Sean Henneman

Patient:
'98 Jeep Cherokee XJ, Sport, In-line 6cyl 4.0L, Manual Trans
+200,000mi...lotsa new parts, as needed.
(J.ust E.mpty E.very P.ocket)
(J.E.E.P.)

Symptoms:
Loss of power.
Sounded funny.
Compression test = low, no compression on cyls 3,4 (from front to back)

Decision:
Operate on patient.

Theories:
1) Cracked head? [Cylinder Head # 0630...so probably not...but worth inspecting]
2) Blown Head Gasket? [a good possibility]
3) Bad lifter/push rods? [had a push rod slip out in the past, cyl 3...push rod 6 (from front to back). Put it back in place...and no problems since...but...]

While I'm at this, I decided to clean, restore all parts removed...see pics.
Drained all fluids.
Antifreeze = bright green, still (recently installed a new water pump, the old ones "fins" had completely dissolved/eroded away)
Oil = black & clean as used oil gets...ie. NOT "milkshake" like...meaning: no antifreeze in oil, as expected with above Theory # 1...hmm...

Today I finally removed the cylinder head, and discovered...see last pics.
What...the.... I wasn't expecting this.

Please, explain what I'm seeing.
Provide details of next step in corrective surgery.
(never been this far into her)

Thanks in advance!

dave1123

Nice pics, but not very informative. It appears there is signs for a gasket blowout between #3 & #4, but what is that crap on top of piston #4? Is that a chunk out of the piston near the exhaust valve? Is that melted aluminum glued to the top of it?

Sean Henneman

@dave1123

That's exactly my question...what is that crap on top of piston #4?!
It looks like rust... Why would there be rust IN my piston chamber?

The spot that looks like a chunk out of that piston near the exhaust valve...is just a bad pic artifact...its fluid.

Will I be needing to remove the pistons?

dave1123

Take a nice clear picture of the head chamber for #4. Clean off the piston and look for cracks. It's possible the head is cracked into the exhaust port.

Sean Henneman

Pic of cyl 3,4...head chamber.
Definitely blew through the head gasket...
That'll be easy enough to replace.
...but the rust? Ugh.

Can I lightly scuff it clean with steel wool?
Or will it all have to be milled?

5-Speed

Fire notched... nice. Most likely it burnt the head and block and they will both need to be resurfaced. Clean everything up and check it with a straight edge.

dave1123

You can use a rotary wire brush in an electric drill as long as you don't round the sharp edges. Then take a straight edge (ruler) across the head surface and see if it's lower there than anywhere else. If you can slide a piece of paper under it, the head may have to be milled. It looks like you were running a low antifreeze mixture and the water content caused the rust. Pay attention to the block deck surface as well. If the metal is washed away between the 2 cylinders, the block should be milled as well. At that point, you may be looking at another engine. A slight burbling of the metal sometimes can be compensated for by a thicker gasket. It all depends weither the steel sealing rings will contain the pressure.

It looks like it's decision time. If you're planning on keeping this jeep, you obviously have a lot of miles in it. You can put it back together with some gaskets and call it good, tear it down and do a total rebuild, or get a replacement engine-either used or rebuilt. OR you could put it back together and drive it while you make your decision. It's your wallet we're talking about. Either way, the head looks like it should be milled.

Turbo X_J

Strip the head and have it hot tanked, that's the only way you'll know what you're working with.

papablista

I would have it tanked & milled or be looking for a new head (tupy head), defiantly check the block too.