Ya, that’s what I said. Gurgle up under the dash when you first start your 1961-1964 Mercury. What is that noise??? Well, it’s common on those years of Mercury’s to hear a gurgling sound under the dash when you first start it up. Sometimes it can get bad enough to gurgle more often.
Better check the water level in the engine. What you are hearing is air in the cooling system circulating through the heater core. Mercury went with a cross flow radiator in 1961. That is what most cars have today. A cross flow radiator means the water flows horizontally through the radiator instead of vertically. The radiator tanks are on the sides if the radiator instead of top and bottom.
For that reason Mercury put the fill tank on the engine. It is a small tank with a radiator cap, mounted where the thermostat housing would be. With this design, it is where the thermostat is located. This tank is where you would add water to the cooling system. For some reason, when the coolant gets low, you hear air in the heater core. Just one of those little quirks those cars did.
The cooling tank acts as an expansion tank too. If you fill it too full, it will barf up coolant on your driveway when you shut the engine off. Not pretty. That doesn’t mean you have an engine problem.
If you look in the tank, you will see a baffle. There is a hole in the baffle where you can see what is below the baffle. Add coolant until it is just up to or slightly over the baffle.
Do not fill to the top of the tank!! That’s when you will have problems. The extra room in the tank is to accept expansion of the coolant and if you have it filled to the top, the coolant will definitely puke out the overflow. This usually happens when the engine is warm and you shut it down.
I have had customers call me thinking they had a problem. They did. They filled the tank full of coolant. Don’t do that!!
What I do is look through the hole in the baffle and if I see coolant, I consider the system full. If however you hear the gurgle sound in the heater core, better check the coolant level.
Food for Thought.