Hello all ..I'm new to these parts and I'm glad to find this forum. I was all set to get a new wrangler and saw this beautiful XJ up the street from me and now I'm on a mission to get a decent cherokee XJ as a weekend car to lift and enjoy and I'll be saving 10's of thousands. I'm the biggest noob to these but have been doing research every day. From what I read the 2000+ models have a bad head. Obviously I'd rather find the newest model I can. If I find a pre 2000, fine but I don't want to be limited. My question is that if I happen to find one in great shape, is the head the only issue? Can I just replace with an aftermarket? Yeah it's a hassle and money but I was wondering if any of you have done this? Any other issues with the 2k+ models? Thanks in advance guys!

 

I've got a 2001 XJ. Other than the fact that I unkowingly bought it with a cracked head it's been great with no issues. I did a complete rebuild on my engine with an older cylinder head and ditched the coil rail for the viper coil mod. If the cooling system is maintained and flushed the head should be fine.

 

I have a 2000 and had no issue with the head. The bore dia/piston skirt length however...

That was an issue that started right around mid 98 and seems to happen at around 220k. Mine was at 227k. I put a new engine in and she's humming along at 259k currently.

 

I have the 01 with 113K miles. No issues. Cooling system has only been flushed once since I bought it in 03. I know, that's bad. Also I put a 205* thermostat in 4 years ago to maintain higher temps fuel economy reasons. Didn't notice anything at all. Pretty much have been doing everything wrong for a 00+ model.

Apparently not all of them are cracking. I might be a lucky one.

If and when it does go, I will do the older head/viper wires mod or V8 swap.

Nothing wrong with the older Renix models either. Once you start modifying your rig, everything eventually gets upgraded or replaced anyway.

 

Heat soak is the other issue that people seem to run into. When the engine gets hot they tend to missfire for a bit when shut off and restarted in a short amount of time. You will notice most of the newer XJ guys when they wheel will leave there rig running instead of cutting it off. You can louver your hood to let the heat escape our quadratec sells a kit that is heat wrap for the plenum and injections to reduce the issue. I plan to pick up a spare hood soon to louver for summer and run the heat wrap kit year round.

 

I think '00's and '01's kinda of get a bad rap. Sure heat soak, cracked 0331 head, etc are not good things. And if you could find the right '98 or '99 probably be better but still don't think is should stop anybody from buying one if you can find a decent platform to work with at the right price. I picked up my '00 pretty cheap. Running but not really driveable. Pretty clean but with some surface rust issues on the hood and roof. AC did and still does not work but heat would melt your face off. Pretty sure I don't have a head issue. But I found a TUPY head for $50 and grabbed it anyway. Could be a $50 door stop though. Never had a heatsoak problem. Run cheapo Champions and the heat shield on top of the manifold. Most of the work I have done has been maintenance. Other then that replaced the radiator in the beginning, a starter down the road, and the front cat later on. When the cat went, started throwing a P0432, just so happened I needed a new muffler and tailpipe. So the timing was good and I just bit the bullet and replaced everything. I also have a habit of replacing things that might or might not need replacing. Like when I did the radiator I just replaced all the hoses. Kinda of a while we are here thing. Majority of the money I have spent has been on installing factory options that the Jeep did not come with.

Not that I needed to do it but since my body guy had to deal with the surface rust issues on my hood and roof I had some '98 5.9 GC Louvers cut in. Saw that other people had done it and just liked the look.


Curious what you think about your gas mileage with the 205* thermostat? I run a 195*. Around town I don't do so good. Probably about 14 MPG. But that is really my fault cause I live so close to work. But on the longer trips I have taken doing about 21 MPG.

 

The idea behind the 205* was that an engine reaching optimal temperature sooner will go into closed loop sooner saving fuel. This was well documented in another forum so I tried it.

To be honest, since I installed the 205*, There have been many changes to my rig. I moved within 3 miles of work, added 3.5-4" lift, 33x12.5 tires, roof rack, regeared to 4:56, and added heavy bumpers. My point of reference is too far back in my memory to make a reasonable conclusion if there was an advantage to installing it. When I eventually address my cooling system, I will return to stock. I might also add that my original O2 sensors might not be working up to snuff but they are good enough to pass DEQ(smog).

I fill up with gas every 2-3 weeks. Here in Oregon, the state requires an attendant to fill our tanks. Now, the attendants are not allowed to top off the tank. Once the gas nozzle clicks, they stop pumping. There are a few exceptions but this is the norm around where I live. Nearly impossible to establish a baseline for fuel mileage.

Sorry I wasn't much help with your question but I kinda gave up calculating MPG.

Nice clean rig BTW.

 

No problem. I had read the same stuff you did. One thing I noticed with my Jeep, cause I have a scanner that graphs live data, is that my Jeep gets to a closed loop status pretty quick. With the exception of a couple things (thermostat, exhaust, etc) I have done as much as I can do about gas mileage. New 4 hole injectors, all new O2 sensors, new tires, etc. I don't care. It is what it is. More a I want to Jeep to run as good as possible and figure gas mileage will follow and be as good as it is ever going to get.

Thanks for compliment. That is an older picture and I too have made some changes. Upgrades of factory options that were not original on the Jeep. Kinda of going for a European Orvis, Limted, Country, Up Country clone thing. Those gas mileage estimates are after I put a little more weight in my Jeep too. Nothing crazy. Factory skids, tow hooks, power drive's seat, etc.

Not wanting to get to far off topic I sent you a PM.

 

131k on my 2001, bought it with 130k on the clock. within 24hrs of ownership I had all the fluids changed, and within 2 weeks of ownership I had the coolant system flushed and the thermostat changed- never goes above 210, sits right below it. I haven't thoroughly examined the head but I have no symptoms of a cracked one. I would say that if you take care of it, don't overheat it- you wont have any issues with the head. I have no worries about it, im pretty strict with maintenance.


my biggest gripe with the 2001 is the emissions BS, the precats, etc..

 

Closed loop occurs when the O2 sensors start signaling the PCM, which is within about 30-45 seconds after a cold start, when the O2 sensors reach a temperature of ~650 degrees.

A 195 degree thermostat is fully open at about 205 degrees, and closed loop is achieved long before 195 degrees is reached. So, how does a higher-temp thermostat help achieve closed loop sooner at the point where both thermostats (195 and 205) are closed?

 

158K, no cracks yet. 2000 XJs with federal emissions don't heatsoak any more than '97-'99 XJs. The '00 and '01 with California emissions have the greater chance to heatsoak with the 2 extra pre-cats on the headers.

 

I'm not disagreeing with you as you are correct. Thanks for pointing that out. One of the conditions of closed loop beginning is when the O2 sensor begins to output a change. That happens when O2 sensor gets warm enough but I don't know the temperature. It did take longer than 30-45 seconds suggesting I might have a weak O2 sensor. Even though I monitored loop status with a Scan Gauge II, I noticed no change.

The information I referred to also suggested that optimal engine operating temperature (212F) also contributed to better fuel economy. It was backed up by a bunch of data from personal testing and testimony. 205* holds the temperature just a little warmer before allowing cooler water in. 205* also is supposed to get closer to optimal temperature and still leave a little buffer before overheating. It was try worthy to me but potentially a death sentence to a week 00-01 head. I thought if I break it I can fix it and put it behind me or if it doesn't then I have a good one. But that's not really a true indicator of head quality.

With my driving habits, modifications, and commute, I see no noticeable performance difference using a hotter thermostat. That's why I mentioned going back to stock. Only cost a couple of dollars to try it.

 

Yeah, you might have a weak heater on an O2 sensor if it's taking a while to reach closed loop. I won't disagree with the possibility of a fuel economy improvement with higher operating temperatures. It makes sense.

 

also not mentioned, which I find not to be a big deal- youll find one of the the weaker of the 2 front axles offered in a XJ in the 2000-2001 model years. Also youre more likely to get a dana 35 rear than the 8.25. my 01 has a d35 rear, but I don't intend on going over a 245/75 so ill be alright. the front axle also im fine with as im already at alittle over 3" and perfectly content- I heard anything over 4" that front axle doesn't like?

 

As long as you don't overheat the motor, they are just fine. If you get a 2000 or 2001, ya can't neglect the cooling system. For those the bought a used one with a cracked head...well, it was overheated at some point.