Mysterious coolant loss saga. Blackstone Labs confirms coolant in the oil, metals in the oil indicate bearing wear. Repair shop results as follows. 119k on the clock, runs great.
1) Coolant pressure test, held pressure for 5 hours.
2) warm idle oil pressure test with mechanical gauge 20psi, dash gauge indicates 15psi
3) compression test, #1 130 #2 120, #3 110, #4 125, #5 125, #6 130.
4) Leak down test, all 6 cylinders 60/60 PSI and pass maximum variation is 30PSI
5) Borescope shows wetness on tops of pistons

Original 00131 problematic head. Oil analysis points to head. Pressure test is good.

Is it worth just replacing the head? Are the engine internals “healthy” enough? Or is a new head and engine rebuild the way to go? If I conclude the “engine” is healthy enough and I can get 25-30k more miles out of it, I’ll just get a new head and hope for the best.

 

There is no one single answer.

Option 1: Pull the head, check for cracks. If nothing seen, take to a machine shop for a pressure test and magnaflux (or dye penetrant test). Get 0331 head back, replace head gasket, keep driving it. Sometimes they last, and don't always crack.

Option 2: Get another head from a junkyard. TUPY heads are always available around me in U-Pull-It yards. Drop the head off at a machine shop for the same treatment, swap head.

Option 3: Rebuild your engine with all new bearings, pistons, and choose one of option 1 or 2 for the head.

Option 4: Buy a reman engine with a warranty.


My opinion is that since it's hard to kill a 4.0, I'd go with option 2. Change the oil and do another oil analysis after a couple more oil changes.

 

Thanks, agreed there is no single option. Motor has no knocks or tapping (yet). Underlying question is with compressions where their at is a new head/valve swap OK?

 

I am thinking I am with agreen on this.
119K is pretty low and while coolant could have been trashing the lower end thinking I would slap a TUPY head on there.
And see what happens.

 

1) although the idle oil pressure is sorta ok I would want to know what weight oil was in there when it was checked and what the pressure is at 2500 rpm or so.
2 maybe more to the point, one way or the other the head is coming off and when it does it would be real easy to look at the valves/seats and see if that's where that 110 is coming from.
( I always wonder when people do compression checks if they first crack the plugs loose a turn or two, tighten them back up, run it a bit, then do the check. Eliminates the piece of crud on the valve seat problem. Also, in your case, a wet compression check would have probably told you if it was rings or valves ...at this point who knows.

 

10w-30 oil which has about 700 miles since changed, oil sample taken at 600 miles. Warm oil pressure at 2500rpm shows just under 50psi on the instrument panel.
As I don’t have the talent or tooling to pull the head myself, I would buy a new head complete with valves/rockers and have it installed. That is if I can gain some confidence the lower end still has life.

 

50psi with warm 10-30 suggests to me the bearings are fine... just don't run it with coolant in the oil or they won't be for long.

Given what you are trying to find out, if it were me I would get someone who has a clue to run a good wet compression test. Good among other things meaning the engine is well warmed warmed up. I'm sorta amazed your "shop" didn't do it.
btw. What's your elevation above sea level? If you happen to live at 10,000' those numbers aren't bad at all

 

I’m in SE Phoenix metro at 1400’.

 

There is a small amount aluminum and copper in every oil analysis. I highly doubt that there is any measurable wear to the bearings in your engine. These engines are simply very easy on bearings.

You need a TUPY head. On Car-Part.com, I see hundreds of TUPY heads for sale in the Phoenix area. They range between $100-$150. Search for 03-04 Grand Cherokee 4.0 cylinder heads.

Purchase one of these heads and bring it to your local machine shop. Ask them to clean it, replace the valve springs and valve stem seals, touch up the valves and valve seats, and have them resurface it. It shouldn't cost more than $150-$250.

Install it yourself with a new head gasket, valve cover gasket, thermostat housing gasket and spark plugs. Replacing the head bolts is a good idea but optional. They can be reused once. You'll also need oil and coolant, of course.

Or bring it to a shop and have them do the job. Just make sure they don't forget to use sealant on the front right head bolt threads.

 

I'm going through the same saga. I pulled the 0331 head and took it to my local auto parts chain shore who sent it to their machine shop. Machine shop quickly examined it and determined it to be cracked. I found a TUPY cylinder head on car-part.com for $150 that I'm picking up later this week from a junk yard. IIRC, the TUPY-marked heads were made 2002-2006 and corrected the engineering defect in the redesigned 2000-year head (had to be redesigned to have mounting bosses for the ignition coil). I'll have the TUPY head sent the same machine shop who will clean, inspect it, pressure test, and reassemble for about $150 or so. I'm not sure if its worth paying the extra $$$ to have them do a full-service valve job on the head though.
A TUPY head is easily identified by looking down the oil cap and seeing the embossed letters "TUPY". Its in the middle of the head. You might be able to find one on facebook marketplace. I noticed that lots of sellers refused to part out engines; they want you to buy the entire engine. Just note that I learned on this forum that a 2002+ 4.0 entire engine assembly may not be plug-n-play but the TUPY head will be.

 

Thanks for the input. Attached is a copy of the Blackstone Labs oil analysis.