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Intermiten Oil Pressure Light When Car is Hot & AC is On


datdudejibril

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Hi all,

 

I have a 2013 Ford Edge that had an internal water pump break in October.  The mechanic changed the water pump, and flushed the engine several times, but the engine was still sluggish when driving after the fix.   We drove it for a month and the timing failed.  The mechanic didn't change the timing chain the first time and had to go back in the engine a month later to change it and the spark plugs..  After the second repair the car drove great however, we got an intermittent oil pressure warning light for a couple of days and it stopped until April.  (The mechanic said it may do that and we should do a couple of 1K mile oil changes to flush anything else out, which we did.)

 

In April the light started coming back on.  I took the car to the dealership but didn't tell them what happened in October and November.  They changed the oil pressure sensor which didn't solve the issue.  The "say" they checked the oil pump but I don't believe they did.  Finally, I explained what happened prior and the service rep immediately said that the bearings in the engine were failing and the engine would die sooner or later.  He said it could be 6 months or 2 years, but it will die.  But the engine sounded fine and the car drives perfectly, minus the off and on chiming.  I took the car to a Lincoln dealership and they couldn't even duplicate the issue, couldn't see any codes and also stated the car drove and sounded fine.  He stated it may be an electrical issue.  Ironically when we picked it up and went the carwash, the light came back on while the car was idling while it was being vacuumed.

I finally figured out the pattern to the intermittent alerts.  The low oil pressure doesn't alert on the highway, it only alerts when idling or during stop and go traffic.  Another thing I realized is that it is also correlated with the AC running.  We went to a "drive-through safari" that is an hour away from home. It was the first crank of the day and immediately got on the highway -- no warning.  But when we got to the safari and was waiting in line (of course with the AC on) the warning light came on and off in long intervals then shorter intervals as we sat there not moving with the AC on.  But I noticed that the short the chiming intervals became the WARMER the AC blew, to the point that I decided to roll down the windows and turn off the AC altogether because at that point there was only outside temp air coming from the vents.  And guess what?  Within a few minutes, the oil pressure warning stopped chiming altogether and stayed off.  15 min later I tried turning the AC back on and the AC blew cold and guess what?  The oil pressure warning starting coming back on and the AC increasing became warmer again.

So my conclusion is that something is overheating and when I'm on the highway the 70 mph air is keeping that part cool to the point the AC stays cool and there is no warning light. But in stop and go or idle traffic, the part is overheating, thus triggering the warning light and the AC to gradually stop cooling.  And that's why the Lincoln dealership couldn't get the light to come on. Even though they drove the car, they didn't get it hot enough and leaving it idling for the light to come on and that part to heat up.  Btw, the engine temp has always shown normal other when the water pump blew and the car was driven no more than 500 feet until the fix.  

 

What part could it be? Thanks in advance for everyone's help.  

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22 minutes ago, datdudejibril said:

It was suggested to check the 2nd fan.  I checked and the driverside fan isn't running at all.   I'm going to get that fixed and see if it changes anything.. 

 

I was going to suggest checking the fan.  Make sure you use motorcraft replacements - the Dorman and other aftermarket fans are junk and half don't work out of the box.  They come with a new integrated module.

 

Still not sure how that would affect oil pressure.   I'm guessing there is a wiring/sensor issue.  

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