Remanuf. 4.7L Low oil pressure at low idle - JeepForum.com
 
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post #1 of 6 Old 07-21-2019, 11:31 AM Thread Starter
RABlvmy88
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Remanuf. 4.7L Low oil pressure at low idle

I so loved my 2007 JGC 4.7L limited that when the engine went, I decided to have a re-manufactured engine installed. I picked a small company that only does engines. Now I am wondering if I did the right thing.

It has all of 300 miles on the new engine, and, only after driving for 30+ minutes, and after coming to a stop, where engine rpm is at 550 or 650 rpm, the low oil pressure light comes on.

It never happens around town when I am local, it takes a good 30 minutes of run time to make it happen. There is no oil leaking that I can tell. The guy who installed it is asking me to drive it for a few more days.

I had a dealer mechanic look at it, he said the oil pan (new when the engine was swapped), had a dent in it, and that this might restrict oil flow. I took a look myself, and it is true that it is slightly dented (probably bumped it when the installed the engine, but the dent is very small, on the bottom surface and only dented the front piece maybe 1/4 inch? It seems hardly worth worrying about. He says it dented right where the oil pickup is. I just dont buy it.

I changed the oil today and the oil filter, just in case the oil filter got plugged with small metal filings. They recommended I do this at 500 miles anyway. About to do a trip home from camp. So will see how it does on the way home.

Any thoughts, Ideas for me? Not sure why Jeep did not put an oil pressure gauge on this vehicle, but they didn't.

What to do next?

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post #2 of 6 Old 07-22-2019, 04:15 AM
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Manufacturers stopped installing oil pressure gauges because too many people didn't understand that it's supposed to rise and fall with RPM and would subsequently complain about it.

You've made the supplier aware of the issue and they haven't told you to pound sand yet, so that's good. Play nice but don't be a push over and have hope that they'll make right.

Fwiw, if an oil filter becomes plugged it will simply bypass and stop filtering. It won't block the system.

If all else fails, run a heavier oil and see if that brings the pressure up.

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post #3 of 6 Old 07-22-2019, 11:23 AM Thread Starter
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So far so good. I called the shop that did the work and they said they would call the company that supplied the re manufactured motor today. They reassured me that the work and the motor are guaranteed, the only challenge is the time and hassle of going through the process. He assumes they are going to need to replace the oil pressure sensor/ sending unit and prove that this is not the cause, but I doubt that is the problem. Seems like if it were, there would be low pressure readings at all temps.



On the oil front, I thought about running a heavier oil, but if the motor has issues its best to get those identified and fixed. That being said, my first 4.7l ran 10w-30. I think that was a 1999. But as gas mileage became more of an issue I think they shifted to 5w-20 to get better fuel economy. So the real question is this. Fuel efficiency aside, does a 4.7 prefer, or was it originally designed for a heavier oil? Always wondered about this.



Thanks for the response.
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post #4 of 6 Old 07-22-2019, 12:29 PM
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The oil pressure sender is super common on the 4.7l engine to fail. Sometimes it is just bad all the time, sometimes it acts like it is reading low. Most chrysler sensors use pressure differential from the atmosphere on the connector side and oil pressure on the other side. When one starts leaking into the connector and plugging up the ability for the air to move freely on the connector side, you trigger the light.

If they swapped your oil pressure sender off your bad motor, there is a possibility this is the problem. The most important thing is to verify the oil pressure is low with a gauge.

One suggestion I would have is to listen to the engine. Engines without oil pressure, especially those with hydraulic lash adjusters get pretty noisy with low-no oil pressure. If it sounds great despite the light being on, that would have me leaning towards the sender failure. NOT 100% though, the pressure test will tell you for sure.

The driving it may be REALLY bad advise. The company that provided the engine may void a warranty claim if the new motor is destroyed (at least put you through the ringer before authorizing the warranty). IF there is an oil pressure problem, the company will want the core back to re-rebuild it. If you drive on it till it blows up KNOWING that the red oil light that told you to stop driving came on, they wont like that, now they potentially don't have a core. the 4.7l is not the easiest to test but its also not super hard (right by the oil filter). Worth the time / money to do the test!

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post #5 of 6 Old 07-22-2019, 03:41 PM Thread Starter
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Thanks, good advice, I will get the sensor/sender tested. I had read on some posts that this is rarely the problem, but it is a relatively cheap thing to test and fix. I will also listen to the engine, the shop asked me this question today. Did I hear noise, tapping, when idling with the low oil pressure light on. I did not get out of the vehicle to listen, but it sure sounds like it runs well and runs quiet. But I will double check this too.



I wondered if just driving it until it failed might be a faster way to get it fixed/replaced, but I did not want to do that just in case it was something that could be fixed. I only have about 400 miles on it since the rebuild, and the amount of time the low oil light has been on while the engine is running is pretty small. Did not want to damage a motor that I might end up owning if it was a fixable problem with out getting a new engine. Thanks!
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post #6 of 6 Old 07-22-2019, 04:48 PM
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Quote:
Originally Posted by RABlvmy88 View Post
Thanks, good advice, I will get the sensor/sender tested. I had read on some posts that this is rarely the problem, but it is a relatively cheap thing to test and fix. I will also listen to the engine, the shop asked me this question today. Did I hear noise, tapping, when idling with the low oil pressure light on. I did not get out of the vehicle to listen, but it sure sounds like it runs well and runs quiet. But I will double check this too.



I wondered if just driving it until it failed might be a faster way to get it fixed/replaced, but I did not want to do that just in case it was something that could be fixed. I only have about 400 miles on it since the rebuild, and the amount of time the low oil light has been on while the engine is running is pretty small. Did not want to damage a motor that I might end up owning if it was a fixable problem with out getting a new engine. Thanks!

Anything is possible on a fresh rebuild. The pressure relief valve could be sticking open, there could be a wrong main bearing installed that is letting oil puke out. It could be a bad sender or wiring. It could be so many things. It would be better to verify and fix something small on the outside or even on the inside dependent on what it is, than to wait for a new engine to ship and wait for it to be installed.

You are on the right track, verify oil pressure, if its good, throw a new sender in it, clean the connector out very well with brake clean and viola.

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