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Discussion Starter · #42 ·
Well, if the coolant is being displaced by air it needs to go somewhere, and that’s a lot of missing coolant. That’s too much to fit into an already filled reservoir.

How’s your oil?
Yeah, it is displaced into the reservoir (it's not completely empty, I think). So every time I "blow" it back into the system, after a short drive it gets pushed back into the reservoir. But the drive is short enough that the remaining coolant doesn't boil, it's just that the circulation fails due to the empty rad hose (and any excess gas/air is pushed through the reservoir).
I don't seem to be losing any coolant right now.

If your question about the oil is if it shows any signs of coolant, then no.
If you mean if there's enough: I would hope so, I topped it up a few weeks before the issue started. I haven't driven it much since.
If you mean if the oil is clean: I think so. It's not "new" clean, a little dark, but not pitch black or something.
 

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I’m a little confused. If the coolant is at the top of the radiator neck when the engine cools down, and the reservoir is near the full line, how is there room in the reservoir for the extra displaced coolant when the car heats up?

Yes I meant if the oil had coolant contamination.
 

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Discussion Starter · #44 ·
I’m a little confused. If the coolant is at the top of the radiator neck when the engine cools down, and the reservoir is near the full line, how is there room in the reservoir for the extra displaced coolant when the car heats up?

Yes I meant if the oil had coolant contamination.
No, the coolant is not at the top of the radiator neck when the engine cools down. It's difficult to explain, but I will try to put it "chronologically":

  • Motor is cold (morning, before drive).
  • I take off rad cap, no coolant visible in rad neck. The cap is wet, though, and I hear a faint "psssht" when I crack it.
  • Coolant reservoir is full with coolant.
  • Radiator hose feels empty (I squeeze and nothing happens, no coolant spilling from rad neck).
  • I lift the small bend in the upper radiator hose, so there is no "low point" where the coolant can settle before it goes back into the engine block (as I only have gravity to assist me there is no way for me to "force" the coolant in).
  • I transfer coolant from reservoir to radiator by blowing into the breather tube. Coolant exits reservoir through hole in radiator neck.
  • I do this until I'm sure the upper rad hose is filled.
  • I close the radiator cap
  • I drive a short distance, where eventually I see the temps creep up to the aforementioned 117degreesC (118 with new temp sensor).
  • When I shut the engine off, the engine itself is not overly hot (as expected from such a short drive), but the rad hose contains air again (and feels hard, but that's probably the high pressure of the air). At this point, all the coolant I transferred to the radiator earlier, is now back in the reservoir. There is no sign of spillage through the breather hose.
  • When the engine is cool again, the coolant is still in the reservoir and is not sucked back into the system. The radiator hose is empty (nothing happens when I squeeze it), and coolant is not at the top of the radiator neck. The hose hasn't collapsed either.
  • I repeat the steps above to get home.

I've been doing this for a few days now, and while it is not a solution, at least now I'm sure that there's a leak somewhere. Whether it is in the coolant system, or because of a headgasket failure, air/gases are entering the system resulting in the upper rad hose to be empty. If hot fumes escape from cylinder into coolant system, it could explain the high temp measured, while the coolant itself is cold to the touch (as well as the engine block itself).
 

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If the reservoir is near the full line and the radiator is low then you are low on coolant.

You may very well have another issue, but right now you are looking at the problem of your coolant being low. If this wasn’t the case then where is the missing coolant?

If I were you, I would go through that routine (again) which I posted earlier, or some version of it. If you do that successfully and you’re not leaking coolant then your radiator will be full when it’s cold since there is nowhere else for the coolant to go.

At that point you will be in a better position to know what’s going on. Your symptoms sound a lot to me like you’re simply low on coolant.
 

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If coolant level not at top of radiator after short drive, and previously you filled it up, then only reason is loose of tightness in coolant system.
I.e. leaks of coolant or leaks of combustion gases thru HG.
If tighten coolant is sucked from the expansion tank when engine cooling down.

Sent from my RMX2170 using Tapatalk
 

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If coolant level not at top of radiator after short drive, and previously you filled it up, then only reason is loose of tightness in coolant system.
I.e. leaks of coolant or leaks of combustion gases thru HG.
If tighten coolant is sucked from the expansion tank when engine cooling down.
I don’t think he is filling up the radiator. Rather, he transfers coolant from the overflow into the radiator. So it sounds to me like he’s just low on coolant and as it circulates the air is getting trapped in the upper radiator hose, and there isn’t enough coolant to naturally bleed out that air.
 

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Discussion Starter · #48 · (Edited)
When I got it back from the garage the last time (after which it behaved for 2 days of careful driving), some coolant did spill.
Since then, I've been doing what jsilva is referring to, and what I've tried to explain.
But the fact that it spilled (during which the temps spiked again) at all, makes me think that at one point I had enough coolant, yet the problem still presented itself.
Nevertheless, I will try adding more coolant (even though the coolant reservoir is half-full after I transfer the coolant to the radiator when the engine is cold, and full (but not overflowing) when "hot").
 

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Discussion Starter · #50 ·
It is significant. But it spilled every time we came with a fix, and I drove it for a distance.
It spills though the breather hose every time we fill the coolant, and I drive it for a distance. Something is pushing it out.
And for 2 days, it "behaved" when I drove it carefully (staying under 2500rpm, and not boosting).

What makes me believe that it is air that is forcing out the coolant (instead of overheating coolant expanding), is the short distance I drive before it happens (the engine block is not even hot to the touch, nor is the coolant). And the only reason the air would be this hot (17 degrees over normal boiling point of water) is that it is heated by the cylinder gases (ie. HGF).
If the air was heated through contact with the engine block, the engine block would need to be hot to the touch. And air is a horrible way to transfer heat.

I may be wrong, but after 3-4 purging cycles over the course of this issue, I would assume that at some point the system is filled with coolant.
And it seemed that way. For a short while.
 

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Ok. Forgive me if you have said that before and I didn’t see it.

Based on what you just said along with other things we’ve discussed I’d agree that the head gasket is likely a possibility.

What is the mileage on your MS6?

I remember you said that people working on their own cars is not common where you are, but perhaps you can make yourself an exception? :) My thinking is that replacing the head gasket will have expensive labour, and since there’s no way to be 100% sure that’s the issue maybe you don’t want to invest the money in a garage to do the work only to find out your head or block is cracked or otherwise damaged. That will be money lost.

If you’re able to do the work yourself, however intimidating that may be, you could conceivably get the head off the car and inspect or take it to a respected machine shop (which you’d need to do anyway to get it resurfaced). If everything turns out ok then you can proceed to order parts and complete the job. Maybe that doesn’t interest you at all though. Just an idea to consider.
 

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Discussion Starter · #52 ·
Normally it would be an option, and I can do things. But to have the head machined, I need a... Car to bring it there.
Also, I don't really have a comfortable place to tinker.
At this point I just want it to work. I'd say money is no objection, but although that is not the case, I'm finding myself to care less and less.
And about people not working on cars, those that do always run into problems when getting parts. It's usually aftermarket, or expensive when you must buy at dealership (but that's not common either).

Also, I'm definitely sure about the rad hose filling with air (it was pressurised just now) as I just let some escape through the rad cap (wasn't hot).
Rad hose immediately deflated and only air escaped.
 

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Ok, I didn’t realise the MS6 was your only car. Most of the people I come across who own them see them as a fun hobbiest car. Even besides taking the head to a shop, your car would likely be out of commission for a while if you did the work yourself.

When I rebuilt the motor on mine I was so busy that it ended up being a 3+ month project. Though of course doing the head gasket is a much smaller job, but if you’ve never done it before then it could take a while.

Hope this process ends up well for you!
 

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Discussion Starter · #54 ·
Thanks mate. I've had a few cars, amongst them a Nissan Primera P11-144 I overrevved (god knows how) that threw 3 of the the rocker arms, which I fixed in an afternoon, an NX2000 for which I soldered in a digital gauge cluster and had it working 100% (first one in the scene), and there's a Pulsar NX waiting for a new engine in my garage.

But I feel the possibility to fuck things up with the headgasket is scary enough to do it.
 

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In my opinion the main difficulty with these engines is that it’s so tight in the engine bay. But with the experience you have I honestly don’t think it’d be too much for you, if you’re at all inclined. Here is what’s necessary if you’re curious:

  • Drain coolant and remove battery.
  • Remove air intake and intercooler/air charge cooler.
  • Remove serpentine belt and power steering pump and set pump aside.
  • Remove throttle body.
  • Remove fuel rail shield.
  • Remove intake manifold.
  • Remove the alternator and set aside.
  • Remove crank pulley.
  • Support engine (jack or similar underneath).
  • Remove passenger engine mount.
  • Remove spark plugs and valve cover.
  • Remove timing cover (a pulley or two might need to come off first).
  • Remove timing chain tensioner and then the chain, etc.
  • Remove exhaust heat shields.
  • Remove the 4 turbo nuts.
  • Remove high pressure fuel pump and the bit it’s attached to (can do that much earlier).
  • Remove cams.
  • Remove head bolts.
  • Remove head along with the exhaust manifold.

I may have missed something and it could be a little out of order, but that’s basically what’s involved. The only extra thing when putting it back together is having the timing tools and making sure you do that right. Also getting the timing cover back on in that tight space and not messing up your silicone sealant is a bit of a pain.
 

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Discussion Starter · #57 ·
@fedosis , @jsilva : no info yet. I decided to not take any chances and bring it to the dealer, for a couple of reasons:
  • Headwork is a bit too much right now, I don't really have a place to work on it, and I do need to have access to a drivable car in case of emergencies (and it is drivable for very short distances).
  • The garage I brought my car to previously felt uncomfortable doing the job, as they have very little experience with this model
  • If they did want to do it, I would either have to buy the parts from Mazda or from a Mazda-specialised seller overseas (very few in Europe), and because I don't really have a proper list of what to buy, I might miss stuff. Or I would have to use off-brand parts for an application where I only trust OEM or better (also, no warranty on parts if they fail afterwards, same goes for the dealer)

So I will bring her to the dealer next Thursday and get a car on loan from them (should only cost me gas).
They're gonna perform a few tests, mainly focused on HGF or issues in cooling system, but I'm already prepared for the headgasket.
For me it's simple. Despite the issues and the milage (about 143.xxx miles), I won't find another car like this, considering the things already done to it (custom exhaust with bypass valve, Corksport TMIC, RX8 rims, Bluetooth adapter, tinting, lowering, and it had a tune somewhere, sometime in the past).

I'll keep you posted.
 

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Glad to hear, and hopefully it won’t be outrageous with pricing!

I also don’t want to get rid of my MS6. It’s a somewhat unique car and I’ve put so much work into it, and it’s fun to drive. So to think of getting rid of it seems impossible :)
 

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Just had a call. The dealer suspects a cracked head.
Did they explain why a cracked head vs. a head gasket failure? Personally I’d be suspicious at an ambitious diagnosis like that, even if they had looked at it in person (unless there are visible cracks, assuming a cracked head vs head gasket failure is not the logical first assumption).

I actually have a spare head. Also in my area it’s not too uncommon to see them for sale for not too much money.
 
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