Bubbling sound from under engine - boiling coolant???
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Joined: Feb 2026
Posts: 67
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From: Sedalia MO
Bubbling sound from under engine - boiling coolant???
I was out working today In my 92 Vette, driving from one location to another across town over the course of a few hours.
On the first few stops, I left the car idling. Didn't idle for longer than probably 15 minutes at a few stops. I shut it off at one stop before exiting the car, and as I walked back up to it about 2 minutes later, I heard a weird noise from under the hood. It was literally a bubbling noise. I know these cars get hot, but damn.
When I got back in, the temp gauge was maxed out, but the digital temp gauge said about 200. I think the digital reading was too low, cuz as I got back on the highway and got up to speed, the temp gauge started going down drastically even though the digital gauge still displayed around 200.
Does this cause any issues? Do these get this hot normally?
On the first few stops, I left the car idling. Didn't idle for longer than probably 15 minutes at a few stops. I shut it off at one stop before exiting the car, and as I walked back up to it about 2 minutes later, I heard a weird noise from under the hood. It was literally a bubbling noise. I know these cars get hot, but damn.
When I got back in, the temp gauge was maxed out, but the digital temp gauge said about 200. I think the digital reading was too low, cuz as I got back on the highway and got up to speed, the temp gauge started going down drastically even though the digital gauge still displayed around 200.
Does this cause any issues? Do these get this hot normally?
Melting Slicks
Joined: Oct 2003
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From: Chapel Hill NC
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I would refrain from driving the car until you check the possible overheating. You'd should also read the sticky in the C4 General discussion titled Corvettes, Summers and High Coolant Temperatures.
Intermediate
Joined: Jul 2024
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From: Charlotte, NC
If you worked on the cooling system I would check for everything being sealed. The system is designed to operate under pressure which moves the boiling point higher, if it isn't pressurized due to a leak (like a cracked radiatior, which happened to me) it'll boil before reaching operating temp and you'll hear it from the reservoir.
Try and isolate where the noise is coming from though, if your AC was running then the high pressure side bleeding back over to the low pressure side after shutdown could sound similar, and is normal.
Your digital temp gauge reads from a sensor in the water pump just before coolant enters the block, and the analog gauge reads from a sensor lower in the side of the block. Generally, the digital will read cooler due to this, but that's assuming both sensors are accurate/functional. If you're unsure as of now, I would treat the higher of the two as accurate to be safe.
Try and isolate where the noise is coming from though, if your AC was running then the high pressure side bleeding back over to the low pressure side after shutdown could sound similar, and is normal.
Your digital temp gauge reads from a sensor in the water pump just before coolant enters the block, and the analog gauge reads from a sensor lower in the side of the block. Generally, the digital will read cooler due to this, but that's assuming both sensors are accurate/functional. If you're unsure as of now, I would treat the higher of the two as accurate to be safe.
Last edited by nb_destroyer; Mar 15, 2026 at 12:57 PM.
