Coolant low, no leak?

[skyfarm1000]

I have a 2016 4runner, bought 2 years ago with 50k miles.

Replaced the coolant first thing when I got it and have put 10,000 miles on it so far. The coolant level was topped off to the max fill line when hot, overnight parking in the same space it always settled to the same spot about a fingers width below Max. I'd check it with my oil every month in the morning before work.

End of the first year (5k miles) I noticed the level dropped about 1". I topped it off and it was consistent level again for about another year until a few weeks ago (and 5k more miles) its 1" low again.

I thought it might just be the cold/winter, so I drove it for about 4 hours on a warmer day but the level still was 1" low. As far as I know its not normal for it to drop ~8oz every 5k miles.

So far I've:
-New radiator cap
-New overflow reservoir cap
-I cant find any coolant residue at all anywhere on the radiator, water pump, engine itself, heater core.

-No smoke on startup, no overheating, heater blows hot, no milky oil..



Any ideas?

 

[Hungryhawk]

I have not personally used them but there are test kits for coolant in oil, And for coolant in exhaust.
It could be a head gasket leak of coolant into exhaust.
If confirmed by these tests you could inspect spark plugs for the super clean appearance of coolant washing.
If caught early a head rebuild job could save the engine.
Any chance the engine was overheated in the past? Evidence might include stiff hoses from overheat, or clues of a new radiator?
Did you get a carfax report, most large shops report maintenance? Your truck also has a Toyota website dealer maintenance history that you can access. I have not used it but there are posts on this topic.
Good luck and it could turn out to be something simple!

 

[skyfarm1000]

I have not personally used them but there are test kits for coolant in oil, And for coolant in exhaust.
It could be a head gasket leak of coolant into exhaust.
If confirmed by these tests you could inspect spark plugs for the super clean appearance of coolant washing.
If caught early a head rebuild job could save the engine.
Any chance the engine was overheated in the past? Evidence might include stiff hoses from overheat, or clues of a new radiator?
Did you get a carfax report, most large shops report maintenance? Your truck also has a Toyota website dealer maintenance history that you can access. I have not used it but there are posts on this topic.
Good luck and it could turn out to be something simple!

Thanks for the advice, I tried one of those bubble fluid testers the first time it happened. The fluid didn't change color.

I bought it from a Ford dealership, low miles 50k. They had the carfax and there was nothing reported other than regular oil changes.


I'll check the spark plugs, I think I may also spring for a shop to run a compression test as well.

 

[Hungryhawk]

Toyota, like all vehicle manufacturers, utilize many sub-contractors for the hundreds of diverse components that go into their products.
One little defective outsourced part can cause labor intensive repairs and expensive new parts.
My 2017 SR5,at 48,000 miles, got first a new torque converter then 3 weeks later a new tranny due to a faulty TC FlexLock mechanism inside the tranny valve body. I was outside the 60 month Power Train basic warranty, but I had purchased a Platinum Service Agreement extended warranty which covered the $8k dealer billings. This experience shattered my belief in the Toyota Reliability myth.

This screenshot was from my internet research on my shudder/chatter drivability issue.

 

[BTO]

Seems like all three of our vehicles "use" a very small amount of coolant. Not enough to be concerned about but enough so that it might need to be topped off once a year. Maybe it's from evaporation?

 

[RRosco]

Only the water content of coolant evaporates, usually from the holding tank. The coolant level in the sealed portion of the system will usually be maintained. I run 4 vehicles and have had to add coolant to all of them. My 2 GMC trucks more than the 4Runner or ES 350. There are no leaks and no bad actors in the coolant system.

I have also gone through a period of adding right after changing the coolant. Appears that it takes a little while to get the air out and the system to settle.

If you have no leaks, smoke or coolant smell you should be fine.

 

[Bmnorm2]

It’s normal for some coolant to evaporate over time from the overflow tank, especially in hot weather. It’s more of a time issue in your case because you are only driving 5k miles a year.

If it drops a significant amount in a short time or any of the other tell tale signs (visual leak, white smoke) then you have an issue.

From what you describe you don’t have an issue.

 

[auspilot]

Yeah my 2020 also consumes a small amount of coolant over some thousands of miles. I can even smell it in the engine bay after driving for several hours. I think it comes out of the vent hole in the overflow tank cap because I can see a little pink crust there.

 

[03_4x4Runner]

I have found it tends to drop less if you do not try to keep it to the max setting all the time. Dont know why but it works for me. Seems like once it drops slightly it stays at that level longer. Mine is a 2014 no parts were ever changed except the antifreeze.