Low oil pressure with the AC running
08-26-2018, 07:26 PM
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Low oil pressure with the AC running While driving last night I noticed my car started sounding a bit different after I turned the AC on and also a lose of some power. I look down at the oil pressure gauge and it was around 5 ish psi. I pulled over and checked the dipstick, noticing the engine bay was very hot, but the car wasn't over heating. Oil was full and looked good. I shut the car off for over an hour and decided to run it with the AC off since I was 45 minutes from home. With the AC off the car ran great, had power back, oil pressure was a little lower than normal but nothing crazy, (around 30psi). I understand a bearing starting to freeze up on the compressor will cause parasitic power lose, but the oil pressure being down so low is what Im not understanding. Wouldn't it shred a belt or something similar before pulling on the pump that much? Its a Melling oil pump on a Gen IV 378 LS. Please help me understand whats going on?
08-26-2018, 07:36 PM
#2
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I bet it's electrical. SOMETHING is sucking electrical power (fans?) when the AC is on, causing the ECM to malfunction, cutting fuel, timing, etc. Check ALL grounds and all other connections.
08-26-2018, 07:37 PM
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08-26-2018, 07:39 PM
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08-27-2018, 08:58 PM
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Did you happen to see where the voltage was when this was happening? Grab a volt meter and hook it to the battery and let the car run and get warm. Then turn on all the lights and the ac on full blast and see what voltage you have, if you can use a meter don't trust the dash gauge until you can confirm it's correct with the meter.
The only way the a/c would pull the car down that bad is if the compressor was trying to seize up internally. The pulley has a bearing and if that bearing was on it's way out it wouldn't matter if the a/c was on or not. '
The a/c being on engages the clutch which turns the inside of the compressor, so if you're thinking it has something to do with the compressor, it would be the guts of it causing issues, not the bearing in the pulley. And when those bearings start going bad they get real loud like any other bearing does.
The only way the a/c would pull the car down that bad is if the compressor was trying to seize up internally. The pulley has a bearing and if that bearing was on it's way out it wouldn't matter if the a/c was on or not. '
The a/c being on engages the clutch which turns the inside of the compressor, so if you're thinking it has something to do with the compressor, it would be the guts of it causing issues, not the bearing in the pulley. And when those bearings start going bad they get real loud like any other bearing does.
08-27-2018, 09:37 PM
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I will certainly check it tomorrow to see and then update you on here. I do remember hearing a noise but with a 9” in a spool in the back and procharger up front it’s not uncommon to hear weird noises. Thanks for the suggestion. I’ll get back with you.
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08-30-2018, 07:52 PM
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Did you happen to see where the voltage was when this was happening? Grab a volt meter and hook it to the battery and let the car run and get warm. Then turn on all the lights and the ac on full blast and see what voltage you have, if you can use a meter don't trust the dash gauge until you can confirm it's correct with the meter.
The only way the a/c would pull the car down that bad is if the compressor was trying to seize up internally. The pulley has a bearing and if that bearing was on it's way out it wouldn't matter if the a/c was on or not. '
The a/c being on engages the clutch which turns the inside of the compressor, so if you're thinking it has something to do with the compressor, it would be the guts of it causing issues, not the bearing in the pulley. And when those bearings start going bad they get real loud like any other bearing does.
The only way the a/c would pull the car down that bad is if the compressor was trying to seize up internally. The pulley has a bearing and if that bearing was on it's way out it wouldn't matter if the a/c was on or not. '
The a/c being on engages the clutch which turns the inside of the compressor, so if you're thinking it has something to do with the compressor, it would be the guts of it causing issues, not the bearing in the pulley. And when those bearings start going bad they get real loud like any other bearing does.
.2 to .4 at the most.