The dreaded symptoms

[TJFett01]

My buddy came over today and we did a compression test and a leak down test.

The two compression tests in the chart below were done dry and the engine cold; Numbers are in PSI. Two different test gauges were used.

Cylinders	1	2	3	4	5	6
Test in 2016	140	145	140	150	145	140
Test in 2021	130	150	148	150	150	150

For the leak down test the engine was cold, the throttle held open, each piston moved manually* to Top Dead Center (TDC), removed the radiator cap, all spark plugs, and oil dipstick. (I understand usually it should be done warm).

*It was not difficult to move the crankshaft.

During the leak down test, cylinders 1, 2, 5, & 6, held pressure fine with minimal pressure loss. Cylinder 3 and 4 leaked air as soon as the compressor kicked in and took significantly longer for them to build up pressure. These two leaked air from the oil dipstick, #3 was leaking more air than #4. We did not detect air bubbles from the radiator (Rad was full), leaking air from the intake/exhaust during each of the 6 cylinders. I believe we didn't see bubbles because the engine was cold (thermostat closed) or something else?

I did inspect the spark plugs, there doesn’t seem to be anything abnormal, except #1 spark plug is the dirtiest of the 6. Prior to the above tests, I looked inside each cylinder with a bore scope camera, and they were dry (no puddles of coolant or water). I can upload pictures of the spark plugs if anyone would like to see.

I am currently compiling a list of parts I believe I will need to repair the engine. I will share it here and include links when applicable.

 

[tr21triton]

heat to be the bearer of bad news but did you do a test putting oil in the cylinders ? you need to do a compression test again and put about a oz of oil in the sparkplug hole before doing each cylinder. if your readings are the same all you need is a valve job. if they go up you need a rebuild...

 

[jeepguy03]

heat to be the bearer of bad news but did you do a test putting oil in the cylinders ? you need to do a compression test again and put about a oz of oil in the sparkplug hole before doing each cylinder. if your readings are the same all you need is a valve job. if they go up you need a rebuild...

I have the factory service manual for my '98, and it says the range is 120-150 PSI, so his numbers are fine. No need to worry about a valve job if replacing the head.

 

[Fishtaco]

Drain the oil and check.

I've seen moisture at these caps cause the exact look you have and were fine.

Just a thought and a prayer for you

So have I, If it is sucking coolant the oil in the pan would be milky as well and obvious enough not to need an oil analysis from a lab, a split hose caused the initial overheat then a leaking clamp, I wouldnt jump straight to a cracked head if there was no water in the oil.
Clear sky Cold misty/moist mornings with hot days can cause moisture in the rocker cover, sounds like Arizona?

 

[Rubicon88]

So have I, If it is sucking coolant the oil in the pan would be milky as well and obvious enough not to need an oil analysis from a lab, a split hose caused the initial overheat then a leaking clamp, I wouldnt jump straight to a cracked head if there was no water in the oil.
Clear sky Cold misty/moist mornings with hot days can cause moisture in the rocker cover, sounds like Arizona?

Yes...it happens and I'd be making damn sure before shit-canning the head

 

[TJFett01]

After doing more research, I ordered a cylinder head from Clearwater!

In addition to the new 0331 head, I will be repairing a stripped threaded hole on the timing cover (removing it and replacing gaskets) with a heli coil insert. The water pump is going (getting a new Mopar one) there seems to be trails of coolant around the weep hole. Lastly I will replace the heater core hoses and lower rad hose. All applicable gaskets and new head bolts will be Felpro.

I am looking to getting an oem style head gasket, is this Felpro 9076PT1 the right one?
https://www.rockauto.com/en/moreinfo.php?pk=446623&cc=1373723&jsn=997

Feedback is appreciated!

 

[bromel]

Great to hear. Please keep us updated on how the Clearwater install goes. I'm so paranoid about my head cracking that I might buy one just in case.

 

[jeepguy03]

So have I, If it is sucking coolant the oil in the pan would be milky as well and obvious enough not to need an oil analysis from a lab, a split hose caused the initial overheat then a leaking clamp, I wouldnt jump straight to a cracked head if there was no water in the oil.
Clear sky Cold misty/moist mornings with hot days can cause moisture in the rocker cover, sounds like Arizona?

Usually not as much gunk as what's found under the valve cover of a cracked 0331 head. The 4.0L engine is known to run pretty hot anyway, and even when doing short trips and not getting the engine up to temp you won't see that much milkshake. I short tripped my 2000 XJ during the commute for my last job (under 3 miles) and even during winter the oil cap was spotless underneath. I would drive it further occasionally on the highway to get everything up to temp.

 

[TJFett01]

I am looking to getting an oem style head gasket, is this Felpro 9076PT1 the right one?
https://www.rockauto.com/en/moreinfo.php?pk=446623&cc=1373723&jsn=997

Anybody use this gasket?

Great to hear. Please keep us updated on how the Clearwater install goes. I'm so paranoid about my head cracking that I might buy one just in case.

Will do! That might be a good idea, along with all the gaskets you'll need.

 

[bromel]

Yeah that will fit, but I'd get the full kit:

https://www.amazon.com/dp/B000HUJUKY/?tag=wranglerorg-20

 

[jeepguy03]

Yeah that will fit, but I'd get the full kit:

https://www.amazon.com/dp/B000HUJUKY/?tag=wranglerorg-20

+1
I've used the above kit a few times and it has worked well.

 

[TJFett01]

Yeah that will fit, but I'd get the full kit:

https://www.amazon.com/dp/B000HUJUKY/?tag=wranglerorg-20

I did get the full kit. This past Thursday my buddy and I removed the cylinder head. It took us about 3 hours to remove all necessary components.

Under the valve cover looks like a milkshake. I have photos showing what it looked like when I removed the valve cover and head.

After cleaning the block, we checked for warpage with a straight edge ruler and it was fine.

With the new head gasket, we put the new clear water head on.

With each new Fel Pro head bolt, I used new engine oil to lube the threads. Going counter clockwise until the bolt "clicked" into the block threads, I hand tightened until snug.

Set my torque wrench to 25, then 45 and finally 110 ft-lbs. It all went smooth until bolt #13 snapped near 100 ft-lbs (my guess based on the others).

Lucky there was enough threads exposed for me to get vise grips and remove the broken bolt. It seemed too easy to remove #13.

Looks like I should have bought arp bolts. Perhaps my torque wrench is out of spec or that bolt cross threaded? I will check the block later.

I used vice grips to set the small knob to 110 ft-lbs and it didn't move on it's own when I was tightening.

 

[sam53]

Wow, sorry to hear of your loss. My 01 sport has 189,000 0n her clock. Have "most" of these bad year heads broke. Do you even dare drive them 400-500 mile trip

 

[bromel]

Wow, sorry to hear of your loss. My 01 sport has 189,000 0n her clock. Have "most" of these bad year heads broke. Do you even dare drive them 400-500 mile trip

I don’t let the fact that I have a 2000 stop me from taking long road trips. I keep on top of my cooling system to make sure I don’t overheat. Same goes for my 99 WJ with 150k.

Certainly most heads don’t crack. There are so many 00-01 TJs and XJs on the road that it’s not “common.” But enough crack that it’s a trend.

 

[sam53]

Thanks so much for the reply. Basically if you don't over heat the engine it probably won't crack?

 

[bromel]

Thanks so much for the reply. Basically if you don't over heat the engine it probably won't crack?

Unfortunately no, these heads still may crack even when perfectly maintained. But plenty go 300,000 perfectly intact. I wish I could give you a solid answer. Just keep it maintained and send it—worst case you’re out $500 and a weekend if it cracks, or $1000 labor at the shop.

 

[sam53]

Again, thanks so much for the reply. Take care

 

[jeepguy03]

Thanks so much for the reply. Basically if you don't over heat the engine it probably won't crack?

It's a flaw in the cylinder head casting. It can crack without overheating, but overheating will make it more likely to crack.

 

[jeepguy03]

I did get the full kit. This past Thursday my buddy and I removed the cylinder head. It took us about 3 hours to remove all necessary components.

Under the valve cover looks like a milkshake. I have photos showing what it looked like when I removed the valve cover and head.

After cleaning the block, we checked for warpage with a straight edge ruler and it was fine.

With the new head gasket, we put the new clear water head on.

With each new Fel Pro head bolt, I used new engine oil to lube the threads. Going counter clockwise until the bolt "clicked" into the block threads, I hand tightened until snug.

Set my torque wrench to 25, then 45 and finally 110 ft-lbs. It all went smooth until bolt #13 snapped near 100 ft-lbs (my guess based on the others).

Lucky there was enough threads exposed for me to get vise grips and remove the broken bolt. It seemed too easy to remove #13.

Looks like I should have bought arp bolts. Perhaps my torque wrench is out of spec or that bolt cross threaded? I will check the block later.

I used vice grips to set the small knob to 110 ft-lbs and it didn't move on it's own when I was tightening.

That sucks about the head bolt. Did you use new bolts? I know technically they can be re-used once, but I've always replaced them just to be safe.

 

[sam53]

I understand it is extremely tough to place a 4.0 out of a grand Cherokee in a TJ but can the head be used? I have access to an engine out of a Cherokee and knowing my luck (now that I have talked about it) my 2001 head will break tomorrow. I would recon this head for insurance. thanks