Want to know if your Golf has a Knock Sensor?
Humour-Impaired: This is a tongue-in-cheek response
Subject: Does my Golf have a knock sensor?
Sorry guys, slightly off subject here....... I have asked this question
before and not received a reasonable reply. How can I tell if my UK '87 Golf
GTI 1.8 8v has a knock sensor.
Assume I have no technical knowledge.
OK. I'll try.
Please read all the instructions, before starting.
DISCLAIMER: Use these instructions at your own risk.
That's all for now.
Stop the car, preferably on flat, level ground. Do not stop near
the edge of a cliff.
Turn the ignition key to the left until it goes no further and
the engine (that's the funny thing making a noise at the front)
Apply the handbrake and make sure the car is in gear.
This stops the car from attacking you if the anesthetic wears off.
Unlock the bonnet (that's the big lid over the top of the engine)
by pulling on the lever below the dashboard, next to the door.
You should feel an hear a clunk as it unlocks.
Get out and walk around to the front of the car. Take the key
with you in case the car gets grumpy and locks you out.
Stand at centre of the front of the car, facing the car with
your shins against the bumper or number plate.
There'll be a "new" gap between the top of the grille (the black
bit with horizontal slats and a VW roundel in the centre) and the
bonnet. Place your less-favoured hand, palm up, with fingers
extended into the gap between the bonnet and the grille.
The bonnet is hinged at the back.
Lift and grasp the bonnet until you feel it resisting further
lifting. That's the action of a safety device to stop you making
a complete fool of yourself if you unlock the bonnet while the
car is moving.
The safety catch is a lever under the centre-front of the bonnet.
Use your favoured hand to push it back, and hold it there while
lifting the bonnet a little further. An inch or so will do for
now (seeing it's a UK model).
Now using both hands, lift the front of the bonnet as high
as your arms will comfortably stretch, hold it there with at
least one arm.
You may be able to stretch further by:
firmly grasping the bonnet with one hand, then
releasing the other hand and turning it palm-down, then
firmly grasping the bonnet with that hand, then
releasing the bonnet with the first to allow you to turn it
as well, then
again grasping the bonnet with both hands.
Warning: This sequence is complicated but important.
If you get it wrong, it can cause serious injury
and mechanical damage.
If you don't feel up to it, don't even try!
If you have not done this stuff before, then practice
with a broom-stick until you are confident.
Because VW recognizes that bonnets can be quite heavy to hold up
due to their weight, they've devised a foolproof device (i.e. a
device which proves that there are fools) to hold the bonnet
open while you, or your mechanic puzzle about what is revealed
as it is opened.
The device is called a bonnet-stay (in english-speaking parts of
the world). VW fit these at the factory and in your model, it is
operated manually. Later Volkswagen products often have
stronger, even heavier bonnets, and this one is already quite
weighty, isn't it?
So VW tend to fit automatic stays which operate on compressed
gas. You can "retrofit" (i.e. add them on) such devices to your
car should you feel that it's a good idea.
But I digress and sense that the bonnet on your car must be
feeling like it's gaining weight.
The manual stay is stored horizontally across the top of the
black steel panel revealed as you opened the bonnet, above the
grille. The stay is a steel rod, about three-eights of an inch
in diameter, usually coated with black plastic, and around 3 feet
long, with a few small bends and a hook in one end.
The stay pivots on a plastic bush on one side, and the (other)
hook-end is held down by a small plastic clip. Well, it was at
Unlucky. So we'll go onto the next step.
Make sure that you are holding the bonnet up with your left hand.
Using your right hand, reach over and grasp the hook end of the
stay, to your left, about four inches from its end. Give it a bit
of a wiggle as you lift it up to help the clip to release.
Remember where it was clipped in so that you can put it back
later. Even professional mechanics can forget that.
Swing the stay up about its pivot to your right until it is
close to vertical. No need for a spirit level or plumb bob.
Near enough is good enough.
If it won't swing up that far, and makes a clunking sound,
then try to lift the bonnet further with your left arm.
Do not do this while standing on a ladder!
The bonnet has several oblong recesses near its front edge.
The hook on the stay fits into more than one of these, but at
this time, we'll only use the one for the sake of simplicity.
We'll use the one which is almost immediately above the stay in
its vertical position.
Gently guide the end of the hook into the oblong recess,
lowering the bonnet with your left hand and moving the stay
with your right hand. Do not allow the bonnet to drop.
It upsets the neighbours.
Confirm that the stay is "docked" into the bonnet by attempting
to lift the bonnet while not holding onto the stay. If the stay
slips out and falls, then try again.
Once you are sure that the stay is secure, you can slowly release
the bonnet with your left hand. It is normal for the side which
you're supporting with your hand to drop a few fractions of an
inch. If it "wants" to go further, check that the bonnet stay
is still in place.
You can put your arms down now.
If you now look slightly down and forward you should see then
engine slightly to the left, the gearbox to the right and further
to the front, the back of the radiator (that's what the engine
needs to keep its cool if you upset it).
It looks a bit odd because the engine is to one side and the
gearbox to the other, but then Volkswagen cars cave always been
Focus you attention on the engine. That's the big lump of metal
with wires, hoses and what have you coming out of it in all
Let's get familiar with it:
The top of the engine has a black cover over it and sprouts a
Underneath that, is what is called the "head", nothing to do
with the naval term, but short for the cylinder head. The head
is made from allow and silvery of matt-grey in colour.
The head sprouts a set of spark plugs and their wires at the
There are also some hoses, but they don't add to this explanation.
These wires all go to the one location called the distributor,
connecting to its cap; a squat, reddish-brown, hard plastic
cap about 3 inches in diameter to the right of the engine as
you're looking at it. The cap has another wire coming out of its
centre which leads to the "coil" which actually "makes" the
spark. The distributor just shares sparks out to the cylinders
as they need them.
Each cylinder has its own spark plug and you should see four of
them, or at least their wires. Engineers like to number things
and by convention, the number one (#1) cylinder happens to be
the left-most as you look at the engine. (Don't want to get too
technical here.) And because engineers are not the smartest
of people, they also make it easy on themselves by numbering the
other cylinders in sequence from left to right.
So you get (#1) (#2) (#3) (#4), in that order as you look at the
engine when standing at the front of the car.
Now, when you look even further down, below the spark plugs,
you'll notice a change of colour, which is supposed to be black,
but it may be rusty-brown (i.e. rust).
That section of the engine is called the "block". It is where
the actual cylinders are located
Your view of it may be obstructed around cylinder #1 by various
bits, most likely being the alternator; have of the miniature
power station that keeps your radio, and the engine supplied
with vital electricity by tapping off some engine power.
About four to six inches down the block, between cylinders #1
and #2 is where the knock sensor is fitted.
If it's not there, then you'll just see a small hole in the side
of the block, with a similar one at the same height between #3
and #4 cylinders.
If it is there, then it is black plastic, about one and a half
inches in diameter, with a cable running out of one side.
There's a bolt down the centre of it (you can only see its
hexagonal head) to hold it to the engine.
Earlier knock-sensors where U-shaped with the cable running out
of the top of the U. Later ones are round, with a squat conical
section tapering toward the bolt, with the wire running towards
All those bits are black because serious bits of machinery are
always silver or black. It's a fundamental law of the universe.
Next week, I'll describe how to close the bonnet...
You don't want to drive along with it up for too long.
Too much snow on the engine is not good.
And now a word from our sponsor: Send royalties my way. ;-)
Copyright © 1999 Bernd Felsche.