Heater Hose Return Line

[rsbrillhart]

Installing the FFR Vintage Air Heater in an MK4. I have the hot supply hose in the port fitting in the rear manifold, but not sure where to route the return line. The FFR instructions don't even mention the return.

I believe it's back to the water pump, but not sure if it's the fitting on top, or the hose bib at the bottom. Or somewhere else entirely? And if not the bib, what is that for and should it be closed off?

Thanks in advance!

[Norm B]

The return line goes to the water pump lower connection. The thermostat bypass line goes to the top. Here is an old picture. Normally the heater feed line goes to the port just behind the thermostat housing.

HTH

Norm

[rsbrillhart]

Thanks Norm, that helps. Would it matter if I used the rear manifold fitting for a cleaner look. I suppose the water temp may not be as hot.

So the return goes on the lower pump hose bib. Curious what folks do with that open bib if not running a heater?

Randy

[Norm B]

Coolant flow is mostly front to rear through the block and then rear to front through the heads. With that in mind, the coolant for the heater might not be as hot if drawn from the rear port and may create hot spots in the head on that side. Maybe an engine building expert will respond with a more definitive answer. The lower port on the pump is normally plugged if not running a heater.

Norm

[rsbrillhart]

Makes sense. Thanks much for the help and the quick reply!