A blown head gasket is one of the most expensive repairs that a car owner may face. If you were told that your car has a blown head gasket, don't panic. After getting a head gasket repair quote, you are probably looking at cheaper alternatives such as using a head gasket sealer.
Which leads you to the next question: "Do head gasket sealers work?" or "What's the best head gasket sealer?"
In this experiment, we have a car with a blown head gasket in which we test one of the highest rated head gasket sealers.
The car that we used for this experiment is a Mazda with a four-cylinder engine. This car overheated and blew the head gasket. The car had a coolant leak but unfortunately, it wasn't noticed in time by the driver.
In this article, you will also learn how to check the head gasket is blown.
Choosing the best head gasket sealer
We were determined to find out the best head gasket sealer on the market. Price wasn't an issue since the alternative solution would be to replace the head gasket which can cost from $1500 up to $3500 in some cases.🔺
Top 5 Best Head Gasket Sealers
Choosing a head gasket sealer that works isn't easy when there are too many head gasket sealants on the market.
- Steal Seal head gasket repair
- Blue Devil head gasket sealer
- Bar's Leak head gasket sealant
- K-Seal Coolant Leak Repair
- CRC Head Gasket & Block Repair
This is only a few of the most popular head gasket sealers and there are many more sealers not listed here. No wonder that trying to choose a head gasket sealant can get confusing.
Which head gasket sealer did we pick?
After several hours reviewing different gasket sealers, specifications, application methods and user reviews we narrowed our search to two gasket sealants.
BlueDevil Head Gasket Sealer
BlueDevil is one of the best-rated head gasket sealers on sites like Amazon. This is how it works. It requires that you partially drain the coolant. Remove the thermostat. The thermostat needs to be removed to allow the sealer to flow through the engine block. Next, you need to reinstall everything, and add the head gasket sealer and let it do its work. Finally drain the coolant again, reinstall the thermostat, flush and refill with 50/50 antifreeze.
Bar's Leak Head Gasket Sealer
We also considered the Bars Leak head gasket sealer which doesn't require the removal of the thermostat or the coolant to be flushed. Add it directly to your radiator, no extra steps. Not only that but it has additives that create an artificial carbon fiber gasket according to the manufacturer. The manufacturer claims it should work with wrapped heads, blown head gaskets and fix head gasket leak.
Out of all the head gasket sealers we reviewed, we picked Bar's Leak HG-1 head gasket sealer. One of the main advantages of this gasket sealer is that it is simple to use. It can be applied without having to remove the thermostat.
Why we choose Bar's Leak:
- Designed to fix head gaskets
- also for intake gaskets
- Meant to work on warped head or block
- We suspect our Mazda5 has a warped head because we are getting low compression on more than one cylinder. It is impossible to test for a warped head without removing it.
- Stop overheating and coolant loss
- Our car was leaking coolant into two cylinders.
- Our Mazda5 would overheat after 15 minutes.
- Fix bubbles entering cooling system
- Our test car had bubbles entering the cooling system, see video below.
Bar's Leak makes several head gasket sealers with varying degrees of strength. Their strongest and best product is Bar's Leak HG-1 Head Seal.
Bar's Leak also makes other gasket sealers such as Block Seal and Head Gasket Fix sealant. One of the main advantages of HG-1 is that it creates a carbon fiber layer when it sets. It also can be left in the cooling system which allows it to stop small head gasket leaks over time.🔺
How we checked for a blown head gasket
Verify that you have a blown head gasket. Don't add a sealer to your cooling system unless it is a last resort. Don't assume that because your car overheats it has a blown head gasket.
Overheating can be caused not only by a blown head gasket but also by a cracked radiator, bad power steering pump, bad thermostat, bad temperature switch or even a bad Engine Control Unit (ECU).
If your check engine light is on, make sure to read the fault codes using a basic OBD2 scanner. Even a cheap $15 will work or stop by at your local auto parts store to get it scanned for free.🔺
Symptoms of a Blown Head Gasket
In our case, we had a car with several symptoms you would expect from a blown head gasket. When you have a blown head gasket coolant leak and get into the oil galleries, leak out of the engine or leak into the cylinders.
Coolant was getting into the cylinders. In our case, we didn't notice oil mixing with coolant but it was probably still happening in small amounts, and an oil test could confirm this.
One of the methods used to confirm a blown head gasket is checking engine compression. In this case, we got 90 psi in several cylinders. That's very low. In a healthy engine, you need to get around 150 psi per cylinder.
Bubbles in the radiator
A common symptom of a blown head gasket is bubbles in the radiator overflow tank or radiator. This is something you can check yourself and doesn't require any tools. Don't open the radiator cap if the engine is hot.
A blown head gasket engine can cause coolant to get into the cylinders. It will foul the spark plugs and your car will crank but not start. If you can get the car to start by cranking it for a long time (not recommended), the coolant may enter the cylinder ending up coming out of the exhaust as white smoke/steam and in extreme cases even liquid.
Fouled Spark Plugs
Coolant can get into the cylinders. When we removed the spark plugs we noticed the spark plugs were fouled. We dried them and reinstalled the spark plugs back into the engine. This was the only way we could get the car to run again. If the car was turned off after a while coolant would reenter the cylinders, and we couldn't start the engine again.🔺
Head gasket sealer instructions
Adding the head gasket sealer is easy. Make sure to follow the instructions that come with your particular head gasket sealer. Below are the steps we followed to install Bar's Leak Head Gasket Sealer.
- Allow the engine to cool down.
- Removed the radiator cap.
Shake the bottle. Add it based on the dosage chart found on the box.
- Add head gasket sealer to the radiator.Filled reservoir with coolant. Fill overflow tank to reach a level between the Min and Max mark.
- Reinstall the radiator cap.
- Start the engine. If the engine doesn't start at first try, wait 15 seconds and try again.
- Turned the heat on. Make sure it is set to HOT setting even if it is summer.
- Let the engine idle until the temperature reaches normal operation. In most cases, this takes about 15 to 20 min in idle. Let the engine run for another 10 min. Total run time of 30 min.
- We allowed the engine cool down overnight.
- Make sure to add coolant if the level is low.
- Do not allow the engine to overheat.
- If your temperature gauge goes to red, turn off the engine and let it cool down.
Head gasket repair cost
Typical costs to change the head gasket range from $1300-$3000. Head gasket parts typically cost under $300. The cost to replace the head gasket is high because this is a very labor intensive repair.
Every engine is different and removing the head is always time-consuming. It takes longer on certain cars than others. In some cars the engine may even need to be removed from the car to replace the head gasket.🔺
Ok, so you want to know the results. Did the head gasket sealer work?
At the start of this test, we had 32080 miles on the car.
Check out how the coolant overflow reservoir looked before applying the head gasket sealer.
The next morning, as we tried to start the car, it would turn over but not start. Not good.
We removed the spark plugs. A couple of them have fouled again. Dried the spark plugs and reinstalled.
This time the engine started.
Next, we checked for bubbles in the coolant overflow reservoir.
While the head gasket wasn't completely fixed you can see that the air bubbles had reduced and required a flashlight to be noticed.
Since the head gasket sealer was starting to have an effect we decided to repeat the procedure a couple more times but without having to add any more additive. We would start up the car, run it for thirty minutes and then let it cool down. We would let the engine warm up, turn it off, let it cool down and repeat a few times. What this does, it allows the sealer to get in places where it didn't get before. We are slowly building up a new "head gasket". At first, we had to remove the spark plugs and dry them because coolant was still getting into the cylinders. Eventually, the car would start right up without needing to remove the spark plugs.
The head gasket sealer is still working. Mileage as of October 2017, 32252 miles.
It is now November and the car has nearly 32450. Unfortunately, it has started to foul the spark plugs again and the engine struggles to start. This is an indication that the head gasket sealer has started to fail.🔺
Do head gasket sealers work?
It really depends on how and where your head gasket has failed. This test is one particular case and doesn't guarantee that you will get the same results. It may not work at all or the sealer may stop the head gasket leak on the first try.
In our case, the head gasket did slow down the coolant leak. Eventually, the head gasket leak returned.
We believe that even if the sealer works, using a head gasket sealer is only a temporary fix. Your head gasket problems may return sooner or later. It may last three weeks or three years. There is no way guarantee.
There may be other head gasket sealants that work just as well as Bar's Leak. It's up to you to decide which is the best head gasket sealer. This tutorial was not written to promote one product over another.
Tested product was purchased and not sponsored by the manufacturer.