1999 c3500 454 oil pressure issue

[evm]

I have a 1999 c3500 454.  The intake gasket started to leak a bit.  Btw this is the second intake gasket i have put on this truck since I owned it.  I think I might have put 15k miles on the truck before this one went.   

 

So I have been topping the radiator off every once in a while until I could get the truck into the shop for a new intake gasket.   Since then the truck developed an intermittent valve tap.  When the check engine light came on i stopped running the truck.  Just started the truck today and after idle for a 15 minutes the check gauge light came on and the oil pressure was really low, about 10 pounds.  What's going on here?  

[riverbanks]

Any milk color on dipstick or under oil cap?

Edited January 9, 2020 by riverbanks
Spelling

[evm]

No coolant in the oil...

[evm]

Is it bad lifters causing the low pressure?

[riverbanks]

Pressure is measured before cam&lifters, did you get the motor hot?heat thins oil,and what about a oil change

[evm]

Yes, i drive the truck for 15 - 20 minutes.  When I parked it and sat at idle for about 3 minutes,  thats when the check gauges light came on.

Oil was changed after that and still low pressure.  No contaminants in oil.

Edited January 13, 2020 by evm

[evm]

Here's my problem.  The mechanic that looked at it said to replace the oil pump, the engine would have to be "pulled" and there was no guarantee that replacing the oil pump would correct the low pressure issue or the valve tap.  He also said that replacing the oil pump would cost just about as much as a re built engine, around 8k.    

 

I really trusted this mechanic but I'm really scratching my head at his decision making process.  I know the oil pump is an 8 hour job.  Is that even close to 8k?  

 

This truck has run perfect for me until this valve tap.  I can't believe this motor is trash. 

 

The only thing I ever noticed with this truck was a weird starting issue that happend 2 or 3 times, over a 2 year period.  It sounded like a back fire inside the engine. 

[riverbanks]

From the mechanics side,reman. motor,it won't come back,oil pump, maybe,in the past,I have had to spray carb. clean thru the oil pan drain plug hole to the oil pump pickup screen,half clogged?so,oil change history? confident? quality oil,proper intervals?

[evm]

Not sure what you mean "reman motor, it won't come back, oil pump, maybe?

I have owned the truck for about 4 or 5 years.  I don't put but maybe 4-5k miles a year maximum, if even that.  I always change oil at 3k miles at jiffy lubes but I don't know if their oil is quality .  When I check the oil on the dipstick, even at 2500 miles in, it's pretty clean on the dipstick.

[riverbanks]

I meant,if he did a remanufactured or rebuilt motor, problem solved,oil pump change,iffy,could still rattle,I figured he was trying to steer you towards a problem free future

[davester]

Charging you $8k for doing the oil pump is a "I really don't want to do this job" quote...

[evm]

So he also says the oil pressure is read at many different points on this engine.  He ruled out sludge, there's no bearing noise, and he also says 10lbs pressure at the pump on this truck is ok.  He says he would replace all the lifters but no guarantee.   

[riverbanks]

There are places to read pressure,but we only have one,oil pressure sending unit, he's correct on the 10#,but,what about 5k more miles,will it drop further?and is it quiet above idle,more rpm,more volume?