Welcome to the forum!

Not sure why but I needed to approve this before everyone else could see it. Free bump for your troubles.

 

U have broken gasket under cylinder head.

Sent from my RMX2170 using Tapatalk

 

As mentioned, we don't think so. There's no real proof of that: No white smoke from exhaust (not even a little during cold start, save for maybe condensation), and oil is clean.

I do follow the logic: Having hot gases blowing past the gasket into the coolant system could result in 2 scenarios:

• Hot gases blasting past the temp sensor, resulting in seemingly high engine temps (though this on its own does not explain the sometimes hot, sometimes cold HVAC).
• The leaked gases could create air pockets, resulting in waterpump functioning incorrectly, meaning bad circulation.

I will, however, ask my mechanic to do a compression test, and check for excessive bubbling in coolant reservoir while revving the engine.
Higher revs should mean more bubbles, especially under boost, no? At the very least the gases should somewhat displace the coolant.
Possibly check for exhaust chemicals in the coolant if they are able to test that.

 

Just had a call, he did a quick flow test for the radiator and to him it seemed to flow a little slow.
He's going to perform a pressurised test now, and see what happens then.
If it turns out to be a (partially) clogged radiator, I hope it can be flushed. Fingers crossed.

EDIT: Unfortunately the radiator flowed just fine.
Next up is flow inside engine block, and compression test of cylinders.

 

If I were you I’d do a pressure test of the coolant system. It’s super easy (if you have the tools) and takes little time. You could have air entering the system due to an old hose or clamp.

 

That's a lot of details and as such, I'll be similarly stumped! I hope someone else can offer their opinion.

 

Thanks all for the replies!

Yeah, other than a blown head gasket, trapped air (either due to bad purging or small leak) seems to be the logical reason for these issues as both the thermostat and waterpump can be ruled out (although the new thermostat could still be faulty, I supplied them a lower temp unit just to make sure, and I've also asked to check the "new" 'stat outside of the car).



Haha, yeah, I don't want to be that guy who only supplies partial info, resulting in a bunch of unnecessary questions. As a "former car guy" (I'm not as active in the scene anymore), I know I hated it when newbies asked a question regarding their car, only for the more experienced guys having to conduct a full blown "mechanical anamnesis" to figure out the exact problem.

When I read this originally it sounded like the system could not reach pressure because the overflow cap was off. The entire system is pressurized and will overheat if not sealed.

I am in the "trapped air" club here. I have a difficult time purging air from by v6 and it required me to take coolant hoses off. Perhaps rapidly and forcefully squeezing different hoses with the overflow off to help?
Mazda has a fairly detailed purge procedure.
My phone does not tell me which heading this is posted in but I saw 2.3 turbo?

The intermittent nature feels like trapped air.
My temp gauge will do what your does or the opposite where the gauge reads low but the heads super heat if I have trapped air.
A coolant temp switch is pretty cheap and may also be on the way out and worth ruling out.

Correct, MS6. I've indeed asked my guy to replace the temp sensor, I don't know if it will have impact, but it's cheap to replace. Hell, might even be the cause due to leakage. Who knows?
As for the overflow cap; I only had it pop off once, right at the start when these issues began. Or at least then I noticed it.
I think I've read somewhere that the system is self-bleeding (also thought this myself due to the way the overflow tank is set up), but I'll forward the purging sequence to the garage regardless.

If I were you I’d do a pressure test of the coolant system. It’s super easy (if you have the tools) and takes little time. You could have air entering the system due to an old hose or clamp.

Would any leak not result in the coolant leaking out? We could not find any obvious coolant leaks.


Again, thanks for the replies, I'll keep you posted.

EDIT: Would removing the temp sensor help with bleeding the air? I know it sits fairly high on the block, and as long as the coolant isn't too hot, maybe it can be used to aid in bleeding?

 

When I read this originally it sounded like the system could not reach pressure because the overflow cap was off. The entire system is pressurized and will overheat if not sealed.

I am in the "trapped air" club here. I have a difficult time purging air from by v6 and it required me to take coolant hoses off. Perhaps rapidly and forcefully squeezing different hoses with the overflow off to help?
Mazda has a fairly detailed purge procedure.
My phone does not tell me which heading this is posted in but I saw 2.3 turbo?

The intermittent nature feels like trapped air.
My temp gauge will do what your does or the opposite where the gauge reads low but the heads super heat if I have trapped air.
A coolant temp switch is pretty cheap and may also be on the way out and worth ruling out.

 

Here’s the procedure for the Mazdaspeed/MPS 6.

 

It should be noted that the above procedure did not entirely work for mine. It would start overheating before I could complete it. Frantically pumping 🙄, blowing hard 🥺, through the coolant hoses with my lungs was what helped, with the heater line fully open and hot of course.

 

I used that once and it worked ok for me. After I rebuilt the engine I didn’t bother I did my own version.

 

Thanks for your input guys.
Latest verdict is insufficient purging of air after thermostat replacement (thermostat was probably the main issue). They spent 2 hours purging the air from the block before no bubbling could be heard in the radiator/coolant system, after I forwarded them the procedure above.

Hopefully this will fix the issue, I will let you guys know tomorrow.

@jsilva: I keep reading your name as "Silvia", but that's due my Nissan background xD.

 

I know this is an old post, but wondered how they purged the air from the cooling system? I bought a vacuum purge system for future use (haven't used it yet) that you pull a vacuum on the cooling system, then allow the vacuum to draw the coolant into the system. The vacuum takes virtually all the air out of the system before you let the coolant in.

I just wondered if this was a good way to evac and fill the cooling system on the newer Mazdas in general? We have a 2014 Mazda 6 and a 2009 Mazda 3. An A/C technician used a similar vacuum system on my 1998 Chevy S-10 and it never needed topped up while running. It was filled right from the start.

These aren't very expensive (maybe $120) but I got mine for a little over 1/2 price because it was an Amazon return. It looked like someone used it for a one-off coolant replacement job and sent it back (a bit dirty) for a refund. Not very honest of the person, but I benefitted from the steep discount.

 

Driving home (<5 miles) driving normal speed (not pushing, max 50mph), I had the issue again.
However, the issue was much more intermittent than before.

I saw temps quickly creep up until they stabilised at normal temps, but then it crept up again and heater turned cold.
Then, when nearly home, it again stabilised somewhat. At home I noticed quite a bit of coolant had spilled out of the breather hose of the overflow tank.
Let it idle a while and did some short 2500rpm runs (not 5 min as this was for testing purposes only). Temp was around 108 degrees C (226F). Heater blew warm, then hot (to a point where I said "ouch").

There was still definitely a lot of air in the system, quite a bit of bubbles in the tank, and I could feel it in the upper hose.

Did some squeezing of both hoses which, after some coolant came out of the breather, made significant improvement to both heater and coolant temp (93C/200F).

But then the upper hose collapsed on me. After some wiggling it was ok again. I'm going to order a new rad cap just in case.

I'm gonna check coolant levels tomorrow again, and test the cooling over the course of a dew days.

If I see no improvement, I will return to the shop and have it pressure tested (I never got around to asking it because they were convinced they found the problem).

 

Whelp, I just found this:

Coolant boiling issues without overheating - Bad rad cap?

UPDATE: To make sure others can find the fix, assuming no coolant leak, if your coolant is bubbling over AND your upper radiator hose is easy to squeeze wall to wall while at full temp, then CHANGE YOUR RADIATOR CAP! Yes a blown gasket can cause bubbling in the coolant, but the system would...

www.mazda6club.com

Can someone confirm pressure rating is about 19psi?

Edit: Nevermind, it says so on the cap I currently have.

The coolant level is much lower now.
Also, this looks empty-ish, no?

 

Man, I have had same issue and complete all the way step-by-step before realize that it is head gasket issue.

Sent from my RMX2170 using Tapatalk

 

Man, I have had same issue and complete all the way step-by-step before realize that it is head gasket issue.

Sent from my RMX2170 using Tapatalk

You mentioned this in your first post, yeah. But then I would expect the bubbling to be present all the time, no? Not just when the coolant is hot.

Also, if there IS an issue with the HG, wouldn't the coolant immediately expel from the breather hose? As the gas trapped in the coolant system would first fill the highest cavities, replacing and forcing out whatever coolant there is between the gas and the only open connection (rad cap if it is off, or breather tube when rad cap is replaced).

EDIT: Tested again just now, temp got up to previously mentioned high temps again. Both rad hoses very hard, could barely squeeze, no coolant spilling, no bubbles. Heater scorching hot.

Turned car off, and heard more bubbles as it cooled. Either rad cap is leaking, I have another air leak, or HG.
If rad cap replacement does not work, I'm taking her back for pressure and compression test.

Sidenote: As someone who has never seen a failed headgasket in person, how thick should the smoke from exhaust be in that case? Like, Steamboat Willy thick, or breath in cold temperatures thin (so basically condensation)? I have a bit of the latter but it hasn't concerned me until now.

 

At early stage of HG lamination high pressure needed to leakage of hot gases from cylinder to coolant, it is the only one way leak. This is how i can imaging this.


Sent from my RMX2170 using Tapatalk

 

Honestly it kind of baffles me that the garage you’re taking to hasn’t already done a coolant system pressure test. It takes less than 5 minutes and will reveal weak points if there are any.

But changing the cap is a good plan. Simple and will either rule that out as the problem or fix the problem.

Personally I wouldn’t put much thought into the head gasket being the issue until you rule out simpler and easier issues to diagnose. But you can get a kit to test for exhaust gases in the coolant system. Here’s a video explaining (there may be better, but it’s the first one I turned up):

It seems to me that if it were the head gasket leaking exhaust gases into a coolant jacket that you wouldn’t hear bubbling after the engine has shut down.

Where are you located SAHE, generally speaking?

 

I'm in The Netherlands. It's not as common for people here trying to fix their own cars, it's usually hobbyists or car fanatics, and I can do many things myself, but we usually lack things like a place to work, no driveways and such.
If I had a place to do it I'd probably tried these things myself.

As for the pressure test, I did suggest it but they were adamant they had found the issue.
So either the trapped air was the issue but they haven't fixed it thoroughly enough, or it was just a symptom and the problem lies elsewhere.
Though I do agree that a pressure test would be less invasive than changing the thermostat even.

I hope to receive the cap next Friday, so hopefully I have more info then. I'm running out of cheap fixes haha, even though the man hours were somewhat expensive. On the other hand, they charged me less than they actually worked. Hell, they even charged me only half of the coolant used (I double-checked that they did indeed use enough!).

Edit: After checking the video, they guy is talking about steamy bubbles coming from the coolant.
This is similar to what I've seen happening a few times. Smoke or steam in the reservoir, but it could also be just super hot coolant.

I'll see if I can source one of those kits in The Netherlands.

Edit2: Garage did tell me they used some sort of sniffing device that measured (amongst other things) for exhaust gases; they could not find anything unusual.

 

I posted a message yesterday but it is awaiting approval from a mod (why? Did I use a bad word?).

Something peculiar I noticed this morning, because I had an epiphany:
The bleeding system on the reservoir was not working properly; I tried blowing coolant into the rad by blowing on the breather tube with the rad cap off (so I was sure the rad was topped off, the coolant in the res is all I have at this moment), and I only blew air.
Turns out the pickup tube in the reservoir was above the coolant level (there was a noticeable curvature in the tube). Yes, the coolant was above LOW, and below MAX.
I rotated it a little, and sure enough, I was blowing coolant from the res into the rad. Did not have time to do a purge but will try tonight.
Could this be the reason why I got so much air in the system? That it just drew air when the coolant cooled and shrunk in volume?

 

I posted a message yesterday but it is awaiting approval from a mod (why? Did I use a bad word?).


?

I don't think so. I suspect that the site is automatically doing it. I've seen a couple of threads where one of our moderators will approve it to be posted when clearly it is not a Spam.

Speaking of Spam, I haven't seen one lately except in the supermarket.

 

Well, that was... Surprising.

After repositioning the pickup hose in the reservoir, temps were very stable.

Warmed up car with small errand drive, let it idle to get up to normal temps.

Hot air
Stable temp (highest was about 105C/220F when the rad fan kicked in and temp dropped to 93C/199F).
Turned on the AC and temps dropped even further to 85C/185F (I have a 82C thermostat instead of 90C btw).
I even actually tried to force the temps by revving to 4000rpm, but again it never got THAT hot.

This is a huge improvement over yesterday!

Temp when rad fan had just kicked in (set it to F for your convenience):

Temps after I turned on AC (and fan):

Tomorrow I will take it for a short drive, but damn.

Pickup tube in coolant reservoir. Who thinks of THAT?!

 

That’s great to hear! Sometimes car issues are ridiculous and frustrating

 

Alas, it seems that the quick fix did not fix things.

Took the car out for a drive in the weekend. All seemed fine, as shown in previous post.
This was a good 15 min drive on highway speeds, and some urban traffic.

Today I went to work (as mentioned before, about 7 miles, 3 traffic lights and about 4 miles of highway), and the issue came back in the last 2 miles.
Coolant warmed up slower than when the issue started (where it would increase about 10 degrees C every minute (can't convert to F, but I would assume about 20-30F)), similarly to the first test drive.
Then I saw it spike back to 117C in the last 2 miles or so.

Parked the car at work, and checked the engine bay:

• Coolant reservoir filled to normal levels for high temp coolant, no bubbling or whatever. No spillage. No smoke in coolant. Did see some black debris! Like, small flakes/specks.
• Both radiator hoses were nice and firm (so the pickup tube fix did to something after all), could not easily squeeze them. To me this tells me that the rad cap is fine. On a side note: How firm is too firm?

Tomorrow she's going back to the garage. Asked them to do both a pressure test on the cooling system and a compression test on the cylinders.
The black debris in the coolant somewhat worries me.

Anyone else have some suggestions? I'm back to square one.

The debris:

 

Sorry to hear! I think there’s a good chance the pressure test will turn something up. Perhaps the issue you fixed was the main part of the overall issue but something still remains.

I wouldn’t be too concerned about the black specs. You could siphon out the reservoir and clean it out if you wanted. Probably came from the hose.

 

About a week later, still no fix.

Last thing they changed was the temp sensor, and on top of it they topped of the coolant to the mounting hole.
Car acted pretty well after, but again, after 2 days I'm back to where I started.
Starting to look more and more to a faulty headgasket, where the issue only manifests when the engine is under load/boost (garage mentioned they only performed compression test, and "sniffer test" during idle).
I think the pressure in the cylinders is low enough for the HG not to leak, but at higher RPMs it will exceed the pressure the HG can "take".
On a side note: Would a compression test show any and all HGF? Or just "from a certain severity"?

Contacted another garage, and they're gonna perform some more tests to determine HGF.
I was this close to contact a local dealership, but as the MPS/MS6 is quite rare, I doubt they would be able to immediately pin it down without doing everything my current garage has performed.
Maybe some more "professional" versions of the testing equipment.
It would be more expensive anyway, and my current garage has given me several discounts already (charging half the coolant, and part of the hours).

 

Won't it be cheaper to inspect head gasket condition and replace it anyway? BTW inspect chain, valve gap and steam seals?

Sent from my RMX2170 using Tapatalk

 

I'm not sure, I mean, replacing the HG would take more hours than any test they can run, I guess. And that would add up quicker as well.
But at this time I might even consider doing this just to be sure.

Would any of those things have impact on coolant circulation/airleaks?

BTW, I realise you mentioned from the start that it would be the HG. Maybe you will be right in the end

 

I was looking for any other reason as you. Problem solved after HG replace. Everything, that have or can have impact on engine overheating were checked and replaced.
So it I'm interesting alot in your case.


Hmm, just now think that it is possible to test HGF by applying high pressured air into each cylinder and check for air leaks in radiator. The only thing is powerful compressor and engine warmed up engine due to termal expansion.

 

So has the garage performed a coolant system pressure test yet? Replacing parts hoping maybe they’re at fault is a waste of time and money. Pressurising the coolant system will reveal weak points. If this hasn’t been done then it really needs to be done.

Replacing the head gasket on this engine is a big job, and many parts should be replaced in the process—timing chain, guides, tensioner, friction washers, head bolts (which are expensive), intake/exhaust/turbo gaskets, etc.—not to mention having specialised timing tools. It is an expensive job. It’s not cheap even if you do the work yourself. I did mine back in Dec 2019 hoping to fix a compression issue, and it was a complete waste of time and money—I didn’t know what I know now.

If they checked properly for exhaust gases in the coolant then you can be pretty confident there isn’t a leak in that direction with the head gasket.

 

They told me that they did pressurise the coolant system and that it did not give any negative result.
They also told me they did a compression test. Which also did not showed any negative result.
They have performed some sort of gas-sniffer test and that they could not find any exhaust fumes anywhere, including the reservoir. I know that there are kits to use on the coolant itself, but I can't really dictate what a professional garage should do.
However, they did the last one at idle.

My thoughts would be that, in order to have a result for HGF (in terms of leakage into cooling system), the pressure in the cylinder should be higher than that in the coolant system, and high enough for the HG to fail. In my mind it could be possible that there's a minuscule crack in the HG that results in a failure/leak only under higher revs/boost, but nothing during idle/low revs).
So maybe they need to perform the test under load?
Additionally: What if the crack in the HG is so tiny, that even a compression test (which would normally be done by removing the sparkplugs, cutting fuel, and using the starter motor to crank the engine) will not show a negative result?

As for the costs for a HG job: Yes, I am aware that things can get expensive.
However, other than going straight to a dealer, I have very limited options to get OEM parts.
Local (read: Dutch) shops only offer aftermarket material. I am aware that OEM is always better than aftermarket, but as it is, the only source I can find is onlinemazdaparts.com (and some other US based companies). Other than that, it's brands like Febi Bilstein, or even more obscure ones like Ajusa (the only brand that even lists the head bolts with the "correct" OEM part number).

(EDIT: Dealers in The Netherlands generally don't sell parts directly to consumers)

If I go with the non-Mazda brands, I can get a full gasket kit, a timing kit (chain, guides, spanner/tensioner) and the aforementioned bolts for about € 350,-. And I should receive it before the end of the week.

For reference:

Complete pakkingsset, motor voor MAZDA 6 Sedan (GG) bouwjaar 2002.06-2007.08 | Winparts.nl - Cilinderkop pakking

Complete pakkingsset, motor 50286000 Ajusa ! Snelste levering in gehele BeNeLux

www.winparts.nl

Kettingset distributie 170105 FEBI voor o.a. MAZDA | Winparts.nl - Distributieketting

Kettingset distributie 170105 FEBI 170105 Febi ! Snelste levering in gehele BeNeLux

www.winparts.nl

Cilinderkopbout set voor o.a. MAZDA | Winparts.nl - Cilinderkopbout

Cilinderkopbout set 81042400 Ajusa ! Snelste levering in gehele BeNeLux

www.winparts.nl

If I will go through onlinemazdaparts.com, the amount would be $ 522, but I would have no idea when they would arrive, and also I will have to pay extra taxes, importduties, etc.
Plus, the material needs to be mounted.

I am aware that I should not "preemptively" address the HG, but at this point I have no reason to believe my garage hasn't done everything they can do to diagnose the problem.

As mentioned:the last time it held up pretty well, albeit for 2 days (whereas before it would not last an hour).
But air/gas enters the system somewhere. And it does not appear to do so under idle/low revs.

I will ask the local Mazda dealer for input, though.

 

Ok, I must have missed that they pressure tested the coolant system.

After you repositioned the reservoir rubber tube have you noticed the coolant level going down at all? Is the coolant up to the radiator neck after a longer drive and cool down?

It’s possible the rubber pickup tube in the reservoir has a crack or hole. Perhaps you could disconnect that tube and blow hard into it with one end blocked. Perhaps even inspect all of those parts—the tube from the radiator neck to the reservoir, the plastic reservoir top, etc.

Personally I’d suggest you wait to order parts for the head gasket until you have definitive reason to think it’s that. You definitely don’t want to do that repair on a guess (unless you’re doing the work yourself, and you’ll need more parts than you linked to).

 

When I repositioned the tube, I did saw a big improvement. It would no longer suck in air that way, when it was cooling down, but the coolant itself (even though I had a collapsed radiator hose right after). Yet, after that it would still "overheat".

I will double check all tubing in the reservoir in a minute. However, this would still not explain why the car behaved for a few days (I even drove some distance on the highway).

BTW, I've asked the local Mazda dealer for a second opinion (it's 1,5 miles from here), I hope to get a quote for diagnosis tomorrow.