Losing oil pressure off and on

[JW]

2003, 4.6L. I’ve been hearing a minor clattering sound consistent with an idler or tensioner pulley that’s getting ready to go, so I didn’t think much of it. This morning it briefly lost oil pressure twice and returned pretty quickly. In searching the forums it appears that it’s common for the harness containing the sender wire to chafe and short out, so I didn’t worry about it. Until it lost pressure and then power.

I parked it right away and walked back to the office, and just now walked over and drove it back; I babied it but it seemed fine. It maintained pressure until I got it parked, then it went away.

Now I am thinking that the noise I’m hearing is a timing chain rattle. I had a problem several years ago with my Ranger where it lost oil pressure, and it turned out to be a deteriorated chain guide, which allowed a lot of slack in the chain and caused the tensioner assembly to come apart. Do these motors have a problem with the timing chain tensioner/guide assemblies?

 

[Exproblems]

Do these motors have a problem with the timing chain tensioner/guide assemblies?

>>>>>>>>>>>

Yes, as far as I know from what I have read in here. Not 100% sure on the 4.6L engines, mostly early 4.0's, but there are many posts on this topic in this forum. Use the search box at the top of the forum page and type in a question regarding that issue and I'm sure you'll find posts on that issue. I know a lot of the engines with timing chain guides breaking apart were from the 2002 model years mostly.

 

[FordFool2]

I am no expert on the internal oil passages of the engine. One reason you can see oil pressure drop then return is because the oil pressure gauge is really not a gauge. Ford did us (them) a favior years ago and configured the oil pressure gauge to read 1/2 scale if the oil pressure switch activates. That is around 7 - 10 psig. If you are lower than that, no oil pressure is displayed, if you are any bit above, then 1/2 scale (normal).

As you see you oil pressure dance up and down from normal to nothing to normal, etc., it means you are either just making and breaking below and above setpoint, a frayed wire, loose connection, or failing pressure switch. It may be worthwhile to check the wiring and consider replacing the switch.

I don't think that failing timing chain guides, by themselves, will cause low oil pressure. On the contrary, low oil pressure could lead to failed guides.

My Mercruiser boat engine automatically cuts power to my engine when it senses low oil pressure, high temperature, or low drive oil level. Not sure if Ford did the same for their engines. It may be that the Engine Control System is cutting power when it senses the loss of oil pressure.

Like I said, chase the wiring and switch before you go off the deep end!

 

[JW]

Wiring checked out, as did the tensioner and all three of the idlers. Because of the noise I was hearing and previous experience, I went with my gut and pulled the passenger side cam cover, and saw there is a tremendous amount of slop in the chain. Looking down inside the timing cover and poking with a long screwdriver, I can see that one of the guides is completely broken off the block, floating around in the cover. I don't think it jumped time but won't know until it's fully disassembled.

Much of the front of the engine is disassembled. I still have to pull the crank pulley (the bolt is out, just need to locate the tool now), the power steering pump, and the cover. I'm going to replace both sets of guides while I'm in there. The whole thing is reminiscent of when I did a double head gasket job on my 5.4L Expedition a few years ago, except this has proven to be easier to work on so far.

If this motor is like my 4.0, the slop in the timing chain and tensioner assembly can result in the drop in indicated oil pressure. On the 4.0, the tensioner is dependent on oil pressure to operate properly, and is right before the pressure sender, so with a large amount of oil escaping past the over-extended tensioner, the indicated oil pressure goes way down. I haven't found anything online to support this yet (though I did find this article that describes broken timing chain guides as being a common problem), but I unquestionably do have a timing chain issue that needs to be dealt with, and I suspect that will fix the indicated pressure issue as well.

 

[HiImBrian]

My Mercruiser boat engine automatically cuts power to my engine when it senses low oil pressure, high temperature, or low drive oil level. Not sure if Ford did the same for their engines. It may be that the Engine Control System is cutting power when it senses the loss of oil pressure.

My Mercruiser did that to me too. I flipped out when it happened...lol

 

[bustedknucles]

I am having similar issues with my 1999 ford explorer sport 4.0L sohc v-6. oil pressure is fine at first but then after driving the gauge flickers with throttle input. the motor has a severe rattle and i have replaced the serpentine belt and idle pulleys. i feel it is the timing chains and maybe the oil pressure sensor. i have inspected the wire harness seems fine. this only seems to happen with engine warm and powering up a big hill.(which is a terrible time to lose oil pressure) i am starting with an oil and sensor change then moving on to the timing chains. any and all suggestions are helpful. Thank you -M.A.

 

[bustedknucles]

was in fact the timing chain guide (that had fallen apart) blocking oil pump pickup.. dropped oil pan removed pieces and oil pressure returned to normal.. rebuilt engine is being dropped in as i type.. I would rather not tear whole engine apart so i found a cheap rebuild from friend who owns salvage yard.. if your 4.0liter sohc has any rattle change timing tensinor's... unbolt from side of heads with a 27 mm socket and replace with improved oil reservoir style tensinor from auto zone (79.99x2) THESE SOLVE ISSUE! If not caught soon enough slides with fall apart on cold starts and end up in oil pump pickup and starve engine of oil resulting in engine destruction...Dropping oil pan is easy and cheap basic oil change plus gasket, will let you know if your slides are damaged, if they are whole engine needs pulled as this funky German design has timing cassette behind flywheel. this is a nightmare that could have been easily avoided had i known about this at oh one hundred thousand miles.