Fritjov

i bought a 1993 cherokee country 2 wheel drive 4 door automatic transmission 4.0 liter 6 cylinder at an auction for 500$ about a month ago, its my first vehicle and the first one ive ever been under the hood of it has 240k on her, she still starts well and sounds well which is surprising, base don the other problems, im very impressed with the resiliancy of the cherokee. I apparently have either a blown gasket or some cracking, yellow sludgy stuff is all over the inside of the valve cover and spitting through the breather hose out into the air filter housing quite a large ammount of stuff, destroyed the filter., also i peeked into the carb, and took that off and looked in the intake, the inside of both the manifold and carb are covered with what seems to be burnt oil, I haven't taken her apart yet, im waiting on a head bolt set in the mail. also im losing coolant at a rapid rate but not out of the engine, i changed my oil because of the sludge, even though i had changed it 2 weeks prior, and it looked like melted chocolate ice cream, very caramely. I have a haynes repair manual for a wrangler and it does make alot of mention on 4.0 6 cylinder engines, and the pictures are extremely similar to my engine. I'm hoping for any advice on this procedure, i already have all the torque specs and tightening loosening sequence for the bolts, and i know to set the timer to TDC, and i can remove the rocker arms, but other than that im completely in new ground. I have confidence i can do this, otherwise i wouldnt. but my most important question, and probably a very simple one, is I am having a heack of a time identfying where the pcv valve is, or where it should be if mine is missing, OR if there even is one in my engine, one source on google told me that a 95 4.0 didnt even have one equipped. thank yous o much to anyone who can help

jeepfreak82

There is actually no pcv valve... Rather, the back elbow on the cover is the return for the CCV (closed crankcase ventilation) There is a small diameter hole in it that will occasionally clog. I just left mine in the cover when I changed the vc gasket and cleaned it out while I had it off. You will find that the 4.0 is a relatively simple engine to perform maintenance on. Mainly, make sure that your head and block surfaces are completely clean when installing the gasket and DO NOT use any sealer or compounds on it as this will cause it to fail again.

Fritjov

thank you so much i was at a lost, yet now i am possibly more confused as to what i should do, i was looking up about ccv, I only briefly glanced at the elbow thing on the inside of the vc while i was out there today, but i remember a little bit, the ccv elbow thing on mine plugs into the vc like the oil cap does, (insert and turn slightly) i dont know it thats standard, i see alot of talk aobut grommets and rubber stuff, but this just goes right in there, i didnt look to see if it was clogged, i didnt think to look, it most likely is clogged, yellow oil/coolant/who-knows-what-else is entering it, and also spitting through the breather tube(if the breather tube is the tube running fromt he front-top of the vc to the air filter, there is litteraly a coffee mug's worth of this foamy mess sitting on top of my now soaked air filter. which is ok because im not driving it anywhere until ive replaced the gasket,...anyways... is the ccv return elbow(sorry i keep calling it that but i dont know what its called or really fully how it differs from a pcv, because the info is not instantly availible via wikipedia) something that can be replaced like a pcv valve, it is all rusted to where it looks like its falling apart, and if its cheap like a pcv valve id really rather just replace it, i did read that a clogged ccv(or pcv, i had looked up about both i didnt know which i had) would result in oil entering the air filter

5-90

CCV = Constant Crankcase Ventilation - with PCV or CCV, the crankcase can be considered "closed", since it doesn't vent to atmosphere (rather, it vents into the intake stream, in an attempt to burn blowby gasses.)

Also note that your XJ doesn't have a carburettor - all 242ci/4.0L engines were port fuel injected from the factory. What you checked and removed was a throttle body, rather than a carburettor.

Having been a hobby/pro wrench (depending on when I was doing it) for the best part of 30 years, and having done the cylinder head on the 242ci engine more than a couple times, I've offered some rather good advice. Unfortunately, it's late and I know I'll miss something right now (it's 0300...) so if you search up at www.naxja.org you should find one of several posts I've done on the job - considering there are tips there that you won't find in the FSM, and you damned sure won't find in Haynes (it's a decent start, but I relegated my Haynes manual to evening up the short leg on my workbench years ago. Gotta cut a new leg one of these days...)

Also, any torque specs that Haynes misses you can find on my website in the Tech Archives section - the 242ci torque specs seem to be consistent from 1987-2001 or so, probably to 2007. All of the torque specs I've listed are from factory literature, which is why they're listed the way they are.

While you've got the valve cover off (since you have to pull it to get the head removed,) take the time to clean it out well. Especially pay attention to the baffles under where the CCV hoses attach - not only will oil collect there over time (which usually results in oil being blown onto your air filter,) but your "chocolate milkshake" oil will have collected up there as well. If necessary, you can usually remove those baffles (what looks like nails are "nails with threads" - just very high-angle threads. You can either drive them back in or replace them with tapping screws of roughly the same size, especially in the aluminum valve cover) and clean under them. You're there anyhow - if you end up having to clean them later, you'll remember this job and end up kicking yourself very hard.

When you've got the head off, take a strong flashlight (every mechanic should have one - I like the SureFire G2. Bright as all get out, and fits neatly in a pocket or on your belt. The polymer body won't scratch or gouge metal...) and check the cylinders, decks, and cylinder head deck surface (the ground bottom surface) and combustion chambers (overtop the pistons, where the valves are) for cracks. Coolant leaking into the oil can be caused either by the head gasket giving way or by the castings cracking - while iron castings don't usually crack, it's possible - I can show you a late XJ head that cracked pretty badly. But - the engine ran quite well with all the cracks - which is also a testament to the longevity of the thing. While they're not always going to be visible to the naked eye, the cracks often are - and anything you suspect is a crack you should clean well and check again - it may be deposits.

Take a can of aerosol carburettor cleaner and blow out your CCV lines as well - point the can into one end (use the straw if you need to,) and hang the other end over a bowl or a bucket to catch the crud.

CCV = Constant Crankcase Ventilation. The seal afforded by the piston rings isn't perfect, so there is some air/fuel mix "blow by" past the pistons. This would collect in the lower crankcase and cause an increase in pressure, which could blow a minor gasket. Crankcase ventilation uses intake vacuum to draw this gas out of the crankcase and into the intake stream - mainly to try to reduce evapourative emissions, but also to try to burn the fuel again (this has more of an effect on fuel economy with modern fuel injection than it did with carburettors.)

PCV = Positive Crankcase Ventilation. This was the "older version" of the system, where the principal difference was the presence of the PCV valve. The reason was that the PCV suction line was taken off closer to the carburettor, and a backfire through the carburettor could set off the fuel/air mix in the crankcase - the valve was designed to shut instantly when any backpressure occurred (which would be due to the backfire through the intake) and prevent seriously blowing out something important. Again, the principal thrust was to reduce evapourative emissions, as it had a negligible effect on fuel economy until the feedback carburettors were introduced (and even that didn't help much - it took fuel injection and closed circuit feedback to finally make a difference in fuel economy.)

Before the PCV was developed in the late 1950's or early 1960's (I think,) any case where the crankcase was vented involved a simple breather filter - often in the oil filler cap - open to the atmosphere. Since it didn't use suction to draw out the blowby gasses, it wasn't very effective

farmfuel

Fritjov,

Welcome to the forum.
I paid 500 bucks for my 93 Cherokee too...and bought it with a bad head gasket off of Craigslist. Congratulations on your purchase.

I chose to replace my engine with a wrecking yard unit, due to the fact that the previous owner drove it hot for who knows how long. Two problems that you must make a decision on are: Is the head cracked due to overheating? If it's an auction vehicle, then you don't know the answer to this. Also ask yourself- how long has that milk chocolate been in the oil pan? Oil fused with water has the ability to damage bearings. Another problem with buying an auction vehicle is that you don't know how long that engine has been running with that oil/water mix. My Jeep had right at 200,000. It didn't sound like it had much compression when it turned over, so I found it easier to just swap the motor.

We're all here to help, and there's nothing on that Jeep that you can't tackle yourself. Just ask.

jeepfreak82

The head gasket will very likely have an obvious place on it where it is blown out or leaking so you should have a fairly good idea just by looking closely once you get the head off.

Fritjov

I was looking at some of the threads 5-90 posted for on NAXJA, and i came across someone switching out the head for a '00, and it was mentioned that sometimes a plate will be needed is the manifold isnt the right type, I'm sill waiting for head bolts in the mail, so ihavent taken anything apart yet, but from the outside i can see a thin sheet of rusted metal sticking out a bit from between the head and the exhaust/intake, i dont know if this is an adaptor plate or just an old gasket. i havent seen any gaskets but the one i got from autozone and it looks like its some kind of composite deal looks like cardboard with metal wires running through it like rebar in concrete. the jeep could possibly have a new manifold, some other parts are new in it from the previous owner, there's evidence of a front end collision, (new radiator, no vent hose coming from the front of the air filter housing, its just a box with breather hose, and hose going to the throttle body, and a square hole in the front of the housing, and a cracked-all-to-hell-what-i-think-is-a-brain-box-for-the-fuel-injectors) my question now is there anyway i can tell what kind of manifold i have or what year it is, so i can properly reinstall it or get a new adapter plate if its crapped too, i.e. serial number, date on the intake, or maybe a site showing PICTURES of what the different intakes look like.

5-90

For starters, verify your cylinder head. If you look down the driver's side of the head, about halfway back, you should see a raised cast-in four-digit number outside of the valve cover.

#7120 - 1991-1995
#0630 - 1996-2000
#0331 - 1999-2007

(The overlap is because the XJ kept the #0630 head a year after the other TJ and WJ did. I therefore listed due to absolute availability, and not the model year of the XJ. Front-end collisions can result in replacing all sorts of parts...)

For the "rusted metal" you're seeing, I believe the OEMR combination manifold gasket is metal-bound composition. Does the metal look like it's been stippled with a pattern punch (sorry, no pix handy)? Aftermarket replacement gaskets are usually composition (as you've noted,) with metal reinforcement - but not metal "binding" or "cladding" like the OEMR. If the composition is up to scratch, it's not different in terms of function (and I always put a thin layer of RTV copper on both sides of the gasket before I put it in anyhow.)

Your 1993 should have a fairly solid one-piece tubular exhaust manifold. I know the later OBD-II (1996-up) were split into two sets of three cylinders fore-and-aft, but the OBD-I manifolds were similar to the early RENIX (1987-1990) manifolds. If you give me some time and your email, I think I have a manifold from your era - probably a year later - around here that I can take a pic or two of for comparison. You should not have an earlier (1987-1990) manifold on, as they have ports for the EGR valve. The EGR valve was deleted for 1991, and would require plugging that port with a threaded bung plug (which would be just above the oxygen sensor, and be fairly obvious.)

Fritjov

do i need to remove the lifters and pushrods to remove the head and if so do i need a special tool to pull out the lifters

5-90

Pushrods? Yes. Lifters? No.

Ideally, use something with twelve compartments to keep everything sorted (or take a board and drill holes in it - that's what I do) so you don't mix everything up. It shouldn't cause any trouble if you do, but it's bad form to mix parts around, and it's a "just in case" thing. General order of operations:

1. Remove Valve Cover
2. Remove Rocker Arms, Pushrods, & Sort
3. Remove Cylinder Head Screws
4. Clean block & head deck
5. Place new gasket
6. Place head
7. Torque head screws
8. Paint head screws (if not already done)
9. Loosely install rocker arms.
10. Turn crank to #1TDC, both valves closed.
11. Torque rocker arms on CLOSED valves to spec (it's on my site, I don't recall what it is offhand.)
12. Turn crank to next set of valves (I'd have to look.)
13. Repeat on torque on next batch of closed valves.
14. Repeat last steps until ALL rocker arms are torqued.
15. Install valve cover
16. Change engine oil
17. Finish assembly and start engine

Painting the head screws is done because the 242ci head screws can be fully torqued only twice - if the heads are already marked with paint, secure replacements before you start.

The head may be removed as a unit with the manifolds attached (I've done it) and the manifold gasket serviced on the bench (it's easier to do there,) but bear in mind that it all makes for an unwieldy and heavy (~80-90#) assembly. I'm a fairly large individual - if you're not, you may want a helpful pair of hands or a hoist to pull it. You can use 3/8"-16 screws in the rocker arm pedestals to secure the chain on the hoist to the cylinder head - just don't use the OEM rocker arm screws.

Suggest you replace the manifold screws and probably the thermostat housing screws outright - the manifold screws are probably 3/8"-16x1-1/4", and the thermostat screws should be 5/16"-18x3/4" or so and 5/16"-18x1-1/2" or so. I like to use silicon bronze for the manifold screws (there is a sound engineering reason for doing so) and brass or CRES (stainless) for the thermostat housing. If you can't source bronze screws for the manifold, you can use SAE5 - if you're stuck with carbon steel, suggest you replace them each time you service the manifold! SAE5 will retain more strength through more heat cycles than SAE8 - I've verified this experimentally (heating and gradually cooling steel will make it fractionally lose strength - the SAE5 screws are less sensitive to this than SAE8. However, screw seizure is still an issue - bronze won't seize, which is why I prefer it.)

If you have to replace the (pitted with corrosion) thermostat housing screws with SAE5 carbon steel, coat the entire screw under the head with RTV - this will give it a protective coating against the coolant. Yes, the original screws had a black oxide coating on them (which didn't work against the water,) and the replacement screws probably have a zinc coating (which doesn't work well against long-term exposure to hot water.) Brass or bronze holds up best - and there isn't much strain on these screws - with CRES being actually a second.

Fritjov

I already had to make some previous ghetto rigged repairs on the thermostat housing, when i first noticed the antifreeze was leaking and she was starting to overheat a bit i replace the thermostat and gasket, the bottom bolt was alot looser than it should have been coming out and it wouldnt fully torque back in, stripped threads, spewing antifreeze from betweenm the 2 faces, so i was hopeing it was just the bolt, so i go buy a new bolt, as i take it off the second time, i realize, the actual thread hole wasnt stripped, it was broken off, a fragment of the head actually snapped off, leaving only half the hole for the thermostat housing screw. the metal didnt fall off before because it was held together by leftover sealant, and i was broke and really didnt want to get a new head for one hole, so i slapped a big glob of JB weld there, flushed the face of the head with a dremmel, and got a die and rdrilled the hole, got one of those spring looking deals that you stick in the hole, i didnt tighten it to much because i didnt want the jb weld to break, and it leaked slightly so i just covered the seam completely around with jb weld, JB weld is also sealing a small crack in the rear gear box both applications are holding very well.

Fritjov

I'm still waiting on those head bolts to come in so I haven't got into there yet. I'm still not sure if i have a different year manifold system than my head, it's sleeting here today and I park on the road so i haven't had a chance to see if my head is stock, I'm going to assume it is until I get a chance to look. However what 5-90 said about a 93 XJ exhaust being one peice, I remember getting under about a week or 2 ago to look for any antifreeze leaks, and i noticed the exhaust being 2 peices that fit next to eachother side by side under the intake, and it looked like a small MIG tac weld holding the 2 peices together, I didnt think anything of it at the time, if that helps you all help me. Also 5-90 recomended copper RTV on the exhaust, I searched around on amazon for some stuff, and i figured it would be cheaper to shop around here, so i got a ride to autozone and picked up some permatex sensor-safe "ultra copper" high temp RTV silicone, is this the stuff? and do I apply it around both sides of the gasket, or is it a gasket replacement? As for the corner head bolt that dips down into a cavity, the Haynes manual suggests i use Loctite 592. I picked up some Permatex high temp thread sealant, will this do the trick.

5-90

And I didn't get a chance to take those pics yet - sorry about that. I'll try to get to it to-morrow (The Blonde Thing wasn't feeling up to scratch to-day, so my priorities shifted.)

Yes, you've got the right stuff - I usually use Permatex Sensor Safe Ultra Copper - comes in a copper-coloured tube. Use a thin layer on both sides of the gasket - it is not RPT NOT a gasket replacement in this application! However, it will help your gasket seal, it will help to hold it in place while you jockey parts about, and it will help protect your gasket if/when the screws loosen (they generally do over time. I check torque on them as part of my annual inspection, and I usually catch a couple having worked loose. I'm still looking for "deformed thread" screws to use, since even LocTite #272 is having a hard time.) Spread a thin and even layer over the entire gasket on both sides, just don't have any "hanging over" into the ports. I probably stop about 1/16" shy of the inner edges of the gasket to prevent this - no sense in creating extra disturbances to airflow. We're hampered enough having a side-draught head instead of a cross-draught...

Fritjov

I just got those head bolts in, it's about 3;30 in the afternoon, and I'm going down there to take her into the garage, not sure if I'll get it all done tonight, here goes, I'll touch in tonight, or if I run into a massive problem that humbles me beyond humiliation.

Fritjov

the long drivers side head bolt near the middle snapped off about 3 threads down, with about an inch of thread sticking up into the cylinder head from the block. All the other bolts are out, the intake and exhaust is still attached to the head, I decided it would be easier to take it out in one piece. tomorrow I'm going down to the hardware store to get a drill bit to drill down the hole, and I'm going to try and re-thread the engine block somehow. if anyone's had this problem before or have any ideas it would be greatly appreciated, because I can't even get the head off the engine block right now.