Cherokee John

After doing a lot of reading on various forums regarding Jeep 4.0L coolant loss & cracked "0331" Cylinder Heads, I put together a summary of the key info. Thanks to all who've shared a lot of useful info!

2000-2001 Jeep Cracked Cylinder Head


Cylinder Head Casting # 0331 (stamped on Driver's Side at top, middle at valve cover edge. Used from 2000-2001
NOTE: "0331" used a mounting boss for the Coil Pack. Switching to an earlier Head ("0630") will require special brackets to Valve Cover to support Coil Pack.


In 2002/2003, Jeep switched to a different casting ("TUPY") from Brazil. Supposed to be stronger, better than "0331" '99-'04 Grand Cherokees's use "0331".


"TUPY" casting is visible through Oil Fill Cap, looking straight down at Head


SYMPTOM:
Unexplained coolant loss.
Oil pressure may go down after starting, warming up.
No heat; Low coolant.
Poor idle; Misfire. Check Engine Light.


CAUSE:
Overheating, lack of maintenance, low coolant. Check coolant, hoses, fan, thermostat often. Flush Cooling system regularly.


EVIDENCE OF COOLANT IN OIL:
1) Oil Sample Test- http://www.blackstone-labs.com/ $20. High in iron (292 ppm, normal being 65) indicates Bearing wear.

3) Pressure Test w/Valve Cover off; coolant will appear at crack between #3 & #4 cylinder.

4) Run engine w/Radiator Cap off- Bubble indicate coolant in combustion chamber.

5) Coolant level going down, oil level going up.

6) Milky substance in Oil Fill Cap or Radiator Cap.

7) Drop in Oil Pressure. (50psi at start, goes down to 10psi when warmed up). 13-20psi at hot idle, 60psi @ 2500rpm. Running Temp: 210

Coolant in the oil will cause deterioration of bearings indicated by a drop in oil pressure. If your compression is still consistent & strong on all cylinders (120+), bearings are ok.

LOCATION OF CRACK:
Under valve cover, between valve springs of cyl.#3 and #4. Sometimes visible looking through Oil Fill Cap. May not see crack but will see crusts of coolant (brown/green).

Also look for creamy-brown emulsion inside crankcase (evidence of coolant mising with oil). If crack is into exhaust, coolant will burn off through tailpipe. If crack is into combustion chamber,
coolant will cause damage to Cam, Main, Rod Bearings. Also may cause gunk/build-up in oil pan and Oil Pump & Pick-Up.


If the crack is between an intake port and the water jacket (or between the combustion chamber and water jacket), the engine might run like it's on 5 cylinders.

Check the plugs and if one of them has less carbon than the others with traces of coolant, you'll know which cylinder is affected.

Most "0331" heads are cracking on the valve spring side (which won't cause a miss).

If it's between an exhaust port and the water jacket, you'll have steam coming from the exhaust but the engine will run fine.

If the crack is only between the water jacket and the crankcase, you'll only have the mystery loss of coolant with the engine otherwise running well.

SOLUTIONS:
1) Addititves to fill crack are not recommended and won't last. Plus, they will only further gunk-up your engine.


2) Use an earlier casting ("0630") from '95-'99. Will also need matching exaust manifold (or adapter), head bolts, head gasket set, custom down pipe and O2 wiring extensions.
The "0630" Heads have smaller ports and do not have retainers for Coil Pack as used on '00-'01.


3) Use a later style Head ("TUPY"). 2002/2003 and up.


4) Aftermarket Head- Alabama Cylinder Heads (800-235-4323)- $510 includes shpg....Currently 75+ back-orders. New, thicker casting in weaker areas.


5) Clearwater Cylinder Heads (800-572-1963)- $455 includes core exchange & shpg. (in stock)

6) J&C Enterprises (800-266-5599)- $439 includes core exhange & shpg.

REPAIR NOTES:
- Coolant in Oil: Replace Cam, Main, Rod Bearings + Oil Pump & Sump.
- Coolant through Exhaust: Flush system, use new FelPro Head Bolts, FelPro Gasket set
- Typical repair shop labor to replace Head: $700+

JCKustoms

Good info...

My 2000 XJ has the 0630 head with the coil pack...I wonder if this is because of the manufacturing date was in 8/99 or from a previous swap???

tjwalker

Almost assuredly from a swap before you owned it.

From the factory (to my knowledge) every single one of the 00-01 4.0 engines cam equipped with the 0331.

My guess is that the previous owner of yours already experienced a cracked 0331 and swapped it with the 0630 (a very good head)

Cherokee John, good post. I will add a link to another comprehensive thread on the 0331 that everyone with an 00-01 needs to bookmark. Knowledge is power here.

http://www.jeepsunlimited.com/forums...d.php?t=391831

I may sound like a broken record, but I'll repeat it again because if it helps one person save their engine, it's worth it.

The #1 symptom of a cracked 0331 head is "unexplained coolant loss". Pop your hood once a week, check coolant level. It takes all of 1 minute.

storm101

Wow good stuff guys! I'm already on my way to posting a link of this lol.

Cherokee John

Looks like my wife's 2000 XJ may be joining the 'Cracked 0331' Cylinder Head Group...
Loosing coolant (no leaks visible). Coolant bottle goes from FULL to ADD after 30 or so mile trips. Still starts good, runs good, no missing. 160,000+ miles. Just replaced Radiator, Water Pump, Thermostat.. Heater Core isn't leaking.

Sooo... Options:

- Replace Head w/reinforced, new casting from Clearwater (Alabama Cyl. Heads is out of stock & back-ordered). $455.

- Replace entire engine and head (assuming coolant leaked into oil, ruined bearings).
$2800 w/labor to R&R, 3yr/250k mile warranty.. Michigan Engine Exchange).

If I just replace the Head, is this wise? Many say that a cracked head is a guarantee that cam, rod, main bearings are shot now. If I do the head, this will obvioulsy solve the coolant loss problem but how long can I expect the engine to last if the coolant affected the bearings?

Appreciate the feedback.


Thanks,

tjwalker

John, if you had a cracked 0331 head, without actually sampling bearing clearances, there is absolutely no way for us to tell you what happened inside of your engine.

It is about the length "time" that the head was cracked. If you catch a cracked 0331 head early enough, you can save the engine. But you really do have to catch it early. If not, you can't. It's that simple (or not).

How long; more importantly HOW MANY MILES have you been experiencing "unexplained coolant loss"??

Cherokee John

Mileage right now is 164,110.

Nov 15th, wife was driving, no heat, engine seemed to be overheating. She drove it directly to our local mechanic. Radiator was leaking. Replaced it at approx. 162,000. A week later, the upper Radiator hose went.
Then, 2 weeks ago, there was no heat again. Replaced Thermostat. Last week, no heat again..Back to shop. Low coolant. No evidence of coolant leaking anywhere. Oil doesn't appear to have coolant in it.

Obviously, best way is to test oil.

Checking coolant everyday now. Adding often.

Don't want to just replace Head if engine bearings are likely degraded.
Then again, if I can save $ by just replacing Head now and worry about replacing entire engine later, that'd save me some $. Of course, I'd save some labor (overall) by doing entire engine/head all at once.

ANOTHER THOUGHT:

Michigan Engine Exhange will replace the existing Engine/Head w/rmfg.
Head will be stock and IF replacement head was cracked, they claim they have them professionally 'flow' welded? and beefed up to prevent future cracking. There work comes with 3yr/250k milegage warranty however, our Jeep lasted 11 years, 165k miles before the head (probably) cracked.
If that's the case, a replacement 0331 head might last beyond the warranty.

Just wondering if I should just get one of the aftermarket (Clearwater) Heads for assurance of longevity.

Thanks for the input!

Cherokee John

I'm going to guess that the coolant/heating problem has been going on for approx. 4000 miles. Never any issue w/starting, performance, missing.

13667

John, I don't want to hi jack your thread but I noticed today that I have the same symptoms. Changed the oil today at the 3000 mile interval and did not notice any water or sludge or brown goop or white goop. The engine has 156K miles.

The coolant bottle on the inner fender was nearly empty. The coolant bottle is stained on the inside, it's not real clean.

I did notice that when I start it up on very cold days there is condensation in the exhaust, but I don't think that's abnormal. I don't smell any coolant in the exhaust, not sure if it would smell sweet like coolant or not if it was being leaked into the exhaust.

Please post what you find, it may help me too. I'll begin to watch to see how long it takes for my recovery bottle to empty.

Thanks...

tjwalker

Cherokee John, I suppose you could drop the oil pan and sample a couple of bearings for clearances. Would be a data point. How is your oil pressure? I don't think you mentioned anything specifically about yours. If you are seeing a drop in oil pressure, that would be a red flag that your bearings are not happy.

As for how much money you want to invest in it, the questions I always ask myself are: How long do I plan on keeping it? How much do I love this vehicle? How much overtime do I want to work?? The answers to those questions always helps with the decision making process on how much to invest in a vehicle. To come out on the new engine on "cost per mile", you would have to drive it quite a while as a $2800 investment would definitely put you "upside down financially" in the vehicle.

Personally, I would not be crazy about any welded 0331 cylinder head, professionally done or not. I've not heard of any success with any types of welding on this problem. The casting is thin there; yes you could probably get it welded and fixed (for now), but I don't think I'd sleep that well knowing that it could crack again in the future. I definitely would NOT go that route. Any new engine I'd be putting in would not sport an 0331 cylinder head, unless it's a TUPY.

Good luck with your decision making!

Cherokee John

Thx for the replies/input TJ...

Wife drives the Cherokee and loves it. Plan to keep it a long time.
Oil Presure today... ranges from 15-45/50 or so depending on cold, hot, stopped/idling and 1500-2500 RPM.
If we had a 3rd car, I'd do the work myself. Part of me thinks... Just replace the Head w/one from Clearwater ($455) and hope the coolant hasn't affected the bearings. If it has, how long will they last until something fails? Then we instantly need a replacement vehicle.

No doubt... $2800 for another engine isn't pocket change however, my options are:
- Do nothing (and keep pouring in anti-freeze; Engine will fail before long).
- Replace the Head (and hope bearings are ok)...$700+ total job w/new head.
- Replace engine & head: $2800- 3yr warranty
- Try and find a reliable vehicle for $2800 and start all over again with all the repairs we've already done on the Jeep over the years.

Ugh.

Omnipotent Octopus

I took option #2. I will find out by next week how my engine runs. IF J&C decides to ship my head this week. Still haven't gotten any updates. If my bearings are done im parking my heep behind the garage and and getting a new vehicle.

tjwalker

John,

The first and the last options are not good ones!

*If you replace the head and the engine does fail, it won't happen overnight and that should still give you time to find a replacement salvage yard engine, you swap your new head onto that engine and you're back on the road. If you are going this route, DO NOT drive the engine until the new head is on there. Know that you are doing more damage every minute that your engine is running right now. Be sure to perform a few very frequent oil changes after the repair to get the contaminated oil out of there!

*Buying the reman engine is a fine option if you can afford it. But check into that head thing. I personally don't like the idea of having a welded 0331. Professionally welded or not. That head casting is a dog and I wouldn't want it on a reman engine. Not for $2800 smackeroos.

viper_venom600gtsr

Looks like I have joined the fraternity of 0331 cracked heads. I bought my 2000 XJ with 78K miles in May 2010, replaced all fluids right away. Not a single overheating issue ever. I check my fluids regularly so noticed a coolant drip last year and promptly replaced it with a triple core radiator, new water pump, thermostat, housing and gasket and coolant flush. Did fine till a month ago, started having poor heat, checked coolant bottle it's empty so poured in about 2 bottles of coolant in small increments till today and a couple of days ago noticed the "white milky" sludge under my oil fill cap. Throughout this whole time that I've owned the vehicle never had temp go past 220 ever. Oil pressure at it's lowest has been probably 14-15psi at idle when warmed up otherwise around 40-60. Just called and spoke with Pat at Clearwater heads and will be getting my new one next week.

Along with this I am getting new head bolts, new upper end gasket kit VICTOR REINZ Part # HS5713A OR FEL-PRO Part # HS9076PT4 (which one would you guys recommend?) Anything else that I should replace while I'm in there? Thanks to everyone who contributed to this thread.

Firestorm500

Cherokee John: "Try and find a reliable vehicle for $2800."

Haven't seen too many of those lately. Those 2 conditions are mutually exclusive.

Seems you can have one or the other, but not both together.

I'd probably buy the engine and fix the Jeep. Many happy miles left then.

Actually, I did do that on my '92.