Under car rattle when cold

[jim83]

83 cutlass y code engine- first start cold has a pronounced tapping coming from under the car varies with engine speed - when warmed up- gone- seemed to have coincided with a recent starter r&r .shouldn't be, but?????
no hoist, so looking for ideas- any guesses?? Does it while stationary or driving - matches engine speed

 

[fleming442]

Is it a rattle or a tap? My first interwebz guess would be exhaust leak.

 

[pontiacgp]

is the cat still the original?...and do you still have the EFE valve?

 

[ostrich]

Rattle, heat shield somewhere?

 

[jim83]

Rattle, heat shield somewhere?

Not exhaust rattle , cat ok seems line it's coming from the rear of the motor- tapping sound not a rattle completely goes away when up to temp - thanks- keep them coming

 

[jim83]

is the cat still the original?...and do you still have the EFE valve?

Where is the efe valve physical;ly located? And would it cause a loud tapping sound when engine is cold? onnce up to temp 180 or so no noise- thanks

 

[jim83]

Rattle, heat shield somewhere?

it's a tapping sound not a rattle- coming from rear of engine - engine is fine- instant oil pressure etc

 

[blk7gxn]

Is it a rattle or a tap? My first interwebz guess would be exhaust leak.

I agree with your assessment!! Every 307 I have seen sooner or later acquires some sort of exhaust leak that sounds like a sharp tapping sound in the engine bay, and when the engine warms up,. everything expands and seals back up.

 

[jim83]

Could you please explain the operation of the efe valve- it's new to me. Noise came on suddenly- the joys of an old car. Been in the family since new now has 70k on it & it's a california car rust free, so worth maintaining. Thanks again- this forum is great, don't really want to pay someone to learn - most "techs" don't know a thing about anything this old

 

[blk7gxn]

Could you please explain the operation of the efe valve- it's new to me. Noise came on suddenly- the joys of an old car. Been in the family since new now has 70k on it & it's a california car rust free, so worth maintaining. Thanks again- this forum is great, don't really want to pay someone to learn - most "techs" don't know a thing about anything this old

The efe/heat riser valve ( Early Fuel Evaporation) is vacuum operated by a intake thermal/ vacuum switch. The theory behind this is the valve integrated into the passenger side, rear of the manifold, ahead of your exhaust, is when the engine is cold, ( the valve is shut) it forces exhaust gasses back into the engine to "warm it up quicker" when the engine warms up the thermal vacuum switch allows vacuum to pull the EFE open for normal operation...HOWEVER, after years of heat, they tend to fail, and can cause issues, stuck open, stuck shut, RATTLE....ill ad a picture so you know what to look for