Cadillac Repair: 94 sts 4.9 northstar, rod bearings, rod bearing

Question

recently picked up a 94 sts and after a week it has a sound like a bent rod  clink clink clink.. I have had 2 places look at it and they say it is a connecting rod and bearing on the crank... is that typical of the 4.9 or should I be looking at the valves instead because I dont have a place to pull the motor and I am hoping they are trying to take me.. no one actually took the car apart or even put it on the computer .. and the diagnosis was almost instant.. What bothers me  is it starts fine has plenty of power but makes the noise .please help this lay man.. mark

Answer
Hi Mark,

     The 4.9L engine design doesn't have a problem with rod bearings going bad. However any engine if abused can damage the rod bearings by overrevving or if coolant gets in the oil and it isn't repaired in a timely manor.

     That said, the way you can tell a rod bearing is going bad is a double knock when the throttle is just opened from idle. It is best to do this at operateing temperature when the oil has thinned out. Basically you would move the throttle lever to aprox. 1200rpm from idle several times and each time a double knock will be heard comming from the lower part of the engine.

      Noises are really tough to diagnos in a forum such as this so since 2 shops say rod bearing take the car to the shop you trust and have them pull the oil pan for an inspection. Otherwise I would price out a new, rebuilt or used engine depending upon the condition of your car or just trade/sell it as is if the cost doesn't justify the repair. Bill