How to Replace the Glow Plugs in a Turbo Diesel Engine

  • 1-6 hours
  • Intermediate
  • 35-250
What You'll Need
Socket set
Extension socket length
Combination wrench
Thin wall socket
Glow plug reamer
Penetrating oil or WD40

A turbo diesel engine has glow plugs instead of spark plugs. They have no ignition system as is understood on a petrol car. This means that diesel engines rely on the glow plugs to heat the engine from cold. These instructions carry general removal and replacement help but cannot relate to every individual vehicle. If you need extra sources of help, consult your make and model manual in the section regarding glow plugs.

Step 1 – Preparation

It is always best to work on a vehicle when the engine is cold and has been sitting for a while. The parts which get very heated during use can cause harm. If your vehicle has a valve cover, remove that before you can start. If there is any other component that denies access to the glow plugs, remove those too.

Step 2 – Disconnection

The electrical connector should be detached. On the transmission dipstick loosen and remove the mounting nut (if it applies to your vehicle). You might also need to detach other components such as the air cleaner. Once you can gain access, remove the glow plug(s) from the cylinder head inside the intake manifold.

Step 3 – The Plug

Unplug the wiring and remove the actual plug from the cylinder head, using the socket set and an appropriate sized fitting. You might see a buss bar (if your car has one) inside where the glow plugs are housed. Glow plugs look very similar to spark plug, except for the pencil shaped element on the other end. Some engines have tiny hand spaces so some plugs, as with sparks plugs, are not always easy to get to with the right socket. Use a longer length if you need to.

Step 4 – Reaming

Reaming is not always necessary, but it is recommended. Use the reamer tool inside the hole where the glow plug came from. Screw the reamer into the socket and then screw it out again. This is to make sure the new plug has a clean and neat fitting to sit in. Coating the new plug in a small amount of anti-seize compound is often recommended too. This will prevent the plugs from seizing up in particularly cold whether and assist in better performance.

Step 5 – New Plug

Like with a new spark plug, the glow plug has a similar relocating procedure. Insert the new plug into the buss bar or hole of the cylinder head and tighten it. Do not over tighten the glow plug because you could cause it damage. You can then reconnect it to the terminal.

Step 6 – Reassembly

Reassemble the parts that were removed for access. If you had to remove the air cleaner or valve cover, make sure they are secured back on tightly. If the cover needs a new gasket you should replace it.