What causes blown head gaskets and how to prevent?

How to avoid this expensive problem in the first place?

 

I think regular engine maintenance like changing oil, coolant, water-pump, and (adjusting valve clearances for 4 cylinder engines). I think this is about right since all of this helps keep the engine from overheating

 

Buy a truck that’s not 20 years old. At some point everything becomes a wear item. You can reduce wear but you can’t eliminate it nor can you turn back the clock.

 

Pretty much what everyone else said. Regular maintenance is best. Trying not to overheat the engine (which is usually pretty hard to do if everything else is functioning properly). Eventually things will break down.

Don't be afraid of it though. There's a man in the NC/SC area who drives 5-600 miles a day for his job. His 4 cylinder Tacoma has 1.2M+ miles with 400k on the current engine. He did very little maintenance to it and the head gasket on the original engine blew at 800k. He opted to replace the engine instead of fixing the gasket.

 

v6 dont need valve adjustments?

 

V6 doesn’t. All it needs is timing belt maintenance

 

Excessive heat can be a factor. If there is small amount of warp in the area it could allow for seepage, blowout.

 

If we are talking about the 3.4 V6 then it does need periodic valve adjustment. It’s a bucket and shim style manual adjustment setup. Someone will correct me if I’m wrong but my 2000 3.4 definitely is.

 

According to the Toyota Field Service Manual (screenshots are 96 FSM), 3.4L does need valve clearances check, and possibly adjusted. As @SLAPS 65 said, bucket and shim, same as 2.7L.

However, most members on here report they don't normally need adjusting like the 2.7L valves do. Many people report 2.7L exhaust valves get too tight. Some have cracked the head.

 

Over heating is most common cause. Causes stuff to warp, gaps to increase. But also causes fuel to ignite early leading to over pressure in the cylinder. If you're lucky, it just pushes the gasket out. If you're unlucky, you have managed to lower the compression in that cyclnder by adjusting the length of the rod.

On boosted engines, if Boosted to high, it can push the gasket out. This usually happens at high load and rpm, thus this form of failure usually comes with molten aluminum and a light show.

Non boosted can also go over pressure in the cylinder if something goes wrong with timing causing an early burn and max psi while piston is still on the way up. This failure mode generally shows up as the bottom rotating assembly leaving the vehicle without delay.

 

Over heating will because of the aluminum heads and cast iron block

Don’t ever let the engine over heat and get a 170 stat

 

170 stat?

 

Also for boosted engines and NA, dont rev the engine while cold. the clearances and such are not were they are when designed so you can pop it easier.

@1997tacomav6

You really don't need a 170 degree thermostat. The 3.4 stock has plenty of cooling and if you are really worried about it, go to a larger radiator. I wouldn't do a colder tstat unless I was doing a full build on an engine. the colder tstats make less power as they are less efficient also.

 

My engine popped a head gasket at 480,000,
The engine over heated while stuck in traffic on a 100 plus day, head gasket failed that same year, probably from being over heated,
After this I had a custom aluminum radiator made and run a 170 Corolla stat,
Im Putting 300hp to the rear wheel at 13 pounds of boost,
Yesterday it was 101 degrees and my motor runs at 175 -180 degrees sitting in traffic,
I'm not going to run my motor at 190-200 plus degrees,
3.4 Aluminum heads are subject to wrapping with added heat, it doesn't take much,
I have well over 100k with the 170 stat.
With all the power I need,
I'm more than happy with positive results.

 

Problems are inevitable when you're bolting aluminum to cast iron. They expand and contract at different rates, the head literally sliding around on the gasket. With the engine overheating it gets really easy for a breach to start and then slowly get worse

Once toyota (and everyone else) went all aluminum the gasket/fluid leaks became less of a problem

 

Overheating the engine causes the heads to warp and the gaskets not to seal properly. Also, if the coolant is never changed and debris is floating around in there it will blow out the gasket eventually. Also some coolants like GM's orange dex-cool are known to eat gaskets, which is why there was a major class action lawsuit. GM advertised it as lifetime coolant or good for 100k miles.

 

My experience and as most of the comments point out that’s it’s overheating that causes most head gasket failure. They do fail due to age and other causes, poor design for example , see Toyota’s 3.0 V6.. but mostly it overheating. Keeping your cooling system leak free, full and functional is the best way to prevent head gasket failure.

 

Head gasket failures are caused from ... (listed below can damage the fire ring of the head gasket causing a failure)


Spark knock

Pre ignition

Excessive cyl pressure

Excessive coolant temps

Running to lean of a/f ratio

Poor head gasket design

Cyl head to deck surface improperly machined ( out of tolerance)


Commonly used term in Drag racing is called " lifting a cyl head " and main cause is from a combination to lean of fuel mixture and excessive cyl pressure . this causes a blow torch affect that will torch the head gasket fire ring and push the head gasket out

The hot exh gasses will burn thru the cyl head or deck surface of the block . Other head gasket failures are caused from a over pressure of the cooling system ( cylinder pressure entering the cooling system from a cracked cyl head or cyl

 

There’s something to this. However, I have driven my 20 year old truck to the east coast and back before (~6,000 miles) without so much as a burnt out blinker bulb. New vehicles made by today’s standards with varying degrees of planned obsolescence built in just seem like disappointments lying in wait, all while the monthly payments keep sapping your bank account of fun coupons. I used to be interested in the third gen Tacomas but I’ve read too many negative first hand experiences that made me lose all interest.

 

holy crap. I recently replaced my old coolant with that stuff cause I had a lot lying around. Figured “It’s Acdelco so can’t go wrong with it”. Will be going full on Toyota red stuff soon then