage (Pressure) pumps oil from the reservoir cannister to the engine priority main oil gallery
Both oil lines are located on the Right side of the oil pan and enter the reservoir tank at the bottom.
The LS7 also uses the reservoir tank as a "catch can" for the revised PCV system. The 2 small lines entering/exiting the reservoir tank on the top are the PCV lines.
Note that the LS7 2 stage OEM oil pump can be blueprinted and ported just like the LS6 single stage pump. The LS7 pump(s) can also be shimmed and a heavier pressure relief spring added to produce a higher system pressure.
The caveat is that the 2 stages must be equalized in flow if modified.
Last edited by DJWorm; 12-14-2006 at 05:44 PM.
12-14-2006, 08:11 PM
#6
Thanks for the post. I would have read up on it but I haven't purchased the shop manual yet. Truth is, I have no experience with dry sump oil setups. So there are two oil pumps?? Hmmm, I wonder why one of them may be failing?
The more I read it sounds like this LS7 is not as reliable as the LS2 has been so far.
The more I read it sounds like this LS7 is not as reliable as the LS2 has been so far.
The dry sump question is unrelated, and a dry sump is actually added protection for better oiling, especially for spirited driving on the twisties. Try high-G cornering with a wet sump only, if you want to see low oil pressure and engine failures. The oil pressures in an LS7 are consistently higher than all LS2s across all temp and RPM ranges.
12-14-2006, 08:50 PM
#7
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The LS7 Dry Sump System uses a 2 stage mechanical Gearotor Oil Pump mounted on the crank snout (vs. a single stage on the wet sump LS6).
1st Stage (Scavage) pumps oil from the engine dry sump pan to the reservoir cannister.
2nd stage (Pressure) pumps oil from the reservoir cannister to the engine priority main oil gallery
Both oil lines are located on the Right side of the oil pan and enter the reservoir tank at the bottom.
The LS7 also uses the reservoir tank as a "catch can" for the revised PCV system. The 2 small lines entering/exiting the reservoir tank on the top are the PCV lines.
Note that the LS7 2 stage OEM oil pump can be blueprinted and ported just like the LS6 single stage pump. The LS7 pump(s) can also be shimmed and a heavier pressure relief spring added to produce a higher system pressure.
The caveat is that the 2 stages must be equalized in flow if modified.
1st Stage (Scavage) pumps oil from the engine dry sump pan to the reservoir cannister.
2nd stage (Pressure) pumps oil from the reservoir cannister to the engine priority main oil gallery
Both oil lines are located on the Right side of the oil pan and enter the reservoir tank at the bottom.
The LS7 also uses the reservoir tank as a "catch can" for the revised PCV system. The 2 small lines entering/exiting the reservoir tank on the top are the PCV lines.
Note that the LS7 2 stage OEM oil pump can be blueprinted and ported just like the LS6 single stage pump. The LS7 pump(s) can also be shimmed and a heavier pressure relief spring added to produce a higher system pressure.
The caveat is that the 2 stages must be equalized in flow if modified.
Zed Six, That is one cool engine.
12-15-2006, 03:31 AM
#8
Burning Brakes
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Uh no, I don't think you have any data with which to draw that conclusion. There is no compelling data that suggests the LS7 failure rate is higher than the rate for the LS2.
The dry sump question is unrelated, and a dry sump is actually added protection for better oiling, especially for spirited driving on the twisties. Try high-G cornering with a wet sump only, if you want to see low oil pressure and engine failures. The oil pressures in an LS7 are consistently higher than all LS2s across all temp and RPM ranges.
The dry sump question is unrelated, and a dry sump is actually added protection for better oiling, especially for spirited driving on the twisties. Try high-G cornering with a wet sump only, if you want to see low oil pressure and engine failures. The oil pressures in an LS7 are consistently higher than all LS2s across all temp and RPM ranges.
I am convinced there is a problem with the setup somewhere otherwise new cars, like a previous poster that bought a 2007 Z wouldn't be having problems.
Although I see your arguments about Oil pressure under high G's, that is certainly not what is causing them to fail. Furthermore, this is why I am beginning to think that the LS2 seems to be more reliable.
Call it a design flaw. There is nothing wrong with Dry sump, definitely better, but something may be wrong with GM's until they admit or figure out what is causing these failures.
12-15-2006, 08:33 AM
#10
Ok, I hear ya. But...... Why then are some people on this forum having spun bearing issues and indicating they saw their oil pressure drop right before the failure? I don't doubt that the Dry sump is a good setup. However, let's not have blind faith? This doesn't mean that GMs version that they are selling us doesn't have a fault in it that would cause it to fail that they haven't discovered yet?
I am convinced there is a problem with the setup somewhere otherwise new cars, like a previous poster that bought a 2007 Z wouldn't be having problems.
Although I see your arguments about Oil pressure under high G's, that is certainly not what is causing them to fail. Furthermore, this is why I am beginning to think that the LS2 seems to be more reliable.
Call it a design flaw. There is nothing wrong with Dry sump, definitely better, but something may be wrong with GM's until they admit or figure out what is causing these failures.
I am convinced there is a problem with the setup somewhere otherwise new cars, like a previous poster that bought a 2007 Z wouldn't be having problems.
Although I see your arguments about Oil pressure under high G's, that is certainly not what is causing them to fail. Furthermore, this is why I am beginning to think that the LS2 seems to be more reliable.
Call it a design flaw. There is nothing wrong with Dry sump, definitely better, but something may be wrong with GM's until they admit or figure out what is causing these failures.
Failures in all complicated machinery, such as aviation for example, occur for myriad reasons (e.g. hard or abusive use, casting defects in one lot of parts, and so on). A perfect design will fail if one bad part is installed, or if one bad owner takes delivery.
12-15-2006, 08:50 AM
#11
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Sorry, I just can't follow your logic here. Neither you, nor I have any data which suggests an abnormal rate of failure compared to any other high performance engine, let's say over 400HP. No other machine ever created has achieved perfection, yet you somehow seem to be expecting it here and then implying that the absence of perfection is proof of a "design flaw."
Failures in all complicated machinery, such as aviation for example, occur for myriad reasons (e.g. hard or abusive use, casting defects in one lot of parts, and so on). A perfect design will fail if one bad part is installed, or if one bad owner takes delivery.
Failures in all complicated machinery, such as aviation for example, occur for myriad reasons (e.g. hard or abusive use, casting defects in one lot of parts, and so on). A perfect design will fail if one bad part is installed, or if one bad owner takes delivery.
