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1979 620 making rattle on acceleration and under load


eekpdx

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Help! My 1979 kingcab is making a crazy rattle sound when I am switching gears or accelerating up a hill or with a load. It started after my mechanic replaced all of my belts. At first it was only happening when shifting between 2nd and 3rd and accelerating but now it does it even when I am not shifting. This isn't an all the time sound and it isn't a ping. It sounds more like ice in a blender or something.

I'm not sure where to begin or what could be causing this.. Also the car seems to be losing power when this is happening. Any ideas help! Thanks!

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Keep it simple. Apply the Law of Parsimony or Occam's razor. The simplest answer is usually the correct one. Take the belt off... if problem goes away... problem solved. If not come back.

 

Ask if he messed with the timing or adjusted anything else.

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  • 2 weeks later...

So I removed the belt to the smog pump and it still made the noise.  My timing hasn't been altered at all and my mechanic was sure it wasn't spark knock.  We replaced the alternator and now it seems to have cured the problem.  Fingers crossed!  Has anyone else had an issue like this with their alternators?  Thanks.

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So I removed the belt to the smog pump and it still made the noise. My timing hasn't been altered at all and my mechanic was sure it wasn't spark knock. We replaced the alternator and now it seems to have cured the problem. Fingers crossed! Has anyone else had an issue like this with their alternators? Thanks.

Come to think of it: Yes!
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Update: the alternator has been replaced and the noise is continuing.. arghh.

Damn! I thought we had it all figured out...Pull the valve cover and see if the rocker arms are in order: one may be displaced. I actually had this happen to me when I was driving one day, all of a sudden there was a tapping noise coming from the engine. So I pulled off to the side of the road popped the valve cover off and the rocker was off and the tappet was on the top of the head. I replaced everything and adjusted just that valve to get me home...then re-adjusted all of them. I got lucky: I had just put my tools back in the truck the day before!
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Help! My 1979 kingcab is making a crazy rattle sound when I am switching gears or accelerating up a hill or with a load. It started after my mechanic replaced all of my belts. At first it was only happening when shifting between 2nd and 3rd and accelerating but now it does it even when I am not shifting. This isn't an all the time sound and it isn't a ping. It sounds more like ice in a blender or something.

I'm not sure where to begin or what could be causing this.. Also the car seems to be losing power when this is happening. Any ideas help! Thanks!

 

 

Damn! I thought we had it all figured out...Pull the valve cover and see if the rocker arms are in order: one may be displaced. I actually had this happen to me when I was driving one day, all of a sudden there was a tapping noise coming from the engine. So I pulled off to the side of the road popped the valve cover off and the rocker was off and the tappet was on the top of the head. I replaced everything and adjusted just that valve to get me home...then re-adjusted all of them. I got lucky: I had just put my tools back in the truck the day before!

 

This is an intermittent sound usually more noticeable under load. A rocker arm that is off or just loose will make noise at all times.

 

 

As this started with the belts being replaced, start there for the answer.

 

Remove belts. With the engine cold take for a (very) short drive. Noise? or not.

 

Get the timing checked. I'm not convinced something was 'adjusted'.

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Pop the hood and start where the mechanic was...anything amiss? Fan shroud not properly reinstalled and hitting fan, fan bolts not tightened, etc...

 

 

This is an intermittent sound usually more noticeable under load. A rocker arm that is off or just loose will make noise at all times.

 

 

As this started with the belts being replaced, start there for the answer.

 

Remove belts. With the engine cold take for a (very) short drive. Noise? or not.

 

Get the timing checked. I'm not convinced something was 'adjusted'.

This was my initial thought too. However, it appears that something may have been overlooked in that regard...or has yet to be discovered in another area....

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Hey all, just an update.. the rattle went away.  I checked my timing and it was retarded quite a bit.  I adjusted it back and with the help of my mechanic we hoisted my truck up into the air and tighted and secured everything we could think of that could possibly rattle.  At this point I'm not super sure what did it.  I know advanced timing can cause spark knock but I wasn't sure if retarded timing would.  We knows.  Thanks for all your help!

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