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Help LOST OIL PRESSURE on my 4.7

#1 Guest_chomot_*

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Posted 03 January 2007 - 08:06 PM

If you were a registered user, you would not be seeing this!

2000 JGC WJ with the 4.7 and 90 k miles, I have used only synthetic oil all its life since I bought it new. Oil pressure is normally at 50 PSI and has been for years. Last week when I was on a road trip for the holidays I was thinking to myself how smooth and well the engine was running, looked over all the gages and was happy that this vehical had had minimal problems.

I guess I thought to soon as yesterday while stopped at a light the check gages warning came one and I about had a heart attack when I saw the oil pressure at zero. I crept over to the side of the road and saw that the pressure came back up to 20 with a little throttle. I listened to the engine and did not hear any rattling etc, checked the oil, still full and clean looking on the stick.

So I nursed home the final two miles during witch time I figured the oil filter had collapsed or something, changed the filter and the pressure came back to a steady 40. I cut open the filter and only noted some black particles in the bottom but could not tell if there was enough dirt etc to cause the filter to bypass or not. I did not see any metal or other debris in the filter paper either.

Today I drove it to work and back and the pressure stayed at 40 all the way there and back until I was about home again, and at the same light, the check gages warning came on again. (I have to find a new route) So I nursed it home again and now I am at a loss for what to do next.

Do these 4.7s oil pumps have a history of failing? If so how hard is it to replace as a DIY? Can the pan be dropped without having to lift the engine?

Thanks for the life saving help
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#2 User is offline   j12l 

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Posted 03 January 2007 - 10:30 PM

First thing I would do is change the oil pressure sensor and put on a oil gauge on to see if there is a oil pressure problem.
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#3 User is offline   JCWCuda 

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Posted 08 January 2007 - 02:52 PM

View Postj12l, on Jan 3 2007, 10:30 PM, said:

First thing I would do is change the oil pressure sensor and put on a oil gauge on to see if there is a oil pressure problem.

I Agree , but i also know 4.7 has a history of a sludguing problem which could also cause your condition
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#4 Guest_chomot_*

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Posted 09 January 2007 - 10:05 PM

Yep that was it, I change the oil pressure sending unit out this weekend and now it is back to normal. The gasket inside the sensor had leaked allowing oil to get into the electronics side causing erratic operaton. Once I pulled the wireing off of it oil started dripping out so I knew I was onto something then.

Thanks for the help
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#5 User is offline   VNT 

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Posted 10 January 2007 - 03:07 PM

please elaborate, assume your referring to the milky oil cap issue. fix is a baffle.

The 4.7 unlike some toyota engines does not sludge.

View PostJCWCuda, on Jan 8 2007, 02:52 PM, said:

I Agree , but i also know 4.7 has a history of a sludguing problem which could also cause your condition

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#6 User is offline   jabroni 

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Posted 15 January 2007 - 12:23 PM

I had the same problem a few years ago on my 98 Grand Cherokee Laredo. My oil pressure sending unit went bad and the oil pressure dropped to zero while idling in traffic. On the 4.0 I6, the OPSU is located directly next to the oil filter. Over some time I guess the mechanic I used to go to must have hit it and caused it to leak. I replaced it myself and problem solved. From then on I did my own oil changes. Part was less than $30 at the dealer and took just 10 minutes to replace.
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#7 User is offline   spidey69 

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Posted 12 August 2007 - 09:49 AM

If you were a registered user, you would not be seeing this!

I have a '96 GC with similar problems. It started showing up intermittently 18 months ago. It was occuring more regularly this summer and I was preparing for an oil pump change.

Anyways, I found this discussion and changed the oil pressure sending unit as discussed. Problem solved.

thanks
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#8 User is offline   Nick512 

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Posted 14 August 2007 - 10:50 AM

View Postspidey69, on Aug 12 2007, 09:49 AM, said:

I have a '96 GC with similar problems. It started showing up intermittently 18 months ago. It was occuring more regularly this summer and I was preparing for an oil pump change.

Anyways, I found this discussion and changed the oil pressure sending unit as discussed. Problem solved.

thanks



Sludging is not likely especially when running a synthetic with that motor, I'm glad to see that you have solved the problem as the sending unit failure is all to common. Even my '94 had the same problem, and I to responded with a near heart attack!
Just curious as to what your oil change intervals are, my neighbor runs synthetic oil at 8,000 miles intervals and currently has 95K on the clock. A look under the valve covers shows a clean motor.
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#9 User is offline   spidey69 

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Posted 15 August 2007 - 08:47 PM

View PostNick512, on Aug 14 2007, 07:50 AM, said:

Sludging is not likely especially when running a synthetic with that motor, I'm glad to see that you have solved the problem as the sending unit failure is all to common. Even my '94 had the same problem, and I to responded with a near heart attack!
Just curious as to what your oil change intervals are, my neighbor runs synthetic oil at 8,000 miles intervals and currently has 95K on the clock. A look under the valve covers shows a clean motor.

I was running conventional oil and changing at 3,000 to 4,000 miles. I switched to synthetic last oil change. I have not seen any issues as of yet with the 'late in life' switch.
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