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What is the most important tip you'd share with MJ owners?


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always have a parts rig in your driveway..or 3.

My 89 4.0 Comanche has 343K and still runs like a top. 

Upgrade your ground cables!!!   Recommend doing the WJ/XJ brake booster conversion. It makes your stopping power so much more.   Replace the hard vacuum lines with rubber hoses of the same inside

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On 1/20/2009 at 8:16 PM, Pete M said:

--Please do not ever spend any money on a Peugeot transmission (manual trans behind 87-89.5 4.0Ls) beyond new gear oil. It is a weak transmission with very expensive parts. Look into an AX-15

 

With this being said I'm having trouble finding an ax15 to swap that won't cost me an arm and a leg any recomendations/will one out of a dakota work

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33 minutes ago, Vandenborg1 said:

 

With this being said I'm having trouble finding an ax15 to swap that won't cost me an arm and a leg any recommendations/will one out of a dakota work

 

far as I know, the ax-15 in a dakotas was only offered in 2wd 4 bangers.  have you tried car-part.com yet?

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On 12/20/2017 at 8:33 AM, Kickin’Chicken said:

Dang! My tip would be to not read this thread. I'm more worried now than a long-tailed cat in a room full of rocking chairs. :laugh:

HAHAHAHA! I'm here reading this carefully at 2am !!! running outside with a flashlight to check small things cause of this thread! better safe than sorry! 

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  • 3 weeks later...

I haven't seen anyone talk about this here, but based on my experience with XJ's and my MJ, the cooling system for the engine is the Achille's Heel of the vehicle.   Not taking care of your cooling system can result in getting stranded somewhere (which is annoying) or, worse yet, an overheated engine with head cracks and/or head gasket issues, (which is expensive).

 

Take care of your cooling system:

  1. keep the coolant clean, and use distilled water when mixing the antifreeze
  2. keep the radiator in good shape.  One that has corrosion in the tubes cannot transfer heat.  Keep dirt/bugs our of the fins by washing it with a hose nozzle once in a while
  3. watch your hoses for soft spots or bulges
  4. use a good working pressure cap on your cooling system.   The ones in the "closed" systems are especially prone to failure, as is the plastic pressure tank.   A cooling system that won't hold pressure will overheat sooner.
  5. keep the factory shroud for your mechanical fan installed as from the factory.  It helps the fan pull air through.
  6. this has been mentioned before, but DO NOT change your thermostat to something with a lower rating than the 195* original level.   A lower temp. thermostat WILL NOT make your engine run cooler.
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  • 3 months later...

Because it came up that another member nearly lost a wheel, which is also a thing that I’ve had happen a few years ago, I’ll add tire rotations to the mix. 
Rotating tires is done to ensure even tire wear across all corners of the vehicle. Unevenly worn tires may have different diameters from each other. This can increase stress on differentials, and in extreme cases can affect braking performance. You also probably want the most life out of your tires that you can get.

I rotate tires every oil change. It’s a good way to remember to do it frequently (assuming you change your oil regularly which if you don’t, change that)

If you have directional tires (winter or performance street tires frequently are directional, some other tires are as well) then you’ll want to swap tires front to rear, keeping them on the same side of the vehicle.

If your tires are not directional, I like to move the rear tires to the front on the same side, and cross the fronts over to the opposite side  on the rear.

Keeping the pattern consistent each time ensures all tires will see all positions on the vehicle, which helps with consistent wear. Some people like to include the spare in their rotation, but I believe the spare tire should always be the best tire, so I prefer to only use it sparingly. (See what I did there?) Tire rotation is a good time to check the pressure in the spare. It would suck to have a flat and find out your spare is also flat. 

 

Once you’ve got your tires rotated and they’re back on the ground the most important step is to torque the lug nuts. Use a torque wrench. If you don’t have one, they’re not super expensive. Torque spec per the MJ and XJ owner’s manual varied from ~70 to 85 lb-ft with no real change in the components involved. I go 85 if I’m using my good torque wrench that gets recalibrated, 100 if I’m using the cheap one that I carry around, because I don’t trust it’s calibration... but exceed manufacturer recommendations at your own risk. Loose lug nuts can always be tightened, stretched or cracked studs need replaced.

The second most important step is to retorque the lug nuts after 20-30 miles. Even if they were correctly torqued before, the wheel may not have been correctly seated on the hub, or there might have been some dirt or debris on the wheel mounting surface preventing it from seating. Driving wobbles the wheel around a bit and gives the dirt a chance to escape and the wheel to seat itself. You want to retorque after this because if something works out, your wheel is now loose. Loose wheels kill.

Use a good floor jack to lift your vehicle to pull the tires off. Chock the tire opposite where you’re lifting. The spare tire jack on most vehicles is intended for the odd emergency use and will not hold up to regular use, they’re not very stable, and reasonable floor jacks are cheap. Once the vehicle is up in the air, support it on good jack stands, or at the very least get something under the vehicle to stop it from crushing you if it falls. You can’t drive your MJ if you’re dead.

 

Rotating tires also gives you the opportunity to see how other components are doing. 
Firstly lug nuts. Looking at them let’s your know they’re still there. Spinning them off regularly helps keep the threads clean of rust. If you have trouble spinning a nut down the threads by hand, run a thread chase down it. If that doesn’t help, replace the nut. If that still doesn’t help, replace the stud. Bad threads could indicate stretched or bent studs. At best they indicated rusty nuts that are likely to seize up on you. It’s better to find out about seized lug nuts in your driveway than at the side of the road with a flat tire, and have them snap off. If you’ve got one bad stud it’s good practise to also replace the studs next to it, but when you’re doing 3/5 on one corner, you might as well replace the others. 
Some people will recommend an anti-seize product on the threads to prevent this, however most manufacturers do not. In fact they mostly recommend against it. I’m going to say the manufacturers know better than I do so I’ll follow them. At any rate, if you keep the threads in good shape it becomes a non-issue.

 

Rotating tires also gives you a great opportunity to inspect your brakes. Not just for wear surfaces, but also to make sure everything is moving as it should. It’s also an excellent time to adjust your drum brakes.

Even with automatic adjusters, I find most people don’t reverse often enough or stop hard enough in reverse to actually adjust them. Adjusting them manually also makes sure the adjuster screws aren’t seized. I usually adjust them so the shoes are just barely loose enough to slide the drums over, then once the wheels are back on get out to a safe place where I can get up to 15mpg or so in reverse, and give a few hard stops to dial them up the rest of the way on their own. Sometimes I do that between oil changes if I feel the brakes are getting suspect. It goes a long way.

 

Rotating tires is also a good time to check for suspension or steering component wear. If you’ve got the wheel off the ground and snug, give it a wiggle in all directions, make sure there’s no clunks or free play anywhere.


Lastly, rotating tires is a good way to inspect the tires. It can be tricky sometimes to see the entirety of the tire when it’s on the vehicle. When they’re off, check for nails other other things in the tread you haven’t noticed, and damage to the inner sidewall.

 

Better to find out about stuff in the driveway than doing 70mpg down the freeway. Those four little contact patches of rubber are literally the only things keeping you on the roads and trails. It’s best to look after them.

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Two things... 

The first being if you are having any running hot problems, the MJ and XJ stock radiators tend to be a little to small for long runs, get hood spacers, https://www.ksuspensionfab.com/store/p3/1"_XJ_Hood_Spacers.html#/ I threw some on mine and it ran great. Along with that very little FOD got into the engine bay, and it still opens and closes easy.

 

The second thing, lift and speed don't mix... always be careful, I got to comfortable and.. uh... decided to not keep the tire on the pavement. Ill live, and the LRM( Little rainbow monster(she is six different colors)) will live as well. 

Copy of Resized_20191201_142302 (2).jpeg

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I know it's a weird tip but it works. Vaseline, yup good old petroleum jelly, it's great for holding marts together, things like needle bearings in a transmission, weird little plastic parts that move against each other (high beam switch slider in wiper switch). Super handy plus it's fun to say!

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  • 1 month later...

When you get your MJ, take the interior out and pressure wash the outside and engine bay of your Jeep. Also, be sure to check over all of the old wiring for spots where mice have chewed wires, any melted connectors, or stuff just not plugged in. And check over your vacuum lines.

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  • 3 weeks later...
On 1/22/2009 at 12:54 AM, Str8OuttaBallard said:

If your a city-slicker and like to wheel in the woods or ORV park always remember a spare door key...

 

If your a city-slicker and park on the street buy a steering wheel club and use it...

 

If you blow through ball joints switch to Moogs...

 

If you have the Renix cooling system get rid of it! it's easier to fix than a newbee would think!

 

for wheels and tires Discount tires has been good to me...

 

If your truck gets fender bendered and the person that hit you leaves a note get a written estimate for repair and see if the person that hit you will pay out of pocket... then do the the work your self and put the money elsewhere into your rig!

 

 

What exactly do you mean renix cooling system

 

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87-90 4.0 MJs had a closed system that can be a challenge to burp.  best way is to point the nose downhill and carefully unscrew the temp sensor at the top/back of the head on the drivers side to bleed the air out.  do not do this with the engine hot, but having it running can help push the bubbles out.  don't completely unscrew the sensor.  only enough to let air escape and then tighten it quickly once the hissing stops.

 

the other potential problem is that any leak in the system can cause overheating.  being a 30 year old truck means the parts are old and especially the pressure bottle and its cap (it's not an overflow bottle, though it looks like one) should be replaced if they look nasty as preventative maintenance.  :L: 

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When looking to buy an MJ, be sure to look at the condition of the body, check for rust and bodyfiller. These are 29 year old trucks at the youngest, so hidden damage is very possible.

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45 minutes ago, 89 MJ said:

When looking to buy an MJ, be sure to look at the condition of the body, check for rust and bodyfiller. These are 29 year old trucks at the youngest, so hidden damage is very possible.

 

yup, bring a fridge magnet with you :L: 

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Don’t force crank your windows, i tried using shin-etsu grease from the honda dealership $14 on the rails/sliders and i can now crank my windows up and down like butter if you can try it night and day difference


1989 4.0
Renix
Scratchy Ba/10
2wd
Stock
Short bed base

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The resister wire on my 91 went bad and caused all kinds of havoc. The truck would intermittently fail to start when hot. Replaced almost everything in the ignition system before I caught the fact that the resister wire running along the side of the engine block was the problem. I added a $5 part from Auto Zone and 3 feet of standard wire to replace the resister wire on the truck. No problems since.

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On 12/22/2020 at 5:58 PM, Pete M said:

87-90 4.0 MJs had a closed system that can be a challenge to burp.  best way is to point the nose downhill and carefully unscrew the temp sensor at the top/back of the head on the drivers side to bleed the air out.  do not do this with the engine hot, but having it running can help push the bubbles out.  don't completely unscrew the sensor.  only enough to let air escape and then tighten it quickly once the hissing stops.

 

the other potential problem is that any leak in the system can cause overheating.  being a 30 year old truck means the parts are old and especially the pressure bottle and its cap (it's not an overflow bottle, though it looks like one) should be replaced if they look nasty as preventative maintenance.  :L: 

 

 

MACS 1987-1990 Jeep Cherokee Aluminum Coolant Tank
$139.99

All aluminum jeep coolant tank for 1987-1990 Jeep Cherokee, Tank comes with new pressure cap
OEM Aftermarket:1987, 1988, 1989, 1990, JST001

 

 

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  • 1 month later...

I 2nd what jeepsouth said, one of the best purchases I have made. My bottle lasted a long time but replaced the cap many times and when the bottle finally split I just didn't want to deal with the plastic anymore.

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  • 3 weeks later...

Ive been looking for this forum because i had a tip i don't think got mentioned!

 

Drop and inspect your spare tire and the cable/hoist assembly!!

They rot out, the cables can snap and losing your spare on the highway is not fun! Ask me how i know.

Maybe grease the cable every once in a while to keep it from rusting if it looks good

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