97+ Washer Reservoir Install on Jeep Comanche MJ

I’m in the process of upgradingĀ the Brake Booster and Master Cylinder on my ’89 Jeep Comanche (MJ) to a unit from ’95 Jeep Cherokee (XJ). Doing so gives me a dual diaphram brake booster and vastly improved stopping power, but the new unit is larger and creates a conflict with the washer reservoir as it is currently positioned in the engine bay. So to make room I’ve decided to upgrade to a ’97+ Jeep Cherokee washer reservoir, which is mounted inside the driver side fender. Doing so actually gives me some great options as the new reservoir is larger capacity, has two pumps (since the Cherokee has a rear wiper) and opens up more room for fun accessories in the engine bay. The only problem is I have to cut the Comanche up a bit to install the unit. This article outlines everything needed to complete the upgrade and will be a work in progress until I’ve completed the upgrade and have all of the items documented.

Items you will need for the upgrade:

  • 97+ reservoir with pumps (I got mine on amazon for $40)
  • 3/16″ drill bit
  • 1/5″ hole saw
  • Measuring Tape
  • Sheet metal cutting tool of choice
  • Silicone sealant (I use Permatex Right Stuff)
  • 2 small self tapping screws
  • 10mm socket and wrench
  • PB Blaster or similar
  • Floor Jack & Jackstand

Remove the older washer bottle

There are 3 screws holding in the washer bottle on my MJ, two on the fender rail and one on a clip within the engine bay. These are all easily removed and once pulled allows you to lift then drain the washer reservoir (if necessary). Once you’ve removed the screws you can place a container under the bottle and pull the hose off the pump. Both the line and bottle will then drain into the container. Once I drained most of the fluid out I dumped the rest out of the fill hole away from the vehicle as that was just faster and easier.

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Removing the inner fender well liner

You will need to remove the inner fender well liner to access the interior of the fender. Doing so will likely lead to you breaking off the bolts that secure the fender flare, since they’re probably as old as your vehicle. If you have the $$ you can forgo trying to save these bolts and just buy new fender mount panels (about $75 on Amazon) or you can try to pull this off without fully removing the fender well liner and simply folding it back, which will also be tough. I chose to remove the fender liner all together to make it easy. I first sprayed the bolts with PB Blaster and allowed that a few hours to soak in, but I failed to remove any of the nuts without breaking the bolts. You’ll need a 10mm socket and ratchet to remove them, or in my case snap them.


After trying removing the bolts remove the liner by popping out the retainer push holders until you’ve freed the liner. I found that many of the retaining push holders were easier to remove from the inside of the engine bay by shoving them out with a pair of pliers. Do you best to keep them from breaking as you’ll need them to put the liner back once this project is done.

Prep the new washer reservoir

One issue with the newer model reservoir is it has a hole near the bottom for the “low washer” sensor and dummy light on XJs. The MJ does not have this feature and as such the hole will need to be plugged to keep the fluid in the bottle. I went with a cheap and easy fix and just covered the hole with a piece of plastic I cut from a coolant bottle, some Permatex Right Stuff and two screws.

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Measure and mark your MJ for the necessary cuts

For the install you will need to cut at least 3 holes, if you want to get fancy, like I did, and cut the fender mounting holes too below are the measurements.

<more to come>

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