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. :bomb:

 

[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.

 

[outlander]

This happened to me, not once but twice! Luckily for me it was easy enough to get them both out and I had spares. It must be a common thing though; water corrodes the top half of the bolt, and causes it to shear off when its over tightened.

If it happens, I would block up the intake, and spray the nut with penetrating oil, then use a product known as a screw extractor
I didn't have one of those, so I tack welded the head back on and that gave me enough leverage to get it out, but if I had one I would have used it.

Thanks for the bolt measurements! For reference mine broke around 40nm. A quick google suggests they should be done to 30nm, so I was overdoing it.

 

[vaxx]

Left handed drill bits a godsend in times like this. Drill the centre out and it will get to the point of unwinding it. Better then easiouts