Radiator pressure issue?

So my 2008 Tacoma has been having this issue where the coolant is being pushed out through the overflow tank to the point where it comes out and I have no idea how much is left in the radiator. The overflow tank is always full to the top. The truck doesn't overheat and I replaced the water pump about 6 months ago. I'm really curious as to what is causing this. My father in law is a Toyota mechanic and thought it was a head gasket but he said it's not fully acting like a blown head gasket. Any ideas on how to fix this would be great! I do have to keep filling the radiator with coolant.

 

First thing I'd do is check/replace the radiator cap, it's not uncommon for the plastic check valve on it to break off after that many years.

 

I replaced the cap already. Didn't affect it all. Is there different pressure option caps? Thanks for sharing all those links.

 

Is the radiator contents foamy?

 

3 things can be happening....
hopefully as stated, hopefully just a radiator cap...
overheat issue....
or worse case scenario, head gaskets are compromised & compression / combustion is getting into the cooling system through the water jacket part of the gasket & overly pressurizing the cooling system, pushing the coolant into the overflow...

Take your cap off & refill your system, run it & let it cool a few times, verify you topped it off correctly / full....
After it cools, recheck it again to verify your radiator is full...

 

Coolant is not foamy. It has never overheated. The coolant must be going somewhere. I've refilled it several times. Cap has been replaced already. I am worried that it is head gasket problem, but do I need to take it to a shop to verify? I know it's pretty expensive for a head gasket job.

 

Well if you dont know how to check it for a blown head gasket, your options are limited...
You could have a leak, a pressure tester is needed to isolate, get it under pressure & get under it & look for drips.
sometimes things only leak cold, sometimes pump only leak when running, ive seen everything...

as far as check for a blown head gasket, this isn't fool proof but its where everyone starts.
You can still have a compromised gasket but not bad enough to fail this test.
Does your coolant put off a strong punjent / different odor if you take a good sniff at the radiator fill with the level lowered some?
Thats not a good indictor.

Anyways back to the test
Buy this tool, lower your coolant lever down a few 2-4 inches+ so you dont suck in coolant in the tester.
Get the truck nice & hot, blast it down the block for 20 minutes after you get it to normal operating temp by just running it in your driveway.
After you get back from the hot-lap,
carefully remove the cap without getting hot coolant all over yourself......
verify coolant level is low enough again so you dont suck in coolant...
put the tester filled with the blue block check fluid filled to the proper fill line over the radiator fill...
violently / agresssively pump the ball for a few minutes & if the blue turn yellow, its dead Jim.....
If blue turns greenish, test inconclusive

Tip, immediately pop the cap & instantly install the tester over the radiator securely before any hydrocarbon gasses escape
If it doesnt change, have someone increase the rpm while you keep pumping

if it doesnt change then, its safe to say, you might not have a head gasket issue

$38 Block Tester BT-500 Head Gasket Combustion Leak Test Kit - Made in USA

https://www.amazon.com/Block-Tester...737335253&sprefix=head+gasket+,aps,188&sr=8-6

 

no foamy coolant means nothing.
not sure where that comment is going...
never seen foamy coolant....
unless we mean intermix??
Thats another thing to check, look on the inside of your oil cap fill, for any milkiness, intermix, moisture.
Thats where coolant will collect over time if coolant is getting into your system due to head, or gasket, issue, etc...

You can also get a cheap pressure tester off Amazon.
pressure tester may show a leak right away if you look around with a good flash light, crawl under it, etc...
or may not show a leak until the next morning, leaving it under pressure overnight...

your just looking for leaks, forget the gauge bleed down #, that means nothing,,,

you park overnight in the same spot, on street or driveway, not on dirt & no puddles / drops?
spotless floor,

 

The single-VVTi 4.0L 1GR-FE is known for headgasket leaks, frequent in 2005-2006 trucks but becoming more common in later years as time marches on. Open the radiator cap, top up the radiator. Start the engine. If you see the coolant bubbling in the radiator, you probably have a headgasket leak. You can then take it to a shop for them to do a cylinder leakdown test and confirm.

 

this is my wheel house, not headlights......

 

leak down my not show much, if it still runs fine & few hours labor...
They can really crank up the air pressure in each cylinder using a leak down & see if the coolant level rises....
But thats not a legit leak down....

I have no knowledge of certain toyota characteristics, common failures etc....
I do know that some V6 tacos did have a common head gasket failure though as had a buddy looking for a toyota mechanic for that reason, no idea what year truck it was...

 

go look in the oil cap or in the sides of the oil cap fill pipe, for sludgy discolored, whitish film, or water droplets, take some pics, that won't cost anything.
if its been doing it long enough & truly an issue, would imagine you may find evidence of the smoking gun...

if theres evidence, no reason to go any further, start calling around for ballpark pricing so you have an idea of what's next...

 

Combustion pressure is way higher than what a shop could pressurize each cylinder with, so a cylinder leakdown test is a legit way of detecting a headgasket leak.

 

a cylinder leak down is a controlled metered, choked down regulated air being pumped into a cylinder using an air compressor, & measuring the % of leaking & isolating the source,
Usually if its not a gross leak, like a valve not seating correctly, a bad ring, etc, it really won't present its self....
The air going into the cylinder is very limited....
But just cuz compression is say 180 psi, which I have no idea if it is...
If you do have a compromised cylinder & you pump say 110psi which a compressor can do, it will 100% show its nasty little head...
may take a minute but coolant level will rise....

any at home compressor can pump out 120psi, shop compressors more....
a leak down tester chokes it down drastically....
even if you have the tester cranked. too much valving & hose restrictions, etc...

Furthermore.....
A leak down tester doesnt allow full pressure from the compressor by its own characteristics due to pull pressure will more the piston & open the valves due to piston movement from where you set-it...
Its a pain in the ass, stately figuring out piston positioning blindly, without too much drama.....

 

text book scenarios, maybe, real shop world is never text book....
easier ways as ive mentioned, prior to wasting resources & money going to a leak down from the get go.
Its very time consuming to do it correctly, costly & not necessary in most cases, for a head gasket issue........

 

OP, you stated that you have refilled it several times. What exactly are you refilling (to the top), the radiator or overflow, both?

 

generally when theres an issue as he stated, the radiator fluid get pushed into the overflow, to the point the overflow get filled & spews out.
Pretty sure overflow is always full & he's topping off the only thing he can, which is the radiator....
He does say he has no idea how much fluid is in the radiator at this point, as he knows its being pushed out & hasn't recently checked.......

Thats my interpretation...

 

When my 2005 had the Head Gasket issue. It Never Over Heated!!! It only did this 3 times in a 9 month period. I would drive home from work which is about a 30 minute drive, Back into the garage, And I could hear what sounded like boiling, It was the coolant rushing into my over flow bottle. It never came out and never filled the bottle to the top. I was never low. I spoke with a friend that had his own shop for 30 plus years. The first thing he said was Take the cap off the over flow bottle while I was there, I did, He said start the truck. We watched for Bubbles. It took a little bit, But Yes there were Bubbles that came into the Over Flow Bottle, That was the Exhaust Gases escaping through the Hole in my Head Gasket, We did do the Block Tester also Just to Double Check. The Fluid changed Color. I had my Head Gaskets done around 136,000 miles. The Tacoma now has just shy of 250,000 miles. So, The easy and Cheap way to check, If the truck is cold, Pop the Cap off, But the Bottle needs to up to the Cold Recommended Level, Start the Truck and go watch for Bubbles. Give it some time, If you see Bubbles you have a Problem.

 

makes total sense...
Have had tons of vehicles come though my bay that had fubard head gaskets & never over heated...
What sucks is sometimes theyre on the early stage & its hard to get a color change on the chemical test...
Ford 4.0 sohc is a perfect example of this,
they would push coolant out of the radiator into the overflow,
They wouldn't fail the chemical test, until the leak was so bad, you started getting misfire codes from coolant intrusion.
Was hard to verify at times, w/o extensive teardown & exploratory money wasting...

 

Yeah, thanks. My first reaction was wondering if the thing is being filled too much to cause the overflow. IDK. The full mark on the overflow tank is marked at the half way point, at the seam. That is the point I reference when things ultimately cool down.