By Tom Carrington
I should have known it was coming. The signs were there. I just chose to ignore them. What signs? For the past month or so, I have been topping off the coolant reservoir. Not much, just maybe a pint every couple of weeks. I was kinda worried that I might have a head gasket problem (most Wasserboxer owners live with this constant fear) but there were no drips or puddles in the driveway, or strange smells from the exhaust. The temperature gauge always read fine, so I happily fed my engine’s habit. Life was good.
Or so I thought.
Note: Click on thumbnails for expanded images!
Just a week ago, the habit turned ugly. I noticed a slight smell of antifreeze after parking the van, but still no drips or other visible signs of a leak. I was more concerned, but not enough to fully investigate the problem. I should have. A day later, my Van was leaving a distintive coolant trail along the path I drove. Hansel and Gretel would have been proud. 
That night, I got under the Van to assess the problem. With the engine running, coolant was spewing out of a small hole in engine, just behind one of the pulleys. No ordinary hole, coolant from this one indicates that one of the seals in the water pump had failed. My preferred FLAPS (Olympic Auto Parts, College Park, MD (301) 474-1030) had a brand new German-made pump in stock, complete with new gaskets and an O-ring for $62.00. A quick check at The Bus Depot web site showed they had a similar pump for $50.00. Since I needed it *now*, off to Olympic it was! 20 minutes later, I had a new pump. Follow along as I go through the steps for replacement!
Tools & Supplies Needed:
- 12mm and 13mm wrenches and sockets
- 3/8″ drive ratchet, 3″ and 6″ extensions and universal joint
- Screwdrivers
- Slip-joint pliers
- Gasket scraper, putty knife or razor blade
- Sturdy jack and jack stands
- New water pump (comes with O-ring and gaskets)
- 2 coolant pipe gaskets
- 2 gallons antifreeze
- RTV silicone sealer
- Large bucket or wide dishpan (To collect old coolant)
The worst part about replacing the water pump is it’s location. Down near the heat shield in front of the muffler with not too much room to work. Mentally prepare yourself for some fancy fingerwork. Some of the work you will do from above the engine, some from through the license plate door, and a little bit from below. In the picture to the right, the pump is behind that single-groove pulley with the belt riding on the top of it. The multi-grooved pulley is bolted on the end of the crankshaft.Step 1 – Disconnect the Battery:
First things first. We will be working near the alternator, so go ahead and disconnect the battery ground strap. The battery is under the front passenger seat. Sure, you could leave it connected, buy why risk it?Step 2 – Drain the Coolant:
Unless you are determined to replace *all* the coolant on your engine, don’t bother following the Bentley procedures for draining your coolant. What I did was remove the hoses from the thermostat housing by loosening the hose clamps and tugging them off. I had a large bucket underneath,
and managed to capture almost all of the coolant. As long as you are there, you might as well disconnect the 2 temperature senders. Once the flow of coolant had subsided, I raised the passenger side of the van with a jack under the frame just forward of the rear tire to get more to coolant to drain out. After the flow slowed to a small trickle, I lowered the Van back down on all fours. The point of all this was to get the coolant level in the engine low enough so that none would spill out when I removed the pump.Step 3 – Remove the Water Pump Pulley
The new water pump does not come with a pulley,
so the one on the old pump needs to be removed. The pulley is held on to the pump with 3 13mm head bolts. The problem with removing the pulley is that there is no good way to hold the pulley still while removing the bolts. If you have an air compressor, no big deal – just use an impact wrench to “zip” the bolts right off. But here’s a trick for the rest 
of us. First, loosen the pivot and adjustment bolts on the alternator just slightly. Lever against the housing of the alternator to tighten the belt *much* tighter than you would normally do. Re-tighten the bolts on the alternator and place the Van in gear. With the belt that tight, and the transmission in gear, the pump pulley should be held still while removing the bolts. A 13mm combination wrench will work just fine.Step 4 – Remove the Coolant Pipes
There are 2 steel pipes that carry coolant from one side of the engine to the other.
On the passenger side of the Van, both pipes are secured to the water jacket with bolts or 
nuts/studs, as pictured to the right. Remove both the bolts and nuts. On the driver’s side, the upper pipe slip-fits into the thermostat housing with an O-ring seal and the lower is bolted to the front of the water pump. It is the bolts that secure the lower pipe to the water pump that will try your patience, seen here to the left. You can just get a 12mm wrench on the bolts, but only about 1/8 of a turn can be made at a time. Take a deep breath, prepare to spend some quality time flipping your combination wrench again and again, and remove the lower bolts.Step 5 – Loosen Hose Clamps
After completing Step 4, you deserve a break, so here’s an easy one. The thermostat housing is connected to the driver’s side cylinder head by a short hose. Loosen the clamps on the hose. You will be removing the water pump and thermoststat housing as a single unit. Now is also a good time to remove the hose that goes from the expansion tank to the top of the water pump. Use a regular pair of pliers to squeeze and and hold the clamps open while you work the hose off the casting.Step 6 – Remove Water Pump
The water pump itself is held on to the
engine by a single bolt and 2 studs with nuts. Use a 13mm socket with a universal joint and extension to remove these. At this point, there should be 
nothing holding the pump to the block, as seen on the right. Once the bolt/nuts are gone, the pump and thermostat housing assembly can be pulled straight back towards the rear of the Van. You may have to wiggle the assembly to get the hose connection from the thermostat housing to the water jacket to break free.Step 7 – Separate Water Pump from Thermostat Housing
The thermostat housing is attached to the water pump by two long, 13mm head bolts.
I had to apply a little of heat with a propane torch to get the bolts to turn freely. The heat helps expand the aluminum of the housing, which releases the housing’s grip on the bolt. Once free, I used a wire brush to clean the bolts, and a drill bit to clean out the bores in the housing. At this point, the disassembly phase of the project is over. If you were thinking of installing a new thermostat, now would be the best time.Step 8 – Clean All Mating Surfaces
Having clean mating surfaces
is the key to preventing leaks around gaskets. Nothing worse than putting everything together and seeing a leak! Use a scaper of some sort to remove any traces of old gasket material from the thermostat housing and the mating surfaces for the coolant pipes. The area on the engine where the water pump mounts should also be cleaned to ensure a good seal. On the left, you can see the sealant residue from the water pump. The view to the right shows the same area, after a good cleaning.Step 9 – Let the Assembly Begin!
Start by installing the thermostat housing onto the water pump. Next, put a *very light* coating of RTV sealer (I like Permatex Ultra Copper) in the o-ring groove on the back of the water pump. Push
the o-ring into the groove, and smear a *thin* coating on the face of the o-ring. Do not use more than a paper-thin coating of sealer! If you do, the excess sealer can get into your cooling system and clog things up!! Put the water pump and thermostat housing assembly back on the engine, and tighten the nuts and bolt. The next step was the worse part for me. Using a new gasket, re-install the lower coolant tube. The bolts are tricky to line up and get started, but take your time. Once both of those are tightened down, take a break….you will want one! The upper coolant pipe goes in much easier. Coat the o-ring with a little RTV, and slide it into the thermostat housing. The other end bolts to the cylinder head on the passenger side. Reinstall the water pump pulley and alternator belt. Put the belt on extra tight to help while torquing the pulley bolts, then loosen the belt back to normal (1/2″ deflection). Re-install all the hoses and tighten the clamps. Hook up the wires for both temperature senders. You are almost done!Step 10 – Adding Coolant & Bleeding Air
Before adding a single drop of coolant, open the engine-mounted bleeder valve located on the “H” shaped housing above the engine, seen here on the right. This will help prevent air from being trapped in the cooling system.
Once you have filled the expansion tank, start the engine. Look for leaks at the pump and all of the hose and pipe connections. As the engine is running, the coolant level in the expansion tank will drop. Keep adding coolant until the level does not drop, and you no longer see air bubbles appearing. Close the bleeder valve.The next step is to get any trapped air out of the radiator. Screw the cap on the expansion tank, and turn off the engine. At the front of the Van, remove the grille around the headlights by turning each of the slotted fasteners about 1/2 turn. Jack up the front of the Van a foot or so and restart the engine. By raising the front of the Van, air bubbles should collect in the top of the radiator. Loosen (not remove) the bleeder screw on top of the radiator 
(seen here on the left) until you see or hear air being pushed out. If you see bubbles, then there is still air escaping. Once only a solid flow of coolant is escaping, tighten the bleeder. Get behind the wheel and rev the engine to about 2000 RPM for a minute or so, then loosen the bleeder again and check for air. Repeat this process several times until no more air is being pushed out when you open the bleeder. Shut down the engine and lower it to the ground. Fill the coolant reservior to the top, and put away all your tools, except for the 13mm wrench. As the engine cools, a vacum will develop in the cooling system, which will cause coolant to be sucked out of the reservoir, and into the system. After an hour or so of cooling time, check the coolant level in the reservoir, and fill if needed.Once done with the bleeding process, I tend to leave the grille off for a few days.
Upon arriving at work or home, I will leave the engine running and crack open the bleeder valve on the radiator. It usually takes about 4 or 6 times before all the air has been purged from the system, in my experience. My new water pump is working just fine….although without the tell-tale trail behind me, I may have troubles finding my way back home! 🙂
