When you buy an older fiesta, no mater what its age or engine size,
if it is blowing black smoke out it has a high carbon build up in the compression chambers
In this guide we show you how to De-Coke a standard 1.1 Head.
This guide is intended for the HCS engine with manual choke but is very
similar for the CVH engines.
First off you need to have your car on a flat surface preferably in a garage
just in case anything goes wrong like the weather changing for the worst.
Tools Needed:
Haynes manual
Screwdrivers
Socket set
Spark plug removal socket/tool
Torque wrench
Torx set
Wire cutters
Drill
Wire brush attachments for drill
Jack and axle stands
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Disconnect it!
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Disconnect the battery otherwise
you will get a shock like I did.
First off you need to disconnect the battery, as wires will need to be unplugged.
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Open your bonnet, Remove the air filter; this is done by removing either 2 or 3
positive head screws from the top.
Pull up the filter and disconnect the vacuum pipe attached to it and tie
it up on the bulkhead of the engine bay.
You will notice that the oil breather pipe and filler cap is connected
to the air filter, simply pull out the filler cap.
Now the filter should be free, place it to the side, well out of harms way.
Remove the two bolts holding the heatshield onto the manifold and remove the heatshield.
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Now onto the spark plugs, pull off the HT leads by grabbing the rubber ends
not the cables, as they will get damaged otherwise.
Now the plugs are exposed, you will need a spark plug removal socket.
Be careful here as you can snap the plugs like I did,
Remove all the plugs and look at the condition of the electrode end.
If it looks like the one below there is something wrong.
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With the plugs removed next comes the messy jobs.
Remove the rocker cover by un-doing the 4 bolts around it.
When removed the cover might be stuck to the head.
If so just give it a gentle tap and it should break free,
this is due to the old gasket bonding the 2 surfaces.
If under the rocker looks like this then you need to give your car a
good flush and oil change.
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Undo the 4-rocker assembly retaining bolts and remove the rocker assembly.
Dismantle these by removing the cotter pins and washers and slide the
rockers and springs off the bar, ensuring you keep their original order.
Clean all these parts with petrol or other cleaning substance ensuring
that the oil traces are clear from debris and dirt.
Examine the rocker head surface where it makes contact with the valves,
if this is pitted deeply then they will need to be ground down to a new
smooth finish. See the guide created.
Reassemble using fresh engine oil to lubricate the rockers back onto
the bar in the correct order.
Clean out the rocker cover and remove the old gasket then place the
reassembled rocker unit inside the cover and set aside.
Make sure you remove the 8 push rods to the rear of the block and keep
them identified from each other
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Drain me!
Now to drain the coolant system. The best way is to jack up the car and place
on axle stands for your own safety.
Now ensure there is a bucket under the right hand (passenger) side of the
radiator where the large drain plug is. Undo this plug as far as it will go,
it wont drop out! And make sure the bucket is catching the water correctly;
loosen the header tank cap off slightly to increase water flow.
Once drained the next step can be carried out. The removal of the thermostat
housing and thermostat.
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Remove the multi wired plug from the sensor on the top of the housing and
the single wire from the sensor on the side of the block and secure out of the way.
Loosen the jubilee clips from the big and little pipes from the housing,
now twist the pipes and pull off, they may be wedged and seized with lime scale,
if so just wedge a screwdriver under the edge of the pipe to break the seal
(you may get wet here). Tie back the pipes out of the way.
Loosen and remove the 2 bolts holding the housing to the block.
Pull up the housing remove and discard the gasket and remove the thermostat.
Test the thermostat in accordance to the Haynes manual and set aside in the
box of bits from the engine that you have started.
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Carb
Removal of the carb is fairly straightforward.
Firstly remove the multi-plug on the inlet manifold underside.
Now remove the small plug wire on the side of the carb.
Disconnect the vacuum pipe from the manifold from the break servo
and secure on the servo out of the way.
Remove the rest of the pipes making sure that you label them correctly.
The last pipe to remove is the fuel inlet pipe, be careful here you
don't want to be smoking near this, prise off the metal clip that secures
the pipe and gently twist the pipe off and immediately plug it with a bolt
or screw and put a jubilee clip around the end ensuring it is secure and put
out of harms way.
Make sure you remember to remove the earth wire and HT lead guide from the inlet manifold.
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Unclip the accelerator cable from the bracket by removing the odd shaped metal clip
and pull the cable out, now unclip the cable from the black cam shaped plastic item.
The choke cable is held on by a metal clip that needs to be prised off with a
screwdriver that will no doubtably be deformed or lost (mine shot off into the wilderness).
These are only 30p from ford new so wont break the bank if it is lost.
Unclip the choke cable from the rubber mount on another cam wheel and secure
the cables out of the way.
On the top of the carb there are 4 Torx headed screws, remove these and
lift the carb free, put it straight into a container with a cloth in the bottom
to soak up any excess fuel left in there.
More than likely the gasket will be brittle and need replacing.
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Exhaust manifold
Take the weight of the exhaust with a jack and release it from its rubber mountings.
Now from the underside of the engine bay remove the 3 nuts that secure the
manifold to the down-pipe and release the 2 parts, be prepared to get
covered in soot/ carbon.
Put the exhaust on the floor out of the way.
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Head bolts
Right now comes the tricky bit!
The head bolts need to be removed in the opposite sequence to what they were installed,
e.g. bolt number 10 first and so on. See diagram below.
They will be very stiff! So use a strong arm or brace. Once all are loosened,
either mark them to say they have been removed from the engine or buy a new set
as they can only be used twice. ALSO mark which number they are, as they need
to be put back into the head in the correct place.
The head will be stuck to the block, as the gasket will be compressed.
Gently tap the block upwards DO NOT rock it, as it will damage it.
Lift the head clear of the engine bay making sure you do not loose the 2
locating plugs from the block/head.
Place the head on some cloths or something soft.
Examine the piston face.
With the block off look at the face of the pistons, if they look like what's
shown below then they will need cleaning. This will be done in another guide.
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Cleaning
At this point you can either remove and clean the inlet manifold or leave it as it is,
But the exhaust manifold needs to be removed and cleaned out.
This is done by removing the 8 nuts that hold it on,
taking care not to remove the studs from the block as well.
With the manifold removed, use a small stiff bristle brush to clean out the
channels and pipes, this is quite messy but needs to be done.
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Now the head
Clean off the top of the head with petrol to remove the grease.
Turn it over to show the valves.
Remove the gasket.
They will more than likely look like the ones shown below,
Get the appropriate sized wire brush attachment in the drill and start cleaning
making sure you wear eye protection and take care not to scratch the heads surface. .
Clean all the surface of the cylinder where the valves are including the valve faces,
repeat for all the chambers.
Once done wipe over with a cloth to remove any residue or carbon.
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The End
Now that's basically it for de-coking the head. While the head is off you can
also replace the valve stem oil seals and clean and paint the head, replace
the piston rings and de coke the pistons and chambers. These will be covered
in subsequent guides on fiestaguides.co.uk
Refitting is removal but in reverse taking into account the correct torque wrench
settings for each nut and bolt that is stated in the Haynes manual.
Ensure that the pushrods are seated correctly into the rockers upon reassembly.
Note that the tappets will need to be adjusted to compensate in their disturbance.
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Guide Written and © On 17 May 2005 by Andrew Whiteman (AW3K)
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