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Water pump leaks wreak havoc on minivan's system

Carrying coolant around to 'top off' isn't the answer to this leaky problem.
Saturday, August 1, 2009 - 00:00

Carrying coolant around to 'top off' isn't the answer to this leaky problem.

Motor Age Garage 2004 Dodge Caravan water pumps leaking water pumps vechile leaks fixing vehicle repair shop training technician training automotive aftermarket

Today's transversely mounted V6 engines are stuffed in really tight engine compartments, particularly in minivans, and handling heat on those platforms is always a serious concern. A healthy emission-friendly engine generally needs to run no cooler than 200 degrees F and not much above 230. With that in mind, it's quite interesting that some electric cooling fans don't even kick in before the Engine Coolant Temperature (ECT) sensor reads nearly 230. That's a pretty tight temperature window, and little things can upset the balance.

Cylinder heads are almost always aluminum nowadays, and they love to warp and blow gaskets if the temperature needle drifts into the red and stays there for too long. Over time, hoses can split, plastic radiators can crack or clog with debris, electric cooling fan motors can fail, water pump bearings and seals can give out and ferrous water pump impellers can be consumed by rust. Electrolysis can cause cavitations on the timing cover or water pump surface opposite the water pump impeller blades, and in some cases, an improperly installed serpentine belt can spin the water pump backwards. Ever seen that?

What complicates matters even further is that so many of today's vehicles have their all-important high temperature coolant flowing through plastic parts at 16 psi. It's a good idea to sell your customer replacements for a lot of those components if their wheels have rolled more than 100,000 miles, because plastic parts that carry coolant often fail suddenly and cause catastrophic engine damage. Spring-loaded belt tensioners can pop without warning as well, but that's another story.

Just about everybody uses aluminum radiators with plastic tanks nowadays, and if that weren't enough, there are plastic heater hose tees and plastic elbows o-ringed on each end that can fail without warning. GM 3.8L engines had two plastic elbows that routed coolant through the belt tensioner bracket (go figure), and earlier 3.8L models had a dandy plastic bypass hose fitting that was neatly concealed behind the alternator and could dump a heap of coolant in short order.

First: Windstar Water Pump

This month's title vehicle is a Dodge Caravan, but before we get to that one, let's talk about a 2002 Windstar that came in for an oil change and wound up getting a water pump along with it. There are several ways a water pump can fail. The guy doing the oil change noticed coolant dripping from the pump, but it wasn't coming from anywhere near the weep hole. There were no leaking pipes or hoses.

This was a strange leak, to be sure, and a pressure test revealed a cracked water pump casting, which (in my limited experience) is extremely unusual. That water pump would have been a cakewalk if it hadn't been for that stiff steel coolant tube that was flanged to the top of the pump. The point here is that aluminum and cast iron parts can develop cracks, too, and when those cracks allow coolant to escape, well, Mom isn't always watching her temperature gauge when it moves into the danger zone.

One way or another, the Windstar had to have a water pump and some fresh coolant. It was a dandy and vitally important upsell that probably saved that Windstar 3.8L from destroying itself.

The Caravan

The Caravan came to us with a water leak somebody had called to this lady's attention some weeks before, and she was carrying a jug of coolant with her everywhere to keep her system full and cool. She was hood-wise enough not to remove the cap when there was pressure on the hose, and she had been diligent in keeping the Caravan topped off. Her door locks were also inoperative, but we'd address that after the water leak was handled.

This leak was old enough that it had seriously stained everything the coolant had drained across under there. The interesting part was that while the water pump pulley had to be removed to access the bolts, the water pump pulley flange was too near the frame to allow complete removal of the pulley, so the pulley had to be rattled around and held out of the way during the removal of the water pump bolts. After the pump bolts were removed, however, the pulley would tend to contact the frame and still be an obstruction to removing the water pump from its cavity. So the engineers were kind enough to design the pulley and flange so as to allow the pulley to be rotated a few degrees and fitted past the flange so it could ride closer to the pump body during pump removal.

That maneuver provides enough clearance that the water pump can almost be removed with the pulley dangling between the flange and the pump body. I say almost because we still had to apply some pry bar pressure in order to move the engine assembly a few millimeters further from the frame to get the water pump out of there, and it took the same amount of engine movement with the pry bar to get the new water pump back in. Product variability in the field probably allows for some pumps to be removed without prying the engine, so I'd keep that in mind.

Sometimes replacement parts are engineered so as to be more sensible – one example would be the replacement harmonic balancer for early 1990s Chrysler V6 engines. The original balancer had a really tight press-fit (no keyway, no timing marks) but the holes or flats on the harmonic balancer for any type of puller were conspicuously absent. We had to drill and tap some 3/8 holes to remove a balancer on one of these cars with our regular slotted balancer puller. But the replacement balancer had nice beefy bosses designed for a three-jaw puller, which would make the job a lot easier for the next man. Later model Chrysler platforms equipped with this odd configuration came off the line with the new style balancer.

Sometimes we encounter situations where the service engineers haven't been so kind as the Dodges were here. GM Quad 4 engines have a timing chain-driven water pump. In the early 1990s, the water pump was splined into the chain driven gear and could be replaced quite easily without the necessity of accessing and removing the timing chain. That was a situation where the engineers were exceedingly kind, but it was too good to be true. A few years later, GM altered that design. For example, the water pump on a 1999 Alero Quad 4 we serviced could no longer be removed independently of its chain-driven gear, so the timing cover and chain has to be removed whenever the water pump is replaced.

Last Fix: The Door Locks

The Caravan's door locks were as dead as the proverbial doornail, and that was a concern that had been mentioned when I made the work order. So we connected our Genisys and gathered two important pieces of data. First, the door lock switches were sending their signals to the body computer quite flawlessly. Second, the door locks wouldn't respond when we commanded lock operation with the scan tool, and they wouldn't operate with the key fob.

I remember a 1998 Mustang I worked on about 10 years ago at a Ford dealer. It came in with inoperative fobs, but the door locks would work with the switches. I noticed that the Mustang's GEM would respond to the fobs in reprogramming mode, but after exiting programming mode, the locks still wouldn't work with the fob. I reset the GEM module (body computer) with the WDS the way I had been instructed in a Special Service Message from Ford, but to no avail. When I called the hotline, they told me to remove a particular fuse from the fuse panel for a few seconds, then reinsert it and reprogram the fob. It was basically a reboot of the GEM module, and it worked.

On the Caravan, we disconnected the battery cables, touched them together, reconnected them, and the locks came to life and worked normally. A little research revealed the availability of a re-flash to prevent that from happening again.

Closing Thoughts

I had a student last semester who loves turning wrenches on his hot rod, and subsequently he missed a lot of class days and eventually flunked out of my program. I told him one day that the work he was doing at home on his hot rod wasn't mechanic work.

He was incredulous until I explained that working on the hot rod is a money-eating hobby, not a money-making job. As it is, the only place he gets money of any kind is from his own mom, and the money she gives him is being wasted along with his time. Fixing minivans for soccer moms is how we earn the money we spend on other things. That's what I want my grads to understand.

Richard McCuistian is an ASE-certified Master Auto Technician and was a professional mechanic for more than 25 years. Richard is now an auto mechanics instructor at LBW Community College/MacArthur Campus in Opp, Ala. E-mail Richard at

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