Re: Hose diagram assembly

Posted by HH56 On 2016/10/23 20:55:52

Your description sounds correct. Unfortunately, neither factory photo shows the optional underseat heater. With just the front heater the front or upper tube from the core returns directly to the water pump and with the underseat heater that second core feeds back to the pump.

Aside from the connection from the head to the valve as the first and most important stop, the order the two cores connect does not matter that much as far as function. Both cores will get warm.

For best operation, typically you would want the front heater to get the hottest water because it has the defroster and also gets the coldest air and the most airflow. It will if it connects to the valve first. If the water leaves the valve and goes to the underseat heater first it loses some temperature before it reaches the front heater. In a lot of cases the underseat heater won't be on so that temperature would be wasted.

I don't remember how the valve is oriented but if you can see the opening in the firewall I believe it has a slight taper. The hose coming from the head would connect to the tube on the narrow end. The issue with the noise is if the engine is turning fairly fast and it feeds into the center tube the water pressure will work against a spring to lift the valve off the seat a tiny amount. The spring pushes back and the valve can click. By going into the tube coming off the side first the water pressure reinforces the spring and assists in holding the valve closed. When the valve is off (cold setting) there is no water circulation in the heater circuit (other than a tiny amount that might get by a not quite closed valve) so the cores will stay cold.