Low Oil Pressure???
05-18-2006, 09:40 PM
#1
Racer
Thread Starter
Low Oil Pressure???
What's your oil pressure like at idle after the car has warmed up.
I've got a 90 ZR-1 with 12,000 original miles...
Here's what I've been noticing... When I first start the car (cold) oil pressure is great at idle and through the entire rpm range. After I've been driving for a bout 15 minutes the oil pressure comes down a bit during idle (about mid scale) and continues to be great while driving. After about 25 to 30 minutes when the car is completely warmed up the oil pressure is still mid range and higher at rpms above 1000.
However when letting off the gas, when the rpm drops to about 500 to 600 and then stabilizes between 500 & 700 or so the oil pressure indication drops all the way to zero and then usually stailizes just barely above the caution zone (hash marks).
I've also recently noticed a slight oil leak coming a hose or something around the top rear part of the engine. Could this be coming from the oil pressure transmitter and could my low oil pressure reading be related to this?
Thank You
Troy
I've got a 90 ZR-1 with 12,000 original miles...
Here's what I've been noticing... When I first start the car (cold) oil pressure is great at idle and through the entire rpm range. After I've been driving for a bout 15 minutes the oil pressure comes down a bit during idle (about mid scale) and continues to be great while driving. After about 25 to 30 minutes when the car is completely warmed up the oil pressure is still mid range and higher at rpms above 1000.
However when letting off the gas, when the rpm drops to about 500 to 600 and then stabilizes between 500 & 700 or so the oil pressure indication drops all the way to zero and then usually stailizes just barely above the caution zone (hash marks).
I've also recently noticed a slight oil leak coming a hose or something around the top rear part of the engine. Could this be coming from the oil pressure transmitter and could my low oil pressure reading be related to this?
Thank You
Troy
05-19-2006, 02:21 AM
#2
Drifting
Troy,
Certainly no normal, mechanical reason for low oil pressure on an engine with only 12,000 miles. I'm not a fan of electrical senders for oil pressure and water temp and the senders have been know to fail on the LT5. The factory gauges do not always read linear, especially the coolant temp.
I recommend a simple test to verify oil pressure. Remove the sender from the oil filter housing (forward & slightly below the oil filter). Install a Tee to allow a mechanical gauge to be installed there also. No need to get fancy for the test, just leave the gauge screwed in, right there by the sender. Use a small dia cheap one that you can pick up at Autozone. Duplicate the conditions again and when it reads low on the dash, pop the hood and see what the gauge indicates. I "think" the service manual says 20 psi @ idle when hot is within spec.
I installed a pillar mount, mechanical, oil pressure gauge in mine and feel much more confident about the oil pressure now.
Both oil pressure senders (1 for the gauge & 1 for the SES warning) are located on the rt-ft of the engine. The leak you are seeing could be from the PCV hoses, but that would also mean you have a sizeable vacuum leak (not consistent with a low idle speed). If you're seeing a leak below the bellhousing, that would probably be from the valley drain tube and the oil would be coming from the crankcase vent housing under the plenum, a very common condition.
Either way, I seriously doubt the "leak" you mentioned would be responsible for low oil pressure. A leak large enough to affect oil pressure at idle would be a stream that would cause a low oil level warning in less than a couple of minutes.
Verify the pressure and then dig further if necessary. Good luck.
Certainly no normal, mechanical reason for low oil pressure on an engine with only 12,000 miles. I'm not a fan of electrical senders for oil pressure and water temp and the senders have been know to fail on the LT5. The factory gauges do not always read linear, especially the coolant temp.
I recommend a simple test to verify oil pressure. Remove the sender from the oil filter housing (forward & slightly below the oil filter). Install a Tee to allow a mechanical gauge to be installed there also. No need to get fancy for the test, just leave the gauge screwed in, right there by the sender. Use a small dia cheap one that you can pick up at Autozone. Duplicate the conditions again and when it reads low on the dash, pop the hood and see what the gauge indicates. I "think" the service manual says 20 psi @ idle when hot is within spec.
I installed a pillar mount, mechanical, oil pressure gauge in mine and feel much more confident about the oil pressure now.
Both oil pressure senders (1 for the gauge & 1 for the SES warning) are located on the rt-ft of the engine. The leak you are seeing could be from the PCV hoses, but that would also mean you have a sizeable vacuum leak (not consistent with a low idle speed). If you're seeing a leak below the bellhousing, that would probably be from the valley drain tube and the oil would be coming from the crankcase vent housing under the plenum, a very common condition.
Either way, I seriously doubt the "leak" you mentioned would be responsible for low oil pressure. A leak large enough to affect oil pressure at idle would be a stream that would cause a low oil level warning in less than a couple of minutes.
Verify the pressure and then dig further if necessary. Good luck.
05-19-2006, 07:24 AM
#3
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