NA Where's my coolant going?

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Lindberg

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Lindberg
I have a 2007 Toyota Matrix. When I had it inspected in March, the guy pointed out the coolant reservoir was empty. Since then, is been empty a couple of times, and I've put about a gallon and a half of coolant in.

My car's never overheated, but when the coolant is gone, the heat gauge does creep higher than usual.

No obvious leaks, nothing on the driveway, no unusual exhaust. So where's the coolant going?
 
I’ve had TINY little leaks that only leaked under pressure and where they vaporized immediately.

Could *sorta* smell coolant now and then. Eventually led me to residue. Was a bugger to figure out.

Also had them in a heater core which had same symptoms. Run your heater and see if you can smell coolant.
 
I'm not a mechanic, but had a similar problem with a 2008 Ranger.

My problem turned out to be a cracked thermostat housing. Undetected for a long time because it only leaked at a certain temperature, then the coolant evaporated before having time to drip, or show evidence on the motor itself.

~David C.
 
There is a dye available at most auto parts stores that glows under an ultraviolet light made specifically to find these types of “mystery” leaks. It leaves a residue even if the coolant immediately flashes off. Put it in, then next time the reservoir is low shine a light on the engine. If nothing shows on the outside it might be burning it up (head gasket, microporous leaks in the head itself, etc.) also keep a close eye on your oil. Is it higher than it should be, or milky…
 
Coolant leaks can be a real bear. Over the years I’ve had a cracked reservoir, a bad head gasket (two of them), cracked radiator, leaking coolant line O-ring, leaky water pump… most would leave

The coolant dye is not a bad idea, though some coolants show up just fine with UV light - and remember that if it’s UV dye for gas or oil, it’s likely not water soluble and will just leave a mess in your coolant reservoir.

Oh, and don’t forget - if you’ve run the system low on coolant, you’ll need to make sure it’s COMPLETELY purged of air, or it can start blowing coolant overboard. Doing that can be as simple as running the engine up to temp with the heater on, or as complicated as a vacuum fill setup.
 
About 50+ years ago I worked in a full serve filling station. Remember those)?
We often had people come in with similar stories. Once the engine cooled down we took off the radiator cap and pressurized the system. It was "usually" (not always) easy t find the leak that way. Especially if they had anti-freeze with a detectable color. It could be thermostat gasket, hose leak, radiator leak or something else fixable. It didn't really help us find blown head gaskets, but if you check the oil and it is brown and foamy, then you have a problem.
 
Seems like there's a consensus forming around a small leak. I'll check with the shop I normal use on if they can do a pressure test. I don't think it's leaking into the oil because the oil level is not increasing. If anything, it's burning a little oil.
 
Could be a leak. I assume no evidence of overflow out of the coolant bottle, right? Small head gasket leak could be present and you're burning it. Check the oil to make sure it isn't ending up in the oil pan, but I suspect you'd see the tell-tale milkshake at the most recent oil change.
 
JOhnH said:
...It could be thermostat gasket, hose leak, radiator leak or something else fixable. It didn't really help us find blown head gaskets, but if you check the oil and it is brown and foamy, then you have a problem.
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Yep.
Easy, quick free check. Pull the oil dipstick AND oil filler port cap after a heat-soaking drive. If the oil in either place looks like a chocolate milkshake, head gasket is blown.
 
A few years ago I had a similar question with a 2004 Subaru at 100k miles. It was gradually consuming coolant and that was a year when they had more than their fair share of head gasket failures. If that happens the repair can cost more than the car is worth. I took an oil sample and sent it for analysis, just like we do with airplanes. I told the lab I was looking for any trace of coolant in the oil. The UOA came back clean so I decided the car had another 10+ years in it and replaced the timing belt, pulleys, tensioner, water pump, etc. While doing this work I noticed the water pump gasket was in terrible shape. After replacing the water pump & gasket it doesn't consume coolant anymore. I got lucky, it wasn't the head gaskets; maybe you will too.

PS: if it sucks the reservoir empty, you may have air in your coolant passages. Don't let that reservoir go empty!
 
The
MRC01 said:
A few years ago I had a similar question with a 2004 Subaru at 100k miles. It was gradually consuming coolant and that was a year when they had more than their fair share of head gasket failures. If that happens the repair can cost more than the car is worth. I took an oil sample and sent it for analysis, just like we do with airplanes. I told the lab I was looking for any trace of coolant in the oil. The UOA came back clean so I decided the car had another 10+ years in it and replaced the timing belt, pulleys, tensioner, water pump, etc. While doing this work I noticed the water pump gasket was in terrible shape. After replacing the water pump & gasket it doesn't consume coolant anymore. I got lucky, it wasn't the head gaskets; maybe you will too.

PS: if it sucks the reservoir empty, you may have air in your coolant passages. Don't let that reservoir go empty!
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The reservoir has definitely gone empty. I refilled the radiator directly, but how do I get the air out?
 
My daughter's 2006 Chevy HHR had very similar symptoms as the OP. It was quite the PITA to diagnose. No external leaks, no sweet smell in the exhaust, oil and coolant looked OK, cylinder leak down was fine, cooling system pressure test OK. Eventually it dawned on me that the leak might be too small to cause the usual side effects. So I left the cooling system pressurized overnight. Next day I removed the oil drain plug and, lo and behold, out came coolant, followed by oil. I removed the oil pan, and could see coolant dripping out of the water jacket near the bottom of one cylinder. The aluminum block casting had become porous at around 170K miles. I ended up putting a used engine in it.
 
flyingbrit said:
My daughter's 2006 Chevy HHR had very similar symptoms as the OP. It was quite the PITA to diagnose. No external leaks, no sweet smell in the exhaust, oil and coolant looked OK, cylinder leak down was fine, cooling system pressure test OK. Eventually it dawned on me that the leak might be too small to cause the usual side effects. So I left the cooling system pressurized overnight. Next day I removed the oil drain plug and, lo and behold, out came coolant, followed by oil. I removed the oil pan, and could see coolant dripping out of the water jacket near the bottom of one cylinder. The aluminum block casting had become porous at around 170K miles. I ended up putting a used engine in it.
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I have saved engines like that with a block sealer that you add to the coolant . K&W block sealer, it works and is permanent.
 
Lindberg said:
The reservoir has definitely gone empty. I refilled the radiator directly, but how do I get the air out?
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If the car is not overheating, any amount of air ingested should be small and naturally bubble out as you run the engine. As it does, it will draw in more coolant from the reservoir. Just check the reservoir before every drive and ensure it's full. Not full to the top, because coolant expands and it will overflow when hot. Keep the reservoir to the top of the "hot" or "cold" fill marks as appropriate. You can fill with distilled water (do not use tap water), or with premixed coolant.
 
flyingbrit said:
My daughter's 2006 Chevy HHR had very similar symptoms as the OP. It was quite the PITA to diagnose. No external leaks, no sweet smell in the exhaust, oil and coolant looked OK, cylinder leak down was fine, cooling system pressure test OK. Eventually it dawned on me that the leak might be too small to cause the usual side effects. So I left the cooling system pressurized overnight. Next day I removed the oil drain plug and, lo and behold, out came coolant, followed by oil. I removed the oil pan, and could see coolant dripping out of the water jacket near the bottom of one cylinder. The aluminum block casting had become porous at around 170K miles. I ended up putting a used engine in it.
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UOA should also detect this condition. The typical case is high Potassium, but there may also be other elements like Sodium involved.
 
I use a vacuum fill to get the air out. Some engines it is a must like the Cat C12. You use compressed air to pull a vacuum and then it sucks in the coolant just like a AC freon fill.
 
Bleeding air: Depends on the engine/vehicle. Some have bleed ports, and elaborate procedures. For many vehicles, any air in the system takes care of itself eventually.
Stop Leak: In my experience, it tends to work well for plugging up your heater core. Not a big deal if you live in Florida. Not so great in Michigan. May or may not actually stop a leak.
Finding the leak: For my Rotax, I ended up using a pressure tester and leaving it pumped up overnight to finally find the leak (water pump seal).
Temperature gauge: If it moves up at all, you are hotter than you want to be. It's not a real gauge.
 
K&W block seal is not like Barrs leak and not left in the system. It also has to sit a couple days after installation
Importantly follow the directions, different than radiator sealer.
My mechanic mentor turned me on to it years ago and it did fix a couple of vehicles we used at work.

I also installed a rebuilt car engine and the rebuilder sent a can of radiator sealer to installed with the engine.
I guess To insure against porous castings?
 
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Capt. Geoffrey Thorpe said:
Stop Leak: In my experience, it tends to work well for plugging up your heater core. Not a big deal if you live in Florida. Not so great in Michigan. May or may not actually stop a leak.
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And radiators. And confirming may not stop a leak.

Back in the day we used a liquid glass metallic seal in a spare race motor that had water leaking into the oil. It was supposed to be for one race, but we used it for at least 10 races. It did work and worked well.

Something like this.

 
The coolant additive that Subaru recommended for the model years that were prone to head gasket failures was Holt's Radweld. It smells like ginger. That car never had this additive when new, but Subaru recommended it later when the head gasket issues became apparent. I did add the recommended amount when I did the timing belt and flushed the coolant system.
 
I’ve been holding off saying it, and am NOT recommending doing it, but I had a similar “mystery” leak in a dodge v-10 about 11 years ago. I needed it to keep going desperately at the time so I threaded a zip tie up through the vacuum break rubber seal in the radiator cap to prevent it building pressure ( the Engine never ran over thermostat opening temperature so I figured I could sacrifice the increased boiling point the pressure provided since it never got even close to 212, let alone 50/50 glycol boil point). “Mystery leak” disappeared, and I haven’t had a single issue with it since (knock on wood). I’ve driven it almost daily since with a atmospheric pressure cooling system.
 
A couple of thoughts.

Most auto parts chains will rent a pressure tester. Very simple to use. You remove your (cold) radiator cap and plug on an their adapter which then plugs into a hand pump with a pressure gauge. You pump up the system to whatever pressure is on your radiator cap. Then listen for hissing or inspect for liquid. The best part of this is you can usually do it yourself and it costs you nothing as you get your money back from the tool.

To remove the air (burp the system) you want to have the highest point of the system open to the atmosphere. As a simple thing, you can do this via your radiator cap. Leave it off and put the vehicle on ramps or a hill to where the cap is the highest point of the system. Then just watch the coolant flow and once there are no bubbles, your job is done.

Good luck.
 
guest user said:
A couple of thoughts.

Most auto parts chains will rent a pressure tester. Very simple to use. You remove your (cold) radiator cap and plug on an their adapter which then plugs into a hand pump with a pressure gauge. You pump up the system to whatever pressure is on your radiator cap. Then listen for hissing or inspect for liquid. The best part of this is you can usually do it yourself and it costs you nothing as you get your money back from the tool.

To remove the air (burp the system) you want to have the highest point of the system open to the atmosphere. As a simple thing, you can do this via your radiator cap. Leave it off and put the vehicle on ramps or a hill to where the cap is the highest point of the system. Then just watch the coolant flow and once there are no bubbles, your job is done.

Good luck.
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Unfortunately there are a lot of newer vehicles that don't operate that way and there isn't a "radiator cap". Vacuum bleeding is often necessary as many of the fill points for coolant are lower than the highest point in the system, no matter what incline you put the vehicle on.
 
SoonerAviator said:
Unfortunately there are a lot of newer vehicles that don't operate that way and there isn't a "radiator cap". Vacuum bleeding is often necessary as many of the fill points for coolant are lower than the highest point in the system, no matter what incline you put the vehicle on.
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Perhaps, but this is a 2007 Toyota Matrix. My advice applies.
 
Too bad our cars didn't stay air cooled, would have so much easier? Don't you think? lol
I am sure we all have stories about leaking cooling systems and trying to limp along.
I remember one time scooping water out of a puddle to put in a beater I was driving about 50 miles from home nothing nearby. I did make it home on puddle water.
In another 100 dollar 67 Biscayne I drove for a few months until I put too much rad sealer in and clogged the whole thing up. Went to the scrap yard at that point.
IMG_4606.HEIC

I don't use it as often as I should. It is a good idea to use during every flush and refill on all vehicles.
IMG_4607.HEIC

IMG_4608.HEIC
 
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