Step-by-Step Guide: Changing the Head Gasket on a Volkswagen T3 with JX or AAZ Diesel Engine

As you know after our trip from Poland to Estonia (600km) with only 3rd gear so approx 50km/h we managed to blow our head gasket.

So if you own a Volkswagen T3 with a JX, AAZ or similar diesel engine and need to replace the head gasket, this step-by-step guide will help you through the process. A failing head gasket can cause issues like overheating, coolant loss, or oil contamination. Along with changing the head gasket, we’ll cover additional steps, such as removing the diesel injection lines and replacing the timing belt and tensioner. Follow these instructions to restore your Volkswagen T3’s performance and reliability.

Disclaimer:
Before proceeding, ensure you have the necessary tools, skills, and a suitable workspace. If you feel uncomfortable or unsure about any step, it’s recommended to seek professional assistance.

Step 1: Gather the required tools and materials
Before starting, gather the following tools and materials:

1. Socket set and ratchet
2. Torque wrench
3. Gasket scraper
4. New head gasket
5. New cylinder head bolts
6. Timing belt and tensioner (if needed)
7. Engine coolant
8. Engine oil and filter
9. Replacement parts (if necessary)

Step 2: Prepare your workspace
Ensure you have enough space to work and organize your tools. Keep a clean work area to prevent dirt or debris from entering the engine during the repair process. Additionally, disconnect the battery to avoid any electrical mishaps.

Step 3: Remove the diesel injection lines
To access the cylinder head, begin by removing the diesel injection lines that connect the injectors to the fuel pump. Carefully disconnect each line at both ends and secure them away from the work area. Also cover the injectors so that no dust or particles get inside the injectors.

Step 4: Find Top Dead Center (TDC)
You may have to remove the exhaust pipe to provide better access to the crankshaft bolt. Use a suitable wrench to rotate the crankshaft clockwise until the timing mark on the crankshaft pulley aligns with the reference mark on the engine block. There is also timing mark seen through the gearbox bell housing hole. This ensures the pistons are at the top of their stroke. Makes the assembly easier.

Step 5: Remove the necessary components
Remove the air filter housing and the intake pipe leading to the turbocharger. Loosen and remove the four bolts holding the turbocharger in place. Carefully disconnect any wires, hoses, or connectors that may obstruct the removal process. I removed also the water coolant flange behind the cylinder head so that the head doesn’t get stuck behind the turbo oil pipe.

Step 6: Remove the cylinder head with exhaust, and intake manifolds
Before you cant get the cylinder head from the engine block you have to remove the timing belt also, if you are not sure how to time your engine later then don’t do it. Anyway then remove the cylinder head along with the exhaust manifold and intake manifold as a unit. This makes the process easier and avoids complications. Cylinder head is held place with 10 bolts, don’t reuse the old bolts! Open up the intake pipe and release the four bolts securing the turbocharger to the manifold. Stuff some fabric or towel inside the turbo air pipes so that you dont get any dirt inside the turbo.

Step 7: Replace the timing belt and tensioner (optional)
If necessary, this is an ideal time to replace the timing belt and tensioner. Follow the manufacturer’s instructions for proper removal and installation of the timing components. Ensure the timing marks are aligned correctly before proceeding. I will post more about timing in future (maybe I already posted it so look around in our blog).

Step 8: Clean the surfaces
Using a gasket scraper or suitable tool, thoroughly clean the cylinder head, engine block, and manifold surfaces. Remove any debris, old gasket material, and oil residue to create clean and smooth mating surfaces. Also if the cylinder head is already removed then see if the surface is even and not warped. If you find out that your cylinder head is warped then you may have to get it machined or new buy a new head.

Also there are gaskets with different thickness market with the notches in the head gasket. Not going to deep into it, if you just want to change the head gasket then use the same. If you get your cylinder head machined then consult with the proper mechanic before buying new gasket.

1 notch – 1.53mm thick to suit piston protrusion of .66mm to .86mm
2 notch – 1.57mm thick to suit piston protrusion of .87mm to .92mm
3 notch – 1.61mm thick to suit piston protrusion of .93mm to 1.02mm

Step 9: Install the new head gasket
Place the new head gasket onto the cleaned engine block, ensuring proper alignment with the cylinder head’s bolt holes. Take care not to damage the gasket during installation.

Step 10: Reinstall the cylinder head and manifolds
Lower the cylinder head along with the exhaust and intake manifolds onto the new gasket. Ensure proper alignment with the bolt holes. Always use new bolts when reinstalling your cylinder head. Usually there is a bolt torque info and pattern with the new head gasket you ordered.

Torque instructions for 1.9TD AAZ
1. 40nm
2. 60nm
3. 90°
4. 90°

Step 11: Reassemble the components and prime the injectors
Reinstall everything.
Refill the engine with fresh coolant and engine oil. Double-check all connections and components for secure fitting.

To ensure proper fuel priming, gently loosen the fuel lines on the injector side before tightening them. Gradually turn the engine over using the starter until you observe fuel flowing from the loosened line, and then securely tighten it.

Once everything is properly assembled, start the engine and let it run for a few minutes while monitoring for any signs of leaks.