Mysterious Coolant Loss in My 2002 Tacoma – Need Help!

Hey everyone, I’m back… and my poor truck has decided to give me another headache.

The other day, I took a short trip out of town (about 6.5 miles), and when I got home, I noticed my temperature gauge was running hotter than usual. My truck is a 2002 Toyota Tacoma PreRunner Limited, 2WD, 3.4L V6.

I popped the hood to check things out, and to my shock, the coolant was completely empty—not a single drop left. I was stunned because I usually check my fluids before heading out anywhere beyond city limits. Of course, the one time I don’t, the coolant is gone. I felt so dumb…

Here’s some background on the truck:
Last July, I did a lot of work, including:

• Replacing valve cover gaskets, intake manifold gaskets, water pump, thermostat & gasket, timing kit
  
  
• Flushing and replacing the coolant, transmission fluid, and filter

I did all this because the valve cover gaskets were leaking oil everywhere, and the coolant looked like a mix of every color imaginable. I knew this truck needed a lot of love when I bought it, and I’ve already put about $5,000 into repairs.

Right now, it’s throwing a P0420 code, but the catalytic converter has already been replaced. I haven’t done the O2 sensors yet, but I plan to soon.

The strange thing is, I don’t see any obvious coolant leaks—at least nothing noticeable enough to leave a puddle. So I’m completely lost on where my coolant could have gone.

Could the disappearing coolant somehow be related to the P0420 code? Any thoughts or suggestions would be greatly appreciated!

 

If you're ruled out cooling/heater hoses....radiator leaks....especially at the crimps

most common place for these to leak is those intake gaskets...

those have to be done well, or they leak again

suspect/investigate simplest first


look for rust or pink slime in the valley between the two heads

 

I'd be highly concerned the coolant is getting into the cylinders via a leaking head gasket or cracked head.

I would recommend you immediately fill and bleed the coolant system, and get on Amazon and order a cheap borescope.

You can inspect your cylinders and the top of your pistons through the spark plug tubes with the borescope. One or more of the pistons is going to look super clean and free of carbon if you're burning coolant.

Hopefully you're just not seeing a really obvious external coolant leak, because an internal one (cracked head, leaking head gasket) is a far greater problem.

 

3rz/2rz are plagued with head gasket issues...5vz ....lesser so

Its the cracks in 5vz heads....that are more common than HG problems

4 bangers suffer from both




A good sign that there is crack in your head......is you lose coolant intermittent
....you'll go a while, and then lose a bunch all at once.....

A leak down test may not reveal the crack unless its passed some threshold.....crack expands with heat on a running engine

Again I'd check simplest stuff 1st......these are tough old girls......if they're assembled correctly

w/ radiator being first suspect.......hair line cracks/ top/bottom crimp failure

if you have the pink stuff......obvious stuff can be ruled out quickly

if you're not using pink stuff.......better be using toyota gasket friendly stuff
.....like Peak10 or Prestone

 

If I have the same issue next time I head out of town I am going to take it back to the mechanic who I had do the gaskets. I didn't trust my abilities to do them so I took her to someone else.

I am gonna check for cracks in the radiator tomorrow and check the hoses again to see if there are any leaks. I hoping to the lord it is simple and maybe me just neglecting my truck to much...

 

These are no longer smart affordable commuters anymore.......they are 'hobbyist trucks'
.....some parts can only be obtained from salvage


That's what corolla's, camry's, matrix's, CRV's are for
most all trucks are gonna eat gas....twice what a sedan uses


if you havent been slowly replacing all the old 20yrs stuff....then you're behind the curve


1st gen Tacoma's are fun/easy to work on....and plenty of videos to guide
...its just having the time and tools

 

yep...unfortunately I don't have the money to keep replacing the parts on my girl...she is my only form of transportation but everything that is left to replace is way to expensive for me to ever be able to do it...
I am just trying to fix her up to get a newer truck. Who knows maybe someone else will be able to keep up with the work...

 

The V6 are definitely more expensive on up keep....
but they are highly sought after......seen them sell in less than a day

Thanks to Donald....401K is down.....but the used trucks are shooting back up to crazy ville again...
sellers market, and need to brace for impact, if buying....all time highs


big sale on TESLA'S tho.......all time low's

 

Oh yes...I been watching the market like crazy lately, but...I don't want to sell but I need a truck that can hold 2 car seats now and not just one...

 

I just bought all that stuff today for my 08 4.0

 

Honestly I say it is worth it. The truck runs so much smoother and cleaner now. gas mileage went up a little but it isn't terrible for small town driving.
I have done well over what I just listed in that short text to this truck. But 100% always recommend doing everything at once so much easier than tearing it apart again on a different day. (depending on how fast you work though LOL)

 

All these high mileage engine woes and yet if done yourself you can put a $2300 dollar fresh jdm motor (plus wear items, new fluids and gaskets) in with all kinds of younger engine peripherals that come with it and make your daily driver truck purr like a kitten again. It's nice to have your cake and eat it too.

 

Sorry to hear that. Hope in your case it's also not a head gasket.

 

My buddy's '98 Tacoma popped its head gasket last October. I went and scored him a junkyard motor for $400 the next day (vin verified the donor truck had just had registration renewed with 171k miles a month prior). Then for another $500-600 he was able to reseal the whole engine and throw a new clutch in it. As soon as we dropped that junkyard engine in, his truck was barking tires (33" MTs) in 2nd again

 

Wow, I thought gas was $5 gallon around there how does your junkyard make money at those prices. What a deal. You should start slinging them for a side gig. Exceptions not the rules.

 

Haven’t confirmed 100% but….reservoir full….radiator emptying. Bubbling coolant. Gurgling sound behind the dash. At 263k I guess I can’t complain
just waiting for the coolant pressure tester to confirm

 

I really have thought about that. Unfortunately our local pick and pull hardly ever gets desirable Toyota vehicles, so that makes it quite a bit trickier