So heres the story, about a month ago, the old Stant thermostat failed on me that was who knows how old. It was failing in the shot position so that no coolant was even making it to the heater. I promply stopped driving the car and ordered a mazda factory thermostat from Mazdatrix that week. I installed the Mazda thermostat, and within the week, It did the same deal. No coolant even to the heater. Mazda express airmailed me a new one that day. Now, a week later, this one is doing the EXACT same thing! The question is 2 part. First, can old coolant cause thermostats to fail this quickly. I know that putting a new thermostat fixes the problem, at least temporarily. Could it just be bad luck with faulty parts? 2nd, On an S4, whats the hottest I can run before damage starts to happen. My temp guage got to 3/4 before I cought it. Thanks to all in advance.

 

Why do you think the bad heater problem are due to bad thermostats?

Have you tested the thermostats in a pot of boiling water?


-Ted

 

umm i don't know i know that i had to do it with my truck but the way some shops do is that they put it the same way angle as they brought the old one out it is because it is supposely for more coolant flow. i don't know.

 

you probably have a clogged cooling system. you should flush your cooling system every year to avoid buildup of 'stuff' in it.

 

You should first prove the thermostat has actually failed. Stick it in a pot on the stove and heat the water. Full instructions are in the FSM Cooling chapter.

 

My theory is that there is a small coolant leak and every time you put a new thermostat in you refill the coolant system letting the heater work effectively for a while. But this is just a hypothesis and I could be very wrong.

 

Can dirty coolant cause thermostats to stick? I am 99% sure the thermostat is causing this. When I temporarily ran my car without a thermostat just to get it home the 2nd time it failed, it ran fine.

 

just take out the tstat like everyone has been saying and try it in a pot of boiling water. Here I'll make directions

1. fill pot (same pot you would make macaroni in) with water
2. through tstat in water
3. turn stove on
4. watch to see if the tstat opens up when it gets hot enough. (if you have a thermometer to varify the water temp then thats a plus.

 

I plan on testing the thermostat and flushing the entire system this weekend. I am a full time student with a part time job, so time is a limitation factor. To add to my comfusion, Im no longer sure the thermostat is the curprit. I called Mazdatrix to ask what could be the problem. They told me that if the thermostat sticks, it would not effect the heater. When my car starts to get hot, the heater blows cold. Since one of the heater lines comes from the lower radiator hose, I figured that if the t-stat stuck, water could not go through the radiator and cutting off water to the heater. Am I wrong? The main reason I believe this is the thermostat is because it is intermittant. Occationally, the heat will kick back in and the temps will drop. I know I need to check my thermostat and that is on my to-do list. I just want to narrow down my options.

 

Any ideas?

 

I tested the thermostat. Its fine. I plan on flushing my coolant this evening. Can I use Zertex or any kind of radiator flush on a rotary? I really dont want to do any further damage to the coolant seals than what might already be done. Anyone have any ideas what else could cause intermittent overheating?

 

drain coolant, fill with water, run car, drain water, fill with water, run car, drain water, fill with coolant, burp car. that's what i did when i drained mine (and replaced stock radiator with koyo rad )

 

its not the thermostat ya dufus...


when you drain the coolant to install the thermostat it drains the heater core as well, all the sludge blocking the heat core basically falls to the bottom of the inlet tank and once you refill and drive the car the heater will work for a few days until that sludge works its way back into all the core fins and obstruct them.

what you need is a coolant system flush kit, not more thermostats...you may also want to backflush the heater core as well to be sure you get all the crap out.

 

So this afternoon, I flushed, refilled, ran, and repeated 4x until the water was fairly clean coming out. I refilled my radiator, bled the air, refilled again, ran the car, cooled down, bled and refilled. I finally took it for a ride to see that it is doing the exact same thing. I am lost.

 

I am not ruling out a bad coolant seal, but it still seems intermitent and Its not smoking, even on start up. Also its pushing a lot of coolant into the overflow, but I guess this is just expantion and displacement of heated coolant.

 

umm i had the same problem i took it to my mechanic that only works on rotaries he simply told me that the coolant seals were all toast . when we took the motor apart you could definetly see where the damage occured. i went through all the same crap you did. i hope for your sake you didn't roast the coolant seals best of luck man.

 

Mine did the same and it was the coolant seals. Car wouldn't over heat around town, but on the highway it wouldn't stay under 190* unless I had the heater on, and in FL in the summer time......that sucks.

 

to drive the car i took the thermastat completley off but the damage was already done . i figured after that you live you learn i guess . sucks and i live in the california desert!

 

I still want to eliminate every possible "cheap" alternative before biting the bullet for a rebuild. I did some reading and read that a bad rad cap or air leak can push coolant out like my car is doing. I went and checked my car, and low and behold, besides having an old, non-stock rad cap, the nipple to my overflow tank was cracked and the hose was loose. I removed the cap and there was almost zero fluid in the motor. My overflow was full and the rad drank 1/2 a gallon. I pulled my EGI fuse and had my dad crank the motor too see if any coolant spewed. I saw a couple bubbles, but, after adding 1/2 a gallon of fluid, Im sure there was still air in the system. It wasnt gurggling or spewing. Even if it was a minor leak (2-3 bubbles per 1 second crank) That would push all my cooland out in 3 minutes would it?? Also, I ordered a new filler neck top with the nipple and a new cap.

 

did you backflush the heater core or just do the standard flushing procedure?

is the cooling system building up pressure quickly with a cold engine indicating a faulty coolant seal?

 

I just did a standard flush. I went and started it up. Still pushing coolant out like crazy. There upper hose doesnt seem too over presured. Also, no smoke and no coolant smell. How would a bad coolant seal overpresurize the hoses?

 

Could it still be a blown coolant seal with no smoke and no smell of coolant? Anyone?

 

Anyone have any ideas?

 

my guess is air bubbles in the system.

 

a bad coolant seal will cause water to GUSH out the rad cap.. exhaust gets into the coolant system and that pressure is what pushes the water out.