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Engine tapping noise under load and cold only

M

mojonba

New member
Hey guys,

I have been unable to find the source of a tapping noise that manifests itself the first 5-10 minutes while the car warms up and only when the engine is under load (not in park/coasting). Basically the engine sounds like a loud sewing machine. The noise only shows up when the car is under load and from 1000rpm onwards. The noise also goes away after 5=10 minutes when the car heats up. Noise came up after I replaced my heads due to an overheat. Noise comes from the rear bank of cylinders. Ive replaced the rear lifters thinking the noise was a collapsed lifter but it was not. My rockers and pushrods are tight and do not have any play. My main issue is that I am unable to replicate the noise in my garage because the noise is only present under load. I can put the car and drive and accelerate while braking but is a pain to do by myself. Any ideas.

Thanks.
 


my 03 gmc had the back manifold bolt fall out, it only had a slight leak at idle and went away after it was warmed up.

being that you just did the heads, maybe when the engine is cold try to tighten up the exhaust manifold bolts, one may have started to back out or was left snug not tight.
 


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