Replace water pump on Dodge truck 3.9 liter V6 engine.
Fixing A Major Coolant Leak:

Replacing The Water Pump On A
1993 Dodge Dakota 3.9 Liter V6

Also Applies To 5.2 Liter V8 Dodge Engine

 

In This Article:

The engine fan and shroud are removed. The serpentine belt is removed. The water pump pulley is removed. The lower radiator hose and heater hose are disconnected. The water pump is removed and the mating surfaces are cleaned up before a new pump is installed.

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Skill Level: 3 (Intermediate) Time Taken: About 6 Hours

By Bruce W. Maki, Editor

Start:

A couple of months ago I knew the water pump on my 93 Dakota was going to fail because I could hear a low grumbling/groaning sound from the engine. I replaced this water pump about ten years ago, so I was familiar with the sound of worn-out water pump bearings on this engine.

A few weeks ago the groaning sound got worse and coolant started leaking from around the pump shaft. It was time to replace the water pump again.

The Dodge 3.9 liter V6 engine.

The red arrow points to the water pump.

Dodge Dakota 3.9 liter V6 engine.

The first thing I did was disconnect the negative battery terminal, just to be on the safe side.

If the coolant level had been normal, I would have drained it through the drain valve on the bottom of the radiator. I use a dishpan to catch coolant, and I re-use it when the job is done.

Removing engine fan, Dodge truck.

Before doing anything else, I loosened the radiator fan from the water pump shaft.

I used a 1/2" wrench to hold one of of the 4 pulley bolts (red arrow), and a big 1-1/2" wrench to turn the hex fan shaft. (Actually, this requires a 36mm open-end wrench, which I don't have, but a 1-1/2" wrench works okay.)

The threads are normal (right-hand threads), so I turned the big wrench wrench to the left to loosen the fan shaft.

 

A view of the water pump pulley and fan shaft without wrenches in the way.

1: Pulley Bolts

2: Fan Shaft

Engine cooling fan, Dodge truck.

By leaving the serpentine belt in place, it helps to hold the water pump pulley, making it (slightly) easier to keep the pulley from turning while loosening the fan.

 

Removing The Radiator Fan Shroud:

Before removing the fan shroud, I removed the upper radiator hose. Normally I would have to drain the coolant first, but so much coolant had leaked out that the upper radiator hose was already empty.

Radiator shroud bolt location, Dodge Dakota 1993.

Using a 10mm socket and extension, I removed two screws on the lower part of the fan shroud.

The screw on the other side is just below the coolant reservoir bottle.

 

I removed two screws at the top of the fan shroud with a Phillips screwdriver. Removing radiator shroud, 1993 Dodge Dakota.

Then I just turned the fan counter-clockwise to spin it off the water pump shaft. Since the threads were not corroded, I didn't even need a wrench to turn the fan shaft.

Fan should be stored standing up, Dodge.

I removed the fan and shroud together. It's impossible to remove one without the other, (unless the radiator is removed first).

Caution: The factory service manual says to store the fan upright, NOT laying down, or else the viscous liquid inside can leak out.

 

The engine with the fan and shroud removed.

The red arrow points to the water pump pulley. The pump is directly behind this pulley.

Dodge truck 3.9 V6 engine showing water pump locations.

 

Removing serpentine accessory belt, Dodge truck.

Removing The Serpentine Belt:

I placed a 15mm wrench on the bolt for the belt tensioner pulley, and pushed to the right to release the tension on the serpentine belt.

Then I slipped the serpentine belt off the water pump pulley. It's easiest to slide the belt off a smooth pulley instead of a grooved pulley.

 

Check The Serpentine Belt Tensioner!

The first time I replaced this water pump, when the truck was just 7 years old, the pump bearings failed because the serpentine belt tensioner had failed. The tensioner had lost its springiness... it would just stick in one position.

In those days I was working as a self-employed carpenter and I didn't have much money, so paying 80 bucks for a new belt tensioner seemed unnecessary, considering the tensioner would pretty much just stay in whatever position I set it too. Well... not exactly. Over time, the belt got tighter, and I had slipped from my habit of regularly checking the belt tension. After a while I started hearing a low groaning sound from the engine, and when I wiggled the water pump pulley, it was kinda loose.

So I had to buy a new water pump AND a new tensioner. So much for saving money. Now, whenever I change the oil on my vehicles, I take two seconds to push on the serpentine belt to make sure the tensioner moves back and forth properly. What's that old saying... "a stitch in time saves nine". Or "proper maintenance surely pays off, but you won't know what things didn't break".

 

Removing The Water Pump Pulley:

Removing the 4 bolts for the pulley can be tricky, because the pulley turns freely. DO NOT hold the pump shaft with pliers! This will damage the threads.

One way to remove the bolts is to use a square-shaft screwdriver to hold the bolts while turning another bolt with a 1/2" wrench or socket.

The easier way is to just use an impact wrench.

Holding water pump pulley with screwdriver.

 

Removng water pump pulley, Dodge truck. I pried on the pulley and it came right off.

At this point I removed the radiator drain plug and let the coolant drain into a dishpan. I only had about 2 quarts come out.

I removed the lower radiator hose from the water pump. After moving the hose clamp aside, I used a hook tool (red arrow) to separate the hose from the metal. Then I pulled the hose from the fitting. Removing lower radiator hose from water pump.

 

Removing heater hose, Dodge Dakota V6. Then I removed the heater hose from the metal tube on the right-hand side of the pump.

 

I removed the idler pulley with a 14mm socket. Removing idler pulley, Dodge.

 

Dodge truck water pump shown colorized.

I "colorized" the water pump to make it easier to see.

The water pump is ready to remove.

Note that there is a "bypass" hose (red arrow) that needs to be removed once the pump is unbolted.

 

I removed the water pump bolts with a 14mm socket. A ratchet wrench (shown) is fine, but I used an impact wrench. Removing Dodge truck water pump with ratchet.

 

4 long bolts used on Dodge truck water pump.

4 of the 7 bolts are quite long (red arrows). The lower 2 of these 4 bolts must penetrate the water jacket, because coolant leaked out when I removed them.

 

First I used a small hammer to tap on the water pump, just to break the seal. Then I pried on the top of the pump and it came loose.

The pump won't fall because it's still being held by the bypass hose.

Prying Dodge water pump from engine.

 

Bypass hose on Dodge truck water pump, 1993 Dakota.

Then I used a pair of Channel-Lock pliers to squeeze the hose clamp (red arrow) on the bypass hose.

I slid the clamp upwards as fast as I could (about a half-inch).

 

I used a short hook tool to work the bypass hose off the fitting, then the water pump came off. Removing water pump from 93 Dodge Dakota 3.9 liter V6 engine.

 

Dodge truck water pump, 1993, inside view. Inside view of the Dodge truck water pump.

 

Outside view of the Dodge truck water pump. Dodge truck water pump.

 

Weep hole in lower side of water pump.

Note the wetness around the underside of the water pump. Most water pumps have a "weep hole" (red arrow) where coolant will drain if the pump shaft seal leaks.

This is clear evidence that the pump was the source of the coolant leak (besides the fact that I could wiggle the water pump pulley by hand and it would move laterally about a quarter-inch).

Often a water pump will leak without the bearings going bad and making noise, so it's necessary to crawl under the vehicle and look for signs of coolant leakage around the weep hole.

 

Cleaning The Pump Mating Surfaces:

The mounting area on the engine. I think the water pump actually mounts to the timing chain cover.

Dodge 3.9 V6 or 5.2 V8 engine with water pump removed.

 

Blowing excess coolant from engine, Dodge.

There was one problem... coolant kept dripping from those 2 "wet bolt" holes.

Coolant dripping across the mating surfaces can interfere with the gasket sealant when the new pump is installed.

So I used an air gun to blow air into the cooling passageway above the bolt hole, and coolant gurgled out of the bolt hole (arrow). Then I blew air into the bolt holes and pushed coolant the other direction. This seemed to clean out the wet bolt holes pretty good because no more coolant dripped out.

Another alternative is to bounce the front of the vehicle to create a wave of coolant in the engine, which causes some to spill out. Also, the front of the vehicle can be raised a few inches so the coolant stays back from the wet bolt holes.

 

I used a right-angle die grinder and a Roloc abrasive disc to clean up the mating surfaces on the engine.

This step is critical. Roloc discs are extremely effective at cleaning mating surfaces on engine parts, and a high-RPM die grinder is the best tool to power the abrasive disc.

Cleaning water pump mating surfaces on engine with die grinder and Roloc abrasive disc.

I've been using a pathetic little 1.5 HP air compressor in my shop (my big compressor is out-of-order) to power my air tools. The die grinder can only run for about 30 seconds before it drains the air tank, and then I have to wait for a couple of minutes for the compressor to catch up. With all that hassle, it's still worthwhile to use the die grinder because it's REALLY EFFECTIVE at cleaning.

I bought this right-angle die grinder a couple of years ago at Sears for about $60 (I think), and it's worth every penny, even though I use it only 2 or 3 times a year.

 

Heater extension tube, Dodge truck.

Before buying a new pump, I needed to remove the heater hose extension tube.

I placed the tube in a bench vise and used a screwdriver to peel away what appeared to be some type of rubber gasket around the base of the tube. Then I wiggled the water pump a bit and to my surprise the tube came out without a fight. (I was prepared to heat the pump with a propane torch to expand the metal.)

 

I buffed the extension tube on a wire wheel (mounted to a bench grinder) until the ends were good and clean. I also pried out the old O-ring. Heater extension tube after buffing.

 

Pup bolts cleaned up on wire wheel. I cleaned up the water pump bolts on the wire wheel. There was a lot of crud on the threads, and I don't want anything interfering with the bolts being tightened properly.

 

The replacement water pump had a silvery-gray coating on it, and there were some uneven spots on the mating surface, so I buffed out the mating surface with the die grinder and Roloc disc.

First I buffed the surface with a coarse-grit disc, then I made a quick pass with a fine grit disc to remove the scratches from the coarse abrasive.

Buffing mating surface of new water pump.

I also used the fine-grit Roloc disc to buff the mating surfaces on the engine.

 

Wiping mating surfaces clean. I sprayed some brake parts cleaner on a paper towel and wiped off the mating surfaces on both the engine and the new pump.

 

Installing The New Water Pump:

Just for shits-and-grins, I applied some thread sealant to the shorter bolts. I did this because there was residue of thread sealant (or thread locker) on the bolts when I removed them. Thread sealant on water pump bolts.

 

Applying gasket sealant to water pump. I brushed some Permatex High Tack gasket sealant onto the mating surfaces of the water pump.

 

Then I laid the gasket in place and smoothed it out.

I also applied a coating of High Tack gasket sealant to the gasket, but I'm not entirely sure if that was a good idea.

Applying gasket to pump, Dodge.

 

Installing new water pump, Dodge truck.

I attempted to install the water pump. First, I slipped the bypass fitting into the bypass hose and lifted upwards to force the hose onto the fitting.

Only it didn't happen that simply.

I had a heckuva time getting the bypass fitting to slip inside the hose, consequently the bolt holes wouldn't line up. I realized that the hose clamp on the bypass hose was too close to the end, preventing the metal fitting from entering the hose far enough.

I tried using Channel-Locks to move the hose clamp upwards, but there was very little room above the bypass hose. I still couldn't get the bolt holes to align.

This is where the second coat of gasket sealant became a problem... the gasket kept sticking to the engine and peeling away from the pump while I fought to get the pump holes aligned. When I pulled the pump off for a minute, I noticed a bare spot in the sealant. A short 2-inch strip of gasket had delaminated and stuck to the engine. So I dabbed more High Tack on the thin section of gasket, cleaned the little scrap of paper gasket from the engine with brake cleaner, and hoped for the best.

Praise For Permatex® High Tack™ Gasket Sealant:

When that little section of gasket peeled away, I figured the thin spot would leak once assembled. But after driving the truck for a few days, I had no leaks. Permatex High Tack Gasket Sealant is apparently good enough to fill in the low spot in the gasket and resist leaking.

 

On the second attempt, I placed one bolt into a hole, on the left side (far away from the bypass hose). Then I could let go of the pump.

Then I used Channel-Locks to move the hose clamp downward, onto the end of the bypass hose. While holding the hose clamp open, I pushed the pump upward (a helper would've been a nice luxury) and the metal fitting slipped inside the bypass hose a little farther, enough to get the pump holes aligned with the engine holes.

Bolt placed in pump mounting hole to align pump.

Then I installed the 3 short bolts. One goes on top in the center, and the other 2 go below the pump shaft.

Next, I installed the upper 2 long bolts.

Applying thread sealant to underside of bolt washer. The final 2 long bolts are "wet bolts", so I applied some thread sealant around the underside of the washer.

 

With all the bolts in place, I tightened them snug with a 14mm socket, while working in a criss-cross pattern.

After the bolts were snug, I tightened them to about 30 foot-pounds.

Tightening water pump bolts, Dodge truck.

 

When I replaced this pump ten years ago, I didn't have all these problems because I removed that little bypass hose to replace it. Getting access to the other end of the bypass hose requires removing the big bracket above the water pump. That bracket holds the A/C compressor and the alternator, so I guess I must have disconnected the wires to the alternator (I know I didn't disconnect the A/C lines) and moved the whole assembly aside. I don't recall all the details of the job, but I must have disconnected the throttle cable at the throttle body, because the cable gets in the way of the A/C plumbing

I had no major grief at all when I replaced this pump before... I remember thinking "this is pretty easy". So if you have the slightest temptation to replace the bypass hose, it will make the pump installation go much more smoothly and you won't have to worry about having the gasket slide around or getting dirt behind the gasket.

 

Heater tube with new O-ring, Dodge truck.

The new pump came with an O-ring for the heater extension tube.

I applied some antifreeze to the O-ring and inserted the tube into the water pump.

 

I had very little confidence in this O-ring not leaking, so I applied a bead of automotive silicone around the connection. Applying silicone around heater tube, Dodge truck.

 

Replacing Hoses?

The first time I replaced this water pump I did the smart thing... I replaced all the hoses: The upper and lower radiator hoses, the little bypass hose, and the heater hoses. At that time the truck was only 7 years old and it made sense to invest in new hoses. The reasoning is simple: While I've got the cooling system torn apart, why not just spend a few extra bucks on new hoses. The additional time is minimal.

It's also a good time to replace the serpentine belt.

This time, the truck is 17 years old, has 184,000 miles on it, and the vehicle is only worth about 500 bucks. Since the body is starting to rust badly, I'm not going to sink any unnecessary money into the truck. At this point, I'm just going to "drive it into the ground". But this Dodge just won't die.

 

Re-Assembly:

I connected the lower radiator hose to the water pump. To make this easier, I dabbed some anti-freeze around the metal where the hose attaches.

I replaced the radiator drain plug, while there was nothing in the way.

Dodge 3.9 V6 engine with new water pump.

I installed the water pump pulley, using a 1/2" socket. I did NOT use my impact wrench here... I could easily over-tighten the bolts. These are supposed to be tightened to 20 foot-pounds. I used a square-shaft screwdriver laid across the face of the pulley to hold the bolt heads.

I installed the idler pulley with a 14mm wrench.

I installed the serpentine belt, using a 15mm wrench to rotate the belt tensioner.

Next I replaced the radiator shroud and fan.

I filled the radiator and overflow bottle with coolant and burped the system to remove air.

Burping Air From The Dodge Truck Cooling System:

As usual, burping the air out of the cooling system wasn't easy. I ran the engine until the temperature gauge showed a normal reading. But the upper radiator hose was still cool, which told me that the thermostat was not yet open. Also, the heater return hose (the one I had to disconnect from the pump extension tube) was only slightly warm. The cooling system was air-locked.

I shut off the engine and removed the heater return hose from the pump extension tube. I could hear gurgling as coolant flowed towards the opening. When I opened the radiator cap, coolant oozed out of the extension tube within a few seconds. I replaced the hose. I started the engine and watched the coolant through the radiator fill opening. To my surprise, the coolant was moving sideways, slightly. The upper radiator hose was hot, too. I think what happened was this: the thermostat finally opened... but not because it was surrounded by hot coolant, but just because the hot metal parts of the engine transmitted enough heat to the thermostat to cause it too open slightly and allow coolant (and air) to pass through. Within a few minutes, the coolant level in the radiator had dropped, indicating the removal of trapped air.

I've seen this problem with a lot of V6 and V8 engines: the thermostat is located in a high spot on the intake manifold, so air gets trapped around the thermostat. But if the t-stat is not bathed in hot water, it won't open to allow the air to flow to the radiator and escape. It's maddening... you run the engine for 20, 30, 40 minutes and air remains trapped. This experience gives me an idea: get the engine hot then shut it off for about 5 to 10 minutes, then restart and see if the coolant is flowing laterally in the radiator.

 

More Info:

Tools Used:

  • Basic Mechanic's Tools: Ratchets, Extensions
  • Sockets: 10mm, 13mm, 14mm
  • Wrenches: 1/2", 13mm, 14mm, 15mm
  • Phillips Screwdriver
  • Pry Bar
  • Curved Hook Tool
  • Gasket Scraper
  • Impact Wrench (Optional)
  • Air Compressor
  • Right-Angle Die Grinder With Roloc Abrasive Disc
  • Air Blow Gun
  • Drain Pan

Materials Used:

  • Water Pump, NAPA part no. 58-481
  • Gasket (included with pump)
  • O-Ring (included with pump)
  • Permatex High Tack Gasket Adhesive
  • Thread Sealant
  • Antifreeze
  • Brake Parts Cleaner

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Written April 29, 2010