Engine Mechanical problem
1999 GMC Sierra V8 Four Wheel Drive Automatic 70000 miles
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Hello,

I am well aware of the dreaded Cold Start Knocking noises that is part of the GM trucks. However, I have noticed recently that the noise does not go away and is only evident under drive load and not while I rev the engine while it is in park. At the same time I have notoced like gurlgling/bubbling sound coming from under the dash where I am ssuming is the coolant flowing in the heater core. There are no collant leakes and the collan level has not dropped. Could the fluid noise and the knocking be related?


Any help would be appreciated.

Thanks in advance.