Water Pump O-ring Replacement Tip

by Lo

I discovered a relative easy way to replace the water pump o-ring, if that is the only source of a leak. I thought it might be a helpful hint in the garage section, but being new to the forum, I was not sure how to submit this for a hint on the water pumps. I cannot express how relieved I was that I did not have to redo the whole timing belt and water pump installation. Here is the story. If someone can tell me how to submit this the garage section, I will forward it on to there.

I installed new timing belt, water pump and all the associated gaskets and seals with doing this job on my 95 Miata. Everything was running and looking good. I was quite pleased with myself after working on my first Miata. Well after about three days of running, I developed a leak at the water pump o-ring when I kicked on the heater. My first though was "Oh Crap" (much edited) I was going to have to tear it apart down to the water pump again to replace the o-ring. Using a mechanic's mirror I was able to see that the o-ring had gotten cut during installation. I also started exploring around and discovered the by-pass went to a fixed pipe with a heater hose on the opposite end. I decided to fix the o-ring from the back side and it worked well. Maybe an hour and half wrench time at the most. Here are the steps.

1. Remove the plastic air intake.
2. Remove the air filter and housing. It is just 3 bolts and makes it real easy to get to the next steps.
3. Remove the exhaust manifold heat shield. The bolts can be a bit tricky to reach at the bottom, but just be patient. You will have to remove the nuts fastening the front shield from the back shield. Use plenty liquid wrench, I cannot emphasize that enough. This was the step that took most of the time.
4. With the heat shield removed you can now see the by-pass insertion point on the water pump and the location of the damaged o-ring. Follow that pipe and it will go to the heater hose. The 95 has a bracket welded onto the pipe that is held in place by one bolt of the exhaust manifold. After soaking the bold in liquid wrench, did I mention soaking it in liquid wrench, remove the bolt.
5. Now the pipe is free to move. From the front grab the pipe and push it back toward the firewall. The hose has enough movement in it that I did not have to remove the hose. The pipe came free relatively easy and there was the damaged o-ring.
6. Replace the o-ring. Again from the front, get a good grip on the pipe and pull it into the water pump with the new o-ring installed on the pipe. It was easy to tell when it seated. Plus since the manifold bolt has to match up with hole on the welded bracket the position cannot be messed up.
7. Bolt the bracket back in place on the manifold.
8. Reassemble the heat shield, air filter housing and air intake. You are ready to go.