RPM and oil pressure variations while in cruise control
08-02-2018, 02:37 AM
#1
RPM and oil pressure variations while in cruise control
I have had my car to the dealer because while driving in cruise control, 8th gear at 52 mph I suddenly see the oil pressure go from 38 psi to 60 and back again rapidly several times, while this is happening the RPM's vary by 100. The first time I brought it back they said it was a bad TC and replaced it. It still does it but when I took it back they said that was normal and when I asked who said it was normal they showed me a service bulletin that stated 6-0 psi was normal or less. When I pointed that out the service MANAGER insisted that was normal. I asked if that was his opinion or if he had called GM tech support. He replied he wouldn't call because it was normal and nothing to call about. again I asked if his opinion or if he had a bulletin to back that up. all he referred to was the one that stated 6-0 RPM or less variation was normal while acknowledging he saw the 100 RPM fluctuation. He refuses to call GM tech support and knows that they will not talk to me. I asked if he would please call while on speaker so i could listen, he refused that as well and said i could take it to another dealer but to him it was normal and wouldn't do anything. Can you help as he is the only dealer for many miles, Bill Crammer Panama City Beach, FL.
08-03-2018, 01:28 PM
#2
Le Mans Master
Variable flow oil pump, it runs self-checks to make sure it's functioning properly. Your dealership is correct, this is normal.
08-04-2018, 08:47 PM
#3
08-06-2018, 02:23 PM
#4
Le Mans Master
I'd say 30 psi ± 5 depending on conditions is where it normally sits during idle and a steady-state cruise. That's just off the top of my head, but the old saying of 10psi per 1k RPM no longer applies with the LT1/4/5 engines.
Exact numbers:
highway cruise - 34psi
hot idle - 28psi
Exact numbers:
highway cruise - 34psi
hot idle - 28psi
Last edited by Kracka; 08-07-2018 at 08:26 AM.
08-14-2018, 02:25 PM
#5
https://media.chevrolet.com/media/us...mallBlock.html
Sounds normal however...
I do find it odd that its going to the high pressure stage however being a Z51 car (per some investigation of previous posts you've made since you did not include what Corvette you drive https://www.corvetteforum.com/forums...e-at-last.html) it could be related to the dry sump stages. Either way, I'd call it normal and drive the ***** out of it.
Advanced oiling system, with available dry-sump system: The LT1 oiling system – including oil-spray piston cooling – was also optimized for improved performance. It is driven by a new, variable-displacement oil pump that enables more efficient oil delivery, per the engine’s operating conditions. Its dual-pressure control enables operation at a very efficient oil pressure at lower rpm coordinated with AFM and delivers higher pressure at higher engine speeds to provide a more robust lube system for aggressive engine operation.
Standard oil-spray piston cooling sprays the underside of each piston and the surrounding cylinder wall with an extra layer of cooling oil, via small jets located at the bottom of the cylinders. For optimal efficiency, the oil jets are used only when they are needed the most: at start-up, giving the cylinders extra lubrication that reduces noise, and at higher engine speeds, when the engine load demands, for extra cooling and greater durability.
An available dry-sump oiling system promotes exceptional lubrication system performance during aggressive driving maneuvers and high cornering loads. It includes two stages: a pressure stage and a scavenge stage. The pressure stage includes the new, dual-pressure-control and variable-displacement vane pump.
Standard oil-spray piston cooling sprays the underside of each piston and the surrounding cylinder wall with an extra layer of cooling oil, via small jets located at the bottom of the cylinders. For optimal efficiency, the oil jets are used only when they are needed the most: at start-up, giving the cylinders extra lubrication that reduces noise, and at higher engine speeds, when the engine load demands, for extra cooling and greater durability.
An available dry-sump oiling system promotes exceptional lubrication system performance during aggressive driving maneuvers and high cornering loads. It includes two stages: a pressure stage and a scavenge stage. The pressure stage includes the new, dual-pressure-control and variable-displacement vane pump.
#PIP5121C: Oil Pressure Gauge Fluctuation After Startup and Over 3700 RPM - (Jun 27, 2018)
The 4.3L (LV3), 5.3L (L83), 6.2L (L86) engines are equipped with a two stage oil pump.
The oil pressure gauge jumping three times is caused by a test routine the engine goes through during the first few minutes of driving to insure that both stages are operable.
The oil pressure gauge going to 60 lb. over 3700 RPM, is the calibrated engine speed the oil pump goes into the high pressure stage.
No repairs should be attempted.
This is normal operation for these engines.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
The 4.3L (LV3), 5.3L (L83), 6.2L (L86) engines are equipped with a two stage oil pump.
The oil pressure gauge jumping three times is caused by a test routine the engine goes through during the first few minutes of driving to insure that both stages are operable.
The oil pressure gauge going to 60 lb. over 3700 RPM, is the calibrated engine speed the oil pump goes into the high pressure stage.
No repairs should be attempted.
This is normal operation for these engines.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
Last edited by Newdude; 08-14-2018 at 02:26 PM.
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