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I ams not a normal human
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Discussion Starter #1
My car has been consuming a lot of coolant lately. At least a couple of quarts every two weeks. But I don't know where it's going. There are no visible leaks or puddles under the car.

Every now and then I get a whiff of coolant, but when I pull over I can't smell it anywhere in the engine bay. I thought it may have been the rad cap going bad, but I don't see or smell anything coming from there. There's no evidence of coolant pooling around the radiator or on the underside of the hood.

Maybe it's the heater core, but I can't find any wet areas in the interior near the dashboard. I do smell coolant inside the car sometimes.

The engine still pulls strong and clean, it doesn't idle rough or anything. I watched it get smog tested on a dyno and it doesn't look like it's burning coolant or anything else.

This is driving me batty. Could it be the heater core, and I'm just not finding any puddles inside? I mean, it's lost quite a lot of coolant, and I'd expect to find something, but maybe it's all pooled up behind the dash somewhere. That's all I can think of.
 

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//banned
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does it overheat at all?
even though you don't see any puddles on the interior, the fact that you smell coolant on the inside leads me to believe something is up with the heater core.
 

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I ams not a normal human
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Discussion Starter #3
The needle crept up stuck in traffic once when the coolant was low, but not very high. Like if normal was around 45 percent, then this would've been around 55 percent. It went back to normal anytime the car was moving, so I pulled in to the nearest service station and topped off the reservoir to get it back home. Since then I've kept an eye on the coolant level and the temp gauge, and it hasn't budged from the normal range again.
 

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The Vorlon
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You might be burning it up. Head gasket?
 

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Hopefully not.

Get under hood with flashlight. Check hoses, water pump, rad, etc. Be persistent, external leaks can be hard to find. And look for white stains around the various parts of the engine that seal off coolant where it's evaporating from the heat after it leaks out.
 

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Check oil, puddles, tail pipe.

Is your overflow reservoir always emptying as well? I have a similar issue. and have done 3 track days since, just keep distilled in the car. No abnormal amount of smoke out the rear, it would have seized my engine bay now if it was being mixed with the oil, overflow always gets empty, it never overheats unless radiator is missing 2qts of coolant.

I was supposed to loop the heater core lines to rule that out, but haven't with SoCal's weather. I also added another overflow bottle AFTER the OEM reservoir... sometimes water get into that bottle, sometimes nothing new is added, but I have to add a quart to 1.5 qt. every 200 +/- 50 miles. In how many miles is it consuming 1 quart?

Eventually I would take off the head, but for now the car drives, and I have no money for a reroute and new rad just yet.
 

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I ams not a normal human
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1,204 Posts
Discussion Starter #7
I sure hope it's not a head gasket. Need to do a compression test to rule it out, but my oil looks clean and it doesn't seem to be smoking even when under load.

But yeah, the coolant reservoir is also getting sucked dry. I'm keeping a jug of distilled in the car too.

The radiator is new, and it's a metal aftermarket 2-row. I don't see any leaky areas from the top, but I haven't gotten under the car with a flashlight yet either. It never lost coolant before the new radiator, though.

Then again, I can never catch the coolant smell under the hood.

I'll keep looking (and sniffing) around.
 

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I ams not a normal human
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1,204 Posts
Discussion Starter #10
You live in CA now so to hell with it anyway. Sell your Miata and buy a G35.
I don't live close enough to a lake to get much use out of a boat like that. Besides, I sunk about $5,500 into my Miata this year, and it's finally getting close to where I want it to be.
 

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Rehabilitation Officer
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Whats your mileage. I've gone through 3 headgaskets on prior miatas and I can tell you I could smell the coolant every now and then before they gave out. I actually got so used to it that I didn't notice it until a passenger would say something

and my car never smoked until they blew and produced a nice big ass cloud behind me
 

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I had the same problem with my car and it turned out I needed my radiator/coolant hoses replaced.

Might check the heater hoses, mine was doing this same issue..The smell and all and turns out the hose had a slight leak.


edit:

Another spot to check if yours still has the 1.6 is the rear coolant plug.. That was a pain in the ass to fix on mine, I JBwelded it shut. http://www.miata.net/garage/CoolingSystemProblems.html
 

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I ams not a normal human
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1,204 Posts
Discussion Starter #13
My mileage is 142,XXX. The car was built in June 1989. I replaced the radiator in August, but I didn't notice a problem until after I drove it out here from Texas a little more than a month ago.

The hoses could be the problem. They looked ok, so I didn't change them with the rad. Was going to save up a little more and replace them all with silicon hoses, but then I had to move out here and put that plan on hold.

Replacing the headgasket is going to be a huge pain in the ass, or really expensive if I have someone else do it. I hope it's not that. But replacing the heater core doesn't sound any easier. Or cheaper.

This sucks.
 

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I have a leak too and mine is where the heater hose goes into the back of the head. I tried to replace it once but it was a pain in the ass to get to and really cold in the garage. I just keep adding water. It doesn't go down that fast. You can see it on the back of the head/bell housing. Check that area.

This weekend it'll be warmer and I may change it.
 

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I'd also definitely check the the heater hoses - they've been known to go bad and only leak slightly.

Did you pull out the spark plugs to check if any of them has deposits on that would suggest there's coolant in getting into one of the combustion chambers? IME compression tests don't help that much finding a headgasket issue unless the head gasket is burnt through between two cylinders as you might not get that much of a measureable drop in compression.

I'd also try to pressurize (or get someone to do it) the cooling system with the appropriate tool to see if it's holding pressure and if it's not, trying to trace the leak.
 

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I ams not a normal human
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Discussion Starter #17
****.

This morning I smelled coolant again, so I took another look. There's something pooling where the block meets the head on the IM side back by cylinder number four. I'm hoping it could still be the fitting on the back of the head, but the bellhousing doesn't look dirty under it. Hard to see for sure with everything in the way, though.

How much does it typically cost to replace a head gasket? I hate to spend that much on a motor that's probably going to need a rebuild in the near future, but I don't think I can afford a rebuild now.
 

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Could be that infamous coolant nipple. I replaced mine a while back (not from it leaking, but as a preventative measure), but the very tip of the cap was cracking around the circumference. I think I bought an OEM HG for around $80, I got ARP studs for it too but if not that, get new OEM bolts. It's only a few steps further than a WP/TB change, if you can DIY.
 
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