Coolant leak location

[boxjohn]

I couldn't find anything on the search, so new thread time.

Car is 06 hatch with auto trans and 85K. Nothing touched since 67K but no idea on history before that.

I have a slow coolant leak (goes from min to max on overflow tank in a couple hundred km) that is draining onto the ground from the driver's side rear of the underbody plastic panel. It appears to be from the rear of the engine and starts relatively high, but I'm not sure because there's a light misting/coating of coolant over most of the engine block and head.

Any ideas where this could be coming from? Thermostat? Is there any coolant going through the intake manifold? It's so minor I have a feeling it's going to be a bear to find.

[greyseason]

I couldn't find anything on the search, so new thread time.

Car is 06 hatch with auto trans and 85K. Nothing touched since 67K but no idea on history before that.

I have a slow coolant leak (goes from min to max on overflow tank in a couple hundred km) that is draining onto the ground from the driver's side rear of the underbody plastic panel. It appears to be from the rear of the engine and starts relatively high, but I'm not sure because there's a light misting/coating of coolant over most of the engine block and head.

Any ideas where this could be coming from? Thermostat? Is there any coolant going through the intake manifold? It's so minor I have a feeling it's going to be a bear to find.

i think there is coolant going to the throttle body, theres a place to check since its close to the front of the engine bay, other than that maybe just grab a flashlight and start looking. Maybe jack the car up and take the splash shield off and get another look from underneath

[silverstarmazda]

remember to only check it when its cold....hot coolant is known to be pretty violent at that temp and pressure. it will most likely cause permanent injuries if your not careful.

check the coolant hoses. there could be a pin hole or puncture. rubber also ages over time and becomes brittle so they could crack and leak a bit.after that, check the connections of the hoses to see if theyre tight. and if thats not the case, start looking at the gaskets.

[gabbygenier]

clean off what you can and try and see where its coming from. if its losing it that fast, it should be easy to spot where its from. start the car and run it for a bit

i had an issue like that but it was one of the hoses by the rad. i could be wrong but i dont remember any hoses going to the back of the engine for cooling. so thats not really a good sign if theres some in the back of the engine

[TheMAN]

unless you have or can borrow a pressure tester, you're best to go to a shop

[boxjohn]

Thanks guys. I forgot about the throttle body on these cars. That's more or less in the right location. I'll check that and the hoses/clamps, and if nothing obvious turns up I'll pick up a pressure tester and see what I can find.

I did look it over, with a few buddies and some flashlights, but it was just in a driveway without taking the underbody tray off or lifting it up or anything.


Is it completely inconcievable that it's a headgasket? I know those usually leak to the inside and I haven't noticed any tailpipe smoke or oil contamination/loss, but obviously if it's a head gasket I want to stop driving on it.

[gabbygenier]

i have yet to see a thread anywhere for a mazda 3 saying the head gasket went. not saying its not possible but considering the amount of threads on here and i used to frequent M3F, its a good sign.

any pics of where the coolant is on the engine?

[Nickzgrl]

if yu still have not fixed i can take a look. we get a lot of older 3's come in with ect sensors that leak or the plastic housing cracks the the ect goes into.

[Nickzgrl]

if yu still have not fixed i can take a look. we get a lot of older 3's come in with ect sensors that leak or the plastic housing cracks the the ect goes into.

just noticed says yur in Scarborough, the ect and housing i mention it near the top of the head, tranny side at the back. much easier to see from underneath but is possible to see from the top.

[boxjohn]

just noticed says yur in Scarborough, the ect and housing i mention it near the top of the head, tranny side at the back. much easier to see from underneath but is possible to see from the top.

Thanks, this sounds like right where I'm seeing the most coolant.



i have yet to see a thread anywhere for a mazda 3 saying the head gasket went. not saying its not possible but considering the amount of threads on here and i used to frequent M3F, its a good sign.

any pics of where the coolant is on the engine?

That's good on the head gasket front.


No pics cause I've been away from the car for a few days, but there's a thin mist of coolant basically all over the rear of the engine bay including the rear of the block, and just enough coolant to run drips from the drivers side rear of the undertray when parked.

[gabbygenier]

quickly looked under the hood of my car. i was wrong, there are hoses that go to the firewall. im guessing the heater unit.

clean those quickly and then check them for leaks as the car is running. my bet is one of those has a small pinhole in them.

[krimsalt]

does your thermostat work PROPERLY not just go to 1/2 temp after driving. My '07 leaked slowly like you described from the coolant temperature sensor

[boxjohn]

does your thermostat work PROPERLY not just go to 1/2 temp after driving. My '07 leaked slowly like you described from the coolant temperature sensor

I'm not sure what 'proper' operation is. it takes maybe 5 minutes to reach the lower middle of the temp gauge, and then stays there pretty much no matter what I do. I haven't noticed a big difference in the way it's operating.

Added to the list to check though.

[gabbygenier]

does your thermostat work PROPERLY not just go to 1/2 temp after driving. My '07 leaked slowly like you described from the coolant temperature sensor

from what hes describing, i dont see it being that. temp sensor is in the front of the engine and he says he has coolant on the back of the engine.

i had one of the front hoses have a pinhole. i noticed the puddle of coolant on the ground and found it easy once i took a look at it. the hose was falling apart.

[boxjohn]

I guess since I'm going to be draining coolant anyway I might as well replace the heater hoses and rad hoses while I'm at it. Cheap insurance. Heck on my other car I just replaced every vacuum and coolant hose I could find replacements for. Probably 10 metres of the stuff. This thing is newer but 6-7 year old rubber is still sorta suspect.

[gabbygenier]

good idea. although ive only ever had to change one of mine, the rest are still fine. 04 with 270000 kms on it.

if youre going to change them all, then change them and hope it was just a hose, which is what i suspect from what youre saying

[boxjohn]

Had to update just because it was so weird:

It's been a month and 3000+km in sweltering heat, hours of AC on idling on the DVP, 4 people and all their crap cottage trips, etc. and there's no sign of any more leakage. It's just... stopped. My best guess is that when I hit the back of the engine with brake clean so I could see any new leakage, that partially dissolved something and re-sealed stuff. It's a new one on me, never even seen it on a customer's car in a year or so in shops. But whatever, if it ain't broke anymore...