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The car in question is a 1991 Ford EA 3.9 litre, centre point injection running LPG.
After a radiator leak that went unchecked a month ago the head gasket blew due to overheating, radiator was repaired (in another thread) but the damage was already done.
Symptoms were steam out of the exhaust, starting in the morning on 5 cylinders and the water level dropping. Other symptoms may be overheating and oil turning milky white due to water mixing with it. It all depends on how the head gasket blew and which passages are leaking.
The E series Fords right through to AU series 1 are renowned for head gasket failure, the material used in the head gasket was prone to failure around cylinder number 6 most commonly, sometimes the water jackets in the cylinder head or block were known to corrode making matters worse.
Ford took ages to find a solution to the problem, until the AU series 2 to fix the problem (over a decade). The answer was a multi layer steel head gasket and longer head bolts with larger heads for better clamping.
The AU series 2 head gasket and bolts fit on the E series engines, 4 litre and 3.9 litre without modifications necessary.
The head bolts used by Ford are a “torque to yield” type bolt, once fitted they stretch and should never be reused. Always use new head bolts.
The new AU series 2 head gasket compressed “thinner” than the regular one, raising the compression ratio slightly making it ideal for a LPG or dual fuel vehicle.
The head gasket should be sourced from Ford and is around $75, bolts were $9 each (14 of them), but my local machine shop got me a set of bolts for $30.
Before you begin.
Note its good practice to loosen all bolts holding a assembly like the inlet/exhaust manifolds a little at a time to avoid warping any assembly’s mating surface.
Keep all bolts in groups, maybe marked in plastic bags or run them back into where you took them out from to avoid mixing things up. Take note of bolts that may be longer than others in a group, like when taking off the inlet manifold the bolts on top of the engine removal bracket are longer than the rest of the intake bolts.
To remove the cylinder head;
Disconnect the battery earth lead (this avoids a short if you do the positive first and touch metal causing a short).
I prefer to remove the battery all together, to make room and to have a nice place to keep your tools while working instead of leaving them in the engine bay, scratching paint.
Get a marking pen and number all the spark plug leads, when unplugging them remember to grip the leads from the plug not the wire and give it a little twist while pulling as they sometimes stick on hard. Unhook all the leads from the clips on the rocker cover and move all the ignition leads over the inlet manifold, out of the way.
If you have thermo fans fitted instead of the factory clutch fan, undo the top 2 bolts holding them, unplug the wiring and pull the whole assembly out to make more room. You do not have to do this but it makes life easier.
Loosen the power steering belt tensioner to release tension off the belt and remove the belt.
On the back of the power steering pump is a bolt to be removed. Then on the front of the head are 2 bolts holding a bracket connected to the front of the pump to be removed. Now you can take the whole pump and move it out of the way carefully without needing to disconnect it. There is now a bracket visible that the rear bolt was bolted to, remove the 2 bolts holding it and remove the whole bracket.
Remove the 4 bolts holding the cast iron exhaust heat shield. Now you can remove all the bolts holding the whole exhaust manifold, you do not need to disconnect the exhaust pipe or oxygen sensor plug, just move the whole cast iron manifold away from the head and leave it there.
Remove the bottom radiator hose from the water pump; this will drain all the water out of the block.
Remove your air cleaner assembly or in my case the LPG mixer and manifold, disconnecting the main LPG rubber hose and a smaller vacuum one. Don’t panic as the power is disconnected and therefore the gas solenoid is in the off position. If your car is a little old and your paranoid, you could go to the tank and shut the main gas valve.
Now remove the top radiator hose from the thermostat housing.
Under the thermostat housing are some electrical plugs that need to be disconnected.
Between the whole thermostat assembly and the inlet manifold is a steel water pipe that is held in position by a bracket held in by 1 bolt on each side of it. Undo the bolt on each side and remove each bracket but leave the pipe in position.
Remove the whole thermostat assembly from the cylinder head by undoing the 2 bolts holding it to the head and now take the water pipe off at the same time while withdrawing it.
Disconnect the PCV valves rubber hose from the rocker cover.
Undo and remove the rocker cover breather hose.
Undo the accelerator cable and move it over to the drivers side out of the way.
Undo the brake booster hose from the brake booster and move it over to the inlet manifold (passenger side).
Remove all the 10mm bolts holding the inlet manifold, a good small socket set (1/4 inch) with extensions and a universal joint can come in handy here. I found it easiest to run my arm from under the inlet manifold from the front where the thermostat assembly was fitted to get to the bottom bolts, top ones are easy to get to. One of the bolts hold the dipstick tube, when you remove this bolt you can withdraw the whole dipstick and tube out of the engine block, this is necessary as the dipstick tube can block access to one of the intake bolts. Now carefully move the intake manifold away from the head and let it sit on the side.
Now you have finished removing all the parts hanging off the head, its now time to attack it from the top down.
Remove the 4 bolts and gasket washers holding the rocker cover down and remove the rocker cover.
Rotate the engine from the harmonic balancer with a socket till the engine is on top dead centre.
Here is a pick of the timing mark, it’s not set right yet, the mark on the harmonic balance must line up with the right mark (not the left one like now) for top dead centre.
Where it is now is near the ignition timing mark, about 10 degrees before top dead centre.
Get some cable ties or electrical wire and tie the camshaft sprocket and the timing chain together. This is in case the camshaft sprocket comes off the chain; the ties mean you will not loose your sprocket position.
Just above the water pump inlet is the chain tensioner assembly bolt running in a 1 inch ring. The bolt running into the tensioner must be removed, and under it a small filter will come out.
Now the chain tensioner has to be locked to take tension off the timing chain.
There are 2 ways to do this.
1/ To do this inset a 3mm Allen key into the hole where the bolt was and rotate it clockwise to lock the tensioer up and stop it pushing on the chain. It can take a little fiddling to get it to lock but you can check it by trying to push back on the chain with a large screw driver from the top of the engine where the cam sprocket is. If the chain feels loose, it’s locked.
2/ Undo the 1 inch ring that the bolt ran in by using a punch and hammer against a hole in the ring to undo it. (Anti clockwise) Withdraw the whole assembly, tensioner etc. Tweezers can help to get it all out and take note of the order of parts.
On the front top right of the cylinder head is a 10mm bolt that runs into one of the chain guides, remove it and note that the chain guide is brittle so try not to bump it when removing of fitting the head.
Here is a pic with the head already off to show the timing chain tied to the camshaft gear, on the right is the guide that’s brittle that the bolt goes through.
Undo the large bolt holding the camshaft gear or sprocket to the camshaft. Pull the sprocket forward a little away from the camshaft.
Undo all the bolts holding all the rocker gear progressively a little at a time. Loosen them all ¼ of a turn, then 1 or 2 turns each again and again till it’s all undone. The point here behind it all is not to bend or warp the rocker gear by undoing one side and not the other, remember the valve springs are pushing up against some rockers and not others. By undoing them all a little progressively you avoid going wrong.
Carefully lift the whole rocket assembly off taking care that no hydraulic lifters (lash adjusters) fall out. Place the whole rocker assembly inside a clean plastic garbage bag to protect it from dirt.
Remove the camshaft and wrap it in newspaper or cloth to protect it from scratches.
Now the last part, the head.
Take care to loosen it in the order of the tightening sequence when torqueing it down.
The torque sequence when tightening is;
............13....9.....5....1....4....8.....12... .Passengers side
Back --------------------------------------- Front
............14...10....6....2....3.....7....11.... .Drivers side
Just loosen each bolt 1/8th of a turn in the order above to avoid warping the head.
After 1, 2 or 3 goes at 1/8th of a turn all the head bolts should be loose and can be removed.
Don’t throw away the old head bolts yet, place them in a plastic bag to keep them clean as we will be using them to avoid getting dirt into the bolt holes when cleaning the cylinder block surface.
Carefully lift the cylinder head off the block. If it’s still stuck to the block use a screw driver to lever it off using a part of the head jutting over the block to lever against.
DO NOT WEDGE AND HAMMER A SCREWDRIVER INTO THE BLOCK/HEAD MATING SURFACE!!!!!!!
Great it’s all in pieces now.
Time to clean and workout where the leak was coming from by studying the head gasket and combustion chambers.
If you look at your pistons and combustion chambers take note of the colour of the carbon. In my case cylinder 1 looked really clean, water has a tendency to clean out carbon deposits, and cylinder 1 also had a rusted spark plug.
Further inspection of the head gasket showed that the metal ring around the gasket had shit itself.
If you cannot find the cause of the leak id recommend getting the head pressure tested while at the machine shop as it can crack and need welding or replacing all together.
Now that the head is off you should check its condition.
Clean any gasket residue with a sharp blade taking care not to dig into the aluminium.
With a straight edge engineers bar check the head for warp.
In my case knowing that it overheated and being too lazy to clean the head surface and wanting to raise the compression a little further, I decided to send my head out for resurfacing and save myself some work.
Cylinder 6’s water passage had been a little corroded in the head and would need to be welded back up again to replace the corroded aluminium justifying sending the head out for resurfacing after welding.
Now is the time to remove the valves out of the head and inspect the condition of the valve seals, guides, valve seats and the valves themselves, especially since I run it on LPG and the hardened seats take a pounding.
To remove the valves give the spring retainer a sharp gentle hit with a hammer to unfreeze the assembly and use a valve spring compressor to dismantle everything.
Number all the valves so they go back into the same place as they came out from.
The back of my valves were full of carbon, obviously the stem seals were leaking and they looked a little hard and brittle. A wire brush on a bench grinder removes the carbon off the valves and brings then up like new. Wire brush just the back of the valves and the side in the combustion chamber; do not scratch the stems themselves as it will cause extra wear on the guides.
The hardened valve seats were all pitted a sign of LPG usage and would need to be resurfaced. The contact point between the valve and seat is critical as it seals the combustion inside the cylinder and is used to transfer heat out of the valve and into the cylinder head for valve cooling.
Head was sent off to a engine workshop for welding ($50); resurfacing ($75) and a valve and seat regrind ($75).
I used, The head job head shop, Newlands road Coburg, very fast same day service….yeah pisser name.
Pity I was in a hurry and forgot to take pics of the damage, but yes LPG gives valve seats a real mother of a workout.
Head was returned and all looked good.
This is the welding, you can see the discolouration where the metal was added.
When a head has warped from overheating or welding the head needs to be resurfaced. In this case I asked the mackine shop to remove the minimum amount of material to resurface it to retain as much strength as possible, here you can see one corner on the edge that hasn’t been touched after machining a sign of how bad it was but the area was not critical for a good seal as it was a oil drain back area.
The valves and seats after being resurfaced.
Time to start cleaning and preparing for assembly.
I cannot stress cleaning all dirt, sand and machine shavings out of all components. It only takes one grain of crud to get into the wrong spot to destroy the engine. Whether it is stuck on the block deck and causes the head gasket to leak again or get onto the cam bearing or lobes which will destroy the cam and fill your sump with metal shavings that will travel further and cause more damage.
Prepare the block deck surface first.
The old gasket residue will be stuck on hard. You must take care not to drop rubbish into the water passages as you can block water flow, or into the bores which can scratch and damage the bore and pistons on start up, into the bolt holes which can bugger up your torque wrench settings, into the oil drain back passages which will drive the dirt into your sump and into the oil passages which could block them or drive dirt up into the cam and rocker assembly destroying everything.
The method I use is to firstly run all the old and clean head bolts back into the block to stop rubbish falling back into them.
Rags and/or paper towels are pushed into the bores and oil drain back passages.
A Phillips head screw driver with a rag over the tip is placed into the oil supply holes to protect them from dirt falling into them.
The water passages are not as important, but you want to avoid pieces of gasket falling inside and blocking the water flow. When cleaning around any hole I prefer to scrape the gasket away from the area I am trying to protect.
My favourite tool for cleaning is a sharp blade.
Once you have the entire gasket off the deck you will notice some reside still left behind and the deck still looks dirty. The best way to finish of the deck and bring it up new and shiny is to use some 180 grit wet and dry emery paper on a rubbing block. Avoid doing it against your fingers as you want a straight and true (level) deck surface, only use your fingers in hard to reach areas and go gently. When done the deck should look like near new.
Carefully remove all rags and paper towels from the bore, oil drain back holes and the Phillips head from the oil supply passages taking care to remove as much rubbish that may have fallen inside with them.
Remove all the old head bolts.
If you have a thread cutter its good practice to run it down each head bolt hole to clean any dirt out.
If you don’t, blow some compressed air down the bolt holes to get any crap out. It’s important that the thread holes are clean so the head bolts don’t bind and give a bad torque wrench reading when assembling.
Get a vacuum cleaner and vacuum out the bores, water passages and oil drain back holes to remove any large bits that may have fallen in when removing the rags and paper towels.
Get a clean rag, put some fresh motor oil on it and wipe the bores, this helps the rubbish stick to it and easier to remove.
The last thing is to clean all oil reside off the deck with methylated spirits or petrol and a rag. Keep changing the rag until no stains are on it after rubbing and cleaning the block deck.
It should look spotless. Here you can see the thread cutter being run one more time after the deck had been cleaned just in case, .better be safe than sorry.
Now cover the block to protect it from dirt with a large garbage bag.
Don’t forget to clean the intake and exhaust manifold gasket surface while your there.
Next step is to clean the head, remember its been to a machine shop and the water passages and intake and exhaust ports may have metal shavings inside.
I use an industrial strength degreaser, brush it on and let it sit wet for 5 to 10 minutes, then blast it off with a high pressure water cleaner or the jet of a garden hose.
Stand the head upright on its end and start blasting water into the water jackets and watch all the metal flakes and shavings pour out the bottom. Blast all the ports, head bolt holes and valve guides to make sure all the rubbish is out. The most important thing is to make sure is that you blast the oil passages clean, very, very important.
Dry with an air hose and place in a clean garbage bag to keep dust and rubbish getting onto it.
Degrease the rocker gear; valve springs, retainers, camshaft and rocker cover while you’re playing with the degreaser, water and air hose to get it all out of the way. Put everything into separate clean garbage bags.
Now its time to assemble the cylinder head, but before you do that the valves should be lapped in first for a perfect seal.
Its good practice to coat the valve faces with engineer’s blue, fit them into the head and give them a spin with a lapping tool. Where the blue has been removed will show high spots, low spots will be a darker blue.
A lapping paste is available with 2 grades (course and fine) in one tube; in this case the valves and seats have been resurfaced so a simple fine lap is all that’s needed to get a perfect seal.
Coat the sealing surface of the valve and place it in the cylinder head, taking care to place it into the cylinder it came out of originally.
Fit the lapping tool (a suction cap on a stick) to the valve and start rubbing your hands together, around the stick, like your trying to start a fire with 2 sticks.
Every now and then stop, remove the valve and wipe it and the seat to inspect the progress.
In this picture you can see a stripe appearing on the sealing face. If you look carefully, you will notice shiny points that are low spots and need more lapping till the whole surface is one even finish.
This is what the sealing surface should look like when done.
When a cylinder head has been machined the corners where the combustion chamber meets the head deck surface can have a sharp edge.
Sharp edges in a combustion chamber can get hot and cause pre ignition (detonation) so its good practice to carefully remove the sharpness with a file or emery paper to round the edges. Be careful not to slip and damage the head deck surface or to go overboard and into the head gasket sealing area. If unsure place the new head gasket over the head and pencil the combustion hole onto the head. Make sure you don’t sand or file any surface that the gasket covers.
Here is a rounded edge.
It is good practice to replace the valve stem seals while the valves are out, their cheap enough. In my case the back of the valves were full of carbon, a sure sign of leaking stem seals. I use a tight fitting socket that sits snugly over the new stem seals to drive them in taking care to drive them in squarely.
Time to assemble the valves and springs, taking care to place the valves back as numbered and place lots of motor oil on the valve stems, into the valve guides and on any shims that the valves may sit on. Point is, if it moves, oil it. Once a valve assembly has been installed give the retainer a sharp whack squarely with a hammer to ensure that the retainers are locked. You would hate to have it fall apart when the engine is running.
You can also install the spark plugs at this stage.
Ford I 6’s running on gas prefer a colder heat range plug and 0.1mm less gap. Factory plug gap is 1.1mm, so mine are at 1.0mm. The plug is NGK ZGR6B-11 for one heat range colder. The 11 on the end is 1.1mm gap and the plug is actually a stock XR6 plug.
These plugs have a v groove in the electrode giving a nicer burning ignition.
Time for assembly
Now go back to the block, remove the plastic garbage bag covering the block and give it a final inspection and wipe making sure the deck is spotless.
Place the new head gasket over the deck, making sure its sitting correctly over the block, oil passages and bolt holes line up etc.
Place a new timing cover gasket in position and place a liberal amount of quality engine assembly silicon sealant on the ends where it meets the steel head gasket, top and bottom. This is a well known leakage point on Ford 6’s so it’s important to have plenty of silicon at this point.
Give the cylinder head deck surface a final wipe and inspection and place the head carefully onto the block.
Take the new head bolts and place a generous coating of motor oil on the threads and under the bolt heads where they contact the cylinder head when clamping. This ensures lubrication of the bolts when tightening so you get an accurate torque setting.
Run the bolts in all the way by hand till they contact the head.
Torque wrench settings for the old head gaskets were 40Nm, and then 90 degrees extra turn.
The new steel head gaskets are 30Nm, then an extra 120 degrees turn.
The torque sequence when tightening is;
...........13.....9.....5....1....4.....8....12... .Passengers side
Back --------------------------------------- Front
...........14....10....6....2....3.....7....11.... .Drivers side
Then an extra 120 degrees in the same order as above.
So set all the bolts at 30Nm in the order above.
Repeat it 2 or 3 times, you will find some bolts may have settled and feel loose, so keep repeating until they are all at 30Nm with none needing to go tighter.
Then in the above order an extra 120 degrees of rotation. A large protractor or a home made jig set at 120 degrees can come in handy, place it over your wrench, note where the 120 degree mark is and rotate (tighten) the wrench till you get to that point.
You should now look like this.
Get the bolt for the timing chain guide, place some thread lock sealant on it and tighten it to 9-12Nm
Put motor oil onto the cam bearing surface on the head and camshaft itself, lay the cam into position in the head.
On the front of the cam is a pin which lines up and goes into a cut out in the cam gear, so rotate the camshaft till they line up and push the cam sprocket onto the cam. Fit the camshaft bolt and torque to 50-60Nm.
Release the timing chain tensioner if you locked it using method 1, or reassemble the tensioner assembly and refit if you used the second method. Using a large screw driver from the top of the engine into the timing chain, check to see if the timing chain is tight and not loose and sloppy.
This is what the pin in the cam sprocket looks like.
Remove any cable ties or wire that was used to tie the camshaft sprocket and timing chain together.
You should now look like this.
Place the rocker gear onto the head taking care not to drop any lash adjusters (hydraulic lifters), their known to sometimes drop out.
Start tightening all the bolts down evenly, 1 or 2 turns each, evenly until all the bolts are all the way down and the whole assembly is bolted to the head. The whole point of this is not to bend the assembly by tightening down one side all the way while the other side is still loose. Torque the rocker gear to 24-34 Nm.
Lash adjusters are under the aluminium dome, on top of the valve stem tip. Check that none dropped out.
The engine should look like this now
Using a new exhaust gasket fit the exhaust manifold and torque bolts to 30Nm. Fit the heat shield.
Reconnect the bottom radiator hose to the water pump and tighten.
Fit the power steering rear bracket to the engine, and then fit the power steering pump.
You should look like this now.
If you had thermo fans fitted, refit them, install and tension the power steering belt.
Now for the intake manifold. There are 2 types of intake gaskets, one for the centre point injection and one for the multi point. The difference is a cut-out for the multipoint injectors, use the centerpoint gasket on a multipoint and the injectors will be blocked by the gasket.
The centre point can use both gaskets.
Here you can see the centre point intake manifold gasket above and the multipoint below. Note the cut-out for the multipoint.
Use a good non hardening sealant like Selleys #3 aviation sealant to coat the intake gasket.
The dipstick tube needs a new o-ring or some silicon sealant over the old one to stop leaks when fitted.
Fit the intake gasket and intake manifold to the head. Fit the dip stick tube and start running the bolts into the head. Don’t bother trying to get a torque wrench inside, make them firmly tight. If you did find a way to get a torque wrench in, tighten to 25 Nm.
Now prepare the solid pipe that runs from the thermostat housing to the intake manifold by fitting new o-rings to each end and coat them in stag joining paste to help guarantee a good seal. The paste helps if the pipe is a little old and pitted.
Ford e series have special thermostats fitted; it’s a good idea to check to see you have the correct one. The correct one is double acting, when it opens it blocks off a hole under it with a plate fitted to the bottom of it.
Fit the solid tube into the intake manifold first (not bolted) then into the thermostat housing. Move the assembly to the cylinder head and bolt the thermostat housing to the head using a new gasket coated in non hardening sealant like on the intake manifold.
Once the thermostat housing is bolted tight (25Nm), bolt the solid pipe holding brackets.
Connect the 2 electrical plugs for temperature sensors in the thermostat housing and connect all the rubber water hoses including the upper radiator hose.
Before fitting the rocker cover pour oil over the cam lobes to lube them up for start up.
Place some silicon sealant around the cam cut outs in the cylinder head (front and back), use a new rocker cover gasket and bolt the rocker cover down.
Torque rocker cover bolts to 4-7 Nm.
You should look like this now.
Fit you ignition leads in the correct order, accelerator cable, brake booster vacuum hose, PVC hose, air cleaner, battery and have a check over the engine bay to make sure you haven’t left any tools inside the engine bay, or forgotten anything.
Fill your radiator with coolant; turn on your heater from inside the car to help bleed all the air out of the system.
Start the car.
Allow it to warm up, keep the radiator cap off and keep the engine revs up around 2000 to 3000rpm to purge all the air out of the cooling system. Allow the thermostat to open and close a few times to give the air an opportunity to get out. Keep filling water as the level drops.
Close the radiator cap, change the oil and oil filter to complete the job.
