View Full Version : help with grand am gt Knock?
05-21-2010, 08:06 AM
hi i have a 1999 grand am gt and one day the oil pressure sending unit went out of it and blew all the oil outta the crankcase...no lights inside came on and i only pulled over when it started rapping.....i changed the unit and put new oil and filter and lucas in it and it still raps...it isnt a rod knock but my dad thinks its a wrist pin or possibly a cam bearing? and idk if they have a counter balance shaft or not...but it u mash the throttle it really isnt noticable...it is mostly like 2500 and up under no load.....any advice is to what it could be....im lookin to get a vid up soon so u guys can hear it...thanks
05-21-2010, 02:02 PM
it could be a conrod bearing. how long was it run after the unit blew out. any amount of time with no pressure can do serious damage. i suggest not driving on it until you can get a mechanics stethiscope to find out where the noise is coming from
05-21-2010, 05:13 PM
Yeah, don't drive it until you find out where the noise is. Probably will continue to do more damage. Could be a bad lifter, as a drop in oil pressure will certainly harm those. Could also be rod knock. Could be several things but it hard to say without seeing the car.
I just find it weird that the sensor blew out. That isn't something that I've ever heard of happening. Was it like extremely rusted or something and maybe the metal was weakened? I'm not surprised that the light didn't come on though. It's not actually a pressure sending unit. It's just a switch that turns on the dummy light on the dash. It's position is normally open, meaning the circuit isn't grounded, and if pressure drops down to 5psi I believe then the switch closes, grounding the circuit and turning on the light. If your sensor was completely off the engine, then it would have nothing to ground to, hence no oil light.
05-26-2010, 07:32 AM
the center of the unit is plastic and im pretty sure thats what blew out...ive noticed that the engine makes the sound when there is no load...and also it cuts the power wayy back when ur pullin a hill...just listening to it it sounds higher in the engine....and i never heard a lifter sound so bad...i mean its like a banging sound......
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