Trail 4
July 26, 2025
Well it's been a couple of years since my last posting in this blog series. So I thought I'd do a quick write up since my hiatus.
The XJ is doing okay. The A/C system is down and has been since last Summer. Can't find the leak but suspect the crappy UAC (Universal Air Conditioning) brand condenser is the problem. It's a simple single tube serpentine affair instead of a cross-flow design which I prefer. So I ordered a new one from TYC as I've had good experiences with their products when I can't get Four Seasons stuff. The compressor and evaporator seems to be in good order so I will replace the drier too. Figuring out the amount of oil in the system will be a challenge since I won't remove the compressor and pour it out. There only two bolts securely holding it to the bracket due to galled threads and I don't feel like Helicoiling now.
I did upgrade the alternator to a 134A after the 90A failed, again. I think I burned it out while using the winch up in the mountains during my trip to Colorado in December 2023. Got into a bit of a bind with an icy hairpin turn with pavement, and a steep drop. Thankfully there were enough trees close enough to hug them and get myself out of the situation.
That trip was more than 5200 miles round trip. Got to play in the snow in my old stomping grounds around Durango. On the return I visited an Auntie near Phoenix, brother and his family in Austin, relatives in Jackson, MS, and a Aunt and cousin in western NC. Great trip and Mom's doing fine since her surgery.
The TJ needs some love even after a failed cylinder head. Yes it was the infamous 0331 but this head didn't crack like so many other pre-TUPY heads did. This one suffered from recessed exhaust valves in cylinders 1 and 5. Dang thing left my daughter on the side of the road twice from it. After two full oxygen sensor swaps it still didn't run. My daughter didn't want it any longer and gave it back to me. So I started working on it little by little and decided to check compression. Cylinder 1 was barely 40PSI while 5 achieved about 100. The others were fine at 140+. So I injected air into the cylinder at TDC on the compression stroke to see where the air was going. Nothing heard from the oil fill in the valve cover. Nothing heard from the throttle body. But a lot was heard from the tailpipe. That was when I suspected a burnt valve. After removing the head it wasn't burnt exactly. It just was recessed from the damaged valve seat. Valve seats in these 4.0L heads aren't inserts. They are simply machined as part of the head. When they become unusable machinists will grind them out for valve seat inserts. I went for a TUPY head if I couldn't find an 0630 head. I found a re-manufactured TUPY head complete with new valves, springs, locks, and seals. Now I've been driving it around at times but it still doesn't have the power it used to. I think it still has a vacuum leak or something. I need to pull the spark plugs and get a look at them to see what might be going on.
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| My baby visiting my brother's place. Hard to see in the windshield but I earned three ducks since my trip to Colorado! Brownie, Lemon, and Uni (a unicorn) |
That's it on the Jeep front. Hopefully I'll have more to add to this trail in the future.
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August 9, 2025
Went over to my brother's place and changed out the A/C drier piece. Put new o-rings on the fittings for the condenser and pulled a vacuum for 45 minutes. The vacuum held over 45 minutes after the pump was shut off so I'm happy with that. While waiting for the draw down and evaluation I did a quick Toe adjustment on the steering. It has been feeling a bit wandery and using the string method confirmed I had a Toe-Out condition. Disconnected the passenger's side heim joint, spun it in one full turn and put it back together.
Also while waiting for the leak down test to finish I did an oil change. She had about 6,000 miles on this one but not worried. T5 Rotella 10w-30 is great! I got a good deal on some T4 so got that this time. Yes, it's diesel oil but it's also tractor oil and the 4.0L is really a tractor engine by design with 7 main bearings, short-stroke, and good reliability. It comes from a long history of this base design from 1964. So I don't worry about the type of oil it is. Sure the piston ring gaps are .040" or more but she runs well, starts every time, and is fun to drive to work or to a campsite off road.
That being said I do have a 1996 or '97 short block in the shed. The cylinder head, an 0630, checked out good and .007" was milled to make it flat before installing it on my '93 engine. The 7120 was getting tired and a couple of exhaust valves were starting to recede into the head not to mention the valve guides were showing excessive clearances. Maybe I can get it to a machine shop that's still open somewhere to have it tested, machined, rebuilt, and ready for another 250K miles. Advance Auto Parts stores closed down all of the Carquest machine shops they got in the buyout late in 2024. Stupid really. A retail chain catering to the DIY'er shuts down their own machine shops DIY'ers need for their builds. Ludicrous! Basically Advance sent all their DIY customer's wanting machining services to their competitors like Napa. Stupid is what stupid does. end rant...
Over this Winter I'm hoping to get the crank checked out and cleaned up with a box of rod and main bearings. My goal is to build it and get it ready to run by Spring next year. The 0630 head will just move over to it after installation in the XJ. Some work will need to be done with the intake manifold power steering mounting bosses as two have stripped out. Those will need to drilled and Heli-coiled in. Everything else will just bolt up where it normally would. Which again means capturing the refrigerant, disassembling the A/C system, cooling system, and remove the hood to get the 4.0L swapped. Yes I really want a 4.6L stroker motor but the costs are just too high for the kit now. It's beyond my reach. The kit I was contemplating versus buying a long block outright is too close with the machine shop work I need done on my block. When the estimate was completed for the two options there was only a few hundred dollars difference and one came with a warranty. So I figured that extra was the price of a warranty. So yeah. I'm rebuilding it stock. It's not necessarily a bad thing as longevity, reliability and total compatibility with my old OBD-I (SBEC-II) ECM. No converting to an aftermarket or later model PCM, tuning flashes, and tweaking here and there. Stock has worked great for the last 316,000 miles so I'll stick with what works.
The plan is to evaluate the cylinders. If they are within tolerances and no scoring is found on the cylinder walls, I'll leave it alone, clean it, and start building from there. The rods are in good shape as the crankshaft is I believe. According the build coding on the block it's a Standard size bearing block. I can confirm that once the crank is finished being evaluated for cracks, which most never have. The rods will be cleaned, weighed, and new pistons installed. There were two pistons available for '96-/97. One with the older 5/54-5/64-3/16 ring dimensions. The newer, lighter weight piston that had all those cracking issues with the piston skirts were shallower ring grooves and metric. The standard SAE sized pistons run about $150 as of this writing.
Other than new bearings, pistons, water pump, oil pump, expansion plugs, and gasket sets I think I'm good to get started in Autumn.
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August 17, 2025
Well the A/C repair wasn't. It leaks as bad as it did before the new condenser and drier were installed. And I still can't see any dye marking anywhere! This is very frustrating! I've ordered an A/C bypass pulley and will install it soon. We're half way through August and there's no point in throwing more money at this. Maybe next year. I'll remove the system, save for the evaporator and save some weight. The bypass pulley will allow me to keep the current drive belt in place and if I decide to try a complete rebuild of the system, well, it'll be ready. I have another engine that needs my attention to prep for this upcoming cool season.
One thing I did find was the vacuum tubing for the HVAC control cracked right at the firewall. It bleeds off fast enough for the mode to switch from anything over to defrost in a couple of seconds. So I may also be pulling the box out of the Jeep anyway for that if I can't get the heat to the floor this winter. Cold feet isn't a nice feeling. Now if that happens then I'll buy a new heater core and a new evaporator since I don't want to have to do it again anytime soon. The cores have been in there since 2018 which isn't long but you know, it's a real PITA when it has to be done. I already download Four Seasons catalog.
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