Mechanics

LOSING COOLANT & NOW A KNOCKING

1995 Pontiac Grand Prix

Engine Mechanical problem
1995 Pontiac Grand Prix 6 cyl Front Wheel Drive Automatic

Dear Sir, My sisiters pontiac has the 3100 v6. She has been losing coolant and had no heat. I replaced the thermostat because when you shut the car down you could hear the water boiling in the rad. Also the relays went bad so I fixed that. The temp never got over 210-212. After the therostat replacement we have heat and no boiling but still losing some water however not as much. Now we had been driving it for about 3-4 days to see if that would take care of it and, last night while driving at @ 20 mph taking it easy a loud knock started but it dosent sound like a rod or a like sound it is intermeinent(excuse the spelling) it appears to be in the top of the motor, where the V6-3100 is writin on the aluminum cover above the intake manifold. Also after replacing the thermostat the same type knocking started got really loud and then stopped all in about 45 secs or so. I thought then it was the water pump knocking, I dont know maybe because of an air lock, It stopped after I added water to top it off. Maybe they are seperate issues but I dont think so. Please any help would be great we cant afford to buy anything but I can repair it or we have a mechanic ay church that will do it but hes a shade tree his self. Thanks in advance and Merry Christmas!
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Kkaj
December 8, 2008.




Ok have you had a leak down test done to see if it is leaking from the intake manifold gasket or if the plenum (upper intake) has a crack and it is leaking? As for the knock I would pull the valve cover and see if there are any bent pushrods or a bad lifter.

Racefan966
Dec 8, 2008.
If the upper intake (penum) is leaking would that cause the overheating? The water in the oil etc. If not then what would a crack cause it to act like? Also I havent done a leak down test on it. All the rockers and springs etc. On the front side are ok. When using an extension to listen by placing it on the upper intake it sounds like the nosie is @ the middle back side of the plenum. I guess the sound is transfering from the lifter I think but I sure hope its the push rod. Am I on the right track? Any other suggestions? Many thanks! We are disabled and broke so this means alot!
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Tiny
Kkaj
Dec 9, 2008.
No you wouldn't have water in the oil if the intake it leaking into the intake runner. If the upper intake is cracked it would also follow the air flow into the cylinder and not get into the oil. Those upper plenums like to crack behind the throttle body. As for the engine noise without being there to hear it I would say with what you discribed yes you are in the right direction. I would also use the stethascope to listen to the injectors and make sure one of them isn't being extra loud before I started tearing the back side apart. Let me know what you find and we go from there. Thanks again.

Racefan966
Dec 9, 2008.

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