This is my first Instructable... Please comment below if it needs further editing. Videos can be seen by opening the video URL in your media viewer.
Here's my experience with replacing a new head gasket on my '91 Civic. But first, some background:
This is a great car! It ain't pretty but it gets almost 40mpg on a good day. About a year ago, it failed to pass several emissions tests. My mechanic told me that the pistons needed new rings. Because the engine would be in pieces, and because of the expense and effort invested already, I agreed to have the water pump, timing belt, and head gasket replaced. Afterwards, the car passed emissions with flying colors and ran very well until recently.
Several weeks ago, the engine began to overheat erratically. After googling the problem, I personally replaced, in ascending order of expense, the radiator cap, the thermostat, and eventually, the radiator, which was very old. Because the problem was intermittent, it seemed that each part replacement solved the problem. I hoped it wasn't the water pump because I knew that would be a huge pain to replace.
In the end, some white smoke and serious engine vibrations told me that it was not the water pump but some cylinder/coolant related problem. I was afraid that it was a cracked cylinder which would have meant replacing the engine block, which didn't seem worth the expense on a 16 year old car with 174,000 miles on it. So, I went into the engine bay prepared for the worst. What follows is my experience and illustrates why your trusted mechanic can't always be trusted....
Step 1: You Are Probably NOT a Mechanic....
To get started you might want the Haynes repair manual, and a couple of impact-wrench quality sockets; I broke a Craftsman socket trying to remove the header pipe from the exhaust manifold. Having a digital camera might also be useful for recording your progress as well as problems you might encounter. You MUST have the following:
About 16hrs total total time: In addition to putting the valve assembly back on the head, putting the timing belt back on MAY require that you remove belts, pulleys, and an engine mounts, just as if you would replace the water pump. In fact, if it's old, plan on replacing that water pump. Also plan on changing the oil a couple of times as well as flushing the radiator. Sorry, but it's a big job, which is why a $30 part requires about $1,000 worth of labor. Don't bother taking shortcuts; I tried to lever the timing belt back on to the valve pulley to avoid the proper way and ended up ripping it. Plan on spending the time to do it correctly....Sorry! But you might as well learn from my boneheaded efforts.
Several Jackstands: You will need these to elevate the car and get deep underneath.
A torque wrench up to 70ft-lbs.: Don't even THINK of tightening the crankcase bolts without one!
A breaker bar: Some of your exhaust system bolts were likely tightened by Lucifer himself. A breaker bar will help release his grip.
3/8" and 1/4" drive socket sets: Also with various extenders, adapters, and universal joints.
Band-Aids: If you don't know why, you'll see soon enough.
Call the local parts supply places for expertise. The counter help might include gals/guys who are going to mechanic school or have rebuilt engines just like this one. Their help may be invaluable.
Step 2: Dig In!
All those hoses and tubes and wires! It's pretty intimidating, isn't it? Before you try to get too deep into it, you will have to get some parts out of your way....for example, removing the exhaust manifold is next to impossible without removing the radiator fans first, and you can't remove the radiator fans without first removing the air intake assembly. So:
1) Remove the large air intake hose from above the radiator fans (easy)
2) Remove the other air intake that joins the air filter box to the carburetor (easy).
3) Mark the spark plug boots and the valve cover and the distributor cap, so you don't have to guess which one goes where, later. Remove the spark plug wires and set aside in a safe place (easy).
4) Put a pan under the radiator hose area and remove the fan brackets, the radiator hose, and the reservoir hose (easy).
5) Gently lift out the driver side fan first....there will likely be a wire that must be disconnected. Watch your knuckles around the radiator fins; they are sharp! Put a bucket underneath to catch your knuckle-blood (not so easy).
6) Gently lift out the other fan....a large harness under and near bottom radiator hose must be disconnected from under the car (you might need extra hands)
7) You don't have to completely disconnect the fans; I didn't. I set them aside near the fuse box.
8) Remove the dipstick.....no, not your helper.....the one in the car (easy). You now have free access to the exhaust manifold.
Step 3: Removing the Exhaust Manifold
1) Remove the manifold cover (AKA shroud)....4 bolts, put the bolts back into the manifold so that you don't misplace them (easy).
2) Disconnect the oxygen sensor wire at the connector (easy).
3) Remove the bolts holding the manifold to the head (easy).
4) Get under the car and remove the 3 bolts holding the manifold to the header pipe. You may need to loosen the exhaust brackets. You might need the extra leverage of the breaker bar. Expect to back out a couple of the studs...no big deal (hard).
5) There may be a manifold bracket that has to be disconnected from below, as well. Lift out the manifold and set aside. Carefully remove the gasket and set in a safe place.
Step 4: Distributor Removal
1) Disconnect the harnesses with the shortest leads, a small screwdriver to release the lock tabs (sometimes not so easy if caked with gunk).
2) Unbolt the distributor assembly and carefully expose the rotor. Mark the rotor so that you don't have to remember its position when you reattach it. Put the screws in so you don't lose 'em (easy).
3) Set the distributor aside....no need to completely disconnect it.
Step 5: Intake Manifold Removal
There is no need to remove the carburetor or any of the items attached to the intake manifold.
1) Remove the accessible nuts holding the manifold to the head (easy)
2) Remove the middle nut under the intake port. Think of some other way to remove this nut if your hands are big! You might need to get under the car and reach up and into it....I don't know. Use the 1/4" drive with an extender (a real bitch....sorry, but it is)
3) Get under the car and reach up and under this manifold. There are two bolts that fix the manifold to the car. They, too, must be removed (not hard).
4) Push the entire assembly past the bolts so that the valve assembly can be removed.
Step 6: Head Removal
1) Remove the spark plugs (easy). Inspect them for deposits, arcing, cracks, corrosion....Oh hell! Just replace them! It's $10 well spent.
2) Remove ground wires and then the valve cover (easy). See video.
2) Inspect the film coating the inside of the cover; see attached video. I've since learned that it if you've been taking care of your engine, it should look like clean motor oil. If not, it'll look like mine did: goobered molasses. Clean it out! Inspect the gaskets as well and replace them all if they look brittle or cracked. The gasket kit costs about $25.
3) Remove the upper timing belt cover, mark the position of the belt with respect to the pulley, if you're re-using the belt, and slip off the timing belt (easy).
4) Mark the exact position of the timing pulley with respect to the head; this is important for reassembly!
None of this marking business is important if you plan to re-set the valves and pistons with respect to TDC, or Top-Dead-Center. If that's your plan, better have the manual handy and follow the directions carefully.
5) Unbolt the head by using a 1/2" drive socket as you'll need all the leverage you can muster. A breaker bar may be required (not that easy, but not hard).
6) Inspect the bolts and set them aside taking care not to ding them in any way.
7) Slip a large screwdriver or pry bar somewhere in between the head and the engine block and carefully lever the head up to see if the unit lift out with just your hands. It should move easily. If not, then you'll need a hammer and putty knife to get into the gasket area itself (see the manual and other sources for this process). Lift the head (easy, for me, at least).
8) Place the head in a large pan because it will drip lots of oil.
Step 7: Inspection
1) Look at the tops of the pistons. In my case, one cylinder was obviously cleaner than the others. This is apparently caused by antifreeze getting into the cylinder and cleaning the surfaces off. Even the top of the piston was scrubbed clean. So, I focused by attention on this cylinder's walls as well as the gasket around it.
If the piston top is clean but has topped out within the cylinder, you'll need to rotate the engine such that it bottoms out and exposes the cylinder walls. If the car is in gear, you should be able to rotate the wheel manually. Otherwise, remove the driver-side wheel and use the breaker bar to turn the crankcase pulley, like instructed in the manual.
2) Run clean finger within the walls and feel around for cracks and such...If you feel anything, you might as well stop right there. This instructable is now officially useless to you.
3) Carefully inspect the head gasket. In my case, there was a small crack/gap between the cylinder and coolant channel.
Step 8: Install New Gasket and Reassemble
1) Before putting on the new gasket, you'll have to remove those old pieces of gasket that have welded themselves to the flange surfaces. I used a new razor blade and carefully scraped away the material without scratching or scraping away the soft aluminum (easy). See video.
2) Put the new gasket on the bottom of the valve assembly. Unless your gasket specifically requires it, do not use any gasket sealer.
3) Place it carefully, and slowly, back onto the head taking great pains to not ding the gasket!
4) Inspect and clean your bolts....remove corrosion and rust. If they show cracks or strips, replace them!
5) A dab of oil is all that's needed to lubricate the threads before inserting them back into the valve assembly.
6) Tighten the bolts as specified in the manual....It's three step process: Finger tight, torqued in a crossed-x pattern to 22ft-lbs, and then again to 49 ft-lbs. Follow the diagram! (easy). See video.
7) Carefully reassemble in reverse order...(pay attention, and don't end up with loose parts!)
IMPORTANT NOTE:As for re-installing the timing belt, loosen the tensioning pulley by accessing the bolt through the lower timing belt cover access port. I did not know that I could do this, and as a result, ripped the timing belt and spent an additional half-day having to uncouple the front engine mount, loosening the alternator, pulling off the belts, pulling off the crankcase pulley, removing the lower timing belt cover, and so on and so on. What a pain!
8) After reassembly, I successfully re-started the car with no problems. However, you may, as I did, end up with a "Check Engine" light. There are a few instructables showing you how to diagnose engine codes. In my case, I had two codes of which one went away after re-setting by completely disconnecting the battery. The other codes was the result of a missed connection; I reconnected the harness and the red LED code went away (Thanks Instructables!)
Good Luck! I hope you learned from my experience!