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Hey guys and gals,

I really tried to do everything I could to figure this out on my own but the problem I am having is driving me absolutely bat s@#t.

First off, trying to retrace my steps on everything I have done over the last few weeks would be dang near impossible. From detailing the engine bay, thermo install, detailing throttle body, accessory belt changes to fine tuning anything and everything that can be tuned.... simply put, the engine bay is just one transmission, cylinder block and cylinder head rebuild from being better than brand spanking new...

The Problem:

Last Thursday or so, I rounded off some finishing touches on my idle, jumped in the car and took it for a test spin to see how she was running. Everything seamed fine until I cranked on the heater... that's when I noticed that it wasn't too warm. Luke warm at best. The next night, after hours of driving all over the place enjoying the start of an awesome weekend despite the rain, the problem still persisted. On start up and sitting at idle and normal operating temperature, everything seemed fine. Idle was smooth, throttle response was quick and accurate (After a well needed Seafoam treatment), and heat was kicking like Jackie Chan through the vents on both circulate and outside vent settings via the climate controls. However, once I got to driving and reached third gear and up with medium range RPM shifting, the temperature gauge drops to nearly bellow "C" and the air coming through the vents gets cooler as if the thermo is stuck open.
Checked Heater Core ~ No fluid leak signs in floor board under dash. Car standing at idle still circulates warm air through vents so coolant is traveling through core.
Checked Temperature Control Switch ~ Car at idle, climate control works fine from cold to hot. Works while moving as well except when accelerating; then heat drops to cooler air.

Parts Replaced After Problem Began:

Thermostat (Fail Safe)
Temperature Sending Unit
Coolant Temperature Sensor

Inspections:

Checked Coolant ~ Super clean. No deposits, no grime. No oil sediment common of head gasket issues.
Checked Coolant levels ~ perfect. Radiator topped off and topped off again after Thermo opens. Overflow tank at "Full".
Checked Oil ~ A little dirty. Almost time for another oil change. No Coolant in oil common of head gasket issues.
Checked Oil levels ~ Full.
Checked for leaks ~ After changing Temperature Sending Unit this afternoon, I noticed a small spot about the radius of a coffee can under the Crankshaft Pulley on the ground of Coolant. The drip appeared to be coming from near the Oil Stick and running down near the A/C bracket. After cleaning up the spot on the ground and then detailing the oil pan, power steering pump, A/C mounting bracket and most of the "Belt" side of the lower engine, I ran up to Autozone and purchased a new Water Pump and then cruised back home. Once home, I checked for leaks in the same area... nothing. No drips, puddles, run-off or anything... completely clean... Checked all fluid levels again and everything was fine. Heating problem, or lack there of still remains.

Recent Work Done:

Intake, Ignition Timing and Idle Speed professionally Tuned. (Last Friday)
Exhaust inspected and hole in joint at down pipe and secondary 3-way cat welded. (Last Saturday)
Rewired Temperature Sending Unit Wire and Connector ~ Wire (B/O) to connector was brittle and frayed. Repaired with butsplice (Dolphin) and thermo-tapped wire as well as replaced connector with crimp-spade female.

Conclusion:

Car runs better than it ever has since I've owned it. Idle is perfect, throttle is amazing, air intake growls and exhaust purrs as if the car was built to run just as it is now. In fact, I don't even think any of the new cars I have owned have run this well. However, heater still does not work. At a stop-light, while idling, temperature will return to normal but drops when accelerating to "C" or bellow and warm air from vents drop. Engine never overheats.

Correct me if I am wrong but isn't what is going on here a complete violation of the laws of thermal dynamics? I am at a loss. It's freaking cold outside and for the life of me I can't figure out what is going on... Any help would be greatly appreciated.

Chris

I know you just replaced it, but I would check and see if the failsafe is stuck open... You never know, maybe while it was pouring hot air like the dickens that one time, the failsafe clicked "open" and now you won't get heat.

that's where I would start.

plus, if you had a faulty water pump that was leaking, it could cause temperature mishaps, it's possible that it did indeed click open. since you've replaced the water pump since, you may need to go BACK to the thermostat and shut it or replace it. You can always just unclip it and close it so you don't have to buy another one.

I think it's the thermo!

I think so too. Headed out to work now. I'll pick up another one on the way home and change it out this afternoon. Thanks, man. I'll let you know the result

If the heater core agrees with the dash gauge, you are indeed having a circulation issue.

I know you've done it probably 10x already, but I'd burp it again.

Let it cool most of the way off.

Open the top rad cap (if it starts spilling out put it back on and wait more, its too hot)
Start the car
Squeeze the bottom hose and the level in that cap should change. Do it for a few minutes, or until you feel the lower hose get hot.

If its super cold where you are, it will be a PITA.


How old is your waterpump? I have actually seen a KL waterpump with enough corrosion that it probably didn't do much pumping...

I agree with Ryan it has to be a circulation issue. My guess would be that the pump is worn out and leaking internally. I.e. the blades are spinning but there is enough clearance between the impeller and the housing that the fluid is just sliding past. At idle it circulates better, but at higher rpm the impeller is moving too fast and the fluid is not circulating much or at all. So what happens is the coolant in the rad cools right down because it's not moving and the thermo sensor takes the temp pretty close to the rad so it shows cold on the dash even though I bet the engine is piping hot.

The water pump has already been replaced. I would recommend a non fail safe Thermo if you replace it but you can reuse your own thermostat so you don't spend extra money

Says that he bought a new pump, but I did not read that he replaced it.

You're better at reading than me

Okay, here it is...

Back when I did my timing belt (worklog) I replaced the water pump with a new one. I just bought another one in case the new one was messed up for some reason. Needless to say, bought a new thermostat today and replaced it as well as went to the Mazda House and got a gasket (didn't do that before). Heater is hot as hell, temperature is perfect and I couldn't be more happier. Now I can take the water pump back. Thank GOD I don't have to replace that again because that job, right there sucked!

What I had done before with the gasket was bought the generic "make you own" gasket roll because no one sells our gasket down here. Of course, after I go to the Mazda House, the parts guy tells me, "Yeah man, you could have just bought one for a..." and like an idiot I remember, PROTEGE'!!!!! 323!!!! I guess I was so panicked about my car being messed up that I forgot about the interchangeability with other vehicles. At any rate, it's fixed. Should have went to the dealer anyways because the gasket was cheep.

Anyways, thanks guys for your input. Another problem solved!

yay! few dollar fix ftw! It sounded like it would be something simple, sometimes you just gotta hear options from someone else.

Yeah I was clearly over thinking that one. I knew it a couple minutes after I typed it.

I feel shame.

LOL! no worries man. I was in panic mode. Hearing the input from you guys that have dealt with these cars for a while helps nonetheless. Much Kudos!

I just noticed this, I had the same problem you can read it in the "cold running b6" and the "no heat" threads.

It turned out being the thermo gasket as well, except I did everything you did plus change the coolant and heater core... imagine my shame