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Hey folks, Cooley again.
Got another one of your emails about high tech cars and modern driving.
This one comes in from Mackenzie E, he's in Jacksonville, Florida.
It says my girlfriend has a 2014 Chevy Sonic LT, 64,000 miles and had to get the head gasket replaced.
She's a conservative driver, he says, so I was shocked that it needed such a major repair so early.
Thankfully, Chevy covered the bill, which was over a grand.
Is this bad engineering or something about how we're driving?
And what exactly is a head gasket?
Well, Mackenzie, I'm glad you asked, because head gaskets irritate me to no end.
And the reason is they really underline, in this modern age, what a Rube Goldberg machine, the modern combustion engine, really is when you get right down to it.
The head gasket, to answer your main question, is this thin thing that seals the engine head to the engine block.
I'm gonna show you what that means over at the engines in just a minute.
It loves to fail.
Even today, in 2019, as you've learned with a late model Chevy, head gaskets still go out.
They're one of the last common catastrophic failures in the modern car to be honest and then when they do so, to add insult to injury, they do so spectacularly.
There are no cheap head gasket repairs, not if you do it right.
They are a major tear down So let's learn why the head gasket is still with us, why it's so important, and why it's such a disaster when it goes wrong.
Let's go to the engine.
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Well here it is, the head gasket.
This is what you just paid $1,000 to replace.
Doesn't look like much, does it?
Unlike gaskets of the old days, it's not made of sort of a fiber composite anymore.
Head gaskets are high tech.
This one you can see is made of very thin metal and also has kind of some rubbery polymer seal traces all around it.
We'll talk about what those are doing But this is it.
It's not an expensive part, and it doesn't really have any moving parts.
What it is though is hard to get to, and its job is critical, sealing the head to the block.
Now let's see what that means.
So here's the head.
The head is the top part of the engine as you might imagine that contains the intake valves that get air and fuel into the cylinders.
Has another set of valves.
The exhaust valves that allow the exhaust from combustion to get out of the cylinders.
And it also contains the spark plugs.
And that's the way that you get all that stuff to combust in the first place.
All of this is sort of the conductor of the symphony that is the engine.
And without the head, the block can't do its job.
The block is where the combustion and compression is done.
Your cylinders down here get filled with the air and fuel, thanks to the head.
They then combust it and explode it, thanks to the spark plug in the head, and then throw that exhaust away, thanks to the exhaust valves in the head.
You see what a critical marriage this is, head to block And the seam between them, right here, is what has to be sealed critically for three reasons.
If it's not sealed, you lose compression, you lose the pressure in the cylinders.
That's the essence of power from an engine, so your engine would be gutless, run rough, maybe not even start if you blow a gasket that allows that pressure to get out.
Secondly, there are coolant channels that run between the head and the block.
Where your antifreeze goes to keep all of this stuff from overheating.
That's a separate set of little channels you'll see in the head gasket and those have to be kept from leaking into the cylinders Then you've got oil channels as well for lubrication.
Ditto.
They've got their own set of channels in the gasket that are isolated, and may not be allowed to leak into the pistons.
If you get coolant in your pistons from a blown head gasket, you'll typically know it by white smoke.
Coming out of your exhaust system.
If some of the oil channels blow, and unseal, and begin to leak oil into the pistons you'll know that because you'll get either a dark grey or a blue smoke and it really smells like an oily fire.
These are things that tell you your engine is in bad shape and it's not gonna be running well when that happens.
To replace this you've got to do a major tear down.
As you can see all of this apparatus above the head and then the head itself has to be unbolted and lifted away so you can get the old damaged gasket out from in between here in the block And put this new one in.
That's a pretty major tear-down, though it typically can be done with the engine in the car.
But that doesn't make it easy or cheap.
Now, as any of you who've had one of these things fail know, one of the first things you do after you become aware of that is run the numbers.
Is your car even worth repairing, since this can be such an expensive repair.
And by the way, $1,000, Mackenzie, that's getting off cheap.
Some cars can cost a lot more than that.
Plus.
there's this while you're in there factor.
While you're in there with the engine torn down you often are encouraged to do other repairs so you get into the thousands pretty quickly.
Sometimes you just want to push the car off a cliff instead or sell it on eBay as a mechanic's special.
I'm annoyed that engines still have head gasket Failures.
They aren't as common as they where, but they are one of those things that remind you this is the most unlikely assembly almost ever invented by mechanical engineers.
And head gaskets are a pretty good argument for.
For electric cars because they don't have one.
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Keep those emails coming.
I'm here to answer your questions about high tech cars and modern driving.
It's cooley@theroadshow.com.
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