Engine Knocking And/or Crankshaft Issue (99 Yukon)

[athenshome]

I am thinking about buying a 1999 Yukon Denali and will be going to see it tomorrow for the first time. The car has about 150k miles on it.

 

The owner has told me that it has a knocking sound and that he has not had it repaired or checked out, but that a mechanic friend told him it is the crankshaft?? I do not know any other details past that, but I would like to try and get an idea of what to look for when I go to see it.

 

Can anyone shed of light on possible causes for the engine knocking and does it make since that knocking could be because of a bad crankshaft? Also, if it is a bad crankshaft, how can I determine this without taking everything about? I know it's kind of a broad question, but any help that anyone could give would be much appreciated! Thanks in advance!

[Nytemare]

I am thinking about buying a 1999 Yukon Denali and will be going to see it tomorrow for the first time. The car has about 150k miles on it.

 

The owner has told me that it has a knocking sound and that he has not had it repaired or checked out, but that a mechanic friend told him it is the crankshaft?? I do not know any other details past that, but I would like to try and get an idea of what to look for when I go to see it.

 

Can anyone shed of light on possible causes for the engine knocking and does it make since that knocking could be because of a bad crankshaft? Also, if it is a bad crankshaft, how can I determine this without taking everything about? I know it's kind of a broad question, but any help that anyone could give would be much appreciated! Thanks in advance!

Bearings.

 

Either Mains or Rod bearings are what cause a n=knock in the crank area. To fix it, it usually means a full bottom end rebuild. its about 300 bucks to get the crank reground, 10-20 bucks a bearing, for a total of 240ish than labor and fluids...the engine has to come out, and if its apart for bottom end you may as well do the top too. your looking at about 2000-2500 in parts and machining for a full rebuild.\

 

But have it checked man....could be something stupid making the noise. I have heard bearings go in AC pumps and alternators that sounded exactly like rod knock.

[MYZ-71]

the 5.3`s are known to have piston slap on cold start-up`s, my 5.3 does it in the mornings even on warm spring mornings, it last for approx. 20 seconds and is fine after that, if it only makes noise briefly after inital start-up it just piston slap, don`t be concerned. If the noise seems to get worse as engine warms up then bearings are shot, the hotter the engine gets the worse the noise.