My mom has a 1997 blazer. She recently called me asking if i could replace her timing chain because her mechanic told her it needs one. She said when she starts it up its makes a noise then goes away as it warms up and when she shuts it off it makes a "rattle" noise. Her mechanic said that as long as she is nice to the truck and lets it warm up she wont need to replace the timing chain for a couple of years. Now call me crazy but it sounds to me as if he is saying two different things. Call me bias but if i noticed my timing chain/belt was bad i would replace it immediately preventing the obvious failure of the motor. I don't personally own a place, and i come from the Honda world but this just seems odd to me. I have heard that if the cam gear is messed up on a honda it can make noise but it just seems odd.

I guess my question for you guys is does this sound like a timing chain problem? Or does it sound as if it would be something else? I was also wondering if there are any good thread on how to change it if it does so in fact need to be changed. I quickly skimmed through to try and find something but any help would be much appreciated.

I thank you guys in advance for any help that you guys can give me. I am going to look at it later this week but again im not used to the v6 set up so i wasnt sure how labor intensive this could honestly be.

Thanks guys!

 

Its possible. A lot of fords make that noise. Not 100% sure about the 4.3s as I've never replaced one but a lot of newer cars have like plastic slides and guides that the timing chain rides on and when the chain starts to get slack in it it will bang around. And with the fords it would usually just do it for like the first 5 seconds after start up

 

Timing chain issues are almost non-existant on 4.3's and they are not equipped with chain tensioners. I service a fleet of 4.3's and several have over 250K, one has over 375K. They all have the original engines, and no chain issues.

4.3L's are known to have piston slap on a cold start up. In the early stages it happens on the first start of the day when ambient temp is ~40 degrees or less, and it usually lasts less than 10 seconds. It's caused by a lack of oil on the lower cylinder wall causing the piston skirt to "slap" or "scuff" the wall as the piston rises the first few degrees of crankshaft rotation after BDC, (bottom dead center). The sound is similar to a worn rod bearing, but it's more of a muffled knock rather than a "hammering" sound. GM's "fix" is to bore the cylinders, and replace the pistons and rings, but there's no guarantee it won't happen again. Ford had the same problem with the 2.3L in the early 80's. Their permanent fix was installing connecting rods with oiling holes that squirted oil on the cylinder walls.

You can check timing chain slack very easily: Remove the distributor cap and manually rotate the crankshaft back and forth until the distributor rotor just begins to move in each direction. Measure the movement in degrees on the vibration dampener. More than ~10 degrees is excessive.

Not sure on the rattle when you shut it off.... possibly a broken substrate in the catalytic converter, or maybe a loose heat shield???

 

Thank you for all of that. I'm sort of thinking that shes actually hearing something else and this mechanic is a crook trying to get money. Ill take a look at it tomorrow and let you guys know what i find.

 

Have to agree with Hook-timing chain issues have never been an issue with the 4.3-yes earlier small blocks had stretch and plastic cog problems-I've never experienced this with these motors! This is not to say that they CANT fail either! Too many variables involved.