Snapped thermostat housing bolt

[vs_wagon]

I thought I'd share this little experience I had not long ago when attempting to replace the thermostat in my VS V6.

One of the bolts (size M8) snapped off when trying to undo it. After a few hours of trying to extract the half that remained (unsuccessfully... I even managed to 'weld' a drill bit into the bolt) I decided to change my plan of attack…

The result:




I drilled and tapped the new M5 holes either side of the original, which I ground down to be flush with the surface. I filled in the hole in the thermostat housing with metal putty (looks like a stick of liquorice) and have used fibre washers with the M5s to help seal the holes. This has been performing perfectly fine for 18 months now.

Lesson 1 – make sure the bolts are cold when you try to remove them, and it probably wouldn’t hurt to spray some WD40 on it the night before.

Lesson 2 – replace your original bolts next time you change the thermostat, they are M8 x 25mm.

[hako]

That's a great fix....I probably would have drilled it out just as you tried and failed. More than one way to skin a cat!

[ScoHar]

did you try an easy out?

[vs_wagon]

did you try an easy out?

I sure did, but in order to do that you need to drill a hole in the bolt first, and the drill bits kept snapping. Finally one of them snapped and welded itself into the bolt.

[excalibur]

so you still havent changed the thermostat though

[hako]

so you still havent changed the thermostat though

Maybe he has - looks like a new gasket and the bolt looks new???

Last time I tried an "easy-out" it snapped in the bolt hole - that was it for me - I slammed the bonnet down and traded it next day.

[vs_wagon]

Yeah I definitely changed the thermostat and gasket. I just changed it again last week (18 months later) as it didn't seem to opening soon enough. Turns out the heater tap was cracked so there was an air bubble in the system and I was losing fluid. $45 for a new tap by the way. All good!

[ScoHar]

Spark Eroder would prob best the next best thing.