Oil pressure concern
Silver Surfer
11-01-2004, 01:41 PM
'92 Grand Am SOHC Quad Four; 151,000 miles
Drove to a nearby town Saturday night (about 12 miles from home). Stopped at a traffic light and the low oil pressure light began to flicker. It did this a couple more times before reaching my destination. Checked dip stick in the dark and the level looked real low which would be highly unusual as this machine uses hardly any oil.
Bought a quart of oil at the nearby 7-11 and poured it in. Three hours later the return trip home was uneventful. Low pressure light stayed off.
Next day checked the oil in the daylight and found that is was overfull (probably by about the quart put in the night before).
Found a pressure gauge in my treasure trove and hooked it up. From a cold start the oil pressure started out at about 55 psig and slowly dropped off to around 30 psig at idle speed while the engine warmed. Decided to rev it up for a few minutes in park. Much to my surprise the oil pressure dropped to a steady 12 psig at idle(it will rise with engine speed).
The manual says the idiot light pressure switch will close at less than 4 psig, of course it may not be accurate after all these years.
What do you think is causing my problem?
Drove to a nearby town Saturday night (about 12 miles from home). Stopped at a traffic light and the low oil pressure light began to flicker. It did this a couple more times before reaching my destination. Checked dip stick in the dark and the level looked real low which would be highly unusual as this machine uses hardly any oil.
Bought a quart of oil at the nearby 7-11 and poured it in. Three hours later the return trip home was uneventful. Low pressure light stayed off.
Next day checked the oil in the daylight and found that is was overfull (probably by about the quart put in the night before).
Found a pressure gauge in my treasure trove and hooked it up. From a cold start the oil pressure started out at about 55 psig and slowly dropped off to around 30 psig at idle speed while the engine warmed. Decided to rev it up for a few minutes in park. Much to my surprise the oil pressure dropped to a steady 12 psig at idle(it will rise with engine speed).
The manual says the idiot light pressure switch will close at less than 4 psig, of course it may not be accurate after all these years.
What do you think is causing my problem?
Madcat455
11-01-2004, 03:11 PM
The oil pressure readings sound OK.... Not what they'd be new, but within tolerances for your milage.
Are you sure the oil level was low when you added the quart?? Run the car for a while like you did that one time.. and see if the level drops again... Could be that you're Oil return Galleys that drain the oil back from the head to the block are getting restricted.
That'd explain why it'd be low after driving for awile, then be over full the next day after sitting.
Only way to check for sure is to try to drive it again to recreate the problem.
Are you sure the oil level was low when you added the quart?? Run the car for a while like you did that one time.. and see if the level drops again... Could be that you're Oil return Galleys that drain the oil back from the head to the block are getting restricted.
That'd explain why it'd be low after driving for awile, then be over full the next day after sitting.
Only way to check for sure is to try to drive it again to recreate the problem.
Silver Surfer
11-01-2004, 09:31 PM
Experimented on my machine today. Duplicated the highway run that produced the flickering oil pressure light. Stopped and checked idle oil pressure. It was 10 psig. Shut engine off and quickly checked oil level. It was normal. Obviously it was not actually low when I put in a quart of oil the other night (dark; bad eyes), because I had to remove a quart earlier today to get it down to the full mark on the dip stick. I'm now convinced that it is draining back to the pan normally.
Put on a new oil filter this evening. Exact same results as before after revving the engine in park for about five minutes. No idiot light, but pressure was 10 psig at idle. Checked idiot light on the bench. It appears to close at about 4 psig decreasing as the spec says it should.
I should mention that this machine has had regular oil changes throughout its life. Oil looks very clean. Have never found any foreign material from the oil pan during changes. Also normal consumption is virtually nil. However, I have to concede that worn out bearings are a possibility.
Any more thoughts?
The oil pressure readings sound OK.... Not what they'd be new, but within tolerances for your milage.
Are you sure the oil level was low when you added the quart?? Run the car for a while like you did that one time.. and see if the level drops again... Could be that you're Oil return Galleys that drain the oil back from the head to the block are getting restricted.
That'd explain why it'd be low after driving for awile, then be over full the next day after sitting.
Only way to check for sure is to try to drive it again to recreate the problem.
Put on a new oil filter this evening. Exact same results as before after revving the engine in park for about five minutes. No idiot light, but pressure was 10 psig at idle. Checked idiot light on the bench. It appears to close at about 4 psig decreasing as the spec says it should.
I should mention that this machine has had regular oil changes throughout its life. Oil looks very clean. Have never found any foreign material from the oil pan during changes. Also normal consumption is virtually nil. However, I have to concede that worn out bearings are a possibility.
Any more thoughts?
The oil pressure readings sound OK.... Not what they'd be new, but within tolerances for your milage.
Are you sure the oil level was low when you added the quart?? Run the car for a while like you did that one time.. and see if the level drops again... Could be that you're Oil return Galleys that drain the oil back from the head to the block are getting restricted.
That'd explain why it'd be low after driving for awile, then be over full the next day after sitting.
Only way to check for sure is to try to drive it again to recreate the problem.
Forkliftguy
11-01-2004, 10:37 PM
have you traced the idiot light wiring all throughout to see if it is grounding out somewhere causing false alarms? Here's a scenario from personal experience: Had a customer that I put a remote starter in his truck. Worked like a charm when before he left the shop. Comes back a few minutes later cause his tach no longer worked, but it did as he was pulling out of shop. Checked things out seemed ok, tach worked again strangely so. Leaves, then comes back again with same problem. Turns out the tach sense wire on remote starter had no wire tie on it so it was sitting close to his exhaust manifold, when he'd leave the shop his exhaust got hot enough to melt the wire and ground it causing his tach to read 0, then when it cooled down and restarted the engine the wire would shake a bit I guess no longer being grounded by manifold and read normal, until manifold heated up again causing the same problem. Just a thought.
Marc
Marc
Slade901
11-01-2004, 11:46 PM
Our 1994 Pontiac Grand Am always shows that red light when it is low and usually happens when I'm close to the 3,000 miles and time for an oil change. After an oil change, I usually add 1/2 quart oil to top it off and then add 1/2 quart oil at around 1500 miles.
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