Blown Head Gasket Repair

Read all of this before you start. There are three repair methods, and choosing the one that matches the damage is what makes the repair last.

1. Gauge the damage

With the engine cold, remove the radiator cap. Run the engine up to full operating temperature with the cap off, so the thermostat opens and you have a clear view of the radiator water, and watch for bubbling.

Continuous bubbling means a head gasket breach, usually above a combustion chamber. The more often and the larger the bubbles, the worse the breach: fine, champagne-like bubbles suggest a minor breach, while vigorous, volcanic bubbling means a substantial one.

2. Choose your method

• Method 1, small pinhole breaches. Champagne-like or slightly larger bubbles. The vehicle isn't consistently overheating and is drivable in most conditions. Uses 245 and tap water only, and the repair happens during normal driving.
• Method 2, small to medium breaches. Champagne to medium bubbles. The vehicle isn't consistently overheating and is drivable in most light traffic. Uses 245 with the Sealing Aid Optimiser, sealed through repeated heat cycles.
• Method 3, medium to large breaches. Medium-sized bubbles. The vehicle is consistently overheating and drivable only for short distances. Uses 245 with the Sealing Aid Optimiser, with the breached cylinder isolated first.

Methods 2 and 3 need the Sealing Aid Optimiser (243), which is available as a 245 kit option.

Why the cool-downs matter. While the engine runs, the breached cylinder pressurises the cooling system and pushes liquid away from the breach. When you switch off, vapour pressure and heat drive the water and sealant into the breach instead. The breach is above 100°C, so the water evaporates and leaves the concentrated sealant behind, which the heat and pressure turn into a solid seal.

3. Prepare the cooling system (all methods)

Method 3 only: find the breached cylinder first (see Method 3 below), then come back to this step.

1. The cooling system must be completely free of glycol (antifreeze/anti-boil coolant), which can stop 245 working properly.
2. Disconnect the top and bottom radiator hoses and flush water through the expansion bottle, radiator and hoses to remove any remaining coolant. Turn the heater on to empty the heater core, then turn it off so no sealing product can get into the core.
3. Put a garden hose into the bottom radiator hose to push out any coolant still in the system.
4. Work out how much 245 you need: 100 mL per litre of total cooling system capacity. A 5 litre system, for example, needs 500 mL.
5. In a clean bucket, mix that amount of 245 with an equal amount of tap water. It goes from thick to thin as it mixes.
6. Pour this pre-solution into the empty cooling system.

4. Add the Optimiser (methods 2 and 3)

1. One 100 g tube of Optimiser treats about 10 litres of cooling system capacity.
2. With the radiator cap off, fill the cooling system from a garden hose while tapping the powder into the stream of water.
3. Keep filling to full, then refit the radiator cap securely. Top up through the expansion tank if needed and refit that cap too.

No radiator cap, only one on the expansion bottle? Don't add the powder through the expansion bottle, as it may not disperse into the system. Instead, disconnect the top radiator hose from the radiator, leaving it attached to the engine. Hold the hose upright and fill the system through it from a garden hose, tapping the powder into the stream. Reconnect the hose to the radiator as the system nears full, then top up through the expansion bottle.

Method 1: small pinhole breaches

After preparing the cooling system:

1. Fill the system to full with tap water and refit the radiator cap. Top up through the expansion tank if needed and refit its cap.
2. Start the engine and idle it up to normal running temperature so the thermostat opens. When the top and bottom radiator hoses feel about the same temperature, the thermostat is open and the 245 has mixed through the system.
3. Turn the engine off and let it cool for about an hour.
4. Drive normally for a week to 10 days, watching the radiator closely for bubbling.
5. With the engine cool, check the radiator for bubbling. None means the breach is very likely sealed. If it's reduced but still there, keep repeating until it stops completely.

Method 2: small to medium breaches

After preparing the cooling system and adding the Optimiser:

1. Start the engine and idle it up to normal running temperature, the centre of the temperature gauge. Check the thermostat has opened: the top and bottom radiator hoses should feel about the same temperature.
2. Turn the engine off and let it cool for about an hour. This is when heat and vapour pressure force the sealant and Optimiser particles into the breach, where a partial seal forms and cures.
3. Repeat this heat cycle six to eight times, cooling for an hour between each one. Every cycle builds a little more seal in the breach.
4. With the engine cool, remove the radiator cap and check the radiator or expansion bottle for bubbling. None means the breach is very likely sealed. If it's reduced but still there, carry on with more heat cycles until it stops completely.

Method 3: medium to large breaches

First, before preparing the cooling system, find the breached cylinder:

1. With the engine cold, remove the radiator cap or expansion bottle cap. Run the engine to full operating temperature with the cap off, so the thermostat opens and the bubbling is clearly visible. The thermostat, often on the top hose, can hide it until then.
2. Stop the engine and remove one spark plug or glow plug. Restart it and check whether the bubbling has stopped.
3. If it hasn't, refit that plug and try the next one. Repeat until the bubbling stops: that plug's cylinder is the breached one.
4. Leave that spark plug or glow plug out.

Then, after preparing the cooling system and adding the Optimiser:

1. Start the engine and idle it up to normal running temperature, around 85°C or the centre of the gauge.
2. Once the thermostat opens and the solution is circulating, refit the radiator caps securely while the engine is still idling.
3. Let it idle for another 20 minutes to build vapour pressure, which drives the sealant into the breach.
4. Let the engine cool, then check the radiator for bubbling. None means the breach is very likely sealed. If it's reduced but still there, repeat until it stops completely.

Finishing the repair (all methods)

1. Drive as normal and watch for the symptoms coming back for a week or more.
2. Don't rush to remove the sealing additives. A few weeks of normal driving with no symptoms is the best sign of a lasting repair.
3. Once you're confident, flush the 245 (and the Optimiser, if you used it) out of the cooling system and refill with coolant.

Which coolant to refill with

Head gasket damage is often blamed on overheating, but it's frequently the result of years running on plain water or low-glycol coolant, which causes cavitation erosion and corrosion that wear through the gasket. There's no way to see the rest of the gasket, so it's common for a second breach to appear soon after the first is fixed.

That's why we recommend refilling with Liquid Intelligence 500. It's formulated to eliminate cavitation erosion, which stops other damaged areas of the gasket getting worse and helps the 245 repair last for years. It's also available with 245 as the Repair & Maintain package.