Air in cooling system - suspected headgasket?
 

Hi everyone. I'm very new to the mazda scene. Just began to like the mazda 3 hatchbacks recently and purchased my first a couple days ago. It's an original owner, 2004, 280k km (170k miles) with all the service records and regular oil changes, and it runs awesome. When i bought it I had checked the oil, coolant, and all other fluids and they appeared normal. The previous owner had known and told me about the air in the cooling system and how when the vehicle was at idle, cool(er) air would come from the heater.

I suspect a headgasket issue for these reasons;
- I tried to "burp" the cooling system, was somewhat successful for 1 day - air got back into the system
- Coolant reservoir smells of exhaust
- Did a 2 minute run above idle when cold and very small amount of pressure had built up in reservoir
- Took cap off and allowed vehicle to warm up, reservoir almost overflowed (however no bubbles were visible entering the reservoir)

Something to be noted is that I drove it 3 hours home without any issues, and around town the last few days with normal engine temperatures.
It's weird because the oil has a normal consistency and the coolant looks like a proper green. The exhaust smells normal, doesn't have a very "sweet" smell.
I'll also add that the thermostat was changed 1000km ago, and the water pump was changed at 200k (120k miles), and a coolant flush was done 5000km ago.

The reason I'm posting here is to see if im missing anything - if for some reason it's not the headgasket and I'm missing something small.

On another note, I also have a CEL on with code P0106 - MAP/BARO. When the temp gauge reads 1/3 i get a tick/quiet knock near the intake manifold/air intake. Apparently this has been on for a while, so naturally the headgasket (potentially) is my main concern.

Thanks everybody! looking forward to your replies.

- Lachlan

look at this:

http://www.tooltopia.com/uview-55000...ricegrabber_r1

i had a similar problem on one of our millenias. i did a water pump, and i had overheat. i even redid the pump, thinking i could have gotten a bad one. on a 2.3, this is a huge job. i did every burp method i could think of, nothing fixed it. upside down coke bottle, lisle funnel, incline, ramp, yada, yada. i was convinced it was air in the system. also, i was getting little to no heat from the hvac system. i finally bought this unit, and it solved all my problems. you need shop air to use this, but it fills the system 100% on a stone cold motor, and you will never have to burp it again. it will pull the thermostat open, so the system gets a perfect fill everytime. it works just like when you pull a vacuum on the a/c. the gauge will tell you if there is a leak, so if you do have a bad headgasket leak, it will not hold a vacuum. when i changed all the cooling hoses on our 2.3's, i had misconnected one, in the worst possible place. when i pulled the vacuum, it showed a leak, and i had to search for it. otherwise, i would have filled the system, then the coolant would have leaked out. i have used this tool many times since. it has always worked. many shops now use the vacuum system, some shops instruct the techs to ONLY fill this way

Looks like a good system but I'm pretty sure there must be a leak. The coolant flush was done 5k ago and somehow air got back in the system.thanks though. Anyone else?

you can rent a cooling system pressure tester from places like autozone, oreilly's, etc. it is easy to use, and it will tell you immediately if there is a leak. most of the time, coolant will visibly ooze from the leak. it will also test your radiator cap. failed radiator caps are common

I'm going to do a compression test tonight and then I'll check that out. Its a weird system, no rad cap per say, but a pressurized oveerflow tank. But thanks I'll check it out tonight.

the millenia 2.3 is the same way. system is filled thru the reservoir. lots of cars nowdays have the same type. if the radiator sits lower than the engine, which most do, then it is easy to get air trapped in the system. most of the time, the air bubble finds its way to the water pump, and it cavitates. the cooler air coming thru the heater at idle is another indication to me that there is air in the system. however, it should still pressurize. a cooling system pressure test is a lot quicker than a compression test, and if there is a leak, it might show where during the test. plus, you can also test your radiator cap.

Oh that's weird. Do you think it could be a fault water pump also? Ii did a compression test and got 190, 190, 186, and 175. Somewhat satisfied by these results. I'm going to change the cap and rebleed the system and if air comes back I'll get the coolant pressure test done ( about 160 to get it done here). Thanks!

160 BUCKS FOR A COOLING SYSTEM PRESSURE TEST? that is outrageous. you can EASILY do it yourself. if you can do a compression test, a cooling system is way easier. you can rent the kit from most any auto parts store, what you do is you leave a deposit equal to the cost of the kit, then when you return it, you get your money back. if you use a check, and return it the same day, you get your check back. the kit has a pump with a small gauge on it, and several adapters. you remove your coolant cap, use the appropriate adapter, connect the pump, then pump it up to probably 1 bar. looking at the gauge, it should not move. if it does, you have a leak. since the system is now pressurized, you look around for leaking coolant. if the gauge dont move, the system is sound. then you use the pump on the cap. the whole think takes like 15 min, tops. if you are getting cold air from the heater, my money is on an air bubble. if you are not successful burping the system, call around and find a shop that does the vacuum fill, and have them do it

Hey keninn.

Unfortunately where I am nobody rents out the pressure testers, I've tried everywhere and they all say you have to get it done. I tried rebleeding and using a new rad cap and unfortunately the air came back. The coolant level looks higher, but there is no loss of coolant. Weird? I'm going to wait until its warmer (still quite cold in northern Canada) and see what I can do. Might have to pay the 160 to get it done. Thanks man.