TheSamba.com :: View topic - Help Reversing Rear Heater Bypass & New Unit Install

Sun Feb 10, 2019 2:34 pm

Used Search and found lots of folks talking about removing the rear heater and how to do a bypass. However, I’m in -5 Montana without a rear heater and finally have all the parts to reverse the bypass and install the rear heater (and make the family much warmer).

Bought a GW rear heater valance replacement, got a new to me blower/heater, got a new Behr core, and got the GW heater hose replacement kit.

Can someone point this visually-inclined DIY-er in the direction of a good play-by-play for installing a replacement rear heater and reversing a bypass?

For the sake of clarity and because SW Montana is sitting in the negatives this February, I would very much appreciate help doing this project the right way, the first time. I’ve got open Ben’s webpage explaining how to replace a core, but wondering about the logistics of clamping and reattaching the coolant lines, if/how to burp the system, and things to do before i try to “turn it on.”

Please, educate this cold fellow or point me to a better resource; advice on other smart things to do/check while on this project is also appreciated!

Sun Feb 10, 2019 5:44 pm

2 sheet metal screws hold the heater unit to the floor
There needs to be a restriction in one of the coolant hoses going to the core to prevent it from robbing the front heater of the most coolant flow, and heat.
Plastic bushing is common, right at the valve, inside the hose. It’s there in your GoWesty Kit, cool.....
Hopefully your wiring is all still decent laying there and no issues with connecting the blower and resistor.
Oil the blower motor bearings NOW while you have it out. Rear is super easy, the front one is obscured by the cage . I use the Hardware Store oilers with the telescoping nozzle to sneak in there and lube the front one.
New core hopefully has a similar bleed screw on top like the factory ones did to make bleeding air a snap.
Run your van to warm it up once connected, crack open the bleeder screw if you have one.
No bleeder on the new core?, tilt the Van on a jack and jack stands with the Rear up higher than the core to help bleed it out IF you need to.

Mon Feb 11, 2019 6:55 am

Thank you JLRftype7 - helpful!

Anyone with a Subaru system able to chime-in specific to (1) undoing the bypass and ensuring the proper hose gets the restrictor and hooked up to the correct/inflow valve on the core (do I trace hoses to engine or from the T under the van?), and (2) any advice using the little black bleeder valve on the new GoWesty valve replacement for the core when I turn the engine over (and pray there isn’t burping issues)?

Mon Feb 11, 2019 8:23 am

While its good to be cautious when delving into new territory, in this case its pretty simple and would be tough to screw up. The core is just along for the ride in the middle of a loop. It will produce heat no matter which way coolant passes through it. Chances are that the hoses are in the proper orientation so that the top hose goes to the top fitting on the core and the lower to the lower. The restrictor is in the same boat. It will slow the flow whether it is in the top hose or the bottom. If memory serves , I think it goes into the top hose though. It almost looks like it might be in the darker of your hoses, the one that isn't kinked. Maybe not but it may be tight up against the nipple joining the hoses. As for bleeding air out, I wouldn't stress too much. Clamp off both hoses, install heater, fire it up. As it warms up you can try the bleeder. After that just run it and top off your pressure tank as the air in the system makes its way there. After a few days you can park with the back of the van up hill and with it warmed up crack the bleeder on the radiator just make sure no air got trapped in the top of it. Have fun and be warm!

Mon Feb 11, 2019 8:59 am

BCgee wrote: Thank you JLRftype7 - helpful!

Anyone with a Subaru system able to chime-in specific to (1) undoing the bypass and ensuring the proper hose gets the restrictor and hooked up to the correct/inflow valve on the core (do I trace hoses to engine or from the T under the van?), and (2) any advice using the little black bleeder valve on the new GoWesty valve replacement for the core when I turn the engine over (and pray there isn’t burping issues)?

There are too many different ways of doing the Subaru bypass to get a reply specific to your setup without more info.

Mon Feb 11, 2019 9:15 am

I know very little about the Subaru installations. That said, it is my understanding that some Subaru installations require a constant flow on the heater circuit in order for the thermostat to function. From the OP's pic showing the hoses, it looks like the previous owner had the hoses simply connected together. Installing the rear heater and placing the valve in the OFF position might cause issues. More info is necessary about the specifics of the Subaru install and the cooling system parts/routing used.

Mon Feb 11, 2019 9:26 am

Looking at the picture of your hoses, since the one hose is effectively crimped by being doubled over, your heater hoses were not functioning as your Subaru heater bypass and thus the heater can probably be hooked back up without issue. Would still be good to know how your Subaru heater bypass was set up. You might want to contact whoever did your conversion and see what they can tell you.

Mon Feb 11, 2019 11:49 am

Wildthings & Waldo - thanks for the quick notes and help troubleshooting.

Took another peek at the underside. Found this fellah on what I believe is one of the radiator hoses:

Able to trace rear towards the engine bay to this Tee:

Then it appears one of the hoses from the Tee leads up behind the right rear trailing arm to potentially another Tee, but i loose sight of it without taking the wheel off.

Easy to ID the two end hoses coming up and into the underseat bay:

When i try to trace the two hoses coming into the seat bay one appears to ultimately connect to the Tee mentioned above, while I loose track of the other with the wheel well visibility being crap; it appears to head back towards the engine bay but need to take the wheel off to confirm.

Any ideas what the first mechanism on the radiator hose is, or further thoughts based on the hose routing shown above?

Mon Feb 11, 2019 12:02 pm

https://www.gowesty.com/product/fresh-air-heating/3386/front-heater-valve

Mon Feb 11, 2019 12:50 pm

Someone added an extra front heater valve in a different location than stock, looks like it could be the Ford valve that I and others have used. That valve needs to be in the fully open position for you to get full flow to your front heater.

Mon Feb 11, 2019 2:34 pm

FWIW here is the cooling system set up in the engine bay:

Is the hose on the far left likely a radiator hose with bleeder? The coolant tank and overflow tank are apparent on the right