The dreaded symptoms

[TJFett01]

Unexplained coolant loss, no apparent leaks.

2001 TJ
181k miles
0331 head

Overheated recently, didn't boil over but lost a lot of coolant. Culprit was upper radiator hose that split at the bend near the A/C lines and valve cover. After it cooled, I discovered the split when I removed the hose to initially replace the thermostat. I ended up replacing both. (it was 6+ years old and it stays 1/16" open at room temp). New thermostat is a MotoRad/Stant 195 degree non "fail safe". Also replaced the Radiator cap (18 psi), pressure tested it recently and it is fine.

Prior to this, I over heated 3 years ago and replaced:
Original radiator with a new oem one (old one got a hairline crack by the cap).
Electronic fan motor (PO did it, I know the whole debate about fans ).
Until recently, there was no issues with coolant missing or leaking other than having to occasionally top of the reservoir.
*I have not needed to replace the heater core or water pump, although that can change.*
*In both instances, I never used any kind of sealer.*

Back to the issue.

The first week after I made the repairs I lost coolant, from full to add, within 60 miles going to work and back. Found a small leak on the clamp between the thermostat housing and upper radiator hose. Tightened clamp, leak stopped, and added more coolant. Next week, same about of coolant loss but no visible leaks. Jeep runs fine, no CEL, no oil pressure issues, no further overheating issues.

I am worried the cylinder head or head gasket could have failed. I do have the 0331 head. I haven't driven it since in case it is a head related problem. I've ordered some tools to help me diagnose the possible issue.

What I plan to do today is:

1) With a proper spill proof funnel, bleed the system of air again (there's a chance I didn't properly do it after I replaced the thermostat since I didn't have this funnel).

2) Do a combustion leak test with the blue liquid.

3) Blackstone labs oil test kit that I can take once the Jeep cools down a little (to see if coolant is mixed with the oil). I have full synthetic oil.

4) I will also pull the sparkplugs, inspect them and stick a bore scope camera into each cylinder.

Is this overkill or am I with in reason to do all these tests?

Do I need to add any pictures?

 

[bromel]

Sounds like you're doing it right. I have the 0331 head on my 2000 and I monitor my coolant like a hawk. ("Crap, does that reservoir look lower or did I just park on an incline?")

Before you go crazy with tests, have you tried peering down into the oil-filler cap with a flashlight? If a cracked head is responsible for losing that much coolant, you should almost certainly see it seeping out a few minutes after turning off the hot engine.

I use Blackstone for analysis too, but it takes them a few weeks and you'll probably want an answer before then.

 

[TJFett01]

Sounds like you're doing it right. I have the 0331 head on my 2000 and I monitor my coolant like a hawk. ("Crap, does that reservoir look lower or did I just park on an incline?")

Before you go crazy with tests, have you tried peering down into the oil-filler cap with a flashlight? If a cracked head is responsible for losing that much coolant, you should almost certainly see it seeping out a few minutes after turning off the hot engine.

I use Blackstone for analysis too, but it takes them a few weeks and you'll probably want an answer before then.

You and I both. lol

I have not but I will look under the oil cap before and after my tests.

I had a feeling it would take several weeks for the Blackstone analysis to come back but I do have another vehicle to drive to work. In the meantime, hopefully I can get some clear results.

 

[TJFett01]

My worst fear has come true, coolant is mixed in with the oil.

Without even starting the engine, I went to remove the oil fill cap but it was stuck and broke off. The oil cap and valve cover have the infamous milkshake color. The oil level is about 1" above the full mark.

There's no need for me to do any of the other tests except maybe the Blackstone oil test to see how much damage is done. This is really unfortunate because it was a smooth running engine with hardly any (oil) leaks and non oil burner.

Thank you bromel for suggesting to look under the oil cap. I can't believe I completely over looked that.

I have a buddy that has rebuilt several engines and restored cars. I will most likely contact him to help me remove the valve cover and header to see how bad it is.

Looks like I'm going to have to comb through the threads about what other people did when this happened.

New head? New engine? Or just the head gasket?

Either way my wallet is in trouble.

 

[bromel]

How many miles did you drive since the crack? I think you'll be OK as long as it wasn't excessive. The good news is that replacing the head isn't that big of a deal. It's a Saturday with a knowledgeable friend.

Here is what I would get: https://www.cylinder-heads.com/product/new-jeep-cherokee-laredo-4-0-0331-cylinder-head-complete/

Clearwater heads are highly regarded. Alternatively, get a used 0331 TUPY head off any 2002+ Wrangler or WJ. Just make sure it's stamped TUPY!

 

[jeepguy03]

How is your oil pressure at hot idle? Your bottom end is likely fine. Spec for the 4.0L engine is 12 psi at hot idle. I've done 2 of the 0331 head swaps. I actually made a how-to thread on another forum about it. You can use a TUPY casting head from a 2002+ TJ/WJ or just buy a new one from Clearwater Cylinder. I opted for the Clearwater both times because they aren't that expensive and I'd rather do the job once with new parts than possibly have an issue with a used head.

The job really isn't that bad, both times I did it over a long weekend with basic hand tools and a buddy helping. The most PITA part is the exhaust especially if it's rusty.

Blackstone labs does great testing, but they can really only tell you the condition of the oil, not your bearings. The minimum oil pressure at hot idle (with fresh oil obviously) will give you a better idea. The only engines I've really seen destroyed from the 0331 head were driven for quite a while with the coolant in the oil, to the point where the oil pressure would drop to 0 PSI at stoplights, which means the cam bearings were bad in that scenario.

 

[bromel]

One last thing: make sure you replace the head no matter what, even if it turns out the head gasket is blown but the head itself is fine. The 00-01 0331 head should never be put back on if it’s removed. Invest the money now and you’ll thank yourself later.

 

[Rubicon88]

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

 

[TJFett01]

How many miles did you drive since the crack? I think you'll be OK as long as it wasn't excessive. The good news is that replacing the head isn't that big of a deal. It's a Saturday with a knowledgeable friend.

Here is what I would get: https://www.cylinder-heads.com/product/new-jeep-cherokee-laredo-4-0-0331-cylinder-head-complete/

Clearwater heads are highly regarded. Alternatively, get a used 0331 TUPY head off any 2002+ Wrangler or WJ. Just make sure it's stamped TUPY!

Since it cracked to where I noticed low coolant in the reservoir the second time (and stopped driving) was about 80-100 miles, in the span of 10 days. Work is 3.5 miles away so my driving is relatively short. I usually let the engine warm up to about 120 degrees (its not very cold where I live) before I leave the house.

Haven't turned it over since. What would be considered excessive driving in this case?

I'm definitely considering a new cylinder head. I'll look into those clearwaters. Would a 2002+ TUPY head be fine if it was remanufactured?

 

[bromel]

Since it cracked to where I noticed low coolant in the reservoir the second time (and stopped driving) was about 80-100 miles, in the span of 10 days. Work is 3.5 miles away so my driving is relatively short. I usually let the engine warm up to about 120 degrees (its not very cold where I live) before I leave the house.

Haven't turned it over since. What would be considered excessive driving in this case?

I'm definitely considering a new cylinder head. I'll look into those clearwaters. Would a 2002+ TUPY head be fine if it was remanufactured?

I think you’re fine. I know people who have driven thousands of miles with a cracked head and replaced with no issues, not saying you should do that of course. Some heads crack in the combustion chamber so most of the coolant is burned, but yours cracked such that oil was heavily contaminated. That said, you didn’t drive it any significant distance. Just don’t drive it until the head is replaced.

 

[TJFett01]

How is your oil pressure at hot idle? Your bottom end is likely fine. Spec for the 4.0L engine is 12 psi at hot idle. I've done 2 of the 0331 head swaps. I actually made a how-to thread on another forum about it. You can use a TUPY casting head from a 2002+ TJ/WJ or just buy a new one from Clearwater Cylinder. I opted for the Clearwater both times because they aren't that expensive and I'd rather do the job once with new parts than possibly have an issue with a used head.

The job really isn't that bad, both times I did it over a long weekend with basic hand tools and a buddy helping. The most PITA part is the exhaust especially if it's rusty.

Blackstone labs does great testing, but they can really only tell you the condition of the oil, not your bearings. The minimum oil pressure at hot idle (with fresh oil obviously) will give you a better idea. The only engines I've really seen destroyed from the 0331 head were driven for quite a while with the coolant in the oil, to the point where the oil pressure would drop to 0 PSI at stoplights, which means the cam bearings were bad in that scenario.

I'm not sure if the oil Guage is measured in psi or not (pretty sure it is). At hot idle, it typically stays around the 40 mark. It fluctuates a little bit back and forth kinda like the temp Guage when the thermostat opens/closes. It goes from 25-55 depending on load. Its been like that since then first day I got it 5 years ago. Didn't see it drop to 0 when running last. I was under the impression oil pressure was substantial higher than the cooling system's 12-16 psi? Or did I misinterpreted something?

I'll have to look up your thread. What is your user name/ thread title in the other fourm?

Ah yes, my exhaust has some rust. I should go and get some pb blaster or something like that. I read somewhere they removed the driver side fender and wheel to access the exhaust better. Doesn't sound like a bad idea.

Very true, I will probably collect this sample of oil anyways and take a second one after I flush the oil a couple of times to see if the contaminates get reduced to acceptable levels.

 

[jeepguy03]

Since it cracked to where I noticed low coolant in the reservoir the second time (and stopped driving) was about 80-100 miles, in the span of 10 days. Work is 3.5 miles away so my driving is relatively short. I usually let the engine warm up to about 120 degrees (its not very cold where I live) before I leave the house.

Haven't turned it over since. What would be considered excessive driving in this case?

I'm definitely considering a new cylinder head. I'll look into those clearwaters. Would a 2002+ TUPY head be fine if it was remanufactured?

A re-man head will be okay, but just MAKE SURE it is the TUPY casting. Many companies selling reman heads will just sell any old 0331 head as fitting the correct models.

Personally, if it was mine I'd just get the Clearwater and be done with it. One of the Jeeps I did was a friend's 2000 XJ at 94k miles. Replaced with a Clearwater and it was running great until it was wrecked at 260k miles.

 

[jeepguy03]

I'm not sure if the oil Guage is measured in psi or not (pretty sure it is). At hot idle, it typically stays around the 40 mark. It fluctuates a little bit back and forth kinda like the temp Guage when the thermostat opens/closes. It goes from 25-55 depending on load. Its been like that since then first day I got it 5 years ago. Didn't see it drop to 0 when running last. I was under the impression oil pressure was substantial higher than the cooling system's 12-16 psi? Or did I misinterpreted something?

I'll have to look up your thread. What is your user name/ thread title in the other fourm?

Ah yes, my exhaust has some rust. I should go and get some pb blaster or something like that. I read somewhere they removed the driver side fender and wheel to access the exhaust better. Doesn't sound like a bad idea.

Very true, I will probably collect this sample of oil anyways and take a second one after I flush the oil a couple of times to see if the contaminates get reduced to acceptable levels.

Here is the thread, it is from Jeepforum.com. I'd like to make a DIY for this forum, but unfortunately as you'll see in that thread all the pics were on photobucket.

https://www.jeepforum.com/forum/f11/0331-head-swap-thread-1371398/
As for the oil pressure, the factory service manual is what specs 12 psi hot ide. I would change the oil with some cheap 10w30, drive it until it is warmed up (10-15 miles) then screw in a mechanical oil pressure gauge where the oil pressure sender screws into the block and start it. You should see more than 12 at a hot idle, and if so you are good. You can rent oil pressure test gauges from Autozone.

 

[TJFett01]

One last thing: make sure you replace the head no matter what, even if it turns out the head gasket is blown but the head itself is fine. The 00-01 0331 head should never be put back on if it’s removed. Invest the money now and you’ll thank yourself later.

I'm definitely leaning more into a new head, still undecided if it will be a brand new one or a used/remanufactured TUPY.

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

I appreciate your optimism, however I peaking under the oil fill cap with a bore scope camera and there is thick milkshake residue all among the valve cover walls and tops of the rockers. Unfortunately its a bit more than some water.

I think you’re fine. I know people who have driven thousands of miles with a cracked head and replaced with no issues, not saying you should do that of course. Some heads crack in the combustion chamber so most of the coolant is burned, but yours cracked such that oil was heavily contaminated. That said, you didn’t drive it any significant distance. Just don’t drive it until the head is replaced.

Thats reassuring, I'm glad I didn't continue driving it. Hopefully the rest of the engine will be fine. I'm thinking I will have to replace the oil pump since its probably gunked up.

A re-man head will be okay, but just MAKE SURE it is the TUPY casting. Many companies selling reman heads will just sell any old 0331 head as fitting the correct models.

Personally, if it was mine I'd just get the Clearwater and be done with it. One of the Jeeps I did was a friend's 2000 XJ at 94k miles. Replaced with a Clearwater and it was running great until it was wrecked at 260k miles.

I'll keep that in mind to double check about it being marked TUPY if I go that route. Did you replace any other internal parts on your friend's XJ?

Here is the thread, it is from Jeepforum.com. I'd like to make a DIY for this forum, but unfortunately as you'll see in that thread all the pics were on photobucket.

https://www.jeepforum.com/forum/f11/0331-head-swap-thread-1371398/
As for the oil pressure, the factory service manual is what specs 12 psi hot ide. I would change the oil with some cheap 10w30, drive it until it is warmed up (10-15 miles) then screw in a mechanical oil pressure gauge where the oil pressure sender screws into the block and start it. You should see more than 12 at a hot idle, and if so you are good. You can rent oil pressure test gauges from Autozone.

Thank you for posting that thread!

Will do, it seems pretty straightforward. Is there any relation to the dash's oil pressure guage to pluging in a gauge to the block? I'm not understanding how the dash would read ~40 (psi?) and the block 12psi?

 

[jeepguy03]

I'm definitely leaning more into a new head, still undecided if it will be a brand new one or a used/remanufactured TUPY.

I appreciate your optimism, however I peaking under the oil fill cap with a bore scope camera and there is thick milkshake residue all among the valve cover walls and tops of the rockers. Unfortunately its a bit more than some water.

Thats reassuring, I'm glad I didn't continue driving it. Hopefully the rest of the engine will be fine. I'm thinking I will have to replace the oil pump since its probably gunked up.

I'll keep that in mind to double check about it being marked TUPY if I go that route. Did you replace any other internal parts on your friend's XJ?

Thank you for posting that thread!

Will do, it seems pretty straightforward. Is there any relation to the dash's oil pressure guage to pluging in a gauge to the block? I'm not understanding how the dash would read ~40 (psi?) and the block 12psi?

I didn't replace any other internals on the XJ. Just replaced the thermostat and I believe a hose or two because they were in sad shape. I did have him do two short interval oil changes, I think one was at 500 miles and the other at 1000 miles.

If your dash gauge seems to work okay it should show very close readings to a mechanical gauge, the one in my TJ seems to when I checked it, but Jeep oil pressure gauges are known to be inaccurate so that's the only reason I verify it with a mechanical gauge. If yours has never hit 0 PSI at a stop light when warmed up, your bearings and everything are likely fine, especially because it seems like you've only driven a short distance since the problem started.

You shouldn't need to replace the oil pump, everything is likely fine. All the gunk collects at the top of the cylinder head/valve cover because that is where the PCV vents are.

 

[TJFett01]

I didn't replace any other internals on the XJ. Just replaced the thermostat and I believe a hose or two because they were in sad shape. I did have him do two short interval oil changes, I think one was at 500 miles and the other at 1000 miles.

If your dash gauge seems to work okay it should show very close readings to a mechanical gauge, the one in my TJ seems to when I checked it, but Jeep oil pressure gauges are known to be inaccurate so that's the only reason I verify it with a mechanical gauge. If yours has never hit 0 PSI at a stop light when warmed up, your bearings and everything are likely fine, especially because it seems like you've only driven a short distance since the problem started.

You shouldn't need to replace the oil pump, everything is likely fine. All the gunk collects at the top of the cylinder head/valve cover because that is where the PCV vents are.

Alright I'm sure my oil pump is okay, I'll do those short interval oil changes as well.

Thanks for clarifying, I'll test the oil pressure on the block as you suggested, it will be good to double check the dash Guage is reading correctly.

On another note:

I contacted my buddy, he's come over Friday to do a compression test and leak test. Hopefully this will determine if it is a blown head gasket or not but I will replace the head anyways. From my understanding, these tests can also determine if the pistons are sealing properly..?

I did write down the numbers when I did a *dry* compression test 4-5 years ago to compare to the one we'll do Friday.

 

[jeepguy03]

Alright I'm sure my oil pump is okay, I'll do those short interval oil changes as well.

Thanks for clarifying, I'll test the oil pressure on the block as you suggested, it will be good to double check the dash Guage is reading correctly.

On another note:

I contacted my buddy, he's come over Friday to do a compression test and leak test. Hopefully this will determine if it is a blown head gasket or not but I will replace the head anyways. From my understanding, these tests can also determine if the pistons are sealing properly..?

I did write down the numbers when I did a *dry* compression test 4-5 years ago to compare to the one we'll do Friday.

Yep, leak down test will determine if the cylinders are sealing. The problem is if the crack is minor, it might not be noticeable with that. Usually you'd have to leave it connected for a period of time. As the engine warms up the metal will expand making the crack larger, so it might not be as obvious on a cold engine.

The crack usually forms between the number 3 and number 4 cylinder, as that is the weak spot in the head. I don't think you will be able to tell if it is a gasket or the cylinder head without tearing it down. I've heard you can see coolant coming out of the top of the head between #3 and #4 with the engine running and looking through the oil fill hole, but I've never been able to spot it.

 

[hear]

If yours has never hit 0 PSI at a stop light when warmed up, your bearings and everything are likely fine,

I thought this sort of thing was indicative of a bad oil pressure sender? Every now and then mine will drop to zero after a hard stop and the check gauges light will come on, but if I give it a little gas it comes right back up. Now you've got me worried about a whole new set of problems.

 

[bromel]

I thought this sort of thing was indicative of a bad oil pressure sender? Every now and then mine will drop to zero after a hard stop and the check gauges light will come on, but if I give it a little gas it comes right back up. Now you've got me worried about a whole new set of problems.

Different issue entirely. 99% of 0 PSI readings are the result of a bad oil pressure sending unit. In this case, we know his head is cracked, and we are assuming the sender is good, so we're trying to discern if the coolant in his oil damaged the bearings such that the oil pressure dropped. If the sender is functioning properly, it should give a decent indication of actual oil pressure.

 

[tr21triton]

I thought this sort of thing was indicative of a bad oil pressure sender? Every now and then mine will drop to zero after a hard stop and the check gauges light will come on, but if I give it a little gas it comes right back up. Now you've got me worried about a whole new set of problems.

mine does the same thing on take off if i dont give her enough go pedal, and then jumps up