The Water Pump

A rather major repair that I had to do at 128000 miles was tied to getting the water pump replaced.

Most water pumps (like the one in the 626 v6) are belt-driven devices that use the engine's power to circulate coolant througout the cavities of the engine block. This circulation is key to keeping the engine from developing hot spots that could warp the engine block and cause a seizure that would lead to having the engine replaced. Because the pump runs constantly (well, whenever the engine is running) the part of it that almost always fails first is the sealed bearings for the pulley. The manufacturers of the pumps have taken into account the eventual breakdown of this component by including a way in which its failure can be detected by either the car owner or an auto mechanic.

The housings on all water pumps include a small weep hole near the neck of the pulley which will allow coolant to escape should the seal on the bearings be compromised. This hole, which actually faces upwards on the pump housing on a 1993 626 V6 (in most other engines it faces down) should be inspected regularly once your car's engine gets past the 85000 mile mark. If you ever see moisture collecting around that part of the pump housing, or more likely if you happen to notice a small puddle of antifreeze on the ground or detect the smell of it wafting from the engine, the pump is probably on its way to failure.

Keep in mind that antifreeze leaks can come from a multitude of sources. That is why I also recommend checking the pump housing for signs of dampness (say an hour or so after having run the engine for awhile). A leaky pump is a sure sign that the bearings will go out on you eventually, and given how important the pump is to the health of your engine, this is not a problem that should be neglected for long.

Despite having the Haynes manual and all kinds of tools for working on my car, I let the Mazda dealership work on this one. The details of what they did are:

Replaced the water pump and pulley (original) and gasket

Replaced the engine's timing belt (should replace when water pump is replaced since re-tensioning a timing belt is considered a "Bad Idea" [tm])
Both drive belts (they were original)
Crank and Cam seals (had to be replaced because getting to the timing belt requires removing the front valve cover on the v6)
Thermostat and gasket
Flushed the system and added all-new antifreeze

Now why did I let the MAZDA dealership work on the car? I knew it was going to be an expensive proposition (it cost me $768 for everything they did, parts and labor) but it was something that I wasn't comfortable with doing on my own. To replace the water pump you have to:

drain all coolant from the engine

brace the engine either with a hoist or with some kind of blocking underneath because you have to...

remove the passenger-side engine mount

remove both engine belts (there is no serpentine unibelt on a 1993 v6)

remove the front valve cover

remove the timing belt cover

remove the timing belt (and check the timing belt tensioner for signs of wear or misalignment)

remove the water pump

clean old gasket debris from the engine block with a putty knife and very fine grit sandpaper (if needed)

place the new water pump on the engine after preparing the new gasket

put the new timing belt on, being very particular to get the timing settings exactly right

put the timing belt cover back on

put the valve cover back on WITH A NEW GASKET and a new PCV

put new engine belts on and make sure that the deflection is within specifications (otherwise you burn out pulleys and components die prematurely)

remount the engine and then remove the blocking

put coolant back in the engine with the proper antifreeze-to-water ratio

start the engine and let everything run for a moment

pray it all works without any leaks or groaning noises. Otherwise you get to repeat all the above steps to find out what you missed

Being something of a novice mechanic, I didn't trust myself to be able to do all of that on my own and ensure that everything worked just fine. Besides, the amount of time that it would've taken me to do all the work by myself was prohibitive because I needed the car for the daily commute to work. That plus the fact that Mazda gives a one year warranty on parts and labor for all shop work that they do made the choice a fairly simple one for me. And really, this was much more than a pump replacement so I don't consider the cost of the job to be all that bad. That doesn't mean that it didn't hurt, though. :)

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Todd Hill
accountant@nabiki.com

Last updated: Saturday, October 18, 2003