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Ask Dodgerench Your Own Question
Dodgerench, ASE Certified Technician
Category: Chrysler
Satisfied Customers: 3401
Experience:  30+ years Dodge/ Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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There's a rattling sound much like a heavy metal lid on

Customer Question

There's a rattling sound much like a heavy metal lid on boiling pot and like a vibration in that is continuous while car is at idle or underway. Could you give me an idea of what this might be? Noise comes from passenger side of engine and not driver's side. Thanks.
Submitted: 1 year ago.
Category: Chrysler
Expert:  Dodgerench replied 1 year ago.

Goood morning, welcome to JustAnswer!. This is Ed.

Your description -- a very good one at that -- reminds me of a cooling system boil-over condition, which does sound just like what you've described. When the engine reaches operating temperature, normal expansion of coolant will pressurize the system, but be managed by the radiator/ cooling system pressure cap to keep it from boiling. If temperatures continue to rise, coolant will begin to boil, despite the efforts of the radiator cap, causing it to vent coolant into the recovery bottle. The act of venting isn't usually smooth and quiet -- quite the opposite -- as the cap releases pressure in that same boiling pot lid manner as pressure is built and released.

To begin with, we need to pop the cap on the pressurized side of your cooling system with the engine cold, or at least mostly cold to prevent scalding by escaping coolant. The pressure cap may be on the radiator (passenger side) or on the recovery bottle, depending on the mood of whoever was running the assembly line that day (seems that way sometimes). If low, examine the area for signs of past leakage, which may show up as white spatter or an orange gloppy mess if it's been going on a long time. If coolant is needed, add enough 50/50 mix of antifreeze (HOAT type/ orange in color) and water, then reinstall the cap.

If leaks were found, you know what to do. If none were present, your cooling system may not be operating the cooling fan, which can cause this sort of problem when sitting in traffic or idling -- any time that you're not moving fast enough to get natural airflow through the radiator. We'll need to verify fan operation next.

Start the engine and recheck your coolant level a few times in the first minutes of cold engine operation as the cooling system sorts out the air and the level may drop. Top off as needed, put the cap back on and wait. Watch your temperature gauge and at a point just past middle, the fan should come on. It can be summoned earlier by turning the A/C on as it's needed constantly for compressor operation.

If it doesn't come on and you go past midpoint on the gauge -- or if your A/C does work, but the fan never comes on -- we've got fan problems. If it does come on, but you were low on coolant (now filled), you'll need to get the leak fixed, of course. Let me know about either situation and we'll go from there. An uploaded pic of the leak area might be helpful.