1. /// Mister-Auto’s DIY Guides
www.mister-auto.co.uk - 0844 338 00 21
*Please note: free and informative document for which Mister-Auto does not accept any responsibility or liability.
INSTALLING GLOW PLUGS
- 1 socket set
- 1 extension bar
- 1 ratchet
- 1 hexagon bit socket set
30 mins
EQUIPMENT
DIFFICULTY
TIME
Only cars with a diesel
engine have glow plugs.
G l o w p l u g s w a r m t h e
combustion chamber. As
opposed to spark plugs,
glow plugs do not produce
a spark destined to create
an explosion. Instead, they
have a glowing tip to heat
up the combustion chamber
to about 800°C. 800°C is the
temperature at which diesel
starts burning. The energy
released by the burning
process is used as driving
power for the pistons and
valves.
GLOW PLUGS
1) Disconnect the glow plugs and
take out your ohmmeter to check
their power. If one or several plugs
do not respond, it need to be
replaced.
2) Take the plugs out of the engine
and test them on a free-standing
car battery. Secure the glow plug
in a bench vice. Then connect the
positive terminal of the battery to
the positive pole of the plug with
a couple of clamps. The negative
terminal of the battery will be
connected to the vice. If the plug
starts glowing and gets warm, it
works. If nothing happens, it needs
to be replaced.
HOW TO FIND OUT IF THE GLOW PLUGS HAVE
GONE BAD?
There are no specific mileage
recommendations for glow plug
change intervals. However there
are symptoms indicating your glow
plugs are going bad. If your engine
has difficulty starting or coughs
and splutters, it is possible you
need to replace your glow plugs.
Before ordering new plugs though,
ensure they really are what is
causing your starting problems.
Similar symptoms will appear if
your starter motor is faulty or your
battery is dying for example.
WHEN DO I NEED TO
CHANGE MY GLOW
PLUGS?
TIPS FROM
MISTER-AUTO
• On certain BMW
m o d e l s y o u h a v e
to replace the intake
manifold gaskets as well
when changing your glow
plugs
• C l o s e l y f o l l o w y o u r
manufacturerinstructions
regarding the tightening of the
glow plugs. If you tighten them
too much, you risk inflicting
irreparable damage to the
cylinder head.

2. /// Mister-Auto’s DIY Guides
www.mister-auto.co.uk - 0844 338 00 21
*Please note: free and informative document for which Mister-Auto does not accept any responsibility or liability.
CHANGING GLOW PLUGS IN 10 EASY STEPS
Gently pull off the plastic engine
cover if your car has one. Do
not apply too much pressure as
this cover is only held in place
by a couple of clamps.
It is possible to only replace the bad glow plug, however we strongly recommend you change all the others
as well to avoid having to repeat the same procedure several times in a short time span. If one glow plug is
going bad, there’s a big chance the others won’t last much longer either.
Step
Step
Step
Step
GLOW PLUGS
Find the glow plugs – generally they will be located
on the top of the engine block. Disconnect the
battery.
The plugs will be protected by a plastic cover. The cover either has clamps and can simply be
pulled off or is secured with screws and needs to be unscrewed. There is a screwed on seat at
either end of the cover as well which needs to be disconnected before the cover can be lifted. On
some cars the injector connectors need to be loosened as well.
Free the glow plug by putting the drive extension
onto its top. Preferably use hexagon bit sockets
as well.
Pull off the engine cover
Gently though!
Here is the glow plug
1
2
3
4
Free the plug

3. /// Mister-Auto’s DIY Guides
www.mister-auto.co.uk - 0844 338 00 21
*Please note: free and informative document for which Mister-Auto does not accept any responsibility or liability.
Gently remove the plug.
Compare your new glow plug with the one
you’ve just taken out of the engine.
Install the new plug after having applied a thin layer of
copper grease. Manually tighten the glow plugs in two
clockwise turns. Finish off tightening the plug with the
ratchet (between 20 and 25nm).
Screw on the retaining nut with a hexagon bit socket.
Repeat the procedure for the other plugs.
6
7
8
9
10
Lift the connection wire.
5
Compare the plugs
Grease your new glow plug
Repeat all the steps
The thread is visible
Lift the plug out
GLOW PLUGS
Step
Step
Step
Step
Step
Step