I wouldn't consider 205* to be overheating..... coolant boils at a higher temp than plain water, and even higher in a pressurized system. Without looking it up, I think it has to reach around 240* or more to boil.

That said, I'm not confident I can analyze your problem as to sucking air into your system. I can, however, verify a couple things about your overflow reservoir. It is part of a sealed system, but the reservoir itself is not sealed -- it needs to be able to vent air as the volume of coolant increases, and draw in air as coolant is drawn back into the radiator.

I'll look at mine tomorrow to see if I can figure out how the tank is made / mounted.

 

How good is yer radiator cap? It's a common failure part as the seal can git compromised over time and temperature. It's an inexpensive part to inspect and replace.

 

And hopefully it’s the cap and not the head gasket seal that is a known issue on the ‘05. I’m fearful of that myself as my mileage is at 213k now.

Also, you’ve had your coolant changed at least once? As for the bottle itself, not sure either. Parts diagram makes it look like it’s part of the radiator fan shroud.

 

As noted, the radiator overflow is not sealed. If it gets too full, it blows liquid on the ground. When less than full, it pushes air out of the bottle to the atmosphere.

As liquid is sucked back into the radiator as things cool, air is sucked back in.

Now I start guessing: I believe the connection from the radiator feeds into the bottom of the bottle. As the bottle fills, liquid is pushed up.

As things cool, the inlet now becomes the outlet, and being at the bottom, will suck the gravity fed liquid first. When you run out of water in the bottle, it will start to suck in air to the radiator. This usually only happens in the case from way up top, where you put too much water into the bottle, and it hit the ground.

I would restore the liquid to the owners-manual-suggested level, and watch it. Check it when cold before a few trips, and make sure its in about the same level.

If its not, you should see liquid on the ground if it leaking when cold. If its leaking only when hot, you probably won't see it cuz its all over the highway.

Good luck.

 

Got very busy today and this slipped my mind until now. I am unable to determine by looking at mine if the reservoir is separate or part of the shroud, as Moose suggested. The shroud is black and the reservoir is clear which makes me think it might be a separate item, possibly glued in place. If it's bolted in, the fasteners are well hidden by the radiator and condenser.

I don't know why you saw air bubbles rising from the drain plug.... that wouldn't explain the reservoir being full of coolant. I suspect the bubbles may have been coming from the bottom of the tube running down inside the reservoir, which means they were being pushed out of the radiator -- most likely with coolant. That tube appears to go down to the area of the drain plug. Easy enough to check -- drive it so it's fully warmed up, to simulate the same condition as when you saw the bubbles. Then remove the end of the rubber hose at the reservoir and check for coolant with air bubbles. Place the end of the hose into a clear container to catch whatever comes out.

 

thanks for the replies, I couldn't be online for a couple of days...

205* is hot for my normal running temps, and clearly enough to fill the overflow higher than I've seen it before. 193* is the hottest i've ever seen it run during this same 200mi round trip i've made over a hundred times, over
summer or winter) the past 10 year

the bubble that I saw, were inside making me think the air leak was at the drain plug

I did drain and refill the radiator coolant before, somewhere near the 100,000 mi mark. since then I had the radiator replaced with an aftermarket one by a friend. shade-tree mechanic... and the radiator cap also...

I don't recall the mileages when these were done?
but it makes sense to next replace the cap this weekend, while I drain and inspect the overflow reservoir system...

 

For sure the overflow tank and fan shroud are a single molded piece. Sorry. Mine started leaking recently as well so I put better clamps on the small hose at the inlet, the stubby rubber piece at the very bottom of the overflow tank, and on the small hose next to the radiator cap. So far leak-be-gone, but we shall see....

Not sure I totally understand the cap on the overflow tank. Underneath is a rubber gasket that is supported by four plastic pieces molded into the cap. It almost seems to me like there is a slight pre-load on the cap but IDK for sure.

Every engine I have had with head gasket problems has manifest itself by bubbles (combustion bubbles) coming up through the radiator and/or overflow tank during warmup. Keep an eye out for that.

 

OP- agree 205 is about 10 above normal at idle.
Fan clutch may be slipping a bit so ECT up 10 degrees at idle then comes back down at speed.
Original water pump?
Combustion gas in coolant easily checked with chem test kit, loan from auto parts store.

 

I guess the most prudent thing to do is to properly diagnose the cooling system with a pressure tester. The kit from Harbor Freight is about $90 and has adapters to test the system but no way to test the cap. Inspect the water pump at the weep hole and see if there is any residue build up. If there is, it will be time to replace the water pump.

https://www.harborfreight.com/radiator-pressure-tester-kit-63862.html

 

it is essentially still running hot... on my same 400mi loop, I drive every other week. 190* - 199* (it used to do this drive, staying under 190*) and I see it (scan-gauge) heat and cool with the up and down hills on the trip...

I did replace the radiator cap, and thought it helped? (more than a month ago)
last weekend I replaced the thermostat... and it, like the radiator cap... didn't really fix the world.


i'm beginning to believe that there is a pressure leak somewhere in the system (as BamZipPow suggested)

perhaps autozone has a pressure tester in their loan a tool program

 

The overflow tank is a symptom, not a cause. It is not pressurized. If it holds coolant without leaking at any temp, it's okay. If it does leak, it's always at the seams, which as pointed out, is a weak point in the design.

You can pressure test the engine coolant system to determine where the leak is.

Harbor Freight has one: https://www.harborfreight.com/radiator-pressure-tester-kit-63862.html

You can make one with a radiator cap & a Schrader valve for a compressor connection.

 

I did a coolant system pressure test today, and cant find any leak...

it held up to 20psi, for 15 minutes and only lost one psi...

I haven't a clue what to think of next.
I know hot engine coolant gets pushed under pressure into the reservoir but it doesn't flow back after cooling, and air takes its place in the radiator...

after running it today after the pressure test, I was able to siphon the coolant from the reservoir and pour it back into the radiator, and had no coolant loss? but in the past I have had coolant loss...

 

update on today...
I used the coolant pressure tester, to also test the radiator cap I just bought a couple of weeks ago (autozone)


so... it horribly failed. holding pressure way above 25psi

it is marked on the top, with an #11. I assumed it means 11psi.

11.4psi is the absolute minimum opening pressure according to Tacoma tsm. with normal operating pressures being
13.5 - 17.8psi

wouldn't it be nice, if my original problem is a bad cap. that I replaced with a brand new, cheap bad cap?
the Toyota dealer said the oem cap will be in Friday...

I'm keeping my fingers crossed...
I was just about to purchase the gasoline mixed with coolant, chemical tester... thinking it may be a failed head gasket.


more later

 

No pressure release in the cap is a dangerous situation as there now is no way to control pressure in the system. Very rare for this to happen. Pressure with no way to go means your whole cooling system now is a test of the weakest point. Seen it blow the gasket right out the side of a brand new water pump we had just installed and our pressure tester would not test it until we found one that would and at max 25psi no release.

Get this right, then fill the radiator and the recovery bottle to the full indicator mark (cold). It may be that your cap was not allowing the coolant back into the radiator and you got an air bubble in the pressurized cooling system which cause the overheat. Get it working right an hope you are OK, or live in a state that allows consequential damages which Va does not. I think California does and their labor rates are much higher than Va.

When properly bled the radiator should always be full when you take the cap off after a hot cycle (must be cold to check). Mark or fill to a mark the recovery bottle and monitor that level for at least a week on a daily basis. Radiator never needing a top off, recovery bottle never needing added coolant to get to established level, YOU ARE OK!!!!!!!!!!!!!!!

If the recovery bottle has a normal pressure cap it is pressurized, it just a flip open lid Not pressurized. Cad Eldorados were pressurized, maybe other GM cars, (not my field of expertise).

 

after my last, finding the new radiator cap being defective... I removed the drive belt, fan & shroud and looked around the water pump. weep hole was dry as if nothing ever came out of it, no stains... nothing. although the 240,000 mi serpentine belt, has some good cracks in it so I bought a new one to put in tomorrow... I had saved the original thermostat I took out 6 or 7 yrs ago... tested it in 180* - 205* water and it passed as it should according to what the tsm says it should do... so I removed the new ish thermostat I got from autozone (not a big fan of their parts, this week) and installed the old good Toyota thermostat...


tomorrow, its install the new belt, the new radiator cap, (from Toyota) bleed the system...
and see what I got?


it is still possible that there is blockage (reduced flow) in the radiator?
all the testing didn't address blockages (there are no leaks)…

more later

 

don't forget to bleed all the air bubble out, it might take 30-45 minutes, make sure u wait till no more bubble coming up on the surface. while u're at it, should replace the reservoir tank too, u could buy a metal one , it would dispatch heat faster and not crack like the plastic one.

 

plastic overflow which I first thought to be the problem, isn't...
the bubbles I saw and perceived to be a leak in the reservoir, was small amounts of air being pushed (under pressure) from the radiator...


but after checking the weep and air port at the water pump, after I had the belt and fan removed...
the water pump shaft isn't as free spinning as the tsm leads me to understand? not sure?
I can turn it easily, but with some minor resistance. I perceived the resistance to be the seal? rubber to the metal shaft... when I tried to spin it quickly as soon as I took my hand away, the shaft would halt. no continued spinning.
I don't know if this is normal?

and I don't know if its defective, could air be entering the system there?
pressure test, showed no leaks...
but still overflow fills, and coolant doesn't return to the radiator after cooling...

I have gotten a "loaner" block tester with the blue test fluid. drained the radiator half way...
gonna test it in an hour or so.
I really hope I pass this test...
i'd rather replace water pump and radiator, than have the dreaded blown head gasket.

more later

 

but still overflow fills, and coolant doesn't return to the radiator after cooling...

This concerns me more than running a few degrees hotter than you are used to seeing (but that's better now, you're making progress).


It is supposed to be simple. As the engine cools, the coolant volume decreases, creating a vacuum inside the radiator. The design of the radiator cap allows this vacuum to draw coolant from the overflow tank back into the radiator. If the cap (which you have replaced) is good -- and the correct type -- the only thing left that I can think of is a problem (split, cut, break, other?) with the hose from the overflow tank to the radiator nipple. If the hose isn't compromised in any way, maybe the nipple itself is cracked or broken.

 

So it's confirmed to be your radiator cap and not a gasket problem? That sucks, but it's not too bad.

 

thanks for the reply...
but nothing has been confirmed.
I did replace the cap, and replaced it again when the new cap failed the pressure test...
good thermostat at the same time as the good cap...
does now run in the 184*-190* range, where before it was 194*-200* range (cap and thermostat did that)

 

seems as I have just failed the block chemical test...
turned from blue to green in less than 2 minutes, didn't go yellow... but still failed
(burned engine gas took the place of coolant in the cooling system)

looks like I'm gonna be pricing to have the head gaskets replaced. (it's not something i'd attempt to do myself)

any suggestions on who to look for?
i'm thinking a local repair place where i've seen some Toyota and Lexus parked in the lot...

does anyone here have a realistic price for having the work done on their own V6 truck?

 

Well that bites! But I would rather know, and bite the bullet, than to continue on with an unsolved problem.


At this point, hopefully it's just (!) head gaskets. Don't blame you one bit for having someone else do the work. I would be in the same boat.


Mine has never had anything done to it besides routine maintenance so I have no clue what you should expect. Best of luck, and continue to keep us informed.

 

Guess I called it originally. I fear this will hit me someday. I’m now over 216k miles. At the repair prices of almost $5k, it’s a real PITA either way. At least labor rates out there are going to be less than here. Maybe it’ll only be $3k? Let us know what it ends up costing.

 

That sucks. Replacing the head gasket can be done at home, with the engine in the bay (maybe - I am not familiar with the layout of your truck), but it is a job. But - if the gasket failed then you really are going to want to have the block checked for warpage, etc. In other words, its not just pull the heads and slap in new gaskets. And since the heads are off, you have already hit all the labor to get to the point of checking valve clearances, inspect the valves and seals, all that. While it is a little more to check those, the bulk of the cost is getting the head off and you are already there. If you have some seals that are off, this is the time to replace them. Check for shops that have rebuilt engines or at least have the tools and skills to remove the head and inspect the engine. Alldatadiy.com tends to list the FSM spec for the number of hours to do these jobs, so it will tell you a tear down and inspection is xx hours per the book. You can then check the labor rates of local shops to see where you are at. But expect to be well over $1,000 for labor.

 

Oh man.. I don't know about you, but this does sound like a real PITA. If it was me, I might as well go look for a replacement car. I don't mean to be a bummer, but the cost and the time needed to fix the problem might not be worth it.

 

Sorry to hear about your car troubles. I too fear this will happen to me one day.

Same engine on the Rav4:

 

Sorry to hear about your car troubles. I too fear this will happen to me one day.

Same engine on the Rav4: How to fix

the Tacoma is the 1GR-FE, 4.0 V6