Please read through all of the instructions here and make sure you understand them before
attempting this procedure!
The most common mode of failure of 12v head gaskets is oil leaks. Unless there has been some
sort of catastrophic cooling system failure, you tend not to see many blown head gaskets or
coolant leaks. If you suspect that coolant is leaking from your head gaskets, you can check
your engine oil to see if it is foamy (thus coolant is leaking into the oil passages), or
pull each spark plug and check to see if one is unusually clean (thus coolant is leaking into
the combustion chamber, and the plug is steam cleaned several hundred times per minute).
Most people associate replacing head gaskets with huge repair bills or huge amounts
of work. Those people are right. Replacing your head gaskets is a very involved process,
requiring lots of tools, time, replacement parts, common sense, and repair experience.
You will be removing a large percentage of your engine to get to the gaskets, and will
probably break something, lose something, or encounter one or more parts or tools that you
need but don't have. This is not the job to do if you've never worked on your car before.
Those of you who aren't checking the balances on your credit cards to see if you can afford
to have your favorite mechanic to do it have probably already rolled your eyes in disgust
and started scrolling down to the procedure, because you are crazy.
To the right-thinking people who are approaching this procedure with a certain amount of
trepidation, it's not actually as horrible as it sounds. It's merely bad. Just remember:
preparation, knowledge, and common sense are sufficient to succesfully complete any repair
task. This article will help with the first two; for the latter you're on your own.
Definitions and Acronyms:
- TDC: Top Dead Center. This is the position of the engine when
the #1 cylinder is up as far as it will go.
- EGR: Exhaust Gas Recirculation. The EGR valve lets exhaust gasses
back into the intake manifold under certain conditions to lower combustion temperature
and NOx emissions.
- NOx: Nitrous Oxide
- ISV: Idle Stabilizer Valve. An electric valve controlled by the
ECU to allow extra air through the intake manifold under certain conditions, to keep the
engine from stalling. Also called the Idle Air Control (IAC) valve.
- Torque wrench. I recommend getting one with a 1/2 inch drive, or the head bolts
will be fairly hard to install.
- Triple-square sockets. You may or may not need these; some head bolts will use them;
others will use a normal hex socket. You can see which you have by removing the valve
- Various sockets. I recommend 6-point sockets whenever possible, as you will be less
likely to round off tight or stuck bolts or nuts.
- Various extensions and adapters for sockets
- 5mm, 6mm, and 8mm allen wrench sockets.
- Magnetic pick-up tool. Trust me, this is just a good thing to have.
- Tools noted in the timing belt replacement procedure
- Tools noted in the oil check valve replacement procedure
Many parts suppliers sell a 'head gasket kit' that combines many of these parts into a less
expensive package. Ask around.
- Head gaskets. You want to replace both of them, not just one.
- Camshaft oil seals
- Intake manifold gaskets
- Valley pan gasket. Technically, you don't need to replace this. However, it's cheap, and you'll be right there.
- EGR valve gasket
- Valve cover gasket
- Lots of assorted vacuum hose
- Head bolts. 8 per head. These are not optional! They are single use only.
- Silicone grease
- Parts noted in the timing belt replacement procedure
- Parts noted in the oil check valve replacement procedure
Stare at the engine
and make sure that you're familiar with where everything is. Do this periodically throughout the procedure, so that
there's less likely to be any question of how things fit back together. This is an important step that many people
forget - and regret later. Grab a pencil and some paper so that you can make notes and draw pictures while you're
- Follow steps 1-20 of the timing belt removal procedure (steps
1-24 if you have a Coupe, Cabriolet, 80, or 90). This gets you as far as draining the
coolant, making some room in the engine bay, and removing the timing belt. It's probably worth draining the oil in
addition to draining the coolant, even though the timing belt procedure doesn't call for it.
- Follow steps 1-23 of the oil check valve replacement
procedure. This gets the intake manifold off. If you are replacing the valley pan
gasket, also do steps 24 and 25. You can replace those valves, too, but I wouldn't
bother unless you really want to. If you took the valley pan cover off to replace the
gasket, put it back on before continuing.
- Remove the valve covers. They are held in place with six 5mm allen head bolts. Each cover has a rubber gasket that
will come off with the cover. Throw it away, you need to replace it.
- Remove the
various parts hanging
off the rear of the heads, including the camshaft position sensor (red arrow) and the ATF dipstick (if you have an
automatic transmission; violet arrow). If your vehicle was manufactured in early 1992, you have a vacuum pump
on the right rear cylinder head; otherwise you have a plate covering a hole there. In either case, remove it.
- There is a coolant pipe that goes into the back of each head - remove.
- If you want to remove the camshafts, now is the time: Remove the camshaft bearing caps. There are four of them,
and each one has a pair of 13mm nuts on it. Remove the two
bearings in the middle first, then gradually loosen the four remaining nuts on the front and rear bearings in a
diagonal alternating pattern. Caution! DO NOT interchange camshaft bearing caps! Identify which one goes
where and don't forget! Removing the camshafts is not necessary for the procedure; however it is necessary if you want to
replace the camshaft oil seals, which I recommend doing.
- Carefully remove the camshaft, noting which side of the engine it's on. Each camshaft will take two oil seals
with it, one in front and the other in back. Note which direction they face and throw them away.
- Disconnect the two harness connections for each oxygen sensor. I found it convenient to also remove the sensors,
but that's up to you.
- Remove the
CO tap tubes
(red arrows) and the exhaust manifold heat shields (green arrows).
- Disconnect the exhaust pipes from the
I found that these were the hardest to remove in the entire project. They're baked on and
rusted on, and were extremely hard to remove. You will probably strip the nuts and have to replace them. You might,
after some cursing and skinning of knuckles, wonder if it would be easier to remove the exhaust manifolds from the
heads instead. It wouldn't be - you would have to pry the manifolds about 2 inches away from the heads to release
them from the studs holding them in place, which doesn't really work all that well. Keep at it!
- Disconnect all spark plug wires. Leave the plugs in place.
- Remove the cylinder head bolts, remove cylinder heads. It's probably worth breaking all eight loose, then going
back around and removing them. Then pull off the heads -- this is much harder than it sounds. The heads will be
very hard to remove. Beat on them with a rubber mallet; resist the urge to pry them off with a screwdriver lest you
damage the surfaces. Keep in mind that there are some passages that extend past the gasket surface, so the heads have
to come straight away from the engine block - they won't slide off. Note that some coolant and oil may dribble out
of the heads when you pull them off.
- Throw away the cylinder head bolts. Throw away the old
head gaskets. Marvel at this unusual view you have of your engine. Show off to your spouse, friends, neighbors, or
whoever you can get to listen. Try not to look worried when they tell you that they won't be impressed until you've
put it all back together and the car runs.
- Heck, take a break. Have lunch or something. You're halfway through! Besides, you'll need your energy for
the job to come...
- Back already? Great. Now it's time to put it all back together. In the immortal words of Robert Bentley,
'Installation is the reverse of removal.' Got it? Good.
- First make sure that the surfaces on the block and heads that will touch the new gasket are clean.
Use a toothbrush or something plastic to clean the surfaces -
don't use a screwdriver or wire brush or anything that might scratch the surfaces! Also make sure that stuff doesn't
fall into any of the coolant or oil passages on the block.
- Place the new gaskets on the engine block. They will have markings that indicate which side is up; mind them.
- Set the heads back on the block. Do this with a minimum of wiggling, but make sure that everything is aligned.
In particular make sure that you've aligned the exhaust manifolds with the exhaust pipes, because this will be a lot
harder to do once the head is tightened on.
- Tighten the head bolts. This will happen in three stages, and each stage must go
The order is important!
Look at the picture!
The numbers you see in the picture (1-8) are the order you need to tighten the bolts in. The order is important because
if you go in a straight line, the gaskets will deform and not seal properly. Even a slight deformation will be a problem,
because of the small amount of space between cylinders. Anyway, in the first stage, tighten the head bolts (in order)
just finger tight. Next, tighten them all again (in order) to 60Nm (44 ft lb).
Finally, tighten them all once more (in order!) an additional 1/2 turn (180°). You will probably find a breaker
bar useful for this last stage. Two 1/4 turns (90°) are OK, but do each bolt at once; don't tighten all eight
bolts 1/4 turn and then go back for the second 1/4 turn.
- At this point, the remainder of the procedure is essentially child's play - you just need to re-install everything
you took off. Start with the exhaust manifolds - reconnect them to the exhaust pipes. Tighten the nuts until the
springs on the bolt heads have compressed about half as far as they can. This isn't exact, so don't worry.
- Reinstall the CO tap tubes and oxygen sensors if you removed them. Notes on oxygen sensor installation
- If you removed the camshafts, reinstall them with new oil seals now. Coat the new seals with fresh oil before
installing them. Coat the bearing surfaces with fresh oil before setting the camshafts down. Use your camshaft
holding tool to make sure that the camshafts are installed at TDC! Install the bearing
caps in the same position and orientation as before. Tighten the nuts to 20Nm (15 ft lbs). If you went
hog wild and replaced your hydraulic lifters, note the time - don't attempt to turn the engine until the camshaft has
been installed for at least 30 minutes.
- Reinstall things like the camshaft position sensor, ATF dipstick, and vacuum pump that you removed earlier.
- Coat your new valve cover gaskets with fresh oil and press them into the valve covers. Apply a small amount of
silicone grease to
the corners where the camshaft leaves the cylinder heads. Reinstall the oil splash guards (those black plastic things
that were sitting on top of the camshaft bearing caps) and then the valve covers. The bolts for the valve covers
should only be tightened to about 10Nm (7 ft lbs).
- Follow the reinstallation steps on the oil check valve replacement procedure.
- Reinstall spark plug wires if you haven't done so already.
- Follow the reinstallation steps on the timing belt replacement procedure. Turn the
engine by hand at least two full revolutions once the timing belt is installed to make sure that the valves aren't
striking the pistons. Make sure that you have camshaft and crankshaft TDC lined up properly!
- That's it! Make sure that you've refilled any fluids that you emptied (notably coolant and oil), reconnected
any connectors that you disconnected, and reconnected any vacuum hoses that you removed.
- Congratulations! You're finished. Wash up, then fire up the engine and see how it works. Pat yourself on the
back, then go to mock those who said you'd never be able to do it. You earned it!
I've tried to make this procedure as complete as possible. However, if you notice any ommissions, or something I've gotten wrong, or have good
quality pictures of your engine while you're in the midst of this procedure, please send me an e-mail. My e-mail address is noted on the main page.
The message board is gone. I don't know why we can't have useful things on the internet without jumping through hoops to avoid spam. But at any rate, I'm not going to do it. Sorry for the offensive amount of crap that was on here recently.