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98 Chevy k1500 oil pressure issues
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Bsmacks76
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Nov 24, 2011, 7:29 AM
Post #1 of 27
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98 Chevy k1500 oil pressure issues
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1998 Chevy k1500 w/ 95000 miles. 5.7l V8. After engine comes to temp I loose oil pressure when at low rpm or at a complete stop. I have replace oil pressure sending unit. Verified oil level. When transmission is in park the gauge will sit at 5-15 lbs, switch to drive and the check gauge light comes on until I engage the throttle and the pressure rises a tad. Had it scanned at the local place but no information. Have grounded the sensor directly to the block,turned ignition and the gauge does peg over 80. Only thing I have not tried as of yet is a mechanical guage in the port. Thanks in advance for any advice.
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Discretesignals
Ultimate Carjunky
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Nov 24, 2011, 8:11 AM
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Re: 98 Chevy k1500 oil pressure issues
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Hooking a mechanical gauge up and confirming an oil pressure problem is a good idea. Low/no oil pressure at idle with the oil warmed up either means you have a worn out oil pump or a bearing problem in the engine.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Tom Greenleaf
Ultimate Carjunky
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Nov 24, 2011, 8:19 AM
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Re: 98 Chevy k1500 oil pressure issues
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Doesn't sound good. Oil pressure would be normally lower at idle especially when warmed up but not that low.
Mechanical test would be a nice idea and test to prove it.
What oil are you using? Not just brand but viscosity rating.
Causes include but not limited to worn engine/bearings, sludged or plugged oil pick up screen, oil contaminated with gas so way too thin a maybe.
If it makes the dull knock at idle IMO it may be late for this engine. If so higher viscosity oil may buy some time,
T
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Bsmacks76
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Nov 24, 2011, 8:19 AM
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Re: 98 Chevy k1500 oil pressure issues
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If the oil pimp was worn would I be able to hear knocking on top of the engine?
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Tom Greenleaf
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Nov 24, 2011, 8:24 AM
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Re: 98 Chevy k1500 oil pressure issues
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Hmmm - IMO lower end bearing knock first for whatever reason oil pressure is low. Damage if so is nasty to fatal for engine.
DS is fast! A higher volume oil pump if all else is fair might help too if these are real readings,
T
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Bsmacks76
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Nov 24, 2011, 8:28 AM
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Re: 98 Chevy k1500 oil pressure issues
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Using 5w30 per recommendation. Previously used 10w. Have not flushed oil system as of yet. Switched to 5w after replacing intake gaskets due to coolant in the oil.
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Tom Greenleaf
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Nov 24, 2011, 8:38 AM
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Re: 98 Chevy k1500 oil pressure issues
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IMO - either oil should have been OK but if coolant found in oil who knows now what got plugged up? Hesitant to suggest an oil flush as it may thrown tons of junk at oil pick up. Rather see frequent oil changes and might be damage is done and not reversible?
T
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Bsmacks76
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Nov 24, 2011, 8:49 AM
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Re: 98 Chevy k1500 oil pressure issues
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Roger that, oil change not flush is what I meant to say. Will perform mechanical pressure test first, then change oil and test again. Will get back when I have more info. Thanks for all the advice, Happy Thanksgiving.
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re-tired
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Nov 24, 2011, 10:00 AM
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Re: 98 Chevy k1500 oil pressure issues
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A 350 of that age and mileage should handle straight 40w well . Unless you live in the land of snow 6 months of the year. But either way you just buying time. Chevys eng's with that mileage dont respond well to just rods and mains, they loose a lot of pressure at the cam bearings. IF you want tio keep the truck a reman long block is in your future. IMO
LIFE'S SHORT GO FISH
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Hammer Time
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Nov 24, 2011, 10:16 AM
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Re: 98 Chevy k1500 oil pressure issues
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A 350 of that age and mileage should handle straight 40w well .
I have to disagree with that one big time RT. This engine is not designed to use anything heavier than 10W30 and it will do serious damage on cold starts with heavy oil.
This is from Alldata
ENGINE OIL VISCOSITY
All Temperatures SAE 5W-30
Above 0°F (-18°C) SAE 10W-30 Using oils of any viscosity other than those viscosity's recommended could result in engine damage. When choosing an oil, consider the range of temperatures the vehicle will be operated in before the next oil change. Then, select the recommended oil viscosity.
The recommended oil viscosity for all vehicles when the temperature is above -18°C (0°F) is SAE 1OW-30.
Engine oil viscosity (thickness) has an effect on the fuel economy and the cold-weather operation (starting and oil flow). Lower viscosity engine oils can provide better fuel economy and cold-weather performance. However, higher temperature weather condition require higher viscosity engine oils for satisfactory lubrication. When the temperature will be very cold and never above 16°C (60°F), SAE 5W-30 should be used in all models.
In areas of the world other than North America, it may be difficult to find oils that display the API STARBURST symbol and that are labeled as meeting the GM4718M Specification.
If you cannot find API STARBURST displaying oils identified as meeting the GM4718M requirements, look for oils that meet the API Service SJ and ACEA A3-96 requirements.
The recommended SAE engine oil viscosity is 5W-30, however, additional engine oil viscosities meeting the API Service SJ and ACEA A3-96 requirements may be used in accordance with the temperature ranges as shown in figure 3.
NOTE: SAE 20W-50 or oils of other viscosity rating or quality designations are NOT recommended for use in any vehicles at any time.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Bsmacks76
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Nov 24, 2011, 11:03 AM
Post #11 of 27
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Re: 98 Chevy k1500 oil pressure issues
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Vehicle will not run with sensor unplugged. Is there another test port for oil or howmdo you get around the sensor. Will it run with the sensor plugged in just not in the port?
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re-tired
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Nov 24, 2011, 11:34 AM
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Re: 98 Chevy k1500 oil pressure issues
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WE are not talking about late model engines with warrenties. I was refering to areas that seldom get into 30,s . For zones below the rust belt a 10w40 is approved by API for older high mileage engines API/CF-2.In the case of an engine that is so loose that its making noises ,you can run a 5-30 or similar and let it hammer itself to death . OR ,move up the weight and by some time . IMO nuff said
LIFE'S SHORT GO FISH
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re-tired
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Nov 24, 2011, 12:37 PM
Post #14 of 27
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Re: 98 Chevy k1500 oil pressure issues
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well we agree to disagree. now about test lights.
LIFE'S SHORT GO FISH
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Hammer Time
Ultimate Carjunky
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Nov 24, 2011, 12:39 PM
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Re: 98 Chevy k1500 oil pressure issues
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It's not just my opinion. That's a manufacturer requirement.
Test lights are great. It's just the way some people use them that is a problem.............LOL
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Bsmacks76
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Nov 24, 2011, 6:57 PM
Post #16 of 27
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Re: 98 Chevy k1500 oil pressure issues
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So is there a way to plug in a mechanical gauge to read and have the sensor plugged in at the same time?
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Hammer Time
Ultimate Carjunky
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Nov 24, 2011, 7:15 PM
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Re: 98 Chevy k1500 oil pressure issues
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I'm not aware of it having a low pressure shut off. That's pretty much not possible because it never has pressure during start up. It is wired as a redundant fuel pump power supply so if you have a bad fuel pump relay, it will rely on the oil pressure switch to run.
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Bsmacks76
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Nov 24, 2011, 7:32 PM
Post #18 of 27
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Re: 98 Chevy k1500 oil pressure issues
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Fuel pump replaced in spring. So,in theory leave sensor plugged in but not in port and place mechanical gauge in port?
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Hammer Time
Ultimate Carjunky
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Nov 24, 2011, 7:40 PM
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Re: 98 Chevy k1500 oil pressure issues
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Unplugging it should make no difference at all. It's not reading pressure if it's plugged in anyway.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Bsmacks76
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Nov 24, 2011, 7:48 PM
Post #20 of 27
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Re: 98 Chevy k1500 oil pressure issues
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Okay, tried it this afternoon with sensor unplugged and it died after a few seconds. The relay part makes sense now. Did also find the ground from block to frame not conected at all.
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Hammer Time
Ultimate Carjunky
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Nov 24, 2011, 7:56 PM
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Re: 98 Chevy k1500 oil pressure issues
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Try jumping out the fuel pump relay by jumping pins 87 to 30 or just applying power to the prime connector..
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Bsmacks76
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Nov 24, 2011, 7:58 PM
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Re: 98 Chevy k1500 oil pressure issues
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Ya lost me on that one.
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Hammer Time
Ultimate Carjunky
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Nov 24, 2011, 8:03 PM
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Re: 98 Chevy k1500 oil pressure issues
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Maybe it's time to take it to a reputable shop for diagnosis.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Bsmacks76
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Nov 24, 2011, 8:04 PM
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Re: 98 Chevy k1500 oil pressure issues
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Yep. Thanks for the help.
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gbrosch
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Jan 2, 2012, 4:56 PM
Post #25 of 27
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Re: 98 Chevy k1500 oil pressure issues
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did you solve your low oil pressure problem? cause i have the exact same truck and it did it to me to. its the oil pump. i replaced mine and the problem went away.
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