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I recently noticed my car has been losing a decent amount of coolant. I fill it up from the thermostat housing and burp the system. If I take it for a drive and bring it back and check the thermostat housing (obviously once the car has cooled) I'm missing coolant. I don't believe I have any large external leaks (I don't see anything dropping under the car).
Do I assume the worst? Is it possible my coolant seals are failing?
When burping the system, before the thermostat opens, there's no air bubbles in the funnel. Once the stat opens, I don't get any large bubbles of air or anything, just a continuous stream of very small bubbles. Is that normal?
Sometimes the bubble test is deceiving. It will tell you if a seal is obviously bad (big bubbles) but I've noticed tiny bubbles sometimes which I don't think are unusual since the coolant can boil now that it isn't pressurized.
Is the car blowing clouds of steam? When you remove the spark plugs, is there green coolant on them?
The surefire test is a pressure test or an exhaust gas chemical test.
It is also possible that your car has a small leak somewhere you haven't noticed, which is letting it inhale air into the system. Basically the coolant should expand when heated into the OEM expansion tank, then get sucked back into the system as it cools. If there is a leak, sometimes it will suck air in instead of sucking the coolant back in.
Sometimes the bubble test is deceiving. It will tell you if a seal is obviously bad (big bubbles) but I've noticed tiny bubbles sometimes which I don't think are unusual since the coolant can boil now that it isn't pressurized.
Is the car blowing clouds of steam? When you remove the spark plugs, is there green coolant on them?
The surefire test is a pressure test or an exhaust gas chemical test.
It is also possible that your car has a small leak somewhere you haven't noticed, which is letting it inhale air into the system. Basically the coolant should expand when heated into the OEM expansion tank, then get sucked back into the system as it cools. If there is a leak, sometimes it will suck air in instead of sucking the coolant back in.
Understood. Based off of just that, then I think it's less likely that the coolant seals are bad. I don't see any obvious leaks, and the car doesn't blow clouds of smoke. It'll smoke on startup, but that's just normal cold start+pre-mix smoke. Once it gets up to temp, there's almost no smoke.
I check the coolant from the stat housing. My coolant reservoir doesn't drop at all. I've had it filled to the max and it has stayed there. But, the coolant in the stat housing and upper rad hose goes down. Would a water pump failing cause this? Or am I off base with thinking that?
The thing with coolant seals is that they can be frustrating to diagnose without the "proper" tools I mentioned above. I had a broken seal (and actually a broken groove on the iron) on a previous engine, none of the usual symptoms.
I think in your case the best thing to do is check for any leaks. I know you said you don't have any, but there are places like the heater core, the barb on the back of the engine for the thermowax, the hardline for the heater core coming from the rad, the fitting at the BAC, etc. These places can sometimes have a small leak that doesn't become obvious, but will let it suck air back in. Look for dried coolant residue in those areas.
Anyways, the only sure ways are to test with the tools I brought up. Otherwise unless there are obvious symptoms we are just speculating. But you can eliminate the other possible issues before paying for the testing tools and hopefully find it's something else.
The thing with coolant seals is that they can be frustrating to diagnose without the "proper" tools I mentioned above. I had a broken seal (and actually a broken groove on the iron) on a previous engine, none of the usual symptoms.
I think in your case the best thing to do is check for any leaks. I know you said you don't have any, but there are places like the heater core, the barb on the back of the engine for the thermowax, the hardline for the heater core coming from the rad, the fitting at the BAC, etc. These places can sometimes have a small leak that doesn't become obvious, but will let it suck air back in. Look for dried coolant residue in those areas.
Anyways, the only sure ways are to test with the tools I brought up. Otherwise unless there are obvious symptoms we are just speculating. But you can eliminate the other possible issues before paying for the testing tools and hopefully find it's something else.
Roger that. I did have a very small leak at the thermowax, but it wasn't leaking enough coolant (or at least so I think) for my coolant level to drop as much as it has. I recently took off the throttle body to delete the thermowax and double throttle system, as well as the fast idle cam. Just waiting on parts to plug the holes in the throttle body left by deleting the throttle blades. Guess I'll revisit this topic once everything is reinstalled and I've got the coolant lines that feed the BAC and thermowax blocked off.
And to answer the aforementioned question, no coolant on the spark plugs.
See picture where the coolant was leaking at the thermowax:
I would first start by making sure all of the air is out of the cooling system. Vacuum bleed it if you have a vacuum bleeder. Next, using a cooling system pressure tester, pressurize the cooling system to cap pressure and see if it holds pressure. If the system does not hold pressure then its likely that you have a coolant leak. If no external leak is found, its likely that the leak is one of the coolant o-rings or a corroded channel for the coolant seal or seals in one or both rotor housings.
So I have an update here. I haven't had the car running in about a month. I've been working on a few other things, and with it being cold here, it's difficult to work outside.
I went out to work on it the other day because we had a spurt of warm weather.
Coolant was low from last time I drove it, so I topped it off at the stat housing. I DID NOT TURN ON THE CAR. I mentally noted what level the coolant was at when I filled it. I came back 2 days later, and the coolant level dropped by about half an inch.
No coolant on the ground, no visible leaks that I can see.
If the coolant seals had failed, would coolant still be able to get into the combustion chamber without the car running?
I was under the impression that with all the coolant flow and combustion pressure, that's when coolant pours into the housings.
I'm speculating here, but I'm guessing over that long a period it could seep into the combustion chamber through a compromised seal, pressure or no.
This does give you a convenient way to test though. You could rotate the engine by hand a few times and see if the spark plugs come out wet with coolant. Or when you do start the car, that much coolant should give you a pretty significant cloud of steam that smells like syrup.
I'm speculating here, but I'm guessing over that long a period it could seep into the combustion chamber through a compromised seal, pressure or no.
This does give you a convenient way to test though. You could rotate the engine by hand a few times and see if the spark plugs come out wet with coolant. Or when you do start the car, that much coolant should give you a pretty significant cloud of steam that smells like syrup.
I've got the clutch fan out, so now would be a convenient time to turn it over by hand. Should I turn it over in the direction that it would normally turn when running?
If the spark plugs aren't wet, what's my next course of action here?
Turning it the opposite direction (counterclockwise as facing from the front) would be more likely to sweep coolant onto the spark plugs, as the coolant will pool at the bottom of the housing. I don't know if there's any harm in turning the engine backwards but I can't see how it would be bad.
If the spark plugs have no coolant on them then you need to start searching for a leak. I know you've already done that, but it can't go nowhere and if it isn't in the combustion chamber it's leaking someplace.
Turning it the opposite direction (counterclockwise as facing from the front) would be more likely to sweep coolant onto the spark plugs, as the coolant will pool at the bottom of the housing. I don't know if there's any harm in turning the engine backwards but I can't see how it would be bad.
If the spark plugs have no coolant on them then you need to start searching for a leak. I know you've already done that, but it can't go nowhere and if it isn't in the combustion chamber it's leaking someplace.
Got it. Any idea what size the main pulley bolt is?
I think 19mm, maybe 21. The solution DR Knight proposes is best, mine is just a simple way of telling if seals are definitely blown. The only surefire way are the proper tests.
I have been having this same issue, but I think mine is a faulty filler cap. The overflow bottle is below the fill up on the thermostat housing on the engine toward the front of the car, so it drips' out and keeps siphoning out, I am guessing until the vacuum was more then the ability to siphon. I tried to put a 1 way valve on it, but it just seeps past it. My next change is to run a long length of hose from that breather tube on that overflow tank to a location closer to the firewall, so it is higher then the filler neck.
I have been having this same issue, but I think mine is a faulty filler cap. The overflow bottle is below the fill up on the thermostat housing on the engine toward the front of the car, so it drips' out and keeps siphoning out, I am guessing until the vacuum was more then the ability to siphon. I tried to put a 1 way valve on it, but it just seeps past it. My next change is to run a long length of hose from that breather tube on that overflow tank to a location closer to the firewall, so it is higher then the filler neck.
That's an interesting take on it...I haven't been checking the level on the overflow tank, maybe I should.
Thought I would update again here, as I did some more poking around this evening.
Definitely not a coolant seal...at least an inner coolant seal. Turned the engine over by hand a few times, and the spark plugs were bone dry. If it was an outer coolant seal, chances are I would see it in the oil, correct?
As for the overflow siphoning coolant from the stat housing, that's a very real possibility. The radiator is completely full, and hasn't dropped since my last coolant flush. The thermostat housing is where I keep checking the level, and it's dropping from there. I checked my overflow, and it's WAYYYY past the "full" line. Going to replace the cap on the stat, and see if that helps.
If anyone else has any suggestions, please feel free! Would love to see if I'm maybe missing something
I've been chasing a similar problem. Where my coolant level drops after driving, and my overflow tank is full/overflowing. Your overflow cap should have one hose that dumps to atmosphere if it's overflowing. Check if you see any traces of coolant from this dump hose.
It's like WondrousBread commented in post #2.
To my understanding when the car is hot pressure builds and coolant expands into the overflow tank once the pressure that your cap is rated at is reached. When the car cools, it siphons coolant back from the overflow into the main cooling system (back past the radiator cap). So what might be happening in your case is the pressure builds and goes to overflow like normal. But once the car cools it's siphoning/pulling vacuum but air is getting sucked into the system as well. This could be from a tiny pin hole leak in a hose, radiator, fitting, etc.
What you can do to check is pressurize your cooling system and see if you hear any leaks. If you don't hear anything obvious, leave it pressurized overtime and see if the pressure drops (what your using to pressurize the system should also have a gauge, see if this reading drops). Also note that the pressure applied should be the same that your cap is rated for. If you pressurize too much you can burst or pop off your coolant lines.
When I pressurized my system before, I found a tiny leak where my upper rad hose mates with my radiator. I fixed that but still chasing hoping it is not my coolant seal as well.
Just another update here. Only things left to do is a pressure test as mentioned above. Gotta pick up a kit and just go for it.
One thing I found odd is HOW I'm losing coolant. The upper rad hose is almost completely empty.
On the thermostat side, if I dribble some coolant in there to fill it just until it crests the hump in the stat housing, I can visibly see the level drop again, as if coolant is seeping past the thermostat.
Should this be happening? Would a bad thermostat or bad water pump/ water pump gaskets cause this?
Again, no coolant in the combustion chamber from what I can tell. I've checked the dipstick and the oil doesn't seem like it has any coolant in it (will verify for sure once I do an oil change). No visible external leaks.
I'm at a loss for words. I have no idea where the coolant is going.
If you want a quick way to test you can disconnect the hose that goes into the overflow tank. Then use this hose to apply pressure. So it would be Pressure Source (hand pump, compressor, bike pump, etc) > hose > nipple where your rad cap is. Again don't over apply pressure.
The OEM Mazda thermostat should have a small jiggle pin. So even if your thermostat is closed a small amount can still bypass the thermostat. I believe the jiggle pin is there to prevent possible air buildup at the thermostat. Is your thermostat new? Is the weep hole of your water pump dry? But you might just be chasing your tail here. Pressure test first and if you have any bad seals/gaskets, you will know.
Sidenote: This thread made me pressure test my FC and I found my leak. Upper rad hose wasn't sealing 100% with the filler neck. My initial leak was upper rad hose to radiator not sealing. Haven't gone for a full test drive yet, but pressure is holding. Your problem can be as simple as this.
If you want a quick way to test you can disconnect the hose that goes into the overflow tank. Then use this hose to apply pressure. So it would be Pressure Source (hand pump, compressor, bike pump, etc) > hose > nipple where your rad cap is. Again don't over apply pressure.
The OEM Mazda thermostat should have a small jiggle pin. So even if your thermostat is closed a small amount can still bypass the thermostat. I believe the jiggle pin is there to prevent possible air buildup at the thermostat. Is your thermostat new? Is the weep hole of your water pump dry? But you might just be chasing your tail here. Pressure test first and if you have any bad seals/gaskets, you will know.
Sidenote: This thread made me pressure test my FC and I found my leak. Upper rad hose wasn't sealing 100% with the filler neck. My initial leak was upper rad hose to radiator not sealing. Haven't gone for a full test drive yet, but pressure is holding. Your problem can be as simple as this.
Got it. My thermostat is fairly new. Less than 5k miles on it.
I'm not aware of a weep hole in the water pump. What is that?
I think I'm just gonna bite the bullet and go buy a pressure tester from harbor freight or something today. I've got a new water pump, gaskets, rad hoses, etc on order anyway, but it'd at least be good to know where my problem stems from
That is something I had never thought of....valid point. Where is the heater hose inside the car? I'm sure somewhere under the dash, which would be a PITA
not sure, it's been a while. feel around where it comes in, around below the center dash etc.........it would not be VERY wet from the amount you are saying, so you might feel under the carpet as well.
could be the heater core or soldering point as it would probably be a pinhole leak. maybe just cover under all of it with newspaper and fillerup and wait a few days.
Water pumps have an internal seal. If you see coolant leaking from the weep hole, it means the internal seal has failed. Air can get in the system and even worse coolant will eventually contaminate your bearing and cause it to fail. A tiny tiny amount initially can be okay, but if it's constantly dripping this is a problem. It's main function is to indicate if your internal seal has failed. If the internal seal has failed, when you do a pressure test you will see coolant dripping from this hole.
I believe I found the root of my problem and resolved it. I'm 99% sure it was the water pump. Me and a buddy of mine replaced it recently, and the coolant level has not dropped. In fact, when I check the level in the stat housing, the level goes UP. I can probably attribute this to the system not being bleed, and the air in the system expanding and contracting due to the outside temperature
I'll pressure test the system to be absolutely certain, but I think the water pump was the culprit
12-26-21, 09:14 AM
