oil pressure needle jumps
09-29-2018, 01:27 PM
#1
Rennlist Member
Thread Starter
oil pressure needle jumps
2004 C4S. When started cold, the oil pressure needle is pegged at 5-ish. As the engine warms up the pressure at idle drops eventually to 2. Mid-way through this process, when the pressure is around 3 or 4, when the engine is smoothly idling, the oil pressure needle jumps around. See attached video. At around 12s you can see a dramatic jump. I suspect the sender but wonder if any of you have seen this sort of thing and think otherwise.
09-29-2018, 04:04 PM
#2
HHHMMM...Your idle is moving around some. Not sure if that is normal. My 2005 C4S does not do that. Having said all of that not sure an @50rpm hunt would cause the oil pressure to fluctuate. In addition, the oil pressure bouncing is significant and rapid. Guess I would start with the oil pressure sender as they are known to be a weak point. Mine puked and cause the bounce to go from normal to zero and back to normal and repeat. Do not wait for that to happen as there is additional costs involved, specifically for new shorts!
09-29-2018, 07:03 PM
#5
Rennlist Member
The engine is still warming up, so I think it’s possible that the oil is mixing at different temps, which can cause slight oil pressure fluctuation. I agree that the jumps are probably the sender over-responding to slight changes. The question is, how long will it stay that way before it fails? I’ve seen some older cars do that for years.
09-29-2018, 11:29 PM
#6
Instructor
I had a similar situation with the oil pressure, except the idle was not moving. I purchased a new sender unit, replaced it and problem solved.
One thing I notice in my case, the old sender unit was completely lose, I was able to unscrew it without the use of a wrench, not sure if this had anything to do with the jumpy gauge or not.
One thing I notice in my case, the old sender unit was completely lose, I was able to unscrew it without the use of a wrench, not sure if this had anything to do with the jumpy gauge or not.
09-30-2018, 08:33 AM
#7
Does the needle stay at 0 when you turn the key to acc but not start the engine?
i believe that if it points to anything other than 0 the sender unit is not 100% and probably should be replaced.
i believe that if it points to anything other than 0 the sender unit is not 100% and probably should be replaced.
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09-30-2018, 11:39 AM
#8
Rennlist Member
Thread Starter
Thanks everyone for the inputs! This forum is awesome.
Good point, rogazilla. Needle is at zero with the key off and moves to just above 0.5 bar when the key is turned to the accessory position.
Time to replace the sending unit.
Time to replace the sending unit.
09-30-2018, 12:39 PM
#9
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I have a similar problem, along with the error message and oil pressure going to zero sometimes when driving. Almost had a heart attack but luckily a quick search in this forum put me at ease. Changing my sender early next week.
10-04-2018, 05:13 PM
#10
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Every now and then my oil pressure light comes on ,land guage starts dancing .I found that the wiring at the oil pressure sensor was poor.I can remove and reinstall connections and it works fine ,must be a common problem.
10-04-2018, 09:43 PM
#11
Mine is also bouncing like that once in a while (RPM is steady tho..)
I will soon clean-up the wires and possibly change the oil sender.
Just wondering if your gauge show ''0'' when you turn the key on the battery before starting the engine. If its showing pressure its a good indication that the oil sender unit have an issue.
I will soon clean-up the wires and possibly change the oil sender.
Just wondering if your gauge show ''0'' when you turn the key on the battery before starting the engine. If its showing pressure its a good indication that the oil sender unit have an issue.
10-05-2018, 01:46 AM
#12
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It all depends on the connection ,but key on engine off there is no oil pressure .I was getting low /no oil pressure warning with the little oil can showing ,the needle was jumping alot and a beeping warning when it started .When I looked at the connection it was not anything obvious but removing it and cleaning the connections with wire brush fixed it and put a light coat of die electric grease on it also .Its something that will probably happen again based on the uncovered /unprotected connection .I knew it had oil pressure as there were no abnormal noises from the engine ,I always check the oil level and coolant before I take it out of the garage.