I have a 1998 GMC Sierra. v-6 vortex. I get a real loud noise which seems to come from the a/c come from the compressor. It doesn't change when the a/c is on or off. The sound sounds like bearings on a boat trailer going out. This is an old work truck and I don't want to sink alot of money into it. What will happen if I just let it go on making the noise?

• Chevrolet C/K( k= 4wd) pickups.
• Chevrolet Silverado?
• Chevrolet Suburban(no)

USA car or not in N.America at all??????????
which one is it, Sierra is a sub model class not a truck actual.
I will guess C1500????? pickup truck? 2wd./
scan the PCM yet, using any OBD2 scan tool for DTC errors?


it is not bad, 99% are not bad so no need to find it.
why not post a problem and not hunts.
the service manual on the car and google searches ends the hunt.



the knock sensor allows the PCM to tune spark timing to use poor grade fuel. and not allow knock and ping. it does that endlessly.
but if say you heard the engine ping, that is a dead EGR

PING (knock or detonation) is caused by poor fuel and crazy high combustion temps.
The EGR system cures it. (and must be cleaned or fails)
some trucks run spec cams that stop PING>
and some use those and a knock sensor..
it is a microphone ,sensor. and if engine bearings pound load

the KS1 sensor lies., to you. (and the PCM)
example rod knock or piston slap noises.


what truck is it,from USA 1998 list
1998 (sierra is a sub class not an actual truck) see?
Toggle C1500 PICKUP
Toggle C1500 SUBURBAN
Toggle C2500 PICKUP
Toggle C2500 SUBURBAN
Toggle C3500 PICKUP
Toggle FORWARD
Toggle JIMMY
Toggle K1500 PICKUP
Toggle K1500 SUBURBAN
Toggle K2500 PICKUP
Toggle K2500 SUBURBAN
Toggle K3500
Toggle K3500 PICKUP
Toggle P3500
Toggle SAFARI
Toggle SAVANA 1500
Toggle SAVANA 2500
Toggle SAVANA 3500
Toggle SONOMA
Toggle T SERIES TRUCK
Toggle TOPKICK
Toggle YUKON
the knock sensor
looks like OIL sender, or desk knob round.
newer 4.3L has 1 KS1, and KS2 sensors one per bank.
1998 , it is one, sensor, rear left of distributor.
left means (USA drivers left side) perspectives.

first google hit found it.




dead egr , cleaned or replaced seen here


https://www.rockauto.com/en/catalog/gmc,1998,c1500+pickup,4.3l+v6,1304659,exhaust+&+emission,egr+valve,4968

The service and repair manual with diagram will provide you step by step to fix the problem easily and you will get the manual from the given link https://toolsnyou.com

Deanna, check to see if your A/C is in the on position, this could cause fan to run a lot. If this is not the case, take truck in for diagnoses at a good shop, could be a faulty heat/fan sensor or sticking relay. Check the attached links,instruction and guides, Good luck
"I hope this helped you out, if so let me know by pressing the helpful button. Check out some of my other posts if you need more tips and info."
Diagnose Engine Cooling Fan Relay Problem
2007 Chevy Silverado Fans Always Run Engine Cooling Problem 2007
cooling fan running all the time

check the sway bar end links they break off

that would be your u joints. probably front

nothing changed. There should be a normal looking bleeder screw on all the calipers/wheel cylinders.

Is it possible for you to post a photo of what you are looking at?

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

when was the last time you've checked the fluid level in the front differential?
Try this, quickly. these gears don't last long when the fluid level is low, and it's a real big job to replace the gears/differential housing.

I hope this helps, ask if you need anything.

The noise is your A/C pump clutch bearings. You can have the clutch replaced or possibly buy the belt for the truck that didn't come with A/C and it may fit without routing it around the pump pulley. If you leave it, the bearing will eventually fail and the belt will shred. You'll lose power stearing, cooling and charging...not good.

Cylinder Head Torque
1st - step, all bolts; - 22 ft./lbs. 2nd - step, long bolts; - turn 75 degrees 3rd - step, medium bolts; - turn 65 degrees 4th - step, short bolts; - turn 55 degrees

Often the closer they get to giving up, the noisier they get. Changing filter might help. I've seen them last 6 mos, or 6 days, but clean filter will easy the work load on it, and may or may not buy you some extra time. If it does go after filter, your not out anything because a new filter should accompany a new pump anyway.