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Frequent Water Pump Failures

3K views 14 replies 6 participants last post by  X6driver 
#1 ·
I've changed my water pump several times. The first replacement pump lasted about 5 years. Last year I changed the pump again and noticed a bit of corrosion and pitting on the gasket surface.

The original factory water pump gasket was a thin piece of metal. Replacement gaskets have been made out of normal gasket material and I applied Permatex Ultra silicone ("perfect for water pumps") to help it seal. My pump is now leaking again after only been on the car for 1 year and I am wondering if the problem is the gasket. Could the leak be due to corrosion on the aluminium pump caused by being against a dissimilar metal - the iron block?

Perhaps I should buy a mazda metal gasket from the dealer to get more life out of the pump?
 
#2 ·
If it's leaking from the weep hole it's very likely your thermostat is bad.

If it's leaking from the gasket surface then yeah... something other.

You need to visualize it when the car is running, eyeballing the weep hole or the gasket area to determine which it is.
 
#3 ·
Why would the thermostat cause a leak from the weep hole ? It only leaks when its quite cold outside. Once the engine is warmed up, it doesn't seem to leak. This is a fairly slow leak, over 12 hrs outside in -15c weather, it will leak about 10 ounces of fluid.

I have a very noisy timing belt pulley - maybe the whinning noise I hear is a pump bearing and not a tensioner pulley bearing...
 
#5 ·
If your thermostat is stuck closed, it puts undue pressure on the pump seal. I noticed parts guys at the stores always ask if you want a new thermostat whenever you're already buying a pump. I finally figured out why... more than once.
 
#4 ·
If the mounting face on the block is pitted then you're going to have a hard time getting any seal to last for long.

In that case possibly the best thing to do would be go without a gasket at all and simply use silicone.
In which case I'd use Permatex or Silastic blue, these have a lot more adhesion compared to the regular black or grey varieties.
 
#6 ·
First, figure out where it's leaking. Weep hole? Get a better pump. Gasket? Thin coating of rtv on both sides of the gasket after cleaning all previous gasket material off.

Thermostat stuck closed = overheating. Even in cold weather.
 
#7 ·
I don't bother with gaskets, RTV all the way.

RTV will be able to handle pitting in both surfaces with no issue.
 
#8 ·
I have been using Valvoline Zerex G0-5 coolant, which from what I've read is one of the better coolants. Lots of corrosion protection and long life. I contacted Valvoline directly to ask if this coolant is compatible with my old Mazda and they said it was well suited for the car. Previously, for the first 320,000 kms, I was using plain old green glycol coolant - 50/50 with soft water.

I notice that when any of the orange Zerex drips out anywhere, it dries up into a white powdery residue, unlike green glycol which dries into a sticky thick liquid. Then I read this article on Popular Mechanics website discussing water pump seals:

"Two perfectly flat rings, one stationary and the other rotating with the pump shaft, are pressed together by means of a coil spring. The rings may be made of carbon or may be ceramic, phenolic, porous bronze, cast iron, etc., in any combination. This allows only enough seepage to keep the elements lubricated. It has a weak link, however, in the form of its rubber parts—the bellows that seals the spring and the rubber seat cup between the rotating element and the shaft. If the engine is ever run dry, the temperature of the pump is apt to rise far beyond what the rubber can survive, and a leak occurs. Another possibility is warpage of the sealing elements, also from overheating.

There's conflicting evidence on whether silicates and phosphates from antifreeze, or other hard particles such as casting core sand, can actually damage the seal faces. Engineers have told us the running clearance is way too small to admit solids of any appreciable diameter."


Could the type of coolant I'm using be part of the problem?
 
#12 ·
with RTV there shouldn't be any leaks.

I would not suggest coating a fibrous gasket with RTV, thats not how they work, theyre meant to soak up a little bit of fluid and expand to fill imperfections in the surfaces.
RTV should be used by itself with both surfaces cleaned so that the RTV will stick.

I've built motors using RTV as a substitute for every fibrous gasket and never had any problem with leaks for the life of the motor.
You can pretty much use anything except for structural stuff like some oil pan gaskets.
I used roof & gutter sealant one one motor back when I was at college and had no money. That motor was fine, didn't leak a drop, mind you it was carb so I didnt have to worry about acetic acid content killing the O2 sensor.
 
#14 ·
There's an equal number of crappy and good water pumps in the aftermarket. Gates is good, anything in the Tru-Flow Line from Napa is good, NPW pumps are good and my personal pick as they're OEM for many makes.

Personally and professionally I've had good luck with putting a very thin coating of silicone gasket maker on fibrous gaskets on many makes/models/years. Five years running haven't had to re-do. Water pump yet. YMMV.
 
#15 ·
I'm debating replacing this "Prestone" water pump for free under warranty, or spending the $50-ish to get a gates from Rock Auto and having peace of mind. I wonder how many F2s can still be running around out in the world - and how many independent manufacturers are still left making this part? Too many times I've paid for the pricey brand name part and found it exactly identical to the cheap offshore one once I took it out of the box.
 
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