Is there such a thing as too much oil pressure?
03-21-2013, 11:34 PM
#1
Instructor
Thread Starter
Is there such a thing as too much oil pressure?
Hi fellow enthusiasts
I have recently begun to see very high oil pressure in my 1993 GTS (automatic with 122k miles). I have used 20/50 Castrol GTX for the last 6 years. In addition, my oil consumption has been very poor. Over the last 740 miles, my oil consumption has been falling also ( 1 qt/825 miles; 1 qt/434 miles).
I have the measured the following pressure vs rpm data once the motor had reached operating temperature. These reading were taken while parked:
650 rpm - 2.5 bar
1,000 rpm - 3.0 bar
1,500 rpm - 3.8 bar
2,000 rpm - 4.5 bar
>2,000 rpm - 4.8 bar
While driving rpm>2,000 rpm the oil pressure is +5 bar and will only drop to ~ 4.8 bar when rpm drops to <2000 rpm.
I recently had a crankcase vent kit installed in hopes of reducing my oil consumption but now see that it is a bit worse than is was pre kit installation. Also, prior to the crankcase vent kit install my oil pressure would never go above 5 bar even under acceleration to red line.
I would like to know if the oil pump has a pressure control regulator. It seems like the high oil pressure and higher oil consumption are related. I have not seen any evidence of oil in the Provent but do see the blue smoke in the exhaust on long downhill roads indicating valve seal leakage.
Any ideas or comments are welcome.
Many thanks!
Joe
I have recently begun to see very high oil pressure in my 1993 GTS (automatic with 122k miles). I have used 20/50 Castrol GTX for the last 6 years. In addition, my oil consumption has been very poor. Over the last 740 miles, my oil consumption has been falling also ( 1 qt/825 miles; 1 qt/434 miles).
I have the measured the following pressure vs rpm data once the motor had reached operating temperature. These reading were taken while parked:
650 rpm - 2.5 bar
1,000 rpm - 3.0 bar
1,500 rpm - 3.8 bar
2,000 rpm - 4.5 bar
>2,000 rpm - 4.8 bar
While driving rpm>2,000 rpm the oil pressure is +5 bar and will only drop to ~ 4.8 bar when rpm drops to <2000 rpm.
I recently had a crankcase vent kit installed in hopes of reducing my oil consumption but now see that it is a bit worse than is was pre kit installation. Also, prior to the crankcase vent kit install my oil pressure would never go above 5 bar even under acceleration to red line.
I would like to know if the oil pump has a pressure control regulator. It seems like the high oil pressure and higher oil consumption are related. I have not seen any evidence of oil in the Provent but do see the blue smoke in the exhaust on long downhill roads indicating valve seal leakage.
Any ideas or comments are welcome.
Many thanks!
Joe
03-22-2013, 12:59 AM
#2
Nordschleife Master
Joe,
Below is post I saved when I had a similar problem, and wanted to keep it as a reference to act upon. My issue was resolved after my next oil/filter change. Haven't seen gauge sticking high since.
Happy Hunting.
Randy:
Restriction or failed pressure relief are my guesses.
First, changed the oil filter recently? Sounds stupid, I know...
I'm inclined to go with a failed pressure relief valve. It's north of the oil filter, screwed into the block. It's the left-hand of the two big bores, the smaller-size bolt head (the right is the bypass valve). If that valve has failed, it could raise - or, rather, fail to limit, the oil pressure as you describe. Should be a simple, if messy, matter to remove it, clean up the spring and piston assembly, and replace.
Aside from that, if something random has clogged or otherwise restricted an oil gallery, pressure would increase through that route and overall sytem pressure should rise, although a properly functioning relief valve should keep it in check.
Below is post I saved when I had a similar problem, and wanted to keep it as a reference to act upon. My issue was resolved after my next oil/filter change. Haven't seen gauge sticking high since.
Happy Hunting.
Randy:
Restriction or failed pressure relief are my guesses.
First, changed the oil filter recently? Sounds stupid, I know...
I'm inclined to go with a failed pressure relief valve. It's north of the oil filter, screwed into the block. It's the left-hand of the two big bores, the smaller-size bolt head (the right is the bypass valve). If that valve has failed, it could raise - or, rather, fail to limit, the oil pressure as you describe. Should be a simple, if messy, matter to remove it, clean up the spring and piston assembly, and replace.
Aside from that, if something random has clogged or otherwise restricted an oil gallery, pressure would increase through that route and overall sytem pressure should rise, although a properly functioning relief valve should keep it in check.
Last edited by MainePorsche; 03-22-2013 at 02:50 AM.
03-22-2013, 01:25 AM
#3
Team Owner
..
Last edited by Mrmerlin; 03-22-2013 at 11:16 AM.
03-22-2013, 02:36 AM
#4
Rennlist Member
Hi fellow enthusiasts
I have recently begun to see very high oil pressure in my 1993 GTS (automatic with 122k miles). I have used 20/50 Castrol GTX for the last 6 years. In addition, my oil consumption has been very poor. Over the last 740 miles, my oil consumption has been falling also ( 1 qt/825 miles; 1 qt/434 miles).
I have the measured the following pressure vs rpm data once the motor had reached operating temperature. These reading were taken while parked:
650 rpm - 2.5 bar
1,000 rpm - 3.0 bar
1,500 rpm - 3.8 bar
2,000 rpm - 4.5 bar
>2,000 rpm - 4.8 bar
While driving rpm>2,000 rpm the oil pressure is +5 bar and will only drop to ~ 4.8 bar when rpm drops to <2000 rpm.
I recently had a crankcase vent kit installed in hopes of reducing my oil consumption but now see that it is a bit worse than is was pre kit installation. Also, prior to the crankcase vent kit install my oil pressure would never go above 5 bar even under acceleration to red line.
I would like to know if the oil pump has a pressure control regulator. It seems like the high oil pressure and higher oil consumption are related. I have not seen any evidence of oil in the Provent but do see the blue smoke in the exhaust on long downhill roads indicating valve seal leakage.
Any ideas or comments are welcome.
Many thanks!
Joe
I have recently begun to see very high oil pressure in my 1993 GTS (automatic with 122k miles). I have used 20/50 Castrol GTX for the last 6 years. In addition, my oil consumption has been very poor. Over the last 740 miles, my oil consumption has been falling also ( 1 qt/825 miles; 1 qt/434 miles).
I have the measured the following pressure vs rpm data once the motor had reached operating temperature. These reading were taken while parked:
650 rpm - 2.5 bar
1,000 rpm - 3.0 bar
1,500 rpm - 3.8 bar
2,000 rpm - 4.5 bar
>2,000 rpm - 4.8 bar
While driving rpm>2,000 rpm the oil pressure is +5 bar and will only drop to ~ 4.8 bar when rpm drops to <2000 rpm.
I recently had a crankcase vent kit installed in hopes of reducing my oil consumption but now see that it is a bit worse than is was pre kit installation. Also, prior to the crankcase vent kit install my oil pressure would never go above 5 bar even under acceleration to red line.
I would like to know if the oil pump has a pressure control regulator. It seems like the high oil pressure and higher oil consumption are related. I have not seen any evidence of oil in the Provent but do see the blue smoke in the exhaust on long downhill roads indicating valve seal leakage.
Any ideas or comments are welcome.
Many thanks!
Joe
The oil pressure figures you quote sound about perfectly normal I would suggest. Oil consumption on these motors is usually about where you operate them. Not sure exactly where the magic number is but I reckon somewhere around 4k rpm oil consumption increases noticeably.
I once did a 1000km round trip up to Dubai not exceeding any limit and did not notice any oil consumption. On other trip with a couple of 40 minute sessions are warp factor 8 and a trip average speed of about a ton I lost about a litre of oil.
This kind of useage as I now understand is associated with the **** poor breather system. Same S4 motor in my GTS chassis, thinking I was doing the right thing, modified the breather system to GTS and the oil consumption was noticeably worse. I am about to correct that.
Thus, if you have just fitted a modified breather kit and oil consumption dips, then suggests you check the installation is correctly installed. No idea what you fitted but if you have some check valves in there make sure you fitted them the right way round for starters. Also check that the pro vent is discharging oil correctly and not filling up with it.
Regards
Fred
03-22-2013, 09:48 AM
#5
Instructor
Thread Starter
Joe,
Below is post I saved when I had a similar problem, and wanted to keep it as a reference to act upon. My issue was resolved after my next oil/filter change. Haven't seen gauge sticking high since.
Happy Hunting.
Randy:
Restriction or failed pressure relief are my guesses.
First, changed the oil filter recently? Sounds stupid, I know...
I'm inclined to go with a failed pressure relief valve. It's north of the oil filter, screwed into the block. It's the left-hand of the two big bores, the smaller-size bolt head (the right is the bypass valve). If that valve has failed, it could raise - or, rather, fail to limit, the oil pressure as you describe. Should be a simple, if messy, matter to remove it, clean up the spring and piston assembly, and replace.
Aside from that, if something random has clogged or otherwise restricted an oil gallery, pressure would increase through that route and overall sytem pressure should rise, although a properly functioning relief valve should keep it in check.
Below is post I saved when I had a similar problem, and wanted to keep it as a reference to act upon. My issue was resolved after my next oil/filter change. Haven't seen gauge sticking high since.
Happy Hunting.
Randy:
Restriction or failed pressure relief are my guesses.
First, changed the oil filter recently? Sounds stupid, I know...
I'm inclined to go with a failed pressure relief valve. It's north of the oil filter, screwed into the block. It's the left-hand of the two big bores, the smaller-size bolt head (the right is the bypass valve). If that valve has failed, it could raise - or, rather, fail to limit, the oil pressure as you describe. Should be a simple, if messy, matter to remove it, clean up the spring and piston assembly, and replace.
Aside from that, if something random has clogged or otherwise restricted an oil gallery, pressure would increase through that route and overall sytem pressure should rise, although a properly functioning relief valve should keep it in check.
All the best,
Joe
03-22-2013, 11:13 AM
#7
Rennlist Member
Hi fellow enthusiasts
I have recently begun to see very high oil pressure in my 1993 GTS (automatic with 122k miles). I have used 20/50 Castrol GTX for the last 6 years. In addition, my oil consumption has been very poor. Over the last 740 miles, my oil consumption has been falling [increasing] also ( 1 qt/825 miles; 1 qt/434 miles).
I have the measured the following pressure vs rpm data once the motor had reached operating temperature. These reading were taken while parked:
650 rpm - 2.5 bar
1,000 rpm - 3.0 bar
1,500 rpm - 3.8 bar
2,000 rpm - 4.5 bar
>2,000 rpm - 4.8 bar
Any ideas or comments are welcome.
Many thanks!
Joe
I have recently begun to see very high oil pressure in my 1993 GTS (automatic with 122k miles). I have used 20/50 Castrol GTX for the last 6 years. In addition, my oil consumption has been very poor. Over the last 740 miles, my oil consumption has been falling [increasing] also ( 1 qt/825 miles; 1 qt/434 miles).
I have the measured the following pressure vs rpm data once the motor had reached operating temperature. These reading were taken while parked:
650 rpm - 2.5 bar
1,000 rpm - 3.0 bar
1,500 rpm - 3.8 bar
2,000 rpm - 4.5 bar
>2,000 rpm - 4.8 bar
Any ideas or comments are welcome.
Many thanks!
Joe
but once I deciphered what you meant, I too am concerned as I will be installing a kit. Pressures are normal, but would not want to go to the trouble/expense and have oil consumption increase. Something is wrong.
Last edited by SteveG; 03-22-2013 at 11:23 AM. Reason: correction
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03-22-2013, 11:31 AM
#8
Rennlist Member
what you do not seem to have grasped is that the oil pressure is limited so that it cannot exceed 5 barg. The oil pump is what we term a positive displacement pump and it will [theoretically] literally rise in pressure as needed until it pushes the required amount of oil for the given pump speed or the drive shaft snaps through mechanical overload. Thus this type of pump is invariably fitted with a relief valve such that when the required pressure is arrived at the valve lifts and the pressure rises no more.
Regards
Fred
03-22-2013, 01:05 PM
#9
Rennlist Member
I was under the impression that our engines will run up to 8 bar of pressure but the dash gauge only shows up to 5.
03-22-2013, 02:04 PM
#10
Nordschleife Master
Another thing, do you have tappet chattering from under the cylinder head covers ?
03-22-2013, 02:42 PM
#11
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The <2000 rpm hot pressures are uncharacteristically high. 2 BAR hot idle is normal.
The OP senders do not seem to fail often. In the one case of a failed sender I've seen it failed reading low not high. Nevertheless before going nuts I would recommend using a external pressure gauge to verify the OE sender's readings and thereby rule out an issue with the sender, wiring, or pod.
Changing the filter and cleaning/replacing the pressure valve are good first steps though.
The OP senders do not seem to fail often. In the one case of a failed sender I've seen it failed reading low not high. Nevertheless before going nuts I would recommend using a external pressure gauge to verify the OE sender's readings and thereby rule out an issue with the sender, wiring, or pod.
Changing the filter and cleaning/replacing the pressure valve are good first steps though.
03-22-2013, 04:21 PM
#12
Instructor
Thread Starter
Joe,
what you do not seem to have grasped is that the oil pressure is limited so that it cannot exceed 5 barg. The oil pump is what we term a positive displacement pump and it will [theoretically] literally rise in pressure as needed until it pushes the required amount of oil for the given pump speed or the drive shaft snaps through mechanical overload. Thus this type of pump is invariably fitted with a relief valve such that when the required pressure is arrived at the valve lifts and the pressure rises no more.
Regards
Fred
what you do not seem to have grasped is that the oil pressure is limited so that it cannot exceed 5 barg. The oil pump is what we term a positive displacement pump and it will [theoretically] literally rise in pressure as needed until it pushes the required amount of oil for the given pump speed or the drive shaft snaps through mechanical overload. Thus this type of pump is invariably fitted with a relief valve such that when the required pressure is arrived at the valve lifts and the pressure rises no more.
Regards
Fred
All the nest,
joe
03-22-2013, 04:23 PM
#13
Instructor
Thread Starter
The <2000 rpm hot pressures are uncharacteristically high. 2 BAR hot idle is normal.
The OP senders do not seem to fail often. In the one case of a failed sender I've seen it failed reading low not high. Nevertheless before going nuts I would recommend using a external pressure gauge to verify the OE sender's readings and thereby rule out an issue with the sender, wiring, or pod.
Changing the filter and cleaning/replacing the pressure valve are good first steps though.
The OP senders do not seem to fail often. In the one case of a failed sender I've seen it failed reading low not high. Nevertheless before going nuts I would recommend using a external pressure gauge to verify the OE sender's readings and thereby rule out an issue with the sender, wiring, or pod.
Changing the filter and cleaning/replacing the pressure valve are good first steps though.
All the best,
Joe
03-22-2013, 04:27 PM
#15
Instructor
Thread Starter
I think my issue is valve stem seals as I have a blue cloud when I decelerate on long downhill grades. The high oil pressure just makes it worse. I will be back in the shop in early April for a look see and will report back.
All the best,
Joe