Author Topic: Engine knock  (Read 199 times)

Offline topp

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Engine knock
« on: January 08, 2019, 06:14:05 PM »
So I tightened the alternator belt on the k10 I recently picked up.  The belt was too loose, but not loose enough to squeal.  I tightened just enough to get about 1/2 to 3/4 inch deflection. Started her up, and get a knock. If I loosen it back, the knock is barely audible. It goes away when throttle is given, but comes back once the engine comes back to idle.

Rod knock/ bottom end??
'90 Suburban TBI 350

Offline bd

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Re: Engine knock
« Reply #1 on: January 08, 2019, 06:47:16 PM »
Can you tell from where the "knock" is emanating - top end, bottom end, crank pulley area or back of the engine?  Does the knock change with engine temperature?  Is the engine full of oil?  Check all of the peripheral mounting brackets and pulleys for looseness and cracks.  Check the harmonic balancer.  When you remove the alternator belt does the noise disappear?  How about when you remove the other belts, one at a time?
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline topp

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Re: Engine knock
« Reply #2 on: January 08, 2019, 09:38:41 PM »
I tried to upload a video. It's coming from the front of the crank. The pulley is tight but the entire assembly from balancer out wobbles when the belt is tightened to proper spec. It knocks or thuds at idle, the goes away when the throttle is goosed or held, and then comes back at idle.
'90 Suburban TBI 350

Offline bd

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Re: Engine knock
« Reply #3 on: January 08, 2019, 10:31:46 PM »
Is there an active oil leak from around the front crank seal?  Do you see a bolt head directly in the center of the crank pulley that retains the balancer to the snout of the crankshaft?  Some possibilities to check out: pulley could be broken; balancer may be coming apart or separating from the crankshaft; crankshaft could be broken.  You need to look very closely.
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline topp

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Re: Engine knock
« Reply #4 on: January 08, 2019, 11:58:09 PM »
There is a slight seepage from the front of the crank behind the balancer. Not enough to even drip. The pulley has the center bolt and the 3 other bolts. All are tight

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'90 Suburban TBI 350