Boys car has wild temperature swings in the morning as well as a gurgle at startup. I drive it for 5 miles and it shot to H then hovered just under the it went down to just inside the heat range at a stop light, thenm it went back up again to highest range an then settled to middle. Engine didnt make any noises, no drivebility issues, no weird idle. heater blows COLD all the time? I grabbed the heater inlet hose and its hot, the return hose is barely warm at full heat. Do I have a plugged heater core or how does this heating system work, is there a heater valve like the old cars or is it just blend doors? Ready to take the supply hose and return off the core and send some water through. I put about 1 liter of coolant back into the radiator thinking he had none but the recovery tank was full, but the rad still took about 1l of coolant to top off? we changed the thermostat and he drove it 5 miles and ended up putting another l into the rad, air pocket? When I started it this morning, same woosh of water heard internally ran it 1 minute, turned it off, checked rad, it was full. let it idle until operating temp was right in middle and the coolant just gradually lingered right at the top of the open rad filler. I would have expected it to be sucked into the open stat once the car got up to temp? No it just stayed there, no movement. Do I have a bad water pump? No noise at all in this motor except injectors ticking.

 

wow ok well all around guessing and not doing proper testing?

The first thing is always scan the ECU 3 area's minimum.
Do a cooling pressure test
The drain a small amount of coolant out the drain plug while the engine is running but not so long that it get to hot.
Then you need to connect up a good diagnostic scanner enter the ECU and find the cooling temperature PID and watch when the temperature reaches 130F or more and useing a hand held digitol tempreture gun measure the upper and lower hoses.

This is your first start....
When you get this far post back and we can move to the next steps.

 

If you start another thread and needing the suggestions to a service-related issue you are going to make it confuse and time consuming for members that may answer and ask the same question
on your 2 threads same related help advise.


Duplicate thread!

2012 M6 2.5 radiator pressure test point - Mazda Forum - Mazda Enthusiast Forums

 

The temp sender is what the ECU reads, correct? so if its hot on the sender, the ECU thinks its hot too? Whats the reasoning draining some coolant prior to testing with IR heat gun at hoses? I think I can rent the pressure tester at my local store. Is the heater core circuit part of the overall cooling or is it a bypass circuit?

 

Debris and contaminates can settle to the lower area of the cooling system which is the radiator. You only need a cup at most. That amount would in no way affect any aspect of the function of the cooling system. As a DIY having and equal cup of new coolant helps for reference of color .

You can rely on the sensor accurate reporting now because of your description of the heating issue which may have damaged the sensors. You can do comparing temperatures manually and what is reported by the ECU.


Good idea about the pressure tester. Make sure before you leave where you rent use of the tester that it has the correct small adapter for your radiator.

 

UPDATE. I changed the pump out as it was pretty cheap and easy to do. I found the original 150,000 mile FoMoCo pump was not very smooth in its rotation and the pulley was mirror smooth. I think this pump was binding causing the belt to burnish the pulley and stop circulation. I replaced the belt too. started it back up and tried the 5000 (Ford) and 3500 RPM (Mazda) for 5 minutes x 4 to burp all the air bubbles out and found the electronic throttle would not allow me to keep those revs in P, it would drop them down with no pedal change until I got off the pedal and it would reset. I read in the manual that is normal but why does the burp process call for that, does it not do that in N? So I made a radiator adapter (pic) that allowed me to screw a inverted 2l bottle onto the filler neck, cut the bottom out and use it as a coolant reservoir that was higher than any part of the engine. They make these systems for purchase. I let it idle with 4 inches of coolant over above the filler neck and watched the bubbles come up...for 20 minutes! WOW, who would have imagined a "full" radiator would have this much air in the system? I used a scanner to monitor the coolant temp and found the stock 185 thermostat would open at about 210 (massive drop in coolant level and would spit some back up if you didnt quickly top off coolant in bottle) and then the coolant would rise back up to about 8 inches, burp a few times and stabilize until the stat opened again with a sudden drop in coolant level. Watched this for about 20 minutes total until I was stable at mid range on gauge, 210-215 on scanner and no more bubbles. Gave it one more rev, fluid dropped only about 2 inches this time and we quickly removed the aperatus and capped the rad off. we then filled the reservoir to the H level and capped that and took it for a 10 mile freeway run. Needle never moved even with AC and lights on. I believe we solved this to: a bad pump (maybe binding?) bad belt (not likely but needed one anyway) or very stubborn air pockets in a refilled system (most likely) this part can be downloaded here: https://cults3d.com/en/3d-model/tool...-and-receivers
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Nice work!

 

Couple things

the Mazda/Ford thermostat is fully opened at between 195 and 205f depending on age , brand and type.

hopefully during your coolant process you had the heater on max temperature


but not to worry your head did not have steam pocket issues in the casting so your bleeding was extra precautionary.

 

yeah, max heat and the scanner showed a rock solid 210F when it was all said and done. At about 214 on the scanner the (new) stat seemed to open as it would raise the level, bubble furiously and then suck it all back in to repeat the cycle. Im not sure where the temp sender is but Its probably not close to the stat temp. I was still getting bubbles but I think it was actually the water boiling out of the unpressurized 50/50 antifreeze @ 223F we use here as it was bubbling for 30 minutes. and there is no way there could have been that much air in the system and I had a gas meter analyzing the bubbles and thre were no hydrocarbons or elevated Co2 detected from a head gasket. Rreally an eye opening experiment to see how much air can collect in a closed system like this when everything is lower than this elevated reservoir. Ill post a vid once I upload it and edit a 25 minute observation to a 1 minute clip.

 

vid link here, just watch it in 2X speed to see what the cooling system does when there is suspected air pockets in it. @8:44 I had to refill my distilled water. It comes down when I rev it and then slowly comes back up, somtimes with vigor! For a closed system, where is all this additional volume coming from? this is a plastic soda bottle with a rubber gasket, a small gatorade bottle works bettter as the opening is almost the right size, just wrap with a rubber glove or pipe tape. It finally seemed to stabalize after 23 minutes of idle at full heat at about 210, I think some of the smaller constant air bubbles were in fact the water percentage of the coolant boiling out as there was no pressure in the system to raise the boiling point of 50/50 mix at 224F.