Cooling System Repairs :

Replacing A Water Pump
On A 4-Cylinder Dodge Dakota

Chrysler 2.5 Liter 4-Cylinder

 

In This Article:

A water pump is replaced after the serpentine belt and several pulleys are removed.

Related Articles:

Skill Level: 3 (Intermediate) Time Taken: About 8 Hours

By Bruce W. Maki, Editor

Introduction:

The first sign of trouble had nothing to do with the water pump. The initial problem was that the engine ran terribly rough whenever it rained. This would be understandable if I drove fast through a puddle and soaked the engine, but the truck would barely run after just being started. The engine would stumble and bog down under load, but ran better if I revved it up. I knew that was a sign of an ignition system malfuntion.

Sure enough, the check engine light came on, and I used a code-reader to determine that the computer had detected a misfire on two cylinders. Weeks before I had noticed a coating of slippery grime on the distributor cap, and when the air was humid I could see tiny water droplets on the cap. When I removed the distributor cap I found more water droplets on the inside.

What's Up? The grime was dried-up antifreeze, which was leaking from someplace around the engine. Antifreeze has a funny property... it is hygroscopic, which just means that it can absorb water from humidity in the air. When the grime absorbed water it became conductive, causing the ignition spark to be shorted to ground instead of going to the spark plug.

I initially figured the coolant was leaking from the radiator, but I discovered that the leak was the water pump, because the pump failed while I had the truck idling in my garage. What luck!

Truth be told, the engine had been making some low grumbling sounds for six months, but I neglected to check it out. I had pulled the truck halfway into the garage to add air to the tires, and I also listened to the engine noise. I noticed that the water pump pulley would ride in-and-out as it turned. "I need a new water pump" I said to myself, as I walked around the truck to drive it further into the garage. Just before I could open the driver's side door the engine started making this loud screeching/squealing sound. It sure picked a good place to conk out.

 

Picture of engine area.

The water pump is hard to see... all you can see is the pulley.

 

Identifying The Water Pump On A Dodge 2.5 Liter 4-Cylinder:

The water pump is almost completely hidden behind a large black pulley at the front of the engine. As on most engines, the water pump is driven by a rubber belt.

Most newer vehicles use a poly V-groove serpentine belt to drive the water pump, alternator, power steering pump, and air conditioning compressor. Of course, there needs to be a pulley on the front of the engine crankshaft to drive the serpentine belt.

 

 

Idler pulleys are used for several purposes, such as belt tension adjustment or to increase the number of degrees that the belt wraps around a pulley. For example, a belt that wraps less than halfway around a pulley cannot transfer as much power as a belt that wraps three-quarters of the way around the pulley.

 

The Major Symptom Of Trouble:

I could grab the water pump pulley and wiggle it. This pulley should rotate freely but not move in-and-out or side-to-side.

 

(Another shot of water pump and power steering pump)

 

Step 1: Draining The Coolant

This is the back side of the radiator. The radiator and cooling system must be drained before the water pump is removed.

 

Way down at the bottom of the radiator is a drain valve (red arrow).

 

 

I opened this valve by hand and coolant flowed out.

Sometimes a radiator drain valve is difficult to open. These plastic valves are easy to break, so use caution.

 

Removing the radiator cap makes the coolant drain quicker because air can get into the cooling system.

Also, I set the heater temperature control to warm, which lets the coolant drain from the heater core.

 

Step 2: Removing The Serpentine Belt

This bolt head is the adjustment for the serpentine belt tension.

The V6 and V8 Dakotas use a spring-loaded automatic tensioner, but the 4-cylinder Dakota uses this cheaper screw adjustment.

 

(Note about loosening the bolt in idler pulley to allow adjuster to work.)

 

I backed off the adjuster bolt and the belt became loose.

 

The back side of the tension adjuster has a block of metal that is moved by the adjuster screw. This block slides in a groove, and the whole mechanism gets corroded.

 

After I got the belt off, I took it in the house and washed it with soap and water to remove the antifreeze residue. I rinsed off all the pulleys to clean off the antifreeze.

 

Removing The Power Steering Pump:

I used my impact wrench with a 13mm socket to loosen the 3 bolts that held the power steering pump.

I tried to loosen one of these bolts with a ratchet wrench but it felt like it was going to break, so I resorted to the serious method.

 

I moved the power steering pump off to the side and supported it with a bungee cord.

 

I colorized these photos to make them easier to see.

I removed the two front bolts that held the power steering bracket in place. (That's the green part)

But it didn't move.

 

There was another bolt behind the bracket, that attached the bracket to the engine block.

I removed this with the impact wrench. All 3 of these bolts required a 15mm socket.

 

The front of the engine after the power steering pump and bracket have been moved aside.

I altered this photo by coloring the water pump blue.

 

I removed the lower radiator hose.

I inserted a hook tool between the rubber and the metal to separate the hose, then it came off without a fight.

 

I removed the water pump pulley, using the impact wrench and a short 1/2" socket.

 

Removing the pulley from the pump shaft wasn't easy.

I had to hold the pulley with one hand and beat on the shaft with a hammer.

 

I removed this heater hose that was connected to the metal tube that goes into the water pump.

 

I also removed this idler pulley, using a 15mm socket.

While this may not be necessary, it should make it easier to get the water pump out.

 

Finally, the water pump is ready to be removed.

The red-colored part is the heater tube that connects to the heater hose shown earlier.

 

I removed the 4 pump mounting bolts. This required a 1/2" socket.

Note that one of these bolts is longer than the others.

 

I pried the pump housing away from the engine block.

 

Then the pump came right off.

 

This is the old pump. That heater tube on the left didn't come with the new pump, so it needed to be removed.

 

The new pump, which is identical except for that heater tube.

 

There is a letter "R" stamped on the impeller. This means that the pump turns in a reverse direction from normal pumps.

 

I clamped the old pump in a vise and tried to remove the tube with an adjustable wrench. The wrench slipped off the hex.

So I used a big pipe wrench to remove the tube.

 

But I could feel the tube collapse while wrenching on it. When I finally got the tube out, I could see what looked like a small hole.

 

I buffed off the rust on a wire wheel, and the hole became very obvious.

 

Hassles:

I called my local NAPA store to find a replacement for this tube. Not available... must be a "dealer-only" part. Of course, this was late Saturday afternoon and the dealer was closed until Monday.

I tried welding over the hole with my MIG welder, but the steel was so thin that I just made a bigger hole.

On Monday I called the local Dodge dealer... the part had been discontinued. He gave me the phone numbers of two dealers elsewhere in the United States that showed the part in their inventory. Hmmm.

I called my local NAPA store again and they set me up with an adapter and some new heater hose to replace the existing hose that was too short.

 

This adapter has a 3/8" NPT pipe thread on one end, and the other end will fit a 5/8" heater hose.

 

To ensure a good seal, I wrapped Teflon tape around the threads about 5 times, then I applied a thin layer of Permatex Thread Sealant with Teflon.

 

I threaded the adapter in by hand and then tightened it a little more than two turns with a wrench.

 

Installing The New Water Pump:

The old gasket must be completely removed. I drew a red line around the gasket to make it easier to see.

I used a razor-blade gasket scraper to remove the old gasket.

 

I used a pneumatic die grinder with a 3M Roloc abrasive wheel to clean up the cast iron surface.

I tried using the Roloc wheel in a cordless drill, but it was too slow.

I used an air nozzle to blow the debris out of the bolt holes. Then I sprayed some brake parts cleaner on a paper towel and wiped off the shiny surface.

A clean mating surface is essential to doing a leak-free repair.

 

I applied a small bead of Permatex 1A Gasket Sealer to the back side of the paper gasket that came with the new pump.

 

I spread the gasket sealer with a putty knife so it formed a thin uniform layer.

 

I placed the gasket over the mating surface of the water pump.

 

I applied more gasket sealer to the other side of the gasket, and spread it smooth.

 

I set the new pump in place.

 

I hand-threaded the 4 mounting bolts into their holes, making sure each bolt turned freely.

 

I tightened the bolts in a criss-cross pattern. The Dodge service manual says to tighten these bolts to 22 foot-pounds of torque.

 

The new water pump after installation.

 

I connected the new heater hose to the heater core connection (at the firewall) and routed the hose towards the water pump.

I cut the hose, leaving a bit of extra length. If the hose was too short it would be prone to kinking and blocking water flow to the heater.

 

I attached the new heater hose to the water pump. FYI: This connection is the inlet. Coolant is drawn from the heater core by this hose.

 

I replaced the lower radiator hose. I also installed new stainless steel hose clamps. I replaced these hoses a couple of years ago, and the hose clamps weren't stainless, so they rusted.

 

I replaced the water pump pulley.

 

Note On Lubricating Bolt Threads:

For at least two decades I've been applying a small dab of grease to most automotive bolt threads whenever I put something back together. This practice makes it a LOT easier to remove the bolts later, since corrosion is greatly reduced.

BUT... grease on bolt or screw threads can sometimes cause problems. 1.) Bolts that go into blind holes (holes that don't go completely through) can experience hydraulic lock if too much grease or oil is applied to the threads. Hydraulic lock happens when the bolt can't move any deeper because there is liquid filling the bottom of the hole. 2.) Bolts on a rotating object (such as this pulley bolt) can fling grease onto places that don't need grease, such as the serpentine belt.

Use lubricant sparingly.

 

I replaced the power steering pump bracket.

 

I replaced the power steering pump.

Note that the bolts go through access holes in the drive pulley.

 

I was about to re-install this idler pulley, when it became obvious why Chrysler used that silly heater hose extender tube...

... the pulley rubbed on the tail end of the hose clamp.

 

So I used my Dremel tool with an abrasive disc to cut off the overhanging tail of the hose clamp. This only took a minute.

 

This idler pulley is really close to the hose clamp for that red heater hose.

I can see why Chrysler used that curved steel tube... if the heater hose needs replacing, I'll have to remove the serpentine belt and this pulley.

Oh well.

 

I replaced the serpentine belt.

After I had the tension adjustment correct, I tightened the idler pulley bolt.

 

Note On Tension Adjustment:

While many vehicles today use an automatic spring-loaded tensioner to maintain the ideal tension on the serpentine belt, the Dodge Dakota 4-cylinder uses an old-fashioned manual tension adjustment.

Belt tension is critical!

If the tension is too loose the belt may slip, causing loss of function in the alternator, air conditioning, power steering and cooling system. Belts usually squeal when they slip.

If the belt is too tight it can cause early bearing failure on any of those systems mentioned above. I've experienced this. About 7 years ago my other Dodge Dakota (which has a V6) had a defective automatic belt tensioner. The spring didn't work but I could swivel the unit with a wrench and apply any belt tension desired. But it didn't always stay that way. Money was tight back then and I didn't want to spend $75 for a new tensioner. Somehow the tension got too high and after a few months of neglect I started to hear a howling sound from the engine. Sure enough, the water pump was making the noise, and the pulley was loose and sloppy just like this 4-cylinder Dakota. I had to replace the water pump AND the tensioner. Some savings! At least it was educational.

Manual Tension Adjustment:

When properly tightened you should be able to push down with about 10 pounds of force in the middle of the longest span of the belt and get about 1/2" of deflection. Now... I don't know how to measure 10 pounds of force with my bare hands, so I can't really tell if I'm pushing hard enough.

Another method of gauging the tension of a belt is to grab the belt on the longest span and twist it. You are supposed to be able to twist the serpentine belt only about one-quarter of a turn.

 

Then I installed the upper radiator hose and refilled the cooling system with antifreeze/water mixture.

While most mechanics recommend using a mixture of 1/2 antifreeze and 1/2 water, I use 2/3 antifreeze and 1/3 water, which has a substantially lower freezing point (about -60 F versus -35 F). In northern Michigan we need the extra protection.

 

After filling the cooling system, I ran the engine and "burped" the cooling system to get rid of any pockets of air. This can be done by running the engine with the radiator cap turned to the "first notch" which simply holds the cap in place while not forming a tight seal. Turning the radiator cap to the "second notch" forms the tight seal needed for proper pressurized operation.

More Info:

Tools Used:

  • Curved Hook Tool
  • Metric Sockets: 13mm, 15mm
  • SAE Sockets: 1/2" Short Impact
  • Pneumatic Impact Wrench
  • Air Compressor

Materials Used:

  • Water Pump, NAPA
  • Gasket Sealer
  • Thread Sealant

Related Articles:

 

 

 

 
 
 
 
 
 
 
 
 
 
 
 

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© Copyright 2006 Maki Media Group LLC

Written December 2, 2006