Low oil pressure at idle after warm - Ford Powerstroke Diesel Forum
 
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post #1 of 7 Old 12-06-2019, 05:10 PM Thread Starter
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Low oil pressure at idle after warm

Good evening!

I'll start by saying I'm new to diesel engines in general. Bought a used 2008 Ford E350 6.0l school bus to toy with. Ran pretty well, one code when I first bought it for the anti theft lockout, chalked it up to it barely starting from low battery voltage. Cleared the code and it didn't come back.

Anyways, on to the problem. Took it into the dealer for an inspection and oil change. They put 15w40 synthetic blend in it. After letting it warm up a little we left the dealership and jumped on the highway for a little bit and the engine warmed up. As soon as I got to the first stoplight and let off the gas the low oil pressure light illuminated and a few seconds later the gauge went to nothing.

If I hit the gas the gauge would recover and the light would go out. It happened everytime I let off the gas and the rpms dropped below 1k.

The issue continues today, it only happens after the engine has warmed up, and the bus seems to run fine when the symptoms are occurring.

Tonight after arriving home (engine was warm) I let it idle for about a minute in the driveway and the light stayed on. I shut the bus off then started it again and it seemed to start right up with no more effort than is usual. I turned it off again and let it sit for a few minutes and the same thing, started right back up.

Most of the situations I read online where people have low oil pressure at idle when the engine is warm also have difficulty restarting the engine when it's warm.

Any ideas for things to check? I presume something could have been messed up during the oil change, but no signs of oil on the driveway and the oil level appears ok. I guess it could also be due to the oil itself? I doubted this because 15w40 was literally written under the hood by the bus company I bought it from.

Any advice is appreciated!
Aaron
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post #2 of 7 Old 12-06-2019, 05:44 PM
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The oil pressure "gauge" is actually just a glorified indicator light
it is operated by a switch that closes at 7psi, located next to the filter housing
the "gauge" only can goto half way or none

I would get the adapter fitting for the port on the oil cooler housing and add a real gauge
I think it is 12mm threads -- need to verify

You didn't say how many miles on the engine
Worn bearings, worn LPOP, or a leak in the HPOP system will cause low pressure at idle
PS: a wrong oil filter/cap combination will also do that -- the housing drain valve is held closed by the filter

sometimes the pressure regulator will get junk lodged in it -- course you have to find where the junk came from

In my defense, I was unsupervised
.
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post #3 of 7 Old 12-06-2019, 05:51 PM Thread Starter
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Thanks for your response. The bus has 112k miles on it. I assumed that the appropriate filter was used because I had the oil changed at a Ford dealer... But I guess I shouldn't assume that.
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post #4 of 7 Old 12-06-2019, 05:56 PM Thread Starter
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If it were a more significant issue like worn bearings, wouldn't the symptoms have shown prior to the oil change? I drove the bus a number of times and on longer trips than the recent ones where I had problems.

I knew that the oil pressure gauge is a false gauge and is either good or bad. I'll investigate getting a real gauge hooked up to the oil cooler.

Aaron
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post #5 of 7 Old 12-06-2019, 06:18 PM
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Could be the sender also, just a clicker switch, but the diaphragm could be ruptured and giving a false pressure

And yeah, post #3, look at that filter to see if it presses the housing drain -- maybe check the seal on the plunger

In my defense, I was unsupervised
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General note:
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post #6 of 7 Old 12-06-2019, 07:10 PM Thread Starter
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This is going to sound like a stupid question, so prepare yourself... In this 2008 bus I believe the oil filter is under the engine (unlike the normal on top of engine filter). Supposedly it has a drain plug incorporated into the cap so you can drain the housing prior to removing it.

Here comes the stupidity. The filter housing and drainback "feature" present in other 6.0l engines seems to be a simple gravity feed type system. So how does drainback happen in a housing that is upside down?

Any leads on where I might find a manual for this?
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post #7 of 7 Old 12-07-2019, 03:32 AM
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I got my manual on eBay. Your problem would be you have a 6.4 truck year with a 6.0 engine. Seems like Ford puts the left over early year parts in other than pick up models until the inventory is gone.

Not helpful I know. FWIW my paper 2005 workshop.manual only covers pick ups and not the E series van not the Excursion. Not a lot of differences, but they exist.

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