Hole in undertray caused thermostat failure.

[Hops128i]

Had a coolant leak, investigated, and found a rusted bolt on the thermostat which popped a crack in the part. The rusted bolt was situated in a way it was exposed directly to the road via a hole in the undertray. The other two bolts looked good. I don't know how long the hole was in the undertray, but it's definitely worth inspecting it!

Anyway, replaced the waterpump, thermostat, and undertray... not the most fun i've had working on the car, especially getting the quick connects off the tstat, but reminded myself of the money saved!

[juld0zer]

Strange. Liquid is unlikely to blow upwards through that hole. That is usually where the 8mm screw goes into?

Also strange that the thermostat bolt rusted too. They are usually corrosion protected.

[Hops128i]

one of the sway bar mounting bolts closest the under tray hole was also corroded noticeably more than the others. Yeah, i don't see how water could be forced through the hole, but maybe splashing upwards on city streets?

[drunkenup]

Sounds like crappy luck. My car hasn't had an undertray in the almost 4 years I've had it and it looks pretty good under there. It's seen 2 rough winters, too

[Hops128i]

Originally Posted by drunkenup

Sounds like crappy luck. My car hasn't had an undertray in the almost 4 years I've had it and it looks pretty good under there. It's seen 2 rough winters, too

Well there was only one corroded thermostat bolt, and that was the one exposed to the roadway by the under tray hole, and this hole could have been there for 8 winters. I don't think it's bad luck it happened, but kinda lucky for me to have the situation to replace the under tray.