Where the #*@! is My Coolant Going??

Does anyone know of any common coolant leaks/locations in the 2nd gen 4.0 V6 Tacomas?

When I changed my oil a week ago, I noticed my coolant was low. Very low, as in almost 2 liters low. I hadn't checked it for a while, and the oil looked like ordinary dirty oil, so I replaced the radiator cap and topped off the radiator. The overflow bottle stayed full, so I figured no worries. Tonight it occurred to me to pull the radiator cap, and sure enough it could use another 2 liters. It also hissed like it was a vacuum in there and sucked in a bunch of air when I opened it. When I look into the filler neck, I can see that the coolant level is right around the top layer of fins/around the height of the bottom of the upper radiator hose, which is exactly where it was last time.

My truck has never overheated, and I haven't noticed any puddles under it, although it's rained a lot lately and I park over dirt/mud/grass at home so I wouldn't normally see puddles unless they happened during the day somewhere else during good weather.

I'm terrified that it's a head gasket (it's a 2005 4.0 V6 with 166k miles and I just read about that issue for the first time), but it's only been about a week/150 miles since the oil change and 2 liters seems like a lot. The check engine light is off. The engine runs fine. There was some ordinary condensation in the exhaust the last time I started it, but nothing that made me think head gasket.

Tomorrow I'm going to use a block tester and check the cooling system gasses. Hopefully it's not the head gasket, considering how much of this truck I just replaced (shocks, ball joints, clutch, throwout bearing, brake lines, bump stops, skid plate, etc).

Has anyone ever troubleshooted a coolant leak on these engine before? Are there any known weak spots aside from the head gasket?

 

Look around the engine compartment, check underneath it. How did the oil look last time?

 

I once had a pinhole in front of the fan that I couldn't find til it got worse. It wouldn't leak until it got hot and the fan blew any evidence away while driving. Was extremely frustrating. That was on a first gen though.

 

Rent a coolant system pressure tester. The mass marketer auto parts stores have them. Go on youtube and check out usage videos. These are good for finding "external" leaks. I had a similar issue years ago. The pressure tester revealed the culprit.

If this doesn't help you may have an "internal" leak - head gasket. Hopefully not.

 

about once a year I have to add to my overflow tank (20k+ miles)

 

https://www.tacomaworld.com/threads/head-gasket-failure-on-4-0-toyota-engines.457364/

https://www.tacomaworld.com/threads/head-gasket-failure-on-4-0-toyota-engines.457364/#post-13509496

 

It does sound like a head gasket.

 

I am telling ya taste your exhaust water drops and spit it out, won't harm you one bit

if it is sweet in any way, head gasket. dead simple and fast test. taste like
plain water ? then run it hard, and check one more time. not sweet, and no water in oil... likely not head gasket

 

Update:
First off, it wasn't 2 liters low this time, it was about 1/4 liter low. Today I used a block tester with mixed results. Every time the fluid started to change color the system burped and it started sipping coolant, and I never got past aqua green. The oil looks fine. Still no codes. There was no visible exhaust out the tail pipe after it warmed up. However, there was still water in the tailpipe after it had been idling for almost half an hour, so I tasted it like 127.0.0.1 suggested, and it was bit sweet...not like candy, but not like water either. I also recall that I heard a swishing noise under the floorboards a couple weeks ago after I started it. I'm thinking it's the head gasket. And I just put $2000 into this truck. FML.

I'm waiting for some shops to call me back with estimates. I've done head gaskets before, but I don't have a garage where I live now, and would be doing it outside with the engine still in the truck. It gets crazy windy here, we get dust storms this time of year, and the weather can change almost instantly. I might be able to do it myself, but getting the heads decked would mean doing it during the week and probably at least 3 days of working on it. In the meantime I don't have another vehicle, so again, FML.

 

How is it shifting?

My 4.0 automatic's radiator failed allowing coolant into the transmission cooler and later into the transmission.. thus causing transmission failure.

Just throwing that out there.

 

If it is the head gasket, coolant will end up either in the exhaust, the oil or both of these.

I don't recommend the taste test, but when it's cooler in the A.M, start the engine and put a pan under the tail pipe end. Catch the condensation. There may very well be some(especially in humid areas). Eye-ball what you've collected. Does it look like clear water(OK) or do you see liquid whose color matches your coolant(not OK)?

Drain your oil. Capture it. Do you see the usual dark looking color(OK) or is it lighter in appearance - more of a chocolate brown(not OK)?

It is my opinion that there are leaking head gaskets and blown head gaskets. Neither are good, but the latter is a for-sure bearing killer. When/if it finally blows, the engine will overheat badly and run poorly. You may also notice a temp increase if it's in the leaking stage.

If a head gasket isn't sealing, your cooling system looses pressure and overheats the engine.

Also - check out post #7 in this thread:

https://www.tacomaworld.com/threads/coolant-reservoir-bubbling-and-filling-up.437255/#post-12676768

 

possible its weeping from your waterpump (especially if your on the stock pump with that mileage)?

 

Tasting any fluid or liquid from a vehicle doesn't sound all that appealing as everyone has different taste bud sensitivities.

 

Pressure test as Lester said.

If you don't find an external leak that way, a compression test will tell you which head is the problem

 

Fluids are different colors for a reason. Color blind can't tell.

All fluids have a different odor. Not everyone has the same reaction to smells. (you can make a living in the fragrance or food industry if you have a hyper sensitive nose)

All fluids taste different. It's why animals like coolant, and die from it if they can drink enough. Heavy smokers or excessive hot sauce users who've killed their buds may not be able to play well.

Point is, it's a fast old mechanic test that has worked for decades. Don't knock it unless you've failed at it.

 

Where is Foampile when we need him??

 

First thing I'd do is replace the radiator cap. Coolant can evaporate through a defective cap, in fact, this happened to me on a fairly new 1998 Corolla.

 

Pink milkshake of doom?!? That sucks. I've only read of one other report here on TW, four years ago in this thread

Thanks for your post.

 

He's still sorting valve shims.