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Blown Head Gasket, what else?

could still be a cracked head...either way you are pulling the head. do not keep starting it though..if the bottom end on the motor is okay it could be rebuilt. once there is coolant in the oil though its realy hard on the pump
 
Well got out on the jeep today, and did a compression test before anything else. Pulled the fuel pump relay and pulled plugs.

Starting from the front to the back, these are the results:
160psi
0psi
115psi
120psi
150psi
165psi

So I dont know what is going on with cylinder 2, but something is definitely not right there, and I know the gasket is blown. So the head bolts are all loose now. I've pulled the fuel rail, coil pack and everything that bolts to the head and the intake manifold. All that is left is to undo the four bolts on the exhaust downpipe and the head/intake/exhaust should all come out freely. Hopefully the gasket is as far as the damage has gone, but I wont know until the head comes off anyhow.

Will probably also drop the oil pan while im down there unbolting the exhaust down pipes, and will check to see how the oil looks.
 
I'd have to guess that the gasket is blown out at the number 2 cylinder. And for it to have 0psi it's gotta be blown out major. Is the oil reading on the dipstick at all?

Sincerely,
Captain Obvious.

Beware, those heads are HEAVY.
 
With that kind of variation (low pressures toward the middle, high at the ends, and a dead hole) I'd bet on a warped and probably cracked head, and a major gasket leak somewhere.

The only time I've ever seen a compression reading anywhere near that low, this is what the gasket looked like:
62902_538512639482_29101008_31603271_3475798_n.jpg


Even my 98 with the gasket blown between the #3 and #4 bores gets 30psi compression readings on those cylinders, you can feel the air come rushing out of the #3 while the #4 is on compression stroke, and vise versa.

0 is a real low number. Did you actually get zero or just round down? I'd almost bet on a broken piston.
 
Well, good and bad news.

Good news is, I know exactly why each cylinder has the amount of compression that it does.

Bad news is, its an ugly sight.

Broken Cylinder 2 Piston, explains the 0psi a little
photo.jpg


And if that doesn't lower the compression enough, this crack in the #2 cylinder head will.
photo2.jpg


And then, to explain the lowered compression which is almost the same in cylinder 3 and 4. I found this crack in the head.
photo1-1.jpg


And surprisingly, the head gasket looks good. There are no breaks in it at all, and by looking at the water passageways, it seems that this wasn't a new issue. Looks like somebody used some kind of stop leak in this jeep and the result was clogged waterways, some of the waterways on the head gasket were actually completely solid as a result of the "stopleak"



Soooo, no need to send the head off to be checked for cracks. Looks like the entire motor is coming out, and I will be looking into the route of a new motor. But, I have plans for this block, I will set it in the garage and rebuild it to go back in the jeep at a later time. That $275 for that jeep front end is sounding really good right now. So I may be acquiring that within the next day or so. As for now, my heep will have to wait.


Btw, that jeep is a 2000 jeep cherokee 4x4 auto and my jeep is a 2000 cherokee 2x4 auto, those motors should be exactly the same right? I've heard sometimes the transmissions make a difference in the rear main or something like that. Will I be able to put the motor out of a 4x4 onto my transmission? I would swap the whole deal into my jeep, but the guy says the tranny is slipping, and i don't want to mess with that right now (maybe in the future when it is more of a convenient 1 weekend swap). As for now I need to focus on the thing running.
 
Glad you caught it before it ventilated the block or something! Looks like you have enough left of that motor to make a stroker eventually.

That motor will swap right in. So will all the 4wd parts from the donor, though it sounds like you might want to find a different transmission.

Any motor swap questions ask away as needed - I've done enough 4.0 swaps / pulls / installs that I know what most of the "gotchas" are by now, so have many others here.

Speaking of which, I strongly suggest you buy an E12 inverse torx socket now and save yourself a lot of heartache, along with two 3/8-16 grade 8 bolts, two 3/8 grade 8 washers, and two 3/8 grade 8 lock washers to replace the stupid E12 headed bolts at the top of the bellhousing. A 15mm flex-head gearwrench will also be very useful when it comes to disconnecting the torque converter from the flexplate.

Almost everything else I can think of will be in your usual metric+english socket and wrench kits.
 
Yea I remember that bolt at the top of the bell housing took me almost an hour to figure out what was going on when I was pulling my ax15 from another jeep.

I will most likely start with the motor, but having the rest of that drivetrain will definitely urge me to slowly swap in parts on the weekends. The only thing i'll be missing is the rear driveshaft, which i can probably find easily. The tranny will be the thing to wait on.
 
The other thing you could do is simply rebuild the 4x4 AW4. I've seen rebuild kits for under 200 on ebay, that plus some gaskets and maybe a rebuilt torque converter (or use yours if it's known good) and you are good to go.
 
Will the 2000 exhaust header fit on the 99' head?

I ended up getting a 110k mile motor for $150 because the people said that it had a "lifter tick", I opened the valve cover and noticed that all the springs and rocker arms are brand new, but they didn't change out the push rods. I also checked the crank and connecting rods, all of which seemed to be pretty decent.

I spent the last 5 nights in the garage until 4am every night working on this thing. This "new" motor now has all new freeze plugs, water pump, push rods, rocker arms and springs, and thermostat. Also switched over the camshaft position sensor (made sure both motors were TDC on the correct stroke before pulling and installing), coil pack, exhaust manifold, torque converter (torqued down tight), fuel injectors and throttle body. Finally I got it in the jeep and it started up last night with a lot of racket.

SOO, I'm pretty sure that the exhaust/intake manifold gasket is shot, I just reused the one that came with the new motor since I wanted to hear this "lifter tick" before I pulled the head and replaced all the gaskets on the top end. But with that racket, I couldn't tell you if there is a lifter tick or not, it just sounds like a bunch of ticking.

NOW FOR QUESTIONS:
So, because my intake was cracked from somebody torquing a bolt too tight, I used the 99' intake. And since my 2000 jeep has the double down pipe exhaust, I used my exhaust manifold on the 99' motor. Will this even work? I assumed it would, but if I go buy a new gasket, which do I buy a 99' or a 2000? And will there be any modifications that I need to do to the exhaust manifold (porting) to make it fit better without leaking? Or will a new gasket just take care of the issue?
 
Last edited:
By the way, the gasket part numbers are the same from both years when I look them up at the local parts store, so they should be the same. But will I need to modify anything with the 2000 year headers so that it is less likely to leak?

I plan on replacing these headers with a full exhaust once I build the old motor back up, I will be starting on that as soon as this and my raptor project gets finished, it was 90% done when the jeep blew and took priority :-/

Like most jeep guys, the old motor has not seen its last days. I'm planning a stroker build with it instead of letting it sit in the corner of the garage.
 
If the 99 motor had mounting spots for the coil rail, it is an 0331 and everything is bolt on. Iirc some late 99s got the 0331? Im no expert on that.

As for the noise - yeah, those gaskets are not reusable, it will leak exhaust and make a racket, probably high idle from intake leaks, and generally be horrible till you replace it. I always forget what gasket to use across the 99/00 break and if you have the later head on the new motor it is moot anyways.
 
Well, as for the 350 I use this as my daily driver as being that I driver 45 miles commute down an interstate everyday, I'll leave the 350 swap for my trail jeep an keep the DD with the i6.

As for the head on the 99' motor, it does not have the mounting holes for the coil pack, and is a 0630, I think that's the right number. Anyway, it is the common head for the 99' and my jeep had the 0331 head on it. So the heads are different, I'm just fabricating a bracket to mount the coil pack to the valve cover or something along those lines, the 0630 is supposed to be stronger anyway, so I'd rather just keep that head.
 
ok, I wasn't sure what was going on there. I think you are right about it being the 0630.

A few things - check port overlap with the new manifolds and the old head, I seem to recall it not being so great, and there being so little overlap between the head and manifolds in a few spots that the gasket can blow out easily. I forget how people solve this problem, but they do...

Also, IIRC one of the mounting bolts of the coil pack is used as a ground, make sure you get good electrical contact on that one.
 
Well, as for the ground on that one mounting hole, I really don't know but that was one of the questions I raised when I was talking about when I was considering the older head.

Temporarily, until I get the mount fab'd up, I could probably put a ground strap on it, similar to the ground strap used on the rear head bolt to the firewall. That would give me plenty of ground for the time being. It not having a good ground has the potential to cause a miss, or a no fire issue correct? Even if the jeep had a miss at this point, I probably could not tell from all the racket, maybe listening to the exhaust pipe would reveal it but I haven't had it running long enough to diagnose that issue.

btw, Haven't been able to run it long enough because in the process of pulling the motor, I ended up cutting a tranny line out of the radiator so tranny fluid goes everywhere. I am picking up a new fitting today, along with EM/IM gasket and possibly lifters.


"I was kidding. Please don't put a 350 in anything."
^^^lol, I love my chevy, but a 350 swap is a bit too time consuming for me, the i6 gives me plenty of power offroad for right now
 
Does anybody know what needs to be done, IF ANYTHING, for the exhaust manifold on my 2000 cherokee to fit the 0630 head?

I've come to the conclusion that the gaskets are the same, I can try to port the exhaust ports to match when I have the head off later today.
 
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