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Gary
Gary, ASE Certified Technician
Category: GMC
Satisfied Customers: 16746
Experience:  GCM master tech over 25 years
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I have a 2007 GMC Yukon Denali with low oil pressure at an

Customer Question

I have a 2007 GMC Yukon Denali with low oil pressure at an idle. We just put in a new oil pump and pressure still drops to zero on idle. Truck runs perfect driving with Rpms up but when slowing down or stopping at idle, drops to zero buzzer comes on and engine begins to tick. Press foot on gas and start driving again- engine noise goes away and engine sounds and runs like.
Submitted: 2 years ago.
Category: GMC
Expert:  Gary replied 2 years ago.
Welcome! My name is ***** ***** I will do my best to assist you with this problem.
is this a 4X4 ? a 5.3 engine ?
Customer: replied 2 years ago.
AWD 2007 Yukon Denali XL 6.2
Expert:  Gary replied 2 years ago.
did replacing the oil pump make it any better or worse ?
Customer: replied 2 years ago.
A little worse. Before I changed it, on idle it would hold just above the red line which I thought was dangerously low. And occasionally it would drop to red which let me know I needed to do something. It dropped to red with the buzzer coming on about 4 times but not consistently as it is doing now.
Expert:  Gary replied 2 years ago.
Thank you for that information
since the oil pump made no difference in the oil pressure and it will tick when it reads low or no oil pressure this engine internally would actually have low or no oil pressure when it acts up v/s no ticking and the oil pressure showing low but actually it has good oil pressure and just the oil sensor would be bad
at this point the issue will be a bottom end main or rod bearing issue with one or a few of the bearings that have opened up spec which will cause this issue especially after it warms up at idle
the next step to take is to remove the oil pan and plastic gauge all the bearings and see if any are out of spec if any are and the crank shaft surface is good then replacing the bearings would correct this issue
Customer: replied 2 years ago.
The mechanic wants to change the oil pressure gauge. What are your thoughts on that. Does the oil send unit just read pressure or does it actually control pressure? Is this a waste of time and money based upon the facts of what I explained?
Expert:  Gary replied 2 years ago.
the oil sensor just reads the pressure
since its ticking and reading low the odds are the oil pressure is in fact low
if there was no noises at all then an oil sensor would usually correct this kind of issue of the sensor bad and reading the oil pressure wrong
the oil pressure is regulated by the oil pump itself and the faster the pump spins the more pressure it makes
Customer: replied 2 years ago.
As for the bearing job, would you recommend just swapping the engine
Or do you think changing the bearings would be easier? Never had bearings changed before. Have no clue how comprehensive or expensive that could be or the level of expertise needed to do so.
Expert:  Gary replied 2 years ago.
if you love this truck and plan on keeping it for a long time it may be best to change the engine as it will be worth the warranty that comes with the new or rebuilt engine you buy
but if the cranks shaft is not damaged it would be a bit cheaper to fix this engine
but it really comes down to what kind of warranty you want on the engine so to say as fixing this engine will have a 12 month 12K warranty and most new or rebuilt engines come with a 5 year 50K warranty
Customer: replied 2 years ago.
Another tech mentioned something about a pickup tube o ring could possibly cause this issue. What are your thoughts on that?
Expert:  Gary replied 2 years ago.
the o-ring would have been changed when the oil pump was replaced and the pick up screen would have been removed also and cleaned and since the oil pan was off we are assuming the inside of the oil pan was cleaned since it was off

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