Replace head gasket ?

Replacing a head gasket is not a DIY job, unless the person has plenty of experience, knowledge, and the proper tools. The fact that a you would even ask, "how to replace 91 honda civic head gasket?", would indicate that you should not try to do that repair.

To replace a head gasket you must remove the intake manifold, exhaust manifold, valve train, and then the head. This is very involved and requires disconnecting lots of sensors and the ignition system. The head must then be checked to see if it is warped, or cracked, and repaired if necessary. You must then know how to put all this back together and torque all the bolts in the proper sequence. This takes training and skill which the average shade tree mechanic does not have.

If you are dead set on DIYing it, get a vehicle specific repair manual and dig in. Good luck China OBD2 car diagnostic tools wholesale on CareUCar

Could be a clogged radiator but most likely a failing head gasket. Inspect the drivers side of the head at the corner nearest the firewall. This is a well known weak spot in many of the engines of this era. Any signs of leakage at any time over the years is a tell tale sign at this spot. The pressure builds when the water passwordng through the engine is superheated as it passes an area of failure of the head gasket or warped head. Not an extremely difficult repair for someone with moderate mechanical skill and experience. Systematic teardown and reassembly after having heads milled. Bad news is that the superheated water takes very little time to damage your block beyond repair especially in the P38. I've been thru it a couple times and even the testing is costly. If you are extremely attached to this particular Rangie buy a new or professionally rebuilt engine otherwise you'll be chasing your tail and blowing a lot of cash in the process. Crates engines, rebuilt to factory specs and thoroughly tested with warranties are widely available on the www starting around $2000+shipping. Good luck. If I can be of any further assistance feel free to repost any additional.

you dont have to pull the whole motor out of car if thats what your asking but theres alot of work involved with changeing head gasket

your thermostat will have no bearing on your heater blowing cold air. My s type is kind of funny with its heating/cooling at times too as are several other models I've observed. Since your blower motor is working and blowing out air (cold or not) you may need to have your heater core replaced (part is around 140 excl labor if you have it installed) might be able to get you a diagram of my jtis software if you're a do it yourselfer. It takes a skilled mechanic several hours to remove the dash to r/r core. Very tedious and if you're not familiar with it I'd recommend having a free weekend to do so. I would pay to have mine replaced to give you a straight answer in this matter.

Removing the heads and replacing the gasket is not that difficult assuming you don't have a problem with the deck surface or other problems with the top end. These issues will require a machine shop and precision machining. Usually there's a reason for the leaking head gasket. Go get the mechanics manual for you car, it will list all torque values and sequences.

I'm going to guess that you have the V6?
Replacing the gaskets is not too difficult for someone with basic mechanical/handyman skills. Go to the website for a tutitorial on the job:
http://www.escape-central.com/1forum/showthread.php?threadid=32550&referrerid=11756
While you have the intake off, make sure you replace the spark plugs.

TO CHANGE A HEAD GASKET IS SKILL LEVEL B MEANING YOU MUST HAVE BASIC KNOWLEDGE OF COMPLEX SYSTEMS.ITS A HARD JOB IF ITS YOUR FIRST TIME.THIS IS A DEALERSHIP JOB BECAUSE MANUFACTURER RECOMMENDS THAT THE ENTIRE POWERTRAIN BE REMOVED FROM THE VECHICLE.BEFORE REMOVING THE CYLINDER HEADS.

You could have what is called a lean misfire which is caused by an intake manifold leak. Only you know if you are skilled enough to change the gasket yourself. Call the dealership and ask them what the book labor time is for the job, that time is for a skilled Tech. with all the proper tools. That will give you an indication of what you are up against.

The most likely cause is a blown head gasket,but it could also be a warped head,was the motor overheated prior to the problem starting? The white smoke is steam,check the underside of the oil fill cap and dipstick for a grayish brown residue,check the coolant for a low level and oil conatamination,either of these conditions verify that a head isn't fully sealed.Unless your moderately skilled mechanically this a job to be done by a shop.A good shop will perform a leakdown test to verify this.

I suggest having a good tech work on it. That's a good engine but difficult to work on.