Heater Core

[Walsted]

My heater core appears to have developed a leak, as evidenced by coolant in the driver's floorboard. I've bypassed it for the moment, but will need to replace it, soon.

Does anyone have any advice about replacing it? I haven't found a good how-to, yet.

Cheapest price I have seen on line for a new core is over $300. Has anyone seen one for less?

LKQ shows some used for around $80 - has anyone seen better deals?

Thanks in advance.

[Majik]

I just did mine this winter. On the 99 you can do it without removing the dash. You remove the plastic panel, and you will see the band clamps holding the metal tubes to the core. Loosen them and the core slides out. This took about 15 minutes. Putting it back in took much longer. I tried to do it without cutting the tubes, but I couldnt get them lined up, and to stay lined up while I tightened the clamps. So I ended up cutting the tubes 3/4 of an inch from the end and attaching the short end to the core and using a piece of rubber hose to attach the long end. A couple of hose clamps and it was good to go.

[SirHustlerEsq]

I have a spare NB heater core that you can replace if you need it in a pinch. I think I paid $30 for it from MT.net.

[Walsted]

I have a spare NB heater core that you can replace if you need it in a pinch. I think I paid $30 for it from MT.net.

Thanks for the offer. I'll let you know this weekend, hopefully.

[ckearns]

Is it the same heater core for NA and NB?

[SirHustlerEsq]

Is it the same heater core for NA and NB?

The both fit in either generation car, but the NA is copper and the tubes are detatchable, the NB is aluminum and the tubes are welded on.

[johnwag]

The both fit in either generation car, but the NA is copper and the tubes are detatchable, the NB is aluminum and the tubes are welded on.

you have it backwards. NA is a pain in the ass and NB is less of a pain in the ass because of the detachable hard pipe.

[SirHustlerEsq]

I'll show you my hard pipe.

[Walsted]

Yours doesn't have detachable tubes?

[gabkwong]

How often dose the heater core broke in the NB, I have two 99 NBs. I wonder I am on borrowed time? I have yet replaced the heater hoses! I heard that the one goes behind the block is real PITA!

[POS Racing]

Old rule of thumb is to replace the hoses every 5 years. Not sure on these new fangled hoses

Considering a blown hose or cracked radiator can kill a Miata motor in seconds I wouldn't worry about it too much.

[Walsted]

Turns out the heater core is good. The metal tube nearer the passenger side is pitted, though, and one of the pinholes occurred just outside of the firewall, where the little plastic and rubber piece that passes through the firewall directed the coolant into the passenger compartment. If only there were aluminum wire that would work with my 110 volt Harbor Freight flux welder, this would be an easy fix.

I don't know what causes the pitting and pinholes in that tube (and not the other). I guess I need to do a flush, though.