After a couple of months that my interior has been stripped. I finally decided to remove the last item, the heater core. I was told that if I removed the heater core that I would need to join the lines back because it also cools the rear housing. So off to home depot to get some tubing and clamps. All is said and done and I let the car sit and wait for leaks. No leaks! After sitting for a while I see that the car is running a little hotter than normal but not high enough to cause concern yet. Since I propably won't drive the car under normal driving conditins for a couple more days I was wondering if anybody after doing this noticed that the car ran warmer afterwards. thanks.

 

When you remove the heater, just cap the nipples.

The heater circuit is a bypass that opens only when Mazda engineers expected you to be dumping heat to the cabin.

FWIW: There is another bypass. It's the hole in the thermostat housing about 1.5" under the stat.
It's normally closed by the spring loaded disc on the bottom of the stat.
So it you ever remove the stat, plug that hole.

(edit) I just remembered the 3rd bypass.
The circuit the comes from the top of the rear housing the the TB thermowax to the BAC to the pump housing.

 

I have to disagree about capping it. there was coolant flowing through. if it was just for the heater that wouldn't be happening.

 

What I believe he was saying was that if no heat is called for, valve not open, so water doesn't flow through the core. Naturally if you disconnect the hoses from the core, wthout any restriction, water will flow constantly.

 

Coolant flows through the heater core ONLY when heat is called by the logicon.
Flow is shut off for cooling.



When he removed the heater, he connected a bypass hose, which reduced engine cooling efficiency.
That’s why I say when removing the heater, cap the engine nipples.

 

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I want to hear from people who have done this. up

 

i have done this. after removing the heater core i cut a piece of pipe from it and used it to connect the two hoses behind the engine and plugged the holes in the firewall. i assumed since coolant flowed through the hoses i should do this...but after reading this thread i'm most likely going to plug the hoses. i did notice a little rise in temperature. i didn't think it was a big deal because my needle still only goes up about a fourth, but it used to only go up about an eighth.

 

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is everyone here running super cool or what im usually running half way in the temp range shouldnt that be normal?!!

 

usually my car runs at 1/8 of the temp gauge. i have an s4 though

 

The stock dash temp gauge is not calibrated, so half scale may be normal for your gauge.

My 87 ran just above half normally.

When it did try to go higher, I had a problem - a worn out fan clutch.

 

i have an s4. your profile says you have an s5. the s5 owners i know run at half way normally.

 

so I was able to drive the car today. first impressions: car was ideling abnormally. was between 2k and 1.5k rpm. normal is 700-900. after I got to a friends house the car started to overheat. the reason why was because there was still air in the line. car also started to idle rough. after bleeding the air out the car was running at normal temps and idle settled down. after some more seat time I will let you guys know how its going.

 

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so what did u use to cap off. i used rubber caps but after 500 miles or so the one on the block started to crack and leak.

 

Where is this "valve" you're talking about, SureShot? I've always thought that coolant flows continuously through the heater circuit, and the only thing seperating the heat from the cabin when you don't want it is the air mix door...Look at the coolant system cutaway in the FSM, section 3- that left side heater hose gets directly fed from the water pump, after it's traveled through the upper left and center-left side of the housings first. If you plug or cap that line, your reducing the number of flow paths (amount of coolant) that goes back through the housings the other way, back to the pump to be routed to the rad via the upper rad hose. That would explain why you guys are running hotter, after capping the hoses, BTW...

 

Super old thread, but I couldn't get a better answer after searching "removing heater core". What was the better outcome, to loop the system or cap off the outlets/inlets?

Thanks,

Andrew

 

I'd say unless you have a way of sealing the nipples off with something other than rubber caps, just use a piece of pipe to connect the 2 heater hoses. I ran my old NA motor for 2 years like this without having any cooling problems.

If you do plug the nipples, make sure it will last. If it blows, you will overheat your motor within ~30 seconds & crack the water jacket.

 

I dont usually post here, but I will chime in for all the newbies:

A guy blew his engine after it overheated, the previous owner capped the nipples, and the one on the block started to leak, all his coolant went out of the engine ,causing it to get mangled all to hell.

If you decide to take out the heater core, (for whatever stupid reason) please loop the lines so you dont destroy your car!


Thank you.

 

Cap them.

 

So, run a hose like this?

 

No, just connect the two existing heater hoses with a 1 1/2 foot piece of ~1/2" pipe. There's already the metal hardline running from the radiator up to the firewall on the passenger-side, so use it.

But really...just fix your heater. It's much better with heat .

 

The hoses and lines are already gone, leaving just the nipples on the radiator outlet and the block. And it's not on my car (I like heat! ) Are there any adverse effects of running a hose the same way, other than being ugly?