I have owned my car for so long I don't remember how the heater originally was, but I can have my car fully warmed up from idling for 20 minutes and the heat still be cold. After I run it hard for a couple minutes it warms up but not to very hot, like my new car does. Is it possible to be a partially clogged heater core causing this? Or is this just how this cars heater is. It's cold right now and just wanted to fix it. This is in no way related to the temperature controller as it functions properly.

 

That's one possibility.

 

http://foxed.ca/rx7manual/2003mazdar..._S01_0648.html

 

the heat in my 8 is warm on pass side but cold on the drv side. some have fixed this by flushing the heater core but ive done mine a few times and it still sucks.

 

likely the air diverter flapper door isn't opening on the drivers side properly

 

I have a near-perfect RX-8 that I bought new in '06. FWIW, I can tell you the heater can heat the interior to toasty levels in cold weather. Now, there have been a couple of instances where the temperature was below 10-15ºF and the car did not get toasty warm. But even in those rare situations the interior certainly got comfortably warm. If your 8 isn't doing that, something's clearly not working properly.

 

It's fine once I hit high rpms, I don't think it's the diverted flap. Just initially. Once it gets heated up its fine the whole time. I'm thinking the heater core is partially clogged.

 

Probably just the water pump sucks at low speed. Maybe air in the system.

If i let my car idle it will overheat but i rev the engine just a little and the temp drops imediately.

 

sounds like you got big problems..

 

There is a restricter in the heater hose line...that is much more likely to clog than the heater core

 

I'll check that hose, but if I'm not mistaken I think I have a silicone replacement on the heater core. I would fix the over heating issue , your playing with fire.

 

Paimon, it might be my radiator is too big/ flow restriction. I have a rebuilt engine all new hoses, oem thermostat, upgraded radiator, oem water pump.

 

If you do not have the restrictor Dannobre is talking about or the other one in the heater hose, the car can overheat at idle.

 

Makes sense, too much water in the heater côre and not enough in the engine.

 

I have had this same issue .

this is what fixed it for me :

Take off both hoses on the firewall going to the heater
With a garden hose and some fittings flush the heater from both directions .
A good trick is to kink the hose then suddeenly unkink it to create a surge of pressure .
Button it all back up and go for an nice warm ride
Top up your coolant.
Then .....Run some radiator cleaning solution through the system per the instructions or the problem will come back again very soon.

 

Herssel, sorry for clogging up your thread, that's not what I was after.

9k, I don't have the restrictor, but I have the line restriceted another way. I capped my heater inlet and outlet on the block.

I went from throttle body heater outlet(back of the block just past the injectors) to the heater core. Then out of the heater core to a ball valve and into the throttle body.

That restricts the heater core to 5/16", but It also gives me a valve so during the summer I can turn off my heater core and throttle body heater. That way all the flow goes through the radiator.

 

Couldn't you just ................... turn off the heater ?

 

Water normally circulates through the heater core even if the heater is off and then recirculates that hot water through the engine. When I have this off it is pulling only cool water from the radiator into the engine. plus the flow rate through the radiator is increased.

 

How many others recommend a solvent / cleaner in the cooling system? I've been told that it ultimately just makes things worse.

 

There was a time when the heater was controlled by the amount of water flowing through it. Cheaper cars (like a couple of Chevies in my family) had a valve under the hood that you'd open or close with the seasons. Nicer cars (like a Chevy Impala vs a Biscayne) had a lever in the heater controls inside the car. You're giving me nostalgia for those old Chevies.

Are you sure that putting more water through the radiator helps? The radiator still has the same area. In the old days if you were sitting in traffic on a hot day and had a car with an inside control for the heater you could get a little more cooling for the car (and a free sauna in the process) by turning on the heater. I assume the same trick would work today, as long as you hadn't put a shutoff valve on the heater hose.

Ken

 

Yep, if you turn the heat on when your temps are up it will definitely drop coolant temps, the heater is basically a second radiator with a fan. Bypassing it makes no sense to me. Plus it causes your car to overheat at idle.........

 

If you shutoff circulation through the heater core, I think that would promote corrosion.

 

+1.

 

How ?

 

Yeah, I got the Idea from big trucks. They have the same shutoff setup. As for corrosion I will have to see. It could, but with Distilled water and 25% coolant it should be just fine.

It's not so much about putting the extra water through the radiator, but you are no longer recirculating the hot water through the engine. Hot engine plus hot water just means the engine gets hotter. If it's only getting cooler water then it will always stay cooler. In the winter that could be a problem of overcooling or shocking the engine with freezing water in a hot engine. So during the winter open the valve.

We know that more flow through the radiator helps that is why people push having the restrictor in place.

During the summer i get a 10F or better drop in coolant temps with the valve closed. I also have a big CSF radiator that is dual core and maybe dual pass I don't know for sure. That gives the water plenty of time to cool off.


LOl, 9k it was doing it before I made the change. I never had the restrictor so this was an easy way of restricting the line.

By overheating I mean hitting 210 and still rising. I've never had it over 215.