I have a 2004 gmc sierra truck. after driving it for about 45 miles or so and it sits for awhile and then is started a cloud of blackish purple color smoke appears from the exhaust and the engine starts ticking. the ticking continues sometimes for up to 20 mins until its back to normal. when we use it in the city for short trips the noise and smoke do not happen. any ideas? we did get the exhaust manifold bolts replaced because some were broken and we thought the problem we fixed but the sound is still happening.

SOURCE: will start in the am,

there would be salt formation in the radiator which would turn the engine off and also may be the spark plug would be weak so try to clean the radiator and change the spark plug also.

Harvey N Tawatao

• 3854 Answers
• Posted on Jul 01, 2009

SOURCE: On a 1995 GMC sierra P/U 5.0L engine. The

NO , just replace the the gasket and exhaust bolt, just make sure you buy a stainless bolt, there not much more but they will out last the truck. and might as well replace the drive's side too since your working on it. Good luck and hope this helps. 

Harvey N Tawatao

• 3854 Answers
• Posted on Mar 15, 2010

SOURCE: Truck makes clicking noise just after starting up!

The smoke if it's white and goes away is just condensation in the exhaust system evaporating and the clicking noise could be the famous GM Piston slap. You can take it to the GM Dealer, there is an upgrade ECM program to help eliminate the piston slap noise when the engine is cold. You can also try adding some Lucas engine treatment to your engine oil to help with the piston slap problem. Start with that and hope it's not overdue for an oil change or low oil level in the engine.
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SOURCE: Plinking noise under GMC Sierra

Your muffler has a dent or slight imperfection in it. Whenever it heats up, is expands and pops the dent one direction, and once it cools enough, it pops back. This is completely harmless, and if you can live with the sound, won't hurt anything. (my '01 does it too)