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Thermostat replacement?

Help, Advice, Owners' Discussion and DIY Tutorials on Volvo XC90s. The XC90 proved to be very popular, and very good for Volvo's sales numbers, since its introduction in model year 2003 (North America).
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Thermostat replacement?

Post by Roger_850T » Sat Jan 26, 2019 4:05 pm

I'm curious. Would you consider a thermostat to be a "wear item" to be replaced at regular intervals just because it's got some miles on it?

I've already got my Volvo apart. (2005 XC90 V8, 140k miles.)

It's not like the aux belt pulleys or tensioner, which have bearings that wear. And I'm replacing the water pump too, because it has bearings and seals that can fail.

I am trying to decide if I should also replace the thermostat. No bearings, no seals. Generally I've only had thermostat failures after replacing them "just because", so there is an argument for leaving it alone and avoiding infant mortality issues.

What do you think? Is there a good reason why I should replace it prophylactically? Or should I leave the old one in there? Discussion please. Thanks.


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Re: Thermostat replacement?

Post by cn90 » Sat Jan 26, 2019 4:39 pm


Most thermostat soft fail (open too early) at around 80K-100K.
I routinely replace my thermostat every 80K-100K.

2004 V70 2.5T 100K+
2005 XC90 2.5T 110K+

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Re: Thermostat replacement?

Post by Masscomguru » Sat Jan 26, 2019 5:55 pm

The spring which allows it to open at temp fails from the heat cycles.

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