Water Boxer's Head Replacement
By Bob Donalds
| So you're thinking its time to replace
the heads on your water boxer, and you're asking yourself if you
can do a job like this. Can this be done on the ground without a
lift? I will try to help you answer these questions.
First, lets go over the most common reasons to remove the cylinder heads.
Make sure to be clear about what's leaking before you begin the job. It
can be oil or coolant that's dripping from the heads. Washing the engine
is very helpful when looking for leaks. If the push rod tubes are
leaking or if a lifter has collapsed, you can use an expanding push rod
tube, which is available at the dealer for $50 each, or in the aftermarket
for about half of that. The most common coolant leak is from a cracking
or splitting rubber outer coolant gasket at the head.
Often this will be accompanied by a corrosive reaction where the rubber gasket contacts the head. Unfortunately, there is no easy way out of this repair. The heads must be removed to replace these gaskets, and at this time a close inspection of the heads will indicate the extent of corrosion. A corroded head will not make the best possible seal with the gasket.
Another reason the heads may need to be removed is pressure build up in the cooling system. This is do to the head gasket at the top of the cylinder leaking compression when the engine is cold.
TEST #1: Pressure Tests for the Cooling System
The first test of the cooling system is done when the engine is cold. A cooling system pressure tester can be installed in place of the radiator cap. Pressure in the cooling system and hot coolant are not something to be treated lightly. Use caution, and never remove the radiator cap from a engine that has been run even for even a short time. After installing the gauge, pump it up to 10 pounds. Look around for leaks if the gauge shows any pressure loss.
Common trouble spots include heads, hoses, water pump and rear heater core. If you smell something sweet when you turn the heater fans on, it may be a coolant leak at one of the heater cores, or simply the O-ring at the rear heater valve leaking. Because there is often more then one leak in the system, it is necessary to continue pressure testing until the system holds pressure.
Start the engine cold with no pressure indicated on the gauge. The pressure in the cooling system builds to aprox 7 lbs at normal running temps looking around for leaks. But if the pressure builds quickly to around 15 lbs the pressure is coming from one of the cylinders through the inner head gasket. This can also show up as a coolant pressure loss in the first test. In extreme cases the cylinder can fill with coolant, and will not turn over. This is know as hydraulic lock, and if you suspect this pull the spark plugs and try to turn the engine again. Pulling the plugs from the engine allows water to escape from the spark plug holes.
DO'S & DON'TS FOR HEAD REMOVAL
and some things to consider before you attempt this job
Yes, head removal can be done on the ground with a good set of heavy duty jack stands. Disconnecting the battery is the first step. I consider cars to be a fire hazard, since there is everything you need to make a great fire in short order. I have set more than one car aflame.
This is a messy job, and you can expect to spill coolant on the ground. No mater how you jump and dance, those last few drops will get you.
Remove the coolant expansion tank cap and the 6mm Allen head coolant drain bolts between the push rod tubes on each side. I also pull the bleeder from the radiator because it allows the cooling system to drain more completely. Next drain motor oil remove the filter. With the fluids draining, start undoing the ground wires on the left head. Tie rap them together so none are forgotten . They will need to be cleaned and inspected before reinstalling, using new bolts and anti seize compound. Labeling the wires saves time and guessing later. Next remove the alternator and the belts, and inspect the belts for wear and cracks. Check the water pump pulley shaft for bearing play by grabbing the shaft at 12 and 6, and seeing if it wobbles. Now check for leaks at the vent hole on the underside of the pump. If its leaking, this a great time to replace it, since its much easier with the heads off and the cooling system drained.
Unbolt the intake manifolds complete with the fuel hoses and injectors, and tie them up out of the way.
Removing exhaust bolts and studs at the head to exhaust connection is one of the hardest parts of this job. Use only six point sockets, trying not to round the heads off. When the head of the fastener is rusted you may need go to the next size smaller socket installed with a hammer or nuts can be spilt then turned off the stud. Drilling or sawing the head off the bolt works, leaving the remainder of the bolt to grab and remove after the head is off the engine. The exhaust brackets are very important and need to be reinstalled they keep the exhaust pipes from flexing and cracking as the engine moves.
Inspect the adjusters when removing the rocker arms. They take a beating and can be hard to get on short notice.
Keeping a parts list is key to a smooth, timely and effective repair. Faced with the option of using something that is junk, or waiting for my second parts order to arrive, I've had to re-use the tired part. I can't have my grocery getter off the road for too long.
WORDS TO THE WISE
Cylinders do get stuck to the head and taping (hitting) the head just below the exhaust ports with a plastic compethan mallet helps. Going from side to side helps to separate the head from the cylinder. You may need to push the head back in place and start again if the head moves more than two inches with the cylinder still attached. The piston in the stuck cylinder should not be at the bottom of its stroke. DO NOT pull the head and cylinder off as one because piston rings cannot be compressed to put the cylinder back on until you remove the piston from the engine. Wrist pins and pin clips are hard to access and remove even when using the expanding pin tool and the oxy acetylene torch to soften up the varnish on the pin. The #1 and #3 the pistons are first to be installed and last to be removed. This means the # 2 or 4 cylinders are in the way and must be removed before the 1 or 3 piston pins can be accessed for removal. Then the time comes to install the #2 and #4 piston pins the inaccessibility of the con rod creates a real challenge. Volkswagen has a special tool (#3090) that supports the connecting rod while you install the wrist pin. One possible solution is to modify a coathanger to do this, but I find it faster to remove the engine and reinstall pistons and cylinders on the engine stand, because I can rotate the engine onto its side. The o-ring at the bottom of the cylinder is not likely to leak if you disturbed the cylinder. I Boston bob have never heard it to be a problem but having said this I'm sure I will now here otherwise.
Pistons, cylinders and rings do not show signs of wear like the air cooled engines.The oil consumption is typically not high and the pistons and cylinders do not need to be replaced normally unless over heated or you are doing a total rebuild.
PARTS NEEDED TO REASSEMBLE
Options for cylinder heads: OEM @$625 each at the dealer, Spanish AMC after market heads @$450 each. We do not use the valves that come with these heads.
There couldn't be a better time to replace the water pump or any weak exhaust pipes, injector seals and high pressure injection hoses. I recommend using only OEM sealant when resealing cylinder heads. Some silicones can be corrosive when used on aluminum.
Most coolants are now suited for aluminum engines, so read the label on the coolant you are thinking of using. Corrosive inhibitors can be purchased to supplement the coolant, but I don't think it is necessary if the antifreeze is changed every two years.
How do I know if it is time to replace the lifters? The lifters are hydraulic, and tired lifters take longer to pump up, if they do at all. Lifter replacement is judged by how long you hear the ticking when the engine is cold. There is no extra labor involved to replace the lifters when the heads are off.
I have tried the procedure in the Bentley book for filling the lifters with oil, and they still take time to quite down when they're new. I recommend soaking the lifters in oil overnight before installing them. This is just as effective.
TIME TO REASSEMBLE
and to find out what we don't have.
Run the tap into the head nuts, making sure they are clean inside. Next, take the 10x1.50mm die and clean the head studs.
The lip that holds the head gasket on the block needs to be inspected for burs and rot. If needed, wire brush and clean. I use Jb weld epoxy in the eroded surface to restore its shape, filing it in aprox. 24 hours when dry.
Install the inner head gaskets in the head with a dab or to of grease to hold it in place. Next do the rubber gasket on the block. Apply the black sealant to the black water gasket in the middle of the gasket. Put the head onto the studs, leaving room to install the push rod tubes. I use the push rods to hold up the push rod tubes until they are all in place. Next start one of the center head nut inside the valve cover to tension the tubes, then inspect the tube gaskets toassure proper alignment. Turn the one head nut you started so you can start the other nuts. I apply the yellow head nut sealant to the opening in the head for the stud and to the nut itself, trying to it keep it from getting in the nut. Using the torque pattern in the book bring the head down evenly. This can take two or three times to get the nuts ready for final torquing. The torque for the heads is 20 ft lbs, then 36 ft lbs with a bar type torque wrench.
The push rods can hang up on the edge of the lifters which results in no compression. There are some simple tricks to installing push rods. First I have heard that greasing the push rod tip when installing the push rod can help. When I install push rods I push them in, then lift the far end and push again. This is done with the rocker arm installed, using light pressure to hold the rocker in place until you feel the push rods are seated, then install the nuts. A good pen light is very useful to see the down in the push rod.
BLEEDING THE COOLING SYSTEM