I have a 1993 jeep Grand Cherokee with the 4.0. I think my head gasket is leaking bad. It is blowing a bit of white smoke out the exhaust. Anywho...I want to replace the gasket. Is this something I need to pull the motor out for or can the head be pulled off with the motor still inside? <img src="/forums/images/graemlins/patriot.gif" alt="" />

Hold on Junior!! If the head gasket is leaking chances are bout 99.5% your coolant is puking itself out the overflow!! If that ain't happening then LEAVE the gasket in place.. Coolant don't get into the combustion chambers unless combustion pressure gets into the coolant and blows the coolant out the overflow.
What most folks don't know about torking down heads is the shape of certain cylinders changes every time the bolts are reinstalled.. That can be a bad thing.
So make SURE you have a leaky head gasket before touching it.
The smoke can be any number of things. Do you notice a loss of coolant which leads you to think of a head gasket? If so Look for an EXTERNAL leak and not an internal one..

But to fully answer your question.. Head gaskets are replaced with the engine in place under the hood.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

In addition to what Jim said, I agree I would do a little more investigating before you go after the head gasket. Not that the gasket isn't a possibility, its just a lot of work to just jump into, and there are other checks you can do to narrow down the possibilities.

First look at your oil and coolant levels, and condition.
ò If you have leak between the cooling jacket and a combustion area you will be getting crap in your coolant, and like Jim said you will be over pressurizing the cooling system and puking it out the over flow.
ò If you have a leak between the cooling jacket and the oil system, you will have oil in the coolant and coolant in the oil. The coolant will get murky and dirty, and the oil will start to look like a chocolate milkshake, and the oil filler cap will get a real nasty build up on it that will be easy to see.
Next do a compression check.
ò If you are leaking combustion into the coolant you will lower compression on the ôbadö cylinder.
Next do a leak down check.
ò If you are leaking combustion into the coolant you will see bubbles in the coolant.
If after all of that you determine you are leaking between a combustion chamber and the cooling jacket, I would check the torque on all of the head bolts. If any of them are low, I would torque per the spec, and repeat the previous test, to see if there was any improvement.
If you still believe you have a leak between a combustion chamber and the cooling jacket, odds are it is most likely the head gasket, in which case, I would get a gasket kit for the top end of the engine and plan a weekend to do the work. The top end gasket set will have the head, valve cover, intake, exhaust gaskets, etc, valve guide seals, and all the little bits and pieces you donÆt really think of. While you have the head off, you might as well replace all the gaskets and seals you can. If your engine is high mileage, you might want to replace the water pump, hoses, thermostat, and flush the cooling system too. I agree you can do the work with the engine in the jeep too, its not too bad.

Sean

Thanks,

You know there is a part that the oil filter attaches to and that part also connects to the engine block. That did leak and I managed to pull it off the block,clean it and put it back on. It stopped the leak for awhile. Now I think it is leaking again. It could be the main seal too. Is that a tough one to replace? I will arrive at my destination shut the jeep down and about 2 hours later I have a small spot of oil about 2-4 inches in diameter. I think it is leaking fairly quick. It drives fine but is making a mess out of my driveway. <img src="/forums/images/graemlins/lol.gif" alt="" />

The rear main seal usually can be repaired by taking the PRESSURE out of the engine.. Put a new pcv on there and clean BOTH hoses to/from the valve cover.. This has stopped many Jeeps from leaking.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

Definately check the rocker(valve) cover gasket! My '93 xj was leaking horribly so, I went ahead and did the rear main seal. Pain in the butt! Only to find the old one looked pretty much new. Put it back together. Same leak! Later on, while planning to get a newer 4.0, I discovered that the gasket was hanging out at the rear of the cover! Dumbass!
$8.00 dollars and ten minutes later, nary a spot of oil on the driveway or on the rear glass!