[BagiMT]

About two weeks ago I noticed that my coolant reservoir was almost empty. This was the first time I noticed any coolant loss. Of course the first things that popped into my mind was head gasket. But there is no sign of that, no white smoke, no coolant in oil. I filled the reservoir up and watched it over the last two weeks. It went down about 1/2 inch, with about 200 miles driven. Next thing I checked was for signs of coolant around the radiator, hoses, and water pump, but again, nothing. So I am a bit at a loss. It's loosing too much coolant to just top it off regularly, but I have no idea where I am loosing it. Any suggestions? This is a V6 with almost 190,000 miles.

[jdc62]

Head gasket leaks are very rare for these engines, especially post 2005 models. It’s likely the radiator. Look for crusty, red residue toward the bottom. I have a 2008 and replaced mine summer of 2017 at 130k. I’ve seen others on the blog with the same issue around this age.

Very easy job. Replaced the upper and lower hoses and thermostat at the same time. Rockauto.com is a good source for parts.

[simple]

08 here also with 130+K. While I haven’t noticed any coolant loss, I did an oil analysis with black stone, and they informed me that they found potassium in my oil. Potassium I guess indicates coolant. Granted you’d think you’d notice with the amount you’ve lost, but maybe it’s worth the oil analysis to make sure nothing is in your oil? I had an 04 years ago that had an empty coolant tank that I kept refilling. I never noticed anything in my oil during my oil changes but it had a blown head gasket.

[T4R2014]

Originally Posted by jdc62

Head gasket leaks are very rare for these engines, especially post 2005 models.

That's a bold statement.

Losing coolant might might be a possible cracked head or head gasket. ASSUMING NO LEAKS no air in system and no steam off. IF a big if there is a very small crack somewhere on coolant system or a tiny cut on a hose it might steam off with no signs of leaks. Lets hope it is this.

If messed up, OIL might not be milky now, it might be starting to. Keep an eye on the oil filler cap for milk shake stuff inside.

Might not show signs of it now, but maybe 5000 miles down the road.

I HOPE I AM COMPLETELY WRONG. BUT I AM TALKING FROM PAST EXPERIENCE.

[earthrealm]

i think a compression test on the engine and radiator will show who the culprit is.

[firebirdguy]

the early 4th gen v6's are very prone to head gasket issues, & it wasnt untill mid-late 06 that the issue was supposedly fixed.

bad head gaskets can show no visible signs like white smoke or milky oil, it can be very gradual that its not enough to create smoke or make the oil milky.

also the filler cap "milkshake" stuff is usually from condensation forming from short drives &/or the aluminum filler tube cooling faster than the rest of the engine & creating condensation build up mixing with oil. it's a very common issue & the 08 4runner i just bought had it when i went to look at it from the prev owner doing lots of short winter driving, & the tube issue. when i drove it 4 hours home, ALL the stuff on the cap was gone & has never shown back up.

the best way to confirm a head gasket if there are no major signs is with a oil analysis or testing for combustion byproducts in the coolant. but also check the radiator as mentioned, i had to replace mine due to a small leak/seepage on the bottom of the tank that the skid plate was catching so there were no drops on the ground, check the rad or look up on top the skid plate for wetness.

[UrbanRunner651]

If it is leaking that fast it is likely your radiator. look for signs of the crusted pink coolant on the 4 corners. I just replaced mine on a 08 v6 and it took me a while to find the area because of the fan shroud. Mine was in the upper driver side corner. Assuming you can't find any wet spots or the engine isn't running hotter than normal?

[Berty_K]

How closely did you inspect your radiator?

Took my a while to find my leak. See post 6 of my thread (link in sig)

If you happen to get a check engine light on with misfire codes 99% sure it is a cracked head/gasket situation.

Look for seepage of coolant. Hope for the best prep for $$$$$$$

[BagiMT]

Thanks for everyone's input. No CEL or misfire. No overheating. No wet spots either. Will check radiator again. I guess unless I visually find a leak next step would have to be pressure test of cooling system and engine.

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