How to seal a cylinder head gasket with sealant

How to seal a cylinder head gasket with sealant
How to seal a cylinder head gasket with sealant

On an engine, a leaking cylinder head gasket is always bad news. It is safer to change it immediately, but you can delay, if the leak is not very large. There are indeed products on the market that can seal cracks in a cylinder head gasket. There are two things one: either it allows you to wait for the repair or the problem is fixed if the crack is of no consequence. Either way, you will need to replace the gasket eventually.


Part 1 of 3: diagnose a cylinder head gasket leak

Fix a Head Gasket With Engine Block Sealer Step 1

Step 1. Remove the plug from the cylinder head cover

When a cylinder head gasket leaks, the main symptom is a kind of "mayonnaise" that you can see very well when you open the oil cap. Without having the texture, the appearance is that of mayonnaise, it must be said that oil is part of its composition.

  • If, when you open your oil cap, you see a mixture that looks like mayonnaise, water has mixed with your oil. This is a sign that the head gasket is leaking.
  • There may very well be a cylinder head gasket leak without causing mayonnaise.
Fix a Head Gasket With Engine Block Sealer Step 2

Step 2. Take a close look at your muffler

Check in particular if white smoke is escaping from it. When a cylinder head gasket leaks, coolant can pass through the cylinders, so it combines with the fuel-oxygen mixture and is burned at the same time. The product of this combustion conventionally emerges through the exhaust in the form of a rather light smoke, which is not usually the case (absence of color if the engine is correctly adjusted, otherwise the smoke is rather dark).

The larger the leak, the whiter the smoke from the muffler becomes

Fix a Head Gasket With Engine Block Sealer Step 3

Step 3. Drain the oil to check for any traces of coolant

Collect the used oil and see if there are traces of coolant. When a cylinder head gasket leaks, coolant manages to seep into the oil circuit, and since the two fluids have different densities, the oil floats on the coolant, which is how we detect a problem.

  • If you see slight eddies in the oil, they are usually caused by coolant.
  • If the leak is large, you will see a lot of coolant and can even identify its color (green, orange or even pink).
Fix a Head Gasket With Engine Block Sealer Step 4

Step 4. Check for misfires

A misfire is caused by the incomplete ignition of an incorrect dosage of the mixture and is identified by a series of small explosions of varying degrees of importance. The consequence is also that the engine speed drops, which can be seen on the tachometer. These misfires can be explained quite simply as the mixture in the cylinders is calculated precisely and if coolant has managed to get in, the explosion is incomplete, hence the noise.

  • Misfiring can cause the engine warning light to appear on the instrument panel.
  • If the engine warning light comes on on the dashboard, it could be due to a failing cylinder head gasket, but there are many other reasons.
Fix a Head Gasket With Engine Block Sealer Step 5

Step 5. Use an OBD II diagnostic tool

If the engine warning light appears, use an OBD II scanner which will display an error code stored in the on-board computer. It will allow you to know the origin of the problem.

  • If the code displayed is for poor combustion, it is likely that it is a faulty cylinder head gasket.
  • If you do not have this device, go to an auto center, where you will be diagnosed with this type free of charge.
Fix a Head Gasket With Engine Block Sealer Step 6

Step 6. Watch the temperature gauge

When the cylinder head gasket fails, the engine is unable to control its temperature, which tends to rise. There is less coolant, the engine exceeds temperature limits and can even overheat.

  • If your vehicle overheats while you are driving, pull over to the side immediately and shut off the engine.
  • Driving an overheated vehicle can only end badly: you will break your engine, we say "tighten" the engine, the expression is very expressive.

Part 2 of 3: drain the cooling system

Fix a Head Gasket With Engine Block Sealer Step 7

Step 1. Elevate your vehicle

In order to access the radiator bleeder (tap or valve) more easily, you will have to raise the front of your vehicle so that you can slide under it. Take out your jack (crank or pneumatic) and place it in one of the two places provided and mount it.

  • Once the vehicle is raised, place two safety stands to properly support the weight of the vehicle.
  • To find out where the jack's anchor points are located, see the manufacturer's booklet provided with the sale.
  • Never work under a vehicle that is supported by only one jack stand.
Fix a Head Gasket With Engine Block Sealer Step 8

Step 2. Place a container under the radiator drain valve

You need a container that can hold the amount of coolant flowing through your circuit. If you only have a small container (because your large container does not go under the car), you will have to take several samples, closing the drain valve each time.

  • Place your container well in line with the drain valve that you have taken care to locate beforehand.
  • As for the volume of coolant that will flow out, consult the manufacturer's manual and you will know which container to take.
Fix a Head Gasket With Engine Block Sealer Step 9

Step 3. Open the radiator bleed valve

It is always located at the bottom of the radiator and can be opened either with a pair of pliers if it is a real tap or with an open end wrench if it is a special bolt. Take it slow and when all the circuit is emptied, turn off the tap.

  • This liquid will no longer be reusable, so transfer it to a container and take it to a recycling center where it will be recycled: it is a polluting product.
  • For a faster and more complete bleeding, open the cap located in the upper position of the radiator.
Fix a Head Gasket With Engine Block Sealer Step 10

Step 4. Fill the water circuit

You have closed the drain valve properly, not by hand, but with an open-end wrench or a pair of pliers. You must now fill the cooling circuit using the upper hole.

  • Replace the radiator cap if it looks damaged, especially if the gasket is fired. You will find it at your dealer or at a junkyard.
  • To find out where the radiator is located, consult the manufacturer's manual, the cap is at the top.
Fix a Head Gasket With Engine Block Sealer Step 11

Step 5. Unplug the thermostat

The thermostat is a part of the cooling circuit that opens or closes depending on the temperature of the liquid, thus controlling the temperature of the circuit. Unplug the thermostat to prevent it from activating during clogging.

  • Disconnect the hose that reaches the top of the thermostat.
  • If you don't know where the thermostat is, check your car's service magazine.
Fix a Head Gasket With Engine Block Sealer Step 12

Step 6. Start the engine with the heater on full blast

Once the cooling system is full of water and the cap is back in place, start your engine. The water pump will circulate the water which will eventually dissolve what remains in the coolant circuit.

  • Run your engine for about ten minutes.
  • Watch the temperature gauge. If the needle enters the red zone, immediately stop your engine.

Part 3 of 3: Pour a sealant into the cooling system

Fix a Head Gasket With Engine Block Sealer Step 13

Step 1. Open the radiator bleed valve

When the clean water has turned sufficiently, bleed the radiator again as was done previously. Patiently wait for all the water to flow into your container. After the last drop, close the purge valve.

  • Proceed exactly as indicated in the previous part.
  • This clean water that circulated has finished dissolving the coolant that remained against the walls of the pipes and hoses: your circuit is now clean.
  • Then reconnect the thermostat that had been removed previously.
Fix a Head Gasket With Engine Block Sealer Step 14

Step 2. Fill your cooling system

Fill it with a mixture of equal parts water and coolant. In the store, ask a salesperson what type of coolant you can put in your system. Two precautions are better than one, so check the container label anyway.

  • There are such mixtures on the market, but it is very easy to prepare it yourself.
  • Pour this water-coolant mixture into the expansion tank and wait for it to diffuse throughout the system. Refill the level as it drops without exceeding the maximum level indicated on the vase.
Fix a Head Gasket With Engine Block Sealer Step 15

Step 3. Pour the sealant into the radiator

After a few minutes, open the radiator cap or the expansion tank cap, and pour in your sealant. So much for the principle, but in this regard, it is best to refer to the manufacturer's instructions for the amount to be put, how to use and the safety instructions.

If you pour in the sealant along with the water and coolant, that will work too. In general, we put half of the product after having half filled the circuit and the other half at the end of filling

Fix a Head Gasket With Engine Block Sealer Step 16

Step 4. Take a road test

After closing the radiator cap, go for a fifteen to twenty minute drive in the car. Thus, the sealing product will spread throughout the circuit and above all, settle where the seal is damaged in order to attach itself to it.

  • Again, if the engine overheats, immediately turn off the ignition.
  • After a good quarter of an hour, switch off your engine and let it cool for a few hours.
Fix a Head Gasket With Engine Block Sealer Step 17

Step 5. See if the product worked

If the leak wasn't too bad, you shouldn't have problems like overheating, a warning light coming on or misfiring. Check all the points mentioned in the first part. Sure, you've fixed the problem, but you can never tell if it's final. This intervention is not always successful.

  • During the days following the operation, closely monitor your engine to verify that the cylinder head gasket is no longer leaking.
  • It is certain that the replacement of the cylinder head gasket is the only intervention which guarantees a repair in the long term.

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