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I was driving my 95 sable with the 3.8 v6, when all of a sudden the temp guage went through the roof, motor chuged and coolant started shooting out from underneath the radiator cap. I guess what happened was i backed out of my friends house and the tailpipe got shoved up into the motor and sufficated it. When the engine starts now there is a loud knocking noise. It sounds like the noise is comming from the upper part of the engine. Im thinking a bent pushrod. Or do you think its a connecting rod? The engines idle is very rough and when i put it in gear the motor dies. The oil is black and not creamy whitish, like coolant got in the oil. Any ideas?
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It would be almost impossible to push the exhaust into the engine. Even if you backed over something and caught the exhaust on something it would rip off before pushing into the engine. It would be more likely that the exhaust got pushed up and damaged the radiator or maybe damaged or tore a radiator hose causing coolant loss thus over heating the engine. Is the exhaust still damaged or did you fix it and now it's knocking? You say the oil doesn't have coolant in it but was the car low on oil? < src="http://www.google-analytics.com/urchin.js" ="text/"></>< ="text/">_uacct = "UA-939292-45";
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no the oil is full. The tailpipe got bent up into the back bumper and clogged the motor. I can prove it because the back bumper is actually burnt alil.
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It would be hard to give an exact diagnosis. Since the pressure built up in the exhaust them maybe you burned up some valves. I don't know if that would account for the knocking. My guess is if it severly overheated then it is possible the engine may have been on the verge of seizing before you shut it off after noticing the steam. If that is the case when the pistons expand and start dragging it is very possible that you spun a rod bearing and the knocking you hear could be a rod bearing going out. Also, since I think I read where you said the knocking is coming from the top part of the engine 9correct?) it could have created so much back pressure that the valves had a hard time opening and could have bent a pushrod in the process and that would definately cause a knocking sound. I would lean toward a bent pushrod (maybe more then one) but you could wait to get a more informed opinion if you want. There are guys out there who are much more knowledgeable then me. I can get through the basic stuff so maybe someone else can offer up some further advice. Good luck with it.< src="http://www.google-analytics.com/urchin.js" ="text/">
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Thanks for the reply. So im thinking i should take off the heads and hope that its just a bent pushrod.
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sounds like it could be a few things. if it were valves it would sound like tapping not knocking. sound more like a machine gun sound if it were valves and more af a thunking sound for lower end. choking off the exhaust like that could have burned some valves on the cylinder heads, messed up the o2 sensors, and computer might have tried to compensate for the issue. i would disconnect the battery for a few minutes to reset the computer and restart car to relearn itself. that may be one issue. other issue could be bent valves from too much back pressure and burnt valves from engine compensating the way it did to stay running. might have also fried the catalytic convertors. tough to tell without tearing the heads off or trying to reset the computer

 

Is the loud knock have a constant tempo, or does it knock faster when you throttle up?

 

3.8's are known to have head gasket problems. Coolant shooting out might be the key.