Many years ago I changed the coolant in my 1994 Mazda Lantis. I had no idea what I was doing, and the result was my water pump broke and started leaking.

The mechanic replaced it and all was good.

When I look at videos like this, https://www.youtube.com/watch?v=s--5ft5YiHg I see no reference to bleeding air from the cooling system during the initial flushes.

This guy filled the radiator up when he was doing the initial flushes, started his engine, and the coolant went down, then he topped it up. On the last fill he squeezed the pipes at the top.

This guide here,


Mentions jacking the car up, and opening the purge vents. What's a purge vent?

Overall though, what happened to my water pump? I obviously did it wrong, but it seems extreme that it would break like that.


  • Will having air in the cooling system destroy your water pump?
  • If not, won't air in the cooling system work its way out when you run the car for a while?
  • Should I fear changing the coolant in my 2005 Mazda Bounty UTE because of my previous experience?
  • 3
    It was probably a coincidence.
    – HandyHowie
    May 30, 2018 at 10:45
  • What is the make, model and year of the car?
    – GdD
    May 30, 2018 at 12:30
  • Did you use the right coolant for your car? I believe some type of coolants should not be mixed and or can cause problems with different types of alloys and metal used in the cooling loop.
    – Granny
    May 30, 2018 at 13:01
  • @Granny They make universal coolants now, which is what shops use to avoid this type of issue.
    – Moab
    May 30, 2018 at 16:04
  • It was a 1994 Mazda Lantis. I guess I am hesitant to touch the coolant in my 2005 Mazda Bounty UTE? Would you say my fear is unwarranted?
    – peter
    May 30, 2018 at 20:52

1 Answer 1


I have found very little about flushing killing a water pump, so it isn't common. This is the only instance I found, TDHofstetter has a story here which is similar,

Replaced water pump two days ago...today antifreeze filling up parking space

I went ahead with the flush. Flushed about 7 times, adding a flush additive as part of one of them. All has gone well and the new coolant is working fine.

Only a small amount of air came out on each flush. I started the engine, left the radiator cap off for a minute and kept filling until it stopped going down. Shut the engine off and put the radiator cap on. Then followed the instructions in my service manual which was to warm the car up gradually.

My coolant came out surprisingly clean considering it hasn't been done for at least 7 years. It was much better than the youtube clips I have watched with dirty broken down coolant. Well overdue though.

I took a sample of the old coolant and mixed it with the new coolant to make sure it wouldn't react or clump. It looked fine.

Based on what I have read it sounds like the HOAT coolant is much better technology. Lasts much longer, doesn't react, and doesn't dissolve gaskets.

In my previous experience killing my water pump, I must have used the wrong coolant, or low quality. It must have reacted with the old coolant and disolved the gaskets in the water pump. Nothing to do with having air in the system, which somebody at the time lead me to believe. I only emptied and refilled so a lot of the original coolant would have been left behind to react with the new coolant.

One further piece of advice, make sure you don't lose the petcock o-ring. I found it in the coolant after one of the flushes.

Hopefully that helps somebody. I have learnt a lot in the process.

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