Not too much drama here.  Last summer I noticed that the Jeep would sometimes turn over a little slowly.  Well, one windy December (2008) morning, Angela was trying to get ‘er running to get over to work, and it wouldn’t even crank over.   So, we all knew what time it was…battery time!

An OE battery that lasted 5 years and 49K miles doesn’t owe you anything, in my opinion.  I replaced it with an Autolite 84-month battery I got at Murry’s.  I spent about $80, and life is good again.  I’m going to wait until the weather is warm again and make sure I thoroughly clean the battery terminals off; I knocked some corrosion off with my screwdriver, but it’s just too cold to mess with right now.

After airing all the tires up yesterday, I walked out this morning and discovered the driver’s side front had gone flat.  It turned out the valve stem wasn’t seating properly.  Well, when I pulled the wheel off to fix that, I took a look at the front brake pads, and it looked like there was nothing left.  Yikes!  Time for a quick brake job.

Well, appearances clearly were deceiving.  There was at least 50% of the front pads left, but the design of the caliper makes it difficult to tell.  May I say, however, that I’ve never run across a better designed  brake caliper than these.  Two bolts remove the caliper piston assembly (it’s actually a dual piston setup), and then the pads easily slide out of the carrier without removing it!  Even better, the pads are identical, so there’s no need to keep track of what came from where.  Even in 20F temps today, it was a very painless brake job; about 20 minutes per side including jacking and R&R of the wheel.  I did not touch the rotors; I mic’d them and they were good, their surfaces were smooth except for a small ridge at the outer periphery of the inside on both, and I just didn’t see the point of having them machined; they weren’t warped.  So it was a $20 brake job.  Not too tough to take.

Trans fluid change

Well, I finally got the chance to change the transmission fluid this evening.  It was fairly straightforward; lift the Jeep up a little to make it just a tad easier to crawl under, put the drain pan down on top of the big “baking sheet” drip catching pan I have, drop the pan too fast and make a mess anyway…

I changed both of the transmission filters.  There is the usual, flat filter that bolts to the underside of the valve body, and then a very *unusual* spin-on type filter that goes on near the point where the cooling return line comes into the front of the trans.  It is actually up inside the pan, sort of forward and to one side of the valve body, and is shaped like a miniature oil filter.  Trouble is, it was a bit “stuck” and ordinary hand pressure wouldn’t break it loose.  It was too small for the cap style oil filter wrench I have.  So I tried my largest pair of channel-lock style pliers, but they weren’t big enough.  Finally, I hit upon the solution: I used one of my 8″ C-clamps as an ersatz wrench.  It was a little clumsy, but it worked great!

Note that there is an oil seal ring for the normal transmission fluid filter that must be replaced.  There are lots of warnings to not put that ring onto the new filter’s tube and just jam it into the underside of the trans.  Apparently they will get loose and cause all sorts of trouble.  Prying the old one out was no joy; it’s a tight fit.  I had to have the secondary spin-on filter removed to get to it with a small screwdriver, but it finally popped off.  Next, putting the new one in required pressing it in place and tapping it with the butt end of a hammer handle.

Other than those things though, a very simple, straightforward, if messy fluid change.  It took about 7½ quarts of transmission fluid before it was finally filled up, so I’ll have to remember to have plenty on hand.

Oil Change

While I was at it this evening, I also changed the oil.  At 41K miles, it was due to have the original synthetic 5W30 swapped out, and Angela needed the Jeep to go to Wisconsin for her dad’s surgery.  So I went down to the quickie lube place and had them throw in regular 5W30 to get it through that trip.  (The Jeep apparently performed great in the 12″ plus snowfalls they had out there, by the way.  She said it just kept right on going with no drama.)  So we were at the 3,000 mile mark on this dino oil a couple of days ago.  Knowing I would have the evening free, I stopped by Walmart and picked up 6 quarts of synthetic.

Now the subtext to this is that gas has hit $4.00 a gallon, and of course, the Jeep being what it is, it averages 12-13MPG in the city, where it gets most of its use.  I’m cool with that; I knew that’s what it would be like, so no worries, but it needs to be kept tip-top so we’re not wasting anything, either.  So I decided to try Mobil 1 0W30 this time because of its advertised fuel saving benefits.  It’s the same price as the 5W30 synthetic, so even if it doesn’t do a thing for fuel economy it will at least not cost anything extra.

Finally, I swapped the air filter out too.  It was fairly dirty, and certainly could use the change.  They’re a bit pricey for this thing at $15 though.  The air filter is a Fram; the oil filter is a Mopar, just for the record.

Old News

About ~1,500 miles previously, I noticed that I hadn’t managed to cure the Jeep of the leak at it’s rear axle last summer.  Upon closer inspection, I realized that it was leaking at the pinion seal, rather than at the back cover as I first thought.  I checked with a friend and found out that the powertrain warranty would cover it, so I took it over to Monicatti and let them work on it.  They noticed that the front outboard axle seals were leaking, as well as the outboard seals on the rear in addition to the pinion seal, so the Jeep got treated to a bunch of new seals for the $100 deductible.

We had a warm day about a week and a half ago, so I took advantage of it and changed out the fluid in the transfer case, using the stuff I bought for the purpose last summer.  I also rotated the tires on this same day, after noticing that the driver’s side tires were 3/32nds of an inch more worn than the passenger side.  I rotated the spare onto the driver’s side rear, and swapped the two front tires for each other, leaving the passenger side rear tire where it was.  Hopefully this will cure the odd “slewing” of the vehicle to the left in the snow that I noticed during our first big snow storm.

The only maintenance left to do for now is a trans fluid change, as well as the 6K-interval oil change that I’ve decided to go with.  I already have the trans fluid and both filters; I just need another warm, dry day…

Recently, there has been an intermittent problem with the oil pressure gauge showing 0 PSI, and the “check gages” warning light coming on.  Sometimes the gauge would just start working afterwards without our doing anything but just driving it; other times the problem would persist through several stops and restarts of the engine.

The OBD-II code indicated that the sensor voltage was measuring too high.  At this point I was starting to wonder how to troubleshoot this; I haven’t been successful so far in finding a reasonably priced used factory shop manual lately.  I finally gave in and spent the $25 for a one-year AllData subscription, knowing that using it just this once would be enough to pay for itself compared to taking it into the shop.

The bottom line is there are a number of tests you can perform, but the most likely outcome is that the sending unit was shot.  I looked at the wiring and didn’t see any evidence of frayed or worn insulation, so I decided to “shotgun” it and throw a new sensor on.  Rock Auto had them for about $15 plus shipping.

While I was at it, I looked through the AllData material and found that I was about 8,000 miles overdue for spark plugs!  I would have thought this vehicle would have 100K-mile plugs, but it turns out it doesn’t.  I ordered those up at the same time; my total with shipping was about $33.

Naturally the oil pressure sending unit was inaccessible with a crescent wrench.  I measured the new one and discovered that I needed a 27MM deep-well socket to get the old one off.   That cost $8.

So, it’s been three days since the swap (done late on Saturday night over Thanksgiving weekend) and the problem hasn’t resurfaced.  It seems fixed.

The sparkplugs were interesting.  For one thing, the OE plugs were *completely shot*.  There wasn’t much electrode left at all; I expect that the truck would have begun to stall sometime in the next 5,000 miles.  For another thing, they’re accessible from the upper side of the cylinder heads, instead of being tucked down underneath the exhaust manifolds.  I didn’t have too much trouble replacing them, but the #8 plug (rearmost on the passenger side) was a bit of a pain; it took as long to do that one as it did to do most of the rest.

I pulled the battery terminals off while I was in there and cleaned them up.  They weren’t corroded, but the posts weren’t shiny.  The cold cranking performance improved considerably after the new plugs and refreshed battery connections.

I’ll have to remember to change those plugs again at 68K miles.

With an average price of $3.20/gallon lately, the Jeep has proven to be pricey to keep on the road. Average calculated fuel economy has been 13.7 MPG.  The trip computer consistently returns higher MPG figures than what I’m observing; I’m not sure why this is.

Having an 8-cylinder SUV during a time of record high gas prices might seem painful, but it has more than made up for it in terms of its performance and capability. I recently borrowed a neighbor’s trailer and towed it behind the Jeep to the scrap metals yard to dispose of an engine block and various other hunks of scrap steel and aluminum; the Jeep acted like it didn’t know the trailer was back there. It’s been quite adept at the light-duty curb hopping and field crawling I’ve put it through recently…more just because I could than out of necessity   And of course, it generally wins the stoplight races and freeway merge contests one gets into in metro Detroit.

A few other notes: The Jeep was changed over to Mobil 1 15K 5W-30 Synthetic when it hit the 3,000 mile mark. Hopefully this will perhaps ease the fuel economy situation, but my real hope is to make cold starts in the wintertime easier and less damaging to the engine. I also replaced the rear differential fluid after discovering a leak that necessitated resealing the diff cover. I used the correct 75W-140 synthetic fluid as well as the Mopar limited-slip additive. It was a messy job!  I have the necessary filters and fluid to change the transmission fluid, and I also have the fluid to change out the transfer case fluid.  I will get to these non-urgent matters as time permits.

Finally, I have discovered the beginnings of some rust along the bottom of the driver’s door at the seam. I will have to wait a bit until I get the necessary cash, but I’m going to have the dealership sandblast and repaint the bottom edge of the door, and then undercoat the entire vehicle. More on this when it gets done, hopefully before the onset of winter.

The Jeep is equipped with Chrysler’s Sentry Key system. What this means (as stated in an earlier post) is there is an RFID chip embedded in the head of the ignition key which is coded to the truck. If a thief hotwires the truck, or breaks the ignition lock cylinder, the engine will start up briefly as the remote keyless entry system transponder attempts to locate the RFID chip. If it doesn’t receive a response from the correctly coded chip, it will shut the ignition down in two seconds. The delay is designed to prevent unburned fuel from entering the exhaust system.

Chrysler uses this system both to enhance the security of the vehicle as well as to enable themselves to bypass certain federal regulations regarding marking individual vehicle parts as an anti-crime (think chopshop) measure. By demonstrating to the federal government’s satisfaction that the system is extremely difficult to defeat, they avoid some of the costs involved in following other governmental mandates.

Anyway, the byproduct of this is that the ignition key is special, and not generally available down at the local hardware store. I’ve heard stories that the keys are available from dealerships at inflated prices. Monicatti Chrysler Jeep quoted me $50.50 for the key blank, plus a $12 programming charge.

I was able to locate an aftermarket key blank on eBay for $8.99, plus shipping, which brought the total to under $17. Lowes cut the key for free. The next step was to program its RFID chip’s ID into the vehicle’s computer.

Fortunately it’s simple — if you have both keys. (If not, you’re out of luck and will have to visit the dealer or a locksmith.) You start out by inserting the first ignition key and turning it to the ‘run’ position for not more than 15 seconds, but not less than 3 seconds. Don’t start the truck. Next, switch it off, and insert the second key. Switch it to run, and wait for the sentry key symbol to flash on the dashboard, indicating the vehicle has entered “customer program mode”. Once that happens, switch the second key off, and insert the key you wish to program, and switch it to ‘run’. Wait up to 60 seconds, and there will be a brief chime. Congratulations, your new key has been programmed in the vehicle computer. According to the owner’s manual, you can do this for a maximum of 8 keys.

I had no trouble doing the above. Since you need to have a minimum of two programmed keys to make it work, it’s probably a good idea to always have three keys in case one gets lost.

I got into the Jeep last night and went to adjust the pedals using the switch on the dash.  Hmmm…it didn’t work.  Even weirder — the switch felt loose in its mounting.

I made my short trip and then sat in the driveway and looked this over.  The switch is mounted in a removable panel that’s right above the steering column.  I popped the panel loose with a little finger pressure and had a look.

It turns out the switch is a relatively simple rocker affair with a pair of contacts.  The contacts are in one half of the assembly, the rocker in the other.  The pressure on the rocker from people using the switch had caused the two halves to separate, breaking one of the tiny plastic tabs holding the works together in the process.

So I dismounted the switch, disconnected it from the harness, and brought it inside the house to play with it.  (It was 30F outside, and pitch dark.)

I found that the components were all there, save the broken tab, but it wasn’t going to hold together on its own without some help from me.

After digging around and finding my tube of epoxy empty (so THAT’s what’s making the shelf all sticky!) I finally decided to try a little Super Glue.

Whaddya know, it worked fine.  I remounted the switch and all is well!

The Jeep has an AutoMate remote starter which was installed by the previous owner.  When I took delivery, I asked the salesman how to operate it.

He played with the keyfob, and managed to get it to start, but it would immediately die out.  When we looked at the dashboard, the Sentry key symbol was flashing as it quit.

It turns out there is an RFID chip in each key that is coded to the Jeep.  Without the presence of the chip, the body controller assumes the truck is being stolen, and so it shuts the vehicle down after two seconds.  The two seconds of runtime is designed to purge unburnt fuel from the cylinders to prevent a flooding condition.

The remote starter has a bypass designed to defeat this.  Essentially, the installer places an RFID chip near the ignition lock cylinder which is somehow controlled by the remote starter module.

I didn’t know all of this, of course — not having had a vehicle with an aftermarket remote starter before — so I called around and found out that ABC Warehouse deals with Directed Electronics products, the makers of Automate.  I took it over to the location on M59, and asked for them to look at it.

$31 later and a quick tweak — placing the defeat device nearer to the lock cylinder — had the remote start working once again.  Apparently the installation was a little sloppy, and the chip had fallen down into the steering column.  At the same time I had the installer point out the so-called “valet” switch to me — it’s dangling from its wires just underneath the dash near the steering column.

I think I might find myself going in later and cleaning up the installation a bit.

Jeepin’ will follow the travels of a 2004 Jeep Grand Cherokee Limited (WJ) in suburban America.

We just purchased our Grand Cherokee two days ago from the used lot over at Monicatti Chrysler-Jeep in Sterling Heights, Michigan.  It is charcoal-gray, with a charcoal-gray leather interior, and has around 32,000 miles.  Equipped with the 4.7L V8 and Quadra-Drive, it is close to, but not quite at the top of the line Overland’s equipment level.

Like most SUV purchasers, we do not expect to use our Grand Cherokee for much other than the most incidental, light off-road travel.  Although it apparently is enormously capable,  it’s really more of a bad-weather commuter and get around town vehicle.  An inspection of the underside of the truck did not reveal any scrapes or dents whatsoever, so it has probably never seen anything more rugged than a gravel parking lot.