Replacing Your Head Gasket
Although John has 20 years experience as a dealership technician, proceed at your own risk; see the Terms of Service.
Preface by Kestas Smalinskas
There are any number of things that'll happen when your blow a head gasket.
- Foaming, bubbling, or "gargling" in the radiator.
- Rapid pressure buildup in your cooling system, before the engine has warmed up.
- Some have even reported coolant overflowing from the reservoir bottle because of the pressure.
All these above mentioned symptoms could also be a cracked head. Either way, the head must come off, the gasket replaced, and the head inspected for cracks. At the same time, check both mating surfaces for flatness before putting on a new gasket so you don't have to repeat the job.
Other symptoms of a blown head gasket include:
- White smoke coming from the tailpipe, sometimes intermittently.
- Water in the oil. When they mix, the oil gets a chocolate milkshake appearance.
- Oil in the coolant.
- Cylinder pressure low when using either the wet or dry compression method.
- Cooling system will not hold pressure when statically pressurized.
Look for any combination of these symptoms to diagnose a bad head gasket.
One curious observation of mine, when a person describes their engine problems, and it looks like a blown head gasket, often they mention that the car just had a new radiator put in, or new cooling fan, or some other repair history that suggests the car was constantly overheating.
If you had white smoke coming from the tailpipe and your head gasket was bad, chances are the O2 sensor may have been poisoned at the same time. Expect to have problems with it. It may need to be replaced.
One of the bigger challenges for the engineer is to design a head gasket that'll seal the aluminum head to the cast iron block. Aluminum has roughly three times the thermal expansion characteristics of iron. That makes it tougher for the head gasket to maintain a seal with all that thermal cycling than in years past with iron heads. Aluminum heads cannot withstand overheating as iron heads could in the past. It is critical to not let your engine overheat. Overheating is the No. 1 cause of scrapping an engine, not oil neglect as some people believe. Even if you don't blow a head gasket, the head may warp and cause premature wear on the valvetrain components as in some early 4-cylinder Mopar engines from the early 80s.
Head Gasket Replacement - (2.2 or 2.5 Liter Four Cylinder Engines) by John Mastriano
- Exhaust flange nuts and bolts
- Head Gasket (preferably OEM)
- Ten head bolts
- Two valve cover end seals
- Tube of RTV silicone
- Disconnect the battery negative terminal
- Drain the cooling system
- Raise the front of the vehicle and support it with jack stands .
- Remove the two 13mm exhaust bolts holding the exhaust pipe to the exhaust manifold , lower the vehicle
- Remove the air cleaner assembly
- Remove the upper radiator hose
- Loosen the 13mm nut holding the dipstick tube bracket to the thermostat housing and remove the coil (if it is attached to the thermostat housing) and unplug the coolant temperature sensor
- Remove the spark plug wires from the plugs , remove the distributor water shield and the distributor cap . (this step is so you don't damage the distributor cap)
- Remove the two uppermost 15mm-head bolts from the top of the a/c , alternator bracket where it attaches to the head and unplug the single wire temperature sending unit
- Remove the upper half of the timing belt cover
- Remove the valve cover
- Disconnect the wiring harness connector that is just to the right of the throttle body
- Disconnect the throttle cables from the throttle body and remove the two 10mm head bolts holding the bracket
- Disconnect the vacuum lines from the throttle body
- Disconnect the fuel lines - NOTE : The fuel lines may be under pressure , use extreme care when removing them
- Disconnect the throttle position sensor connector and the EGR valve connector (if equipped)
- Carefully lift up the throttle body wiring harness , the fuel lines , and the vacuum lines together and use a bungee cord to hold them out of the way
- Remove the ground strap that is attached to the intake manifold from the fire wall
- Remove the 15mm-head bolt holding the battery ground cable to the engine
- Disconnect the vacuum hose from the power brake booster and the heater hose from the intake manifold left side
- Use two plastic tie straps to secure the timing belt to the camshaft pulley and remove the pulley . Hold upward tension on the pulley and secure it with a bungee cord to the right hood hinge - NOTE: be sure to hold the upward tension with the bungee cord so the timing belt doesn't jump a tooth on the lower pulleys
- Remove the head bolts and lift the head off the engine block . (I suggest having an assistant help to lift off the head) With the head removed , carefully check the head casting for signs of cracks . Also use a straight edge to check the head casting for warpage (maximum allowable warpage is .00
- Clean all the head gasket mating surfaces and wipe clean with a little brake cleaner on a rag . Use a round plastic bristled brush to clean out the head bolt holes in the engine block and blow them out with compressed air .
- After the gasket surfaces are prepared , set the new head gasket in place and CAREFULLY place the head into position , take extreme care not to place the head on the head gasket until it is in the proper position .
- With the head in place , install the head bolts . You will need to tighten the head bolts in a circular pattern starting from the center and working your way out . I recommend hand tightening all the bolts before beginning the torque sequence .
Head bolt torque:
For older style 10mm head bolts : 35 - 45 - 45 - and a 1/4 turn
For newer style 11mm head bolts : 45 - 65 - 65 - and a 1/4 turn
- Use the two rubber valve cover end seals and a bead of RTV silicone to reseal the valve cover .
- Do Not let the silicone skin-over before setting the valve cover into place and tightening the bolts, also be sure that both mating surfaces of the valve cover are clean and oil free .
- After the head is reassembled you will need to reset the base timing to specs. You will also want to double check the timing belt position . Use a variable timing light and set the timing mark on zero degrees . Save the setting on the timing light and shine it through the inspection hole in the top of the upper timing belt cover . If the belt timing is correct , you will see the oblong hole in the camshaft sprocket centered in the inspection hole .
Derek Beland wrote: "Most of the websites I could give advocate doing a 'quickie' change where you unbolt the head, put a jack under the cat and lift the head a few inches up to slip in a new gasket. This is fine if your head and block are straight, but if you've overheated it in losing the gasket you should get them checked or you'll be doing it again."
Damien Civiello wrote: " I agree. I was going to go that route with my old Lebaron and a mechanic friend said I was nuts for it. If the head it warped then the new head gasket will just follow the old. Sure enough when I had it checked it was warped. Only cost about $50 to get it checked and fixed. Also, make sure they clean the head for you. The guy who did it for me left that step out and it was a pain to get it clean. Worth the extra money in my opinion....
"I have seen someone say that one of the reasons for the failure is the way the head bolts are positioned as the corners receive more pressure than the rest of the block and the gasket gets compressed too much in these locations. From seeing the failure mode of the gasket in the Lebaron I'd have to agree to this in part. The front passenger corner was crushed into the cylinder lining slightly and in short order the engine had it destroyed.
"The MP gaskets are supposed to be better about this, though the people who posted this info made some aluminum washers to correctly space the dec when the gasket was on and the head was properly torqued."
The group generally thought the Mopar Performance (MP) gaskets were better than the Fel-Pro.
The consensus of the EEK mailing list regarding head removal on a turbo 2.2/2.5 was that removing the head with the manifolds and turbo attached is the only way to go. Bert Neily wrote:
Removing the turbo plumbing, etc. really wasn't as hard as I envisioned. I've removed the engine accessories, AC compressor, and the AC bracket since I'm changing the water pump and timing belt while everything is apart.
I'd like to relate the story of a screw-up in hopes of saving someone else from the same mistake some day. Things were going *way* too well last night when I decided to remove the upper coolant line where it attaches to turbo.. I slipped a 19mm flare nut wrench on the fitting, got a good grip, and applied moderate pressure. I felt the nut let go, thinking that I was lucky that it released so easily. Then I realized that the short brass tube, between the nut and the turbo, had snapped off at the turbo!
Adding insult to injury, I then realized that I really didn't have to remove that line until after I'd pulled the head/manifold/turbo assembly - the line simply ran from the thermostat water box to the turbo. Once I get the head off, I'll soak the broken thread stub with Liquid Wrench and see if gentle application of an Easy-Out will remove the threads. With 20/20 hindsight, I realize that I should've left that line in place and removed it on the bench, using a wrench on the brass fitting block to take the torque of the flare nut wrench.