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‘16 Mercedes GLE450 amg,’15 Mercedes gla, coupe,’07 Mercedes w221,’12 Audi A
No heat and out of options
Hello everyone,
I am seeking advice on a persistent issue with no heat in the cabin, which has been ongoing for approximately two years. Despite numerous repairs, including replacement of the water pump, thermostat, changeover valve, auxiliary pump, and a heater core flush, the problem remains unresolved. As winter approaches, I am eager to find a solution. It is unusual that the hoses near the firewall, involved in the cooling system, remain cold, while the upper and lower radiator hoses and those connected to the coolant expansion tank are extremely hot. I have attached a picture of the hoses in question. The vehicle's operating temperature is normal, and I have verified the blend doors' operation. Could a stuck-open thermostat or a defective water pump be the cause of this issue, and if so, would these issues not trigger other problems, such as overheating or signs of water pump failure?
Can you remove the 3 hoses from that T-piece and test that each of those 3 is not blocked?
Even when the car is cold (and the thermostat is closed) the hoses to and from the heater core should be "open" iirc.
Classic symptom of a clogged heater core. All new parts won't help if the core itself is blocked. Hot hoses everywhere except the firewall ones mean coolant isn't flowing through the heater core. A flush often can't clear a severe blockage. The core needs to be replaced. It's a known issue and the most likely culprit after everything else you've done.
‘16 Mercedes GLE450 amg,’15 Mercedes gla, coupe,’07 Mercedes w221,’12 Audi A
Update: I operated the vehicle again, as the thermocure remains in the system, adhering to the instructions. Following my initial post, I ran the car for approximately 30 minutes, then shut it off. After completing a few errands, which took around 45 minutes, I inspected the inlet/outlet hoses to the heater core and was surprised to find them hot. Approximately three hours later, I restarted the vehicle, allowed it to warm up, and rechecked the hoses, finding them hot again, despite no heat emanating from the vents. In my assessment, the thermocure appears to be effective. I suspect that the stepper motors controlling the blend doors may be faulty. Tomorrow, I plan to connect the Mercedes star diagnostic tool to identify any potential issues with the stepper motors.
‘16 Mercedes GLE450 amg,’15 Mercedes gla, coupe,’07 Mercedes w221,’12 Audi A
I believe the last time I utilized this feature was through Mercedes Star, but the actuators controlling the blending doors are audible when switching from hot to cold. Additionally, I have watched an instructional video detailing the removal of the dashboard's upper portion, should the motors need to be removed. As this vehicle is not a daily driver, I have the luxury of taking my time if needed.
‘16 Mercedes GLE450 amg,’15 Mercedes gla, coupe,’07 Mercedes w221,’12 Audi A
I'd like to provide an update and seek input from others. After flushing the heater core multiple times, water flows through it without any restrictions. Following the flush, the inlet and outlet hoses were reattached. I've been hearing great things about the Prestone coolant system flush, so I decided to give it a try. I added the product to the system and used tap water. The car was idled for 20 minutes with the cabin heat on high, but unfortunately, there is still no heat, and the hoses connected to the heater core are not warming up. However, the upper radiator hose is extremely hot, while the lower radiator hose is only lukewarm. I'm getting frustrated, so I took a break to think about other potential causes. On a related note, I've verified that the auxiliary pump is working correctly, as I can hear it turn on when I press the 'rest' button. This pump is supposed to provide residual heat in the cabin for about 10 minutes, but since I don't have heat, it only stays on for about 10 seconds before shutting off.
Out of curiosity, I rechecked the hoses leading to the heater core and made a surprising discovery. The hoses, as well as several others connected to the change-over valve, were warm to the touch. This finding has sparked some concerns. Despite the car reaching its normal operating temperature of 184 degrees without overheating, I'm beginning to wonder if the thermostat is malfunctioning and stuck open. Additionally, the lack of cabin heat remains unexplained, and I've eliminated airlock issues as a potential cause.
‘16 Mercedes GLE450 amg,’15 Mercedes gla, coupe,’07 Mercedes w221,’12 Audi A
I recently ran Star and photographed a random sensor in the engine bay with two wires that are not connected. The Star computer displayed an error code of 90A2. When I utilize the climate controller and press the air circulation button while the heat is on, the air blows warm; however, turning off the circulating air button causes the air blowing from the vents to become much hotter. The error code indicates that the issue is likely due to either a faulty or clogged change-over valve, which was recently replaced, or a clogged heater core. As I type this, the Prestone cleaning solution is still circulating through the system, and I am hopeful that it will resolve the issue.
‘16 Mercedes GLE450 amg,’15 Mercedes gla, coupe,’07 Mercedes w221,’12 Audi A
As evident in the picture, the temperatures are increasing as desired, although I wish I had taken a picture before using the Prestone total flush and cleaner. The temperatures have exceeded 95 degrees and are still rising. Both heater core hoses are hot. Replacing the changeover valve is an option, but it is possible that the issue is now fixed.Can Anyone tell me the degrees they get with the heat on so I can compare.
‘16 Mercedes GLE450 amg,’15 Mercedes gla, coupe,’07 Mercedes w221,’12 Audi A
More peace of mind than anything else. The picture shows what seems to be a sensor, but it is not connected to any other component. To its right is another sensor, which is correctly plugged into a harness.
‘16 Mercedes GLE450 amg,’15 Mercedes gla, coupe,’07 Mercedes w221,’12 Audi A
I am fairly certain that this image confirms the widespread suspicion that the heater core was clogged. Upon close inspection of the fluid, which consists of Prestone cleaning solution mixed with tap water, one can observe tiny particles that are likely debris from within the cooling system. Unfortunately, I am compelled to note that the vehicle's previous owners did not adequately maintain the car. I acquired this vehicle in September 2018 and have since endeavored to implement upgrades while rectifying issues caused by the previous owners. As evidenced by the flush, the cooling system did not receive proper servicing prior to my ownership. Hopefully, I will be able to perform multiple flushes and successfully remove the contaminants from the system.
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