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Right after fixing another problem with one of my cars ( 98 Mazda 626 GF 2L ), I revved the engine and all of a sudden heard the tell tale hiss of a coolant leak:

enter image description here

As you can see, this hose just sprang a leak. Not a big deal, it's probably the original hose, and almost 18 years old.

However, I've had three different hoses go like this in a short period of time, just a few hundred kilometers of driving ( all on the hot side between the heater core and radiator ). Now, I've already replaced the thermostat, which was stuck shut and to which I attributed the previous two hose leaks, but this new leak has got me worried that maybe something else is causing pressure build up in the system.

There is no noticeable overheating, and I'm using a 1.1 radiator cap ( WSM calls for between 0.95 - 1.25 ).

Can I reasonably attribute this to old hoses and coincidence, or should I be looking for some other problem?

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Robert S. Barnes
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5 Answers5

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I believe (and this is a gut check) you can chalk this up to deteriorated hoses which all have gone bad in the same period of time (coincidence). Each has probably served a long fruitful life and now it's time for replacement. Especially considering where you live and overheating as well, this does not seem unreasonable to me.

I'd suggest if you have any other hoses which have yet to be replaced, you take care of it. I don't think there is a systemic issue which is going to cause new hoses to rupture again (considering your description). There is no way I could guarantee this behavior (obviously), but considering the history, I'd say after new hoses the vehicle should be in pretty good shape from this aspect.

Fred Wilson
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Pᴀᴜʟsᴛᴇʀ2
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Remember that the reliability of any system of components will only be as strong as the weakest link.

Coolant lines are pressurized under regular operation and the walls of the hoses will weaken with many, many heat cycles.

It is expected that a coolant leak will spring at the weakest point of the system. The moment you replace this hose, the weakest point will shift to some other location (likely another hose). This is why it seems like one hose fails after another.

Zaid
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A leaking head gasket can lead to exhaust pressurizing the cooling system. This will generally fail the current weakest link in your cooling system. As you replace one component, the next weakest component will fail.

D K
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It could be a stuck or blocked radiator cap. Did you change the cap at any stage? If the level in the coolant reservoir fails to rise and fall with engine temperature that could be a clue.

Barry
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If the pressure relief valve was (or still is) stuck, as well as the thermostat, quite likely you have weakened all the hoses. Or, they are all dying of old age, though three in quick succession seems an unlikely coincidence. Pragmatically, after 3 failures I would replace all the hoses and clips, plus I would test the relief valve is opening at the correct pressure. If you get more failures after that, then keep looking until you find the root cause of all of them.

alephzero
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