Swapping heater core inlet and outlet hoses
 

Can I swap the heater core inlet and outlets? Like literally run the hose from under the manifold to the left port, and the hose behind the head to the right port?

The line going under the manifold is leaking, and it’s too close to my downpipe for comfort. If i just get a 90* bent hose then i can easily send it straight into the left port and keep it away from my downpipe. The hose that goes behind the head has enough free play to go onto the right port. Seems like it should be fine to swap them right?
https://cimg6.ibsrv.net/gimg/www.mia...0f033c5f0.jpeg

https://shop.advanceautoparts.com/p/...rm=dayco+80401

Planning on using this as the new hose, I’ll just cut it down to size

Direction of flow through the heater core does not matter.

I'd try to find a silicone 90 degree hose or put a cool sleeve on a rubber hose due to the heat right there.
Something like this
Metallic Heat Shield Sleeve Insulated Wire Hose Cover Wrap Loom Tube 3/4" 3 Ft | eBay

If you've done a re-route you can also add a heater control valve like this

This has to be installed in a cooler location and will require longer hoses to connect. That valve fits a bunch of Toyotas, is 5/8 on both sides, will seal off totally, and will hold open or shut without anything else.
From Toyota it is $140, aftermarket as low as $15 and the inexpensive valves seem to work fine. I put them in lots of cars now days (heater control valve are a thing of the past regarding newer cars).
I've found nothing else that works as well as the Toyota valves
It should be installed in the inlet hose (from back of cylinder head).
This will eliminate a 200 degree heat source from inside the car during the summer months.
This is important in Texas, probably Georgia as well...

If you haven't installed a re-route it will most likely blow your head gasket as the heater core itself is the main flow path from the back of the cylinder head in OEM configuration.

I detest worm drive clamps especially on thin ass heater connections. The worm clamps distort the shape of both the hose and the aluminum tube. The tubes can be straightened using 1/4 drive deep sockets of variable diameters and careful manipulation.
The spring clamps (I call them strangle clamps) do not distort the tubes and never loosen. The worm clamps always loosen with age.

I put mine in the return line, but made sure the flow arrow was correct. I don't see how it matters which is used, as the pressure in the system is from the static head, and not due to the water pump dynamic head. Allowed me to not have to use an extension to keep it away from the manifold heat.


https://cimg8.ibsrv.net/gimg/www.mia...8241f6b36.jpeg


Thanks for this, by the @technicalninja

@Joe Perez Some time back, you asked about the ability of the A/C to cool your Miata (in N/C, I believe). This will help... if you have a re-route.

Note: I plan to log the coolant warm-up curve with this valve on and off, to see if blocking the flow pre-thermostat makes any difference. Full disclosure: I don't remember which thermostat I have, but am pretty sure it has a bypass jiggler.

DNM

I logged from cold start on successive days. Similar overnight temps. Once with heater valve closed, once opened. This is with a Skou re-route block,

Open heater valve came to 191 in 242 seconds
Closed heater valve came to 190 in 237 seconds

So... No difference to the engine / thermostat.

DNM

Is there any difference in the cabin temp with the valve closed?

Qualitatively, Yes.