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How to replace head gaskets

03-09-2008, 05:30 PM
This was done on my ‘97 4WD Blazer, 4.3L V6 with 145,000 miles on it, vin “W”. I had lots of coolant in the oil and smelled burning coolant, but my exhaust wasn’t any worse than usual. I decided to go all out and do the head gaskets myself. If you’re doing this, you will need to get the kit with the head gaskets, exhaust manifold gaskets, lower intake manifold gaskets, and valve cover gaskets. I bought this kit from NAPA (Part Number HS 9354 PT-6) for about $50 that had all the gaskets I needed and more.

Follow this link to get everything up to the intake manifold removed (great work by drdd):

Some things you will need:
- An extra set of hands.
- 7/16-14 NC tap and die
- Head puller tool
- Fan puller tool (can rent from Advance)
- 1/2 inch breaker bar and ratchet with 1/2 to 3/8” adapter
- 3/8 breaker bar and ratchet
- set of sockets, elbows, various extensions; including deep-well; some frequently used sizes:
-- 8, 10, 13, 14, 15 mm
-- 1/2, 9/16, inch
- plenty of flashlights/spotlights, etc.
- wrenches – open end, crescent, etc.
- torque wrench – the kind that clicks is best
- small magnetic tool on retractable rod to pick up dropped sockets and screws
- small mirror on retractable rod
- rubber mallet
- jack/jack stand
- permatex #2 sealant
- anti-seize (for spark plugs)
- penetrating oil such as WD-40 or PB Blaster
- plenty of degreaser and clean rags
- putty knife
- acetone (about 1 qt or less)
- brake parts cleaner
- wire brushes
- fluid drain containers (for oil and coolant change)
- 9 qts of motor oil – 4.5 to flush, and 4.5 to fill
- 3 gallons coolant (mixed)
- Sandwich baggies, zip ties, and a sharpie

Also you'll need to have plenty of patience and time. Don’t expect to get this done in one day. It took me the better part of two weekends to do, even with help.

Also consider what else your vehicle needs to have replaced soon – for example, spark plugs, plug wires, cap, and rotor, to do a tune up at the same time; serpentine belt, water pump, etc. Might as well do it now while everything is accessible and disassembled.

A few things regarding the instructions in the link above for intake manifold gasket replacement and disassembly. TAKE THE TIME TO LABEL THE WIRES – some of them look alike, and the alternator wires could be mistaken as grounds. Pictures are good, but don’t always rely on them. Also, I did not have to remove the tensioner pulley. Leave it on.

Bag and label all nuts, bolts, and other parts. Sandwich bags and a sharpie works great. (

Again, follow the link above. It’s probably best to do what drdd did and remove the intake manifold before the valve covers so that you don’t drop or damage anything in the valvetrain. The extra clearance is helpful though.

Disconnect negative battery terminal.

Disconnect sensors from cold air intake and remove cold air intake assembly and airbox.

Disconnect all electrical connections from the intake manifold, A/C compressor, and alternator.

Remove fan shroud (10mm screws) (
Remove electrical connections and hoses into the intake manifold.

Disconnect hoses from PCV valve, brake booster, coolant and EGR at the intake manifold, and coolant hose into the thermostat.

Remove bolts holding various brackets to the intake plenum including the throttle cable bracket. Put these in a baggie and mark them. Move throttle cables aside.

Remove 4 bolts from A/C compressor and set compressor aside – just be careful not to damage the aluminum hoses and connections to the compressor. Don’t forget to disconnect the coolant temperature sensor which is connected to a bracket on the right side of the plenum. This is identified by the small wire going down to the sensor on the right side of the engine block.

Remove filler tube for power steering fluid. Do NOT disconnect PS lines. Unbolt power steering pump housing (9/16” bolts) and pull forward away from the engine a few inches for clearance. There are a few tough to find bolts. (
Look below the larger bolt for the PS pump pulley housing. There is another one for a bracket holding to the housing to the block. (
P/S pump moved forward for clearance. (
Remove nut holding P/S filler tube bracket, then pull the filler tube out. ( (
A/C compressor moved aside, and Valve covers removed. (
This is what happens when coolant and oil mix for a week. It was like runny peanut butter. Bad. Very very Bad.

Disconnect two hard fuel lines at the rear of the intake manifold. Cover with sandwich baggie and zip tie tight to keep fumes at a minimum. (

Removing hard fuel lines near the distributor.

Disconnect plug wires from plugs, and remove two (T-20) torx screws from distributor cap.

VERY IMPORTANT: With White-Out/Sharpie or some other type of good marker, mark the position of the distributor cap, distributor, and intake manifold, all in line. This is CRUCIAL in order to keep the engine in proper time when you put the distributor back in. (

Remove distributor cap. Remove bracket screw for distributor (10mm), and pull the distributor out.

Remove the serpentine belt by rotating the tensioner pulley down with a 3/8” drive ratchet.

Using the fan puller tool, loosen the large hex nut between the fan and the engine block. One wrench fits over the four screws on the pulley, and the other goes on the nut. It might be difficult to loosen, but it is right hand threaded (counterclockwise loosen)

Remove the three 1/2” bolts holding each valve cover on. You’ll have to work around all the wiring to get the cover off. Be sure to lift straight up, then rotate if necessary, so that you don’t damage any components underneath.

Intake manifold bolts are ½”. You do NOT need to remove the plenum from the intake manifold. The entire assembly can come out as one. (
Intake manifold assembly removed. (
Right side rockers and pushrods removed. (
Keep all of the valve components in their sets.

Valve-train components and other bolts cleaned and separated. At minimum, note which cylinder and whether it is for exhaust or intake. You can tell which it is by whether there is an exhaust manifold port in-line with the pushrod and rocker.

Remove the nuts (1/2”) holding the twelve rockers and remove the rockers, spacers and pushrods. Keep each set separate. Clean with degreaser, dry, and place in separate marked baggies. It is easiest to do this whole procedure one valve set at a time so that you don’t mix them up or forget which cylinder it came from.

Remove spark plugs so they don’t get damaged. Inspect, check gap (0.060”), and replace if necessary.

Unbolt exhaust manifolds from the block (15mm) and also from the down tubes. There are three bolts on the down tube collector at the flanges (13mm). This is where the penetrating oil will help. Let it soak in before using a breaker bar with extensions and elbow. A combination of accessing from underneath the vehicle and also through the wheel-wells will make it easier. Even with a 1/2 inch breaker bar it took quite a bit of torque to loosen the bolts. Take out the old exhaust manifold gaskets. They're toast.

Remove the three 14mm bolts on the back of the heads. Two on drivers side – one for hard lines bracket, and one for a ground. The one bolt on the passenger side also has two grounds going to it. These will have to have Permatex sealant on them when you put them back in. A ratcheting wrench works best. There is not enough clearance for sockets. (
Grounds and bracket bolts removed from rear of heads. (right head already removed) (
Remove the bolt holding the bracket for this wire behind the tensioner pulley.

You don’t need to remove the alternator mounting bracket from the front of the passenger head. It can all come out as one unit.

Time to unbolt the heads.

Leave two or three head bolts loose inside the valvetrain to use with the head puller tool. Make sure they are loose and there is a gap so that when you tighten the head puller tool, there is some room for the head to lift up against the underside of the bolt.

Remove the rest of the head bolts. There are a total of 13 on each side. 6 bolts are along the exterior of the head near the exhaust manifold bolts. The rest are inside under the valve covers. Keep track of them and where they go. Note that there are three different sized bolts. You’ll need to put them back in the same holes they came out of.

Use the head puller to pull the heads away from the block. Clamp on to thick parts of the heads – not the areas around the ports. The worm gear on the clamp sits on the head of the loose bolt and pushes the bolt down while pulling up on the two ends of the clamp and head. Don’t use any sharp object to pry between the mating surfaces. If necessary, use the rubber mallet to persuade the head away.

Clean the bolts with the 7/16-14 NC die and clean the holes with the tap.

Remove 10mm bolt holding oil dipstick to block. Carefully reposition dipstick to the side. (
Right side head removed. (
Both heads removed. Note the exhaust manifolds separated from the block and exhaust for clearance. (
Left side head removed. (
Be careful how you set the heads and the intake down. It looks like the head is resting on the intake, but it is not. Any damage to the mating surfaces could ruin the seal. Clean the heads completely, to remove any sludge and coolant. Clean mating surfaces with a putty knife, very carefully. Use brake parts cleaner. Finish with an acetone wipe of the mating surfaces. Run your finger around the gasket area. It should be clean, dry, and smooth.

Now is a good time to drain the oil and coolant if you haven’t done so already. There is a drain plug on the bottom passenger side of the radiator. As for the oil, when the oil drain plug was removed, all of the water that built up in the engine came rushing out, followed by the oil/sludge mixture. Separate the fluids before turning in for recycling.

Pour new oil in the valley and over the valve components and allow it to drain. This helps flush most of the sludge, but also try a quart of Rislone as a substitute for one qt of oil later when you refill the oil.

Put the oil plug back in and pour some more oil over the valley and valve components. You’ll finish refilling the oil later. Keep track of how much you put in so you don’t over or under-fill later.

Replace the radiator plug and pour some new coolant in. You’ll finish refilling this later. (
Cleaning out the head bolts using a 7/16 tap – careful with the ratchet. Start by hand-threading to make sure you don’t cross-thread.

Clean all surfaces on the block. Make sure all water is out of the cylinders. Place rags over the valley and the ports in the block to ensure that nothing falls in during cleaning. Use the putty knife carefully on the mating surfaces. Use brake parts cleaner on the mating surfaces on the block, then finish with acetone and a clean rag. Surface should be clean and smooth, without oil or dust.

New gaskets!!!

Place the new head gasket on the block using the alignment dowel pins for positioning. (
Left gasket and head installed. Right side gasket in place.

When placing the head back on the gasket, set it straight down, and do not slide it around on the gasket or you could cause damage. You’ll feel the head meet up with the alignment dowels.

Follow the steps in the Haynes manual to torque the head bolts down. First, put them in finger tight, then there are multiple torque steps in the specified pattern. For the 97’s the last step is to rotate the bolt a given angular rotation based on the size of the bolt (55 degrees for short bolts, 65 for medium bolts, and 75 degrees for the long bolts). See the picture below. A good trick is to draw the angle out on a piece of cardboard. Simple trig will give you the lengths of the right-triangle’s legs. Tan(a) = opposite/adjacent where a = the angle you need. Place the cardboard so that one leg is along the wrench handle, and the vertex of the angle is as close as possible to the bolt and socket. Rotate the wrench until the wrench handle lines up with the hypotenuse of the triangle. You’ll have to go in order of the pattern, and keep track of which length each bolt is so that you use the correct angular rotation. (
Angular rotation for final torque spec for head bolts (65 degree angle shown). You'll need to construct three triangles - one for each angle of 55, 65, and 75 degrees. (
Clean valve covers!!!

Re-install the three bolts on the back of the heads that hold the grounds and hard-line bracket. Use permatex #2 sealant on the threads.

Re-install the exhaust manifolds using the new gaskets supplied in the kit.

The rest of the installation and assembly is reverse of removal…for the most part. DON’T FORGET TO TOP OFF THE OIL AND COOLANT!

Follow the link by drdd at the top of the page for the lower intake gasket installation details. Same rules apply: clean all surfaces, place gaskets down using alignment tabs, lower intake assembly straight down, and torque bolts to the spec in the Haynes manual.

NOTE: For 97’s, the torque spec for rocker nuts is 20 lb-ft. Valve cover bolt torque spec is 106 inch-lb.

NOTE: If you labeled your wires like you should have, then you’ll know that there are two connections going to the alternator. One should have a rubber boot and be coming from the battery wire harness. The other comes from another wiring harness on the passenger side and could easily be mistaken as a ground. Do NOT mistake this as a ground or you will blow a main fuse when you hook the battery back up. (
Intake manifold back in. Don't forget to make sure the hard fuel lines at the rear of the intake connect near the firewall. Tighten them back down. (
Valve covers back on.

Once the hoses and everything else is reconnected, don’t forget to REFILL YOUR OIL AND COOLANT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!! (
Finished product. Congratulations, you just saved yourself a boatload of money. Enjoy.

03-09-2008, 06:28 PM
WOW GOOD JOB, suggest moving this to the HOW TO

Good job once again

03-09-2008, 07:07 PM
+1 for how to section.

Great Job BlackBlazOn

03-09-2008, 07:14 PM
Great job!

that liquid peanut butter is nasty!

you gonna drop the oil and filter after 500 miles just to make sure the gunk is out ?

03-10-2008, 05:48 PM
Yes, I changed the oil after 1 week, and plan to do it again next month just to make sure. The dipstick has been pretty clean, but there may be some gunk in there still.

03-12-2008, 10:15 PM
I don't hear alot on the forums about head gaskets needing replaced on Vortecs ... they seem to be tough little engines below the notorious lower intake gasket ...

... just curious ...

over the life of your truck, was there one thing that you think may have lead to the head gasket leak?

was it overheated repeatedly?
do you beat it up 4X4 off road?

... just curious ...

Yes, I changed the oil after 1 week, and plan to do it again next month just to make sure. The dipstick has been pretty clean, but there may be some gunk in there still.

03-23-2008, 10:36 AM
I don't hear alot on the forums about head gaskets needing replaced on Vortecs ... they seem to be tough little engines below the notorious lower intake gasket ...

... just curious ...

over the life of your truck, was there one thing that you think may have lead to the head gasket leak?

was it overheated repeatedly?
do you beat it up 4X4 off road?

... just curious ...

Not sure. I don't do much off road, so I'd guess it was due to the thermal stresses from overheating the engine over its lifetime. i am the second owner..bought it with 86K on it. The first owner used it to tow a lot, and ended up having to rebuild the tranny at 75K. Since I've had it there were a number of cooling issues leading to overheating - including the water pump around 100K, and radiator at 140K that had to be replaced.

11-16-2008, 09:02 PM
i was doin my transfer case motor today and noticed some antifreeze comin from the top of my transmission and leaking on my exhaust pipe. all my hoses are fine no leaks anywhere. cant really see the back of the block but could this be a head gasket? i dont see any water in my oil. isnt the heater core, any ideas?

02-23-2010, 10:18 AM
Outstanding write up.
I'm mechanically inclided, and wasn't afraid of the task at hand – but it’s always good to read through what your getting in to.

Tough little engines they are! My problems came about like this… Warming up too much, with Dex-Cool and air in the system. My overflow lead (radiator cap to overflow) got plugged from Dex-Gunk in the process; eliminating the system to properly bleed & re-fill.
In addition to the gunk in the that line, the radiator wasn’t operating too efficiently because of the same problem. She got heated up a few times – once in a mountain pass snow storm (towing another truck) and when we were passed by Semi-Trucks the snow/sleet froze-over of the grill, thus no air to the radiator. I accidently cooked her good – while doing “white-knuckle-driving” in a white-out!

The only thing I’d add to the instructions BlackBlazeOn posted, is when you take them down this far, you should spend the few bucks and have the heads resurfaced.

This is a pre-project post. I’ll make sure to re-post after the project is done for any additional tips and tricks.

Best regards to all.

P.S. >> to ( thanks for providing a website like this!

03-07-2010, 02:51 PM
This was a awesome writeup.

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