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Bypassing heater unit - HOWTO


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Seems like a lot of people are having the problem mentioned in this thread:


Basically the cause is most likely a stuffed heater core, which involves pulling your entire dash apart, and its maybe 6-8 hours of work.

So for those that don't just want to do that just yet (but its recommended).. you can actually bypass the heater core altogether. Means you get no heat, and no proper climate control, BUT it also means you don't get leaking coolant, which can mean overheating and then the end of your engine!

For those interested: the heater core just works via coolant (which is heated from the engine) passing through a small radiator, which is in turn stores heat, and warms the car. The coolant then passes back through the firewall, and into the rest of the cooling system.

So, here we go:

1. Leave your car overnight, or at least a good few hours to let everything cool down, and water to settle back into the system.

2. First of all, remove the two hoses that go into the firewall (as shown). One is like the "in" and one the "out" coolant flow.

They are held on via clip type things. Undo the screws using a philips head or even an adjustable wrench. They can be a bitch to get to if not facing an easy direction, so slide them around if you can. A bit of coolant should come out, but when i did it, there wasn't much.

3. Use a piece of hose that will fit in between the two hoses to bridge the two. Luckily i had one that gave a tight fit @ 21mm outer diameter. Hopefully the small diameter hose doesn't cause a noticeable restriction in the cooling system(??). Probably a plastic pipe of correct size would be the most secure way to do it (didn't have one on hand).

4. Tighten up the clamps as tight as possible. Make sure its all secure, and try and angle things so the rubber hose is not too close to the engine.

5. Start her up and give it a test, check for leaks, and any sudden rise in temperature during a test-drive.

I did a short test run, and everything seemed to be normal and running ok.. but keep a razor eye on that temperature guage, and any leak from that area.

I hope this all ok, wrxhoon or the like might be able to have a quick check to see if i've done something no-no. I take no responsibilty for any damage caused by anything in this thread!

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No need to plug anything.. The heater can just sit their disconnected without any problems. The heater core is just a small radiator really, where water flows in, and then straight out, heating it in the process.

Its possible you can just plug both ends of the hoses at the engine side, but i think keeping the original "flow" in and out of the engine would be best.

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  • 7 months later...

Have a look around the firewall they must be there somewhere....i'd imagine they would put the heater in the same spot?!? Try unplugging some hoses and if you pull off the hose and see the yellow heater core plugs then you know u r on the right track. Perhaps have a look under the car - maybe they have mounted them lower if they aren't on the top

Anyone done this on a GTR? Where are the 2 hoses?
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yeah was the same place, just more crowded around the area, bypassed it for now, need to source a new heater core, i've been told copper is best, will last forever (well alot longer than a normal one)... then gotta get my dash out to replace it.... not really looking forward to it

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