Have any 5th Gen owners experienced a head gasket failing? This mechanic says the 4th Gen 4.0L Toyota engine (5th Gen also has) has a problem with head gasket failures over 120k miles???? I’ve never heard of this being a common failure on the 4.0L engines. My 5th Gen has 130k miles on it so this video has me a little worried. I change my oil every 5k and change my engine coolant every year (overkill I know) other than that how do you prevent this from happening? Thanks. https://www.youtube.com/watch?v=9WKUxVR7wIU&feature=youtu.be

Never heard of a problem with the head gasket in a 5th generation. Nothing you can do about it, anyways.

Supercharged at 80K miles and went to 145K before my 2010 Tacoma was totaled without issues and that was with numerous full throttle runs. The early engines 05 maybe 06 did show some headgasket issues but that's almost 20 years ago.

No one wants to fess up but the red coolant (OAT) causes gaskets to swell more than green (IAT) and compromises the good factory seal.

I remember just enough of high school chemistry to know that it’s just as bad to keep adding fresh coolant because the new stuff is what REACTS, old stuff is stable and has already gotten into the gaskets and expanded.

You’re doing a good thing for the COOLING system keeping fresh coolant in there, but those engine gaskets keep having a fresh supply of red that has not yet reacted with the gasket material and expanded further.

Like the old LLY GM Duramax trucks with 300k+ miles on them have heads done at least once. Usually at around 160k. The ones without head jobs were owner maintained (read: oil changes only) and left the original coolant in or just topped it up as needed.

Counterintuitive as all hell but makes sense when you think about it. A manufacturer would never advise you to NOT get something done - they have a vested interest in you getting fluid changes and the subsequent engine work thereafter.


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Are you saying that changing coolant at specified intervals is what causes head gaskets to fail? I have never heard or read anything like that. Is this your own theory? If not, would you provide a link to where you got this info? I would be interested in reading it. Thanks

That is fascinating I’ve never heard of this but it makes sense.

Head gasket fails... Take a weekend and replace it?

Specifically with red, yes. I wished they used green.

Hits Tacomas and 4Runners alike: Head gasket failure on 4.0 Toyota engines | Tacoma World

Here’s a good short read with pictures of what happens. It’s a GM article but all red OAT (organic) coolant behaves this way: http://www.zr1specialist.com/HAT%20W...d%20Gasket.pdf

Plenty of anecdotes: Top 78 DexCool Reviews


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The people you won’t hear from are the ones who trade before they even have enough mileage to see these kind of problems. I believe 4Runners are traded up more often than Tacomas.

For those of us in this for the long haul, 140k miles is too early for head gaskets to go. I’d expect that out of a Jag or Range Rover, but not Toyota.

I don’t want to crap on Toyota but I really need to know if flushing and switching to green will void my warranty. I am asking for future reference - I only have 1000 miles on my 4Runner LOL

I have several domestics that don’t even have a pressurized overflow tank (they have a flip cap) and have zero issues at 300k miles and are driven 10-15k miles a year each.

This style below. Not secure at all but the level has not had to be topped off since the last time it was drained. (Water pump several years ago). But it’s green so that doesn’t matter.

https://cimg3.ibsrv.net/gimg/www.che...347a24a962.jpg


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I wouldnt worry about your head gasket.

This is not a common enough problem to stress over. Ive had a 95, 03 and now 08 and monitor my parents 2018.

Head gasket issues were common prior to 2005. (1st, second, 3rd gen). Vehicles manufactured 12/2005 and later are low risk for head gasket issues, assuming normal use and maintenance. As noted heat is not your friend, so dont let your engine overheat and keep an eye on the coolant. I would continue to follow the maintenance recommendations and recommended fluids.

Even with bullet proof reliable toyotas, occ issues come up with head gaskets, transmissions etc, but are relatively uncommon in comparison to other vehicles

Not looking to argue, but I didn't have that information fixing cars the last 10 years. Not sure I'm convinced. Also, I'm pretty sure the gaskets are MLS. How does that gasket swell?

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Toyota Red is not OAT coolant, it is IAT (Inorganic Acid Technology). It is similar to the old "green" coolant you refer to. Don't base what happened with GM engines and DEX-COOL with Toyota engines. I don't believe the head gasket failures in the late 90'-early 2000's were due to red coolant.

Your 2021 Toyota has PINK coolant which is OAT.

I've been driving Toyotas since 1974 , have always used the factory recommended coolant and have never had a bad head gasket.

My 2016 4R has pink coolant and I trust Toyota info saying that this is the best coolant for this engine. Use green if you want, it is your vehicle.

If it’s not fiber then it shouldn’t do it. The ones in the link were fiber over steel.

I guess we rule that out for the Toyota’s. What do we think is causing the gasket failures?


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Good to know for the earlier ones - as for me, I guess we’ll see. I’m already planning on halving the fluid change intervals. 10k for oil is too much for my brain to accept. 5k should be ok since I’m going in for tire rotation anyway.

Just daydreaming, I wonder what would happen if I ran straight Water Wetter, LOL!


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The head gasket issue affected the 03-05 4th gens. It was resolved with the facelift 4th gens starting in 06.