Bypassing Heater Core

I bypassed my leaking heater core using a pipe nipple.
My question is, do I have to have the former heater hoses in the circuit, or can they be removed and plugged?

Right now, it discharges out, passes through the nipple and goes right back to motor. Seems like I should be able to plug things off and keep from circulating the coolant thats not needed.

Ultimately, I'm going to install my coolant filter in those lines but doesn't look like I'll have time anytime soon.
Thanks

loop it from the thermostat housing nipple to the pipe that comes out of the waterpump and you're good to go. it serves as a bypass for the thermostat you cannot just plug the whole thing off.

I just plugged the whole thing off on my XJ for like a year, but I probably shouldn't have.

It did have funky temp related issues during that time now that I think about it...

Loop the hoses like GrimmJeeper said.

There's no other path back to the water pump, and it needs that flow for closed-thermostat operation. The water needs to circulate by the back of the thermostat for it to operate properly.

pipewrench said:

I bypassed my leaking heater core using a pipe nipple.
My question is, do I have to have the former heater hoses in the circuit, or can they be removed and plugged?

Right now, it discharges out, passes through the nipple and goes right back to motor. Seems like I should be able to plug things off and keep from circulating the coolant thats not needed.

Ultimately, I'm going to install my coolant filter in those lines but doesn't look like I'll have time anytime soon.
Thanks

Click to expand...

Loop bypass - connect the thermostat housing to the pipe off of the water pump.

As far as the heater core proper, I would suggest that you blow as much of the coolant out of it as you can. Then, dump in about a half-pint of denatured alcohol - this will bind with remaining water and make it evapourate off at a lower temperature, which should dry the heater core out more quickly. You'd rather have it dry, to help prevent idle corrosion.

As mentioned, I would not just cap the feeder hoses, as it does also serve as a bypass circuit for the engine cooling system.

Yup, what they said. Loop the waterpump to the tstat housing. You may also want another hose clamp on the looping hose itself and clamp it to pinch the hose and reduce some flow. The heater core restricts flow in a normal system. Pinching your loop back hose will mimic this.

Thanks for all the advice. I'll def add the hose clamp.
One thing I really need to do is replace the nipple coming off the block, it looks like it is severely rusted.

Someone has hacked this up before, there's a nipple off the block, a section of hose, then another steel nipple, then heater hose all the way to the core. I'm afraid if I break it though it will be a real nightmare...

pipewrench said:

Thanks for all the advice. I'll def add the hose clamp.
One thing I really need to do is replace the nipple coming off the block, it looks like it is severely rusted.

Someone has hacked this up before, there's a nipple off the block, a section of hose, then another steel nipple, then heater hose all the way to the core. I'm afraid if I break it though it will be a real nightmare...

Click to expand...

That hole is threaded 3/8" NPT - so you can get a standard pipe nipple from the hardware store to fit it. The heater hose should slip overtop of a standard metal 3/8" pipe nipple - although I'd cut the threaded end off and deburr it before sliding the hose one, then double-clamp the hose (allow min 1/8" between the clamp band and the bitter end of the hose, min 1/8" between clamp bands, and min 1/4" between the clamp band and the cut end of the pipe nipple.)

If you're going to do that, you can simplify things and gain control at the same time - instead of using a hose clamp to try to regulate flow, just add a valve and another pipe nipple (trimmed as above) to regulate your flow instead.

If you want to do it nice, just get the heater valve from an 85 or so. It switches to bypass mode and routes the coolant back to the motor.