? about 2012+ cooling system

Owen

I have a 2012 that appears that the car wont build pressure in the cooling system. I would take it for warranty work, but I'm afraid they wouldn't fix it under warranty (I had the radiator replaced due to failure and used a csf).

This started with the occasional smell of coolant. While looking for the source, i noted that the water level was low. It was also noted that the techs who installed my radiator had swapped the high and low coolant pressure caps (high pressure cap on the overflow bottle), which I installed the correct way.

This progressed into noting that the coolant level was low every time I drove it. I never noted coolant dripping from car, but given the volume of water that was going through the engine I figured there should be a visible leak. On first run through I coulnd't find one, but while scratching my head on what to look for next, coolant started gushing out of the bottom. It was quickly traced to the overflow tank. Over the course of the 6 minutes or so, the fan would cycle. When the fan was off, the overflow level rises, when the fan was on the level would drop. After a few minutes, enough coolant is blown out that the leakage stops.

Mystery 1 solved. It wouldn't start losing coolant until a couple of minutes after start-up and would stop after 10 miuntes or so. No apparent puddles or leaks, but lots of cooant loss.

With volume of the breathing, I checked the firmess of the hoses. Nope. They were cold squishy. Brand new factory radiator cap goes on, and the bleeding starts. Except it never bleeds. Front end up in the air. Drivers side air cleaner off, radiator bled. Over the course of a week, numerous hot cold cycles, heater on/off and a couple gallons of coolant. The behavior is still the same. Lots of expansion during warm up (which blows coolant out) and lots of contraction during cool down and no apparent firmness of the lines.

During one of the cold starts, I was filling the high pressure side and noted that the fluid level in the overflow tank was rising too. On a hunch, I disconnected the overflow line from the high pressure cap to the tank and started it up. Lo and behold, not one drip of fluid comes from the cap during warm up, but the expansion/contraction cycke of fluid in the overflow tank persists.

Mystery 2 solved. The cooling system is not building pressure. This causes excessive coolant expansion which the overflow tank was not designed to contain.

Myster 3 solved. With the line on the top of the overflow tank disconnected, there is only one path left - the line from the bottom of the overflow tank to the heater line. So the flow MUST be from the heater line.

This is where I am stumped. In studying the 2012+ coolant system there is no apparent way for it to be a pressurized cooling system. According to the schematics, the overflow tank (typically low pressure) is connected directly to the heater tube (typically high pressure). What am I missing? Is there supposed to be a check valve somewhere? Why is there even this second attachment to the heater tube?

Ideas?

O