Why is my radiator knocking
Foster03GA82
Member Posts: 3
Please help! I have an 03 Grand Am 3400 that continues to run hot. Over a period of time I have replaced the exhaust manifold gasket, head gasket, timing cover gasket, water pump, and now the thermostat, coolant sensor, and radiator. After replacing the radiator, coolant sensor, and thermostat, I refilled the system (it only allowed 1/2 gal of coolant. I started the car an let it come to operating temp. Still could not add more coolant. I opened the bleeder screw but it never ran coolant. After 45min I started to hear a knocking sound near or from the thermostat housing almost like the sound of positive pressure engaging then release pressure. After a few more minutes the temperature red lined and the car started to over flow from the reservoir. Also cycled the heat in and off once car came to temp. Why is this happening?
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Best Answer
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imidazol97
Member Posts: 27,596
I am guessing the knocking sound is the coolant overheating to a boil in the engine. Then the steam expands, cools a little and contracts.
If it were mine, I'd guess the thermostat was in backwards or was the wrong thermostat. It may need a bleed hole that some GM thermostats had for the air to bleed through. That was place high if the thermostat was not in a horizontal position so that the air could get through. There was a small steel ball held over the hold to prevent coolant from easily getting through and bypassing the thermostat when the valve was closed.
IF the lower return hose from the radiator is not soft and collapsing internally when the water pump sucks water from the radiator...
I would take the thermostat housing off and the thermostat out. Start pouring water into the radiator and be sure if flows out the thermostat opening. I'd probably crank the engine and see if the water pump pulls coolant from the radiator and spurts if out the thermosat opening.
I recall rare cases where a water pump was not the right model for certain applications and the impeller was being spun backwards resulting in little pumping for that application, even though the water pumps were physically able to fit. Since you had this trouble before the water pump was replaced, that is not as likely the problem.
To see if the thermostat is the problem...
I'd put the thermostat housing back in without the thermostat and try to fill the coolant system. Look online for a special procedure to get all the air out of that system when filling. In some cases, starting the engine would pull the coolant down in the radiator and more could be added. Then you continued adding until the radiator was full and put the cap back on the radiator while the engine was still running.
I'm sure you had the pellet end of the thermostat toward the engine.
And the more recent GM thermostats went into the groove in the middle of a single rubber ring that was crushed between the thermostat housing and its cap to seal. I recall a few cases where 3800 engines had the thermostat just laid in and the rubber seal put on. Coolant bypassed the rubber seal and gave varying coolant temps as the engine was running because the thermostat wasn't controlling most of the flow.
If you're able to get the engine filled and running without the thermostat, that should mean everything else is good. You can drive it to get the engine to slowly come up to temp depending on how cold it is where you are, but the engine will run cold in most cases without the thermostat.
Then put your thermostat back in. I'd boil a pan of water on my stove and drop in the thermostat to be sure it opens at 190-195 since the water should be boiling above that.
Then drain water from radiator and refill with coolant to bring your antifreeze mixture up to the proper freeze protection level.
2014 Malibu 2LT, 2015 Cruze 2LT,
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Answers
The design of the thermostat housing makes it impossible to put it on backward and the location makes it a headache to remove because you have to remove the throttle body and almost everything else on the right side of the engine.
It is horizontal so no bleed hole on the thermostat itself, but I am starting to wonder if autozone is giving me the correct thermostat. This is the third one. It is the one with the rubber ring around it, so I think if I ran it without a thermostat it would just leak from the housing. Once the car got to temp the upper hose was warm and the lower hose was cool, so I think there was some flow at least. Also, the car ran for nearly 30min before it redlined.
This engine is the 3400 SFI that has the historically problematic cooling system. There is no cap on the radiator. It has the pressurized expansion tank. While trying to fill it I left the cap off and had the bleed screw open. Unlike some others I see, mine doesn't have a bleed screw at the thermostat housing. It has a connector for the return line. In addition to having the cap and valve open, I pulled the return line from the reservoir so I could see when coolant started to flow. It never did. Only steam
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I think I'm gonna try removing the hose from the thermostat housing and pouring coolant directly into the radiator that way. I also considered disconnecting the heater core hoses and pouring coolant directly into the heater core. Maybe this will help to displace any air pockets. Other than that, I am at a loss. Thanks for the advice and please let me know if you think of anything else.
Have you seen these videos on the 3400 engine in various applications and filling them to get the air out?
https://www.google.com/search?q=2003+grand+am+3400+how+to+get+air+out+of+coolant&rlz=1C1AOHY_enUS709US709&oq=2003+grand+am+3400+how+to+get+air+out+of+coolant&aqs=chrome..69i57.12754j0j4&sourceid=chrome&ie=UTF-8
2014 Malibu 2LT, 2015 Cruze 2LT,