Erratic oil pressure
Thread Starter
Race Director
Joined: Oct 2004
Posts: 18,401
Likes: 3
From: Retired but working
Cruise-In VI Veteran
Erratic oil pressure
Question???
Drive to work today and oil pressure was running 35-38 at idle and 47 52 at 6.
Left work and pressure was 7-10 at idle and 25-28 at 65. Car is performing well and no strange noises etc.
Happened one time before and was corrected at next start, two hours later.
New pump, new sending unit, etc??
How hard is it toinstall a new pump? Steps ets.
Thanks in advance
Jim
Drive to work today and oil pressure was running 35-38 at idle and 47 52 at 6.
Left work and pressure was 7-10 at idle and 25-28 at 65. Car is performing well and no strange noises etc.
Happened one time before and was corrected at next start, two hours later.
New pump, new sending unit, etc??
How hard is it toinstall a new pump? Steps ets.
Thanks in advance
Jim
Burning Brakes
Joined: Mar 2008
Posts: 983
Likes: 36
From: Middle Of Kali CA
Oil sending unit maybe (usually peg needle when they fail) The pump I doubt it is of cause. An augered bearing will lower pressure but you should here it. I would just drive it and see what it it's reading.
What year and how many miles?
What year and how many miles?
Thread Starter
Race Director
Joined: Oct 2004
Posts: 18,401
Likes: 3
From: Retired but working
Cruise-In VI Veteran
99 with a 383 LF with 110k. Replaced the sending unit once as the oil pressure had pegged out.
Last time this happened it was 18 degrees out and after being parked for 2 hours it was back to normal.
.
Thanks.
Jim
Last time this happened it was 18 degrees out and after being parked for 2 hours it was back to normal.
.
Thanks.
Jim
Tech Contributor
Joined: Dec 2006
Posts: 10,962
Likes: 28
From: Van Buren Arkansas
Wounded Warrior Escort '11
Most likely its the sending unit/sensor. If you suspect the oil pump itself, the dealer has a special test device that goes on in place of the oil filter and they can verify your pump.
Tech Contributor
Joined: Jan 2007
Posts: 19,115
Likes: 1,038
From: Dyer, IN
on both suggestions. Install a mechanical gauge to verify the oil pressure. Don't bet on it being a bad OPS.
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Tech Contributor
Joined: Jan 2007
Posts: 19,115
Likes: 1,038
From: Dyer, IN
Tech Contributor
Joined: Jan 2007
Posts: 19,115
Likes: 1,038
From: Dyer, IN
.....not if the OP really has an oil pump getting ready to go out. At least with a mechnical gauge installed, he can immediately verify his oil pressure, when it reads low. No guessing.
Tech Contributor
Joined: Jan 2007
Posts: 19,115
Likes: 1,038
From: Dyer, IN
That's cool. Some like to change parts until they fix the problem(by accident). I'm just one of those weirdos who enjoys isolating the issue, and attacking it in a logical fashion.......but that approach is obviously not for everyone.
Intermediate
Joined: Mar 2011
Posts: 45
Likes: 0
I can see both sides of the argument, but I'm a pretty picky guy when it comes to oiling issues. I've got a '99 z28 that has a pump on it's way out, but I'm gunna keep on spraying the hell out of it till she does 
Something more along the lines of my C5, I'd like an immediate answer, that I only need not but a few seconds of run time to verify. Lack of oil, causes too much wear, way too rapidly, upon starvation. Not something I'd like to troubleshoot over any signifcant amount of time, with "what-ifs".
But like has been said, sometimes the cost and time involved, evens out, just depends on which side of the fence you're walking
Something more along the lines of my C5, I'd like an immediate answer, that I only need not but a few seconds of run time to verify. Lack of oil, causes too much wear, way too rapidly, upon starvation. Not something I'd like to troubleshoot over any signifcant amount of time, with "what-ifs".But like has been said, sometimes the cost and time involved, evens out, just depends on which side of the fence you're walking
Safety Car
Joined: May 2008
Posts: 4,237
Likes: 11
From: Lacombe Louisiana
I have been an ASE Master Tech for over 30 years.What I would do in the shop or even at home is quite different from what a back yard inexperienced guy may do. I was just saying it would be simple and quicker for that sort of fella to change the sensor and he would achieve the same results and findings without buying tools he may never ever use again.Unless he is a gear head of course.Since the problem is errattic and "cures" itself as he states,I would lean more towards an electrical issue,specially since he has no engine noises and the car runs fine.
Instructor
Joined: Jun 2008
Posts: 233
Likes: 1
From: Austin Texas
If it is intermittent pump output the engine is being subjected to expensive progressive damage each and every time the pressure drops - not good.
What if it eventually turns out to be just an electrical connection? Replacing the sensor, in addition to a big hassle and expense, wouldn't change anything and may lead to the OP replacing the oil pump unnecessarily.
An independent gauge is money well spent considering the potential downside of an oil-starved engine. Very interesting thread!
Last edited by Cratecruncher; Mar 8, 2011 at 01:15 PM.
Pro
Joined: Apr 2008
Posts: 628
Likes: 4
From: Columbia SC
I've read a lot of oil pressure posts since joining the Forum, but don't think I've ever seen someone state that a bad sensor gave low readings. Does it happen? As I've only seen people getting high readings from a bad sensor I'd like to know.
Instructor
Joined: Jun 2008
Posts: 233
Likes: 1
From: Austin Texas
Benpup,
Just buy a cheapo plastic oil gauge and tape it to the dash until your good gauge goes screwy then toss it.
I once bought a car with a recently rebuilt engine that had low oil pressure. Of coarse the seller told me he had put another gauge on it and "it's fine, the gauge just needs recalibration". Yeah, right. It was a gorgeous car and a great deal so I decided to take a chance he was telling the truth. (Trust though verify.) I trailered it home and bought a cheapo aftermarket oil pressure gauge from one of the parts stores for about $20 and plumbed it up. Both gauges read exactly the same thing. (That lie'n sack a...) The oil pressure was indeed only 20 psi when warm when it should have been more like 45 at idle. Since the motor had a recent rebuild I suspected the worst. However, it turned out to be a spongy $2.00 bypass spring. I replaced that little spring and pressure went right up to spec! Then it was on to the rich carbs. But that is another story.
Just buy a cheapo plastic oil gauge and tape it to the dash until your good gauge goes screwy then toss it.
I once bought a car with a recently rebuilt engine that had low oil pressure. Of coarse the seller told me he had put another gauge on it and "it's fine, the gauge just needs recalibration". Yeah, right. It was a gorgeous car and a great deal so I decided to take a chance he was telling the truth. (Trust though verify.) I trailered it home and bought a cheapo aftermarket oil pressure gauge from one of the parts stores for about $20 and plumbed it up. Both gauges read exactly the same thing. (That lie'n sack a...) The oil pressure was indeed only 20 psi when warm when it should have been more like 45 at idle. Since the motor had a recent rebuild I suspected the worst. However, it turned out to be a spongy $2.00 bypass spring. I replaced that little spring and pressure went right up to spec! Then it was on to the rich carbs. But that is another story.
