Oil pressure dropped when slowing down to a stop

Tiny
CHRIS KINARD
  • MEMBER
  • 2000 FORD MUSTANG
  • 3.8L
  • V6
  • 2WD
  • AUTOMATIC
  • 20,000,000 MILES
I was just going down the street and looked at the oil pressure gauge and when I was coming to a stop I saw the gauge drop all the way, but then came back up to normal. Please help. Thanks
Friday, January 8th, 2021 AT 10:44 AM

3 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Did it do this one time or did it just do it once? Either way, I would do two things. If you can get this to do it again, put a mechanical gauge on it and make sure this is not a sensor issue. If another gauge shows the same thing then we have an internal issue.

If that is the case then due to you slowing down, I suspect you are low on oil so we need to check it and even do an oil change. When you slow down the oil rocks to the front of the pan. When you are low on oil the oil pickup tube that is in the back of the pan sucks air due to the oil not keeping it submerged and the pressure drops.

Here are some guides that help with this:

https://www.2carpros.com/articles/high-or-low-engine-oil-pressure

https://www.2carpros.com/articles/how-to-change-engine-oil-and-filter

Let's check this info and go from there. Thanks
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Saturday, January 9th, 2021 AT 4:59 PM
Tiny
CHRIS KINARD
  • MEMBER
  • 89 POSTS
My car also has a self diagnostic test. I did the test and on the oil test it read 255 engine off and 000 engine on and also I took the hose and the PCV valve off to clean it it was full of oil.
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Saturday, January 9th, 2021 AT 8:06 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
I think you are talking about the key on engine off test. This code points to an issue as talked about below but it does not account for an oil pressure issue. It could be a sensor issue as this is an input to the PCM but again, this is why we need to confirm the oil pressure is okay with a mechanical gauge when this happens.

However, the fact that this happens when you are slowing down points to a mechanical issue and not an electrical issue.

If the PCV is full of oil, that clearly needs to be changed but that points to a possible ring issue as it puts pressure in the crank case and pushes oil into the PCV valve. This supports the idea that we need to check the oil level and even do an oil change, change the PCV and then retest it.
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Sunday, January 10th, 2021 AT 4:19 PM

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