Does anyone know if the thermostat housing bolt holes (22re) could be extended deeper without danger of hitting a water passage or anything? A broken bolt and subsequent botched removal of said bolt inspired this post. My plan is to drill/tap a deeper hole, and use a longer bolt.

 

Eventually you will hit the coolant passage in the intake manifold. A little sealer on the bolt should cure any problem that may arise. However, you don't have much room in the first place. If you ruined the threads all the way down, it may be time for a new intake manifold or a helicoil.

 

How deep does the hole go? IOW, did the original bolt go all the way down anyway? I had stripped threads in the head for the cam bearings on my wife's 3vze. Fortunately, the bolt hole was longer than the bolt itself and even threaded all the way down. So, I was able to use a longer bolt without drilling or tapping.

 

Yeah, upon further inspection, I can see how the coolant passage runs under the bolt holes, and it doesn’t look like there is much room.

The hole is 18mm deep and the top flange is 15mm thick for a total of 33mm. I think the original bolt is only 26-27mm long, so I should have some room at the bottom for a longer bolt. Right now, my biggest problem is a broken off screw extractor stuck in the sheared off bolt. I’m going to try to deal with that tomorrow and see what I can do.

Thanks a lot for the replies.

 

Oh, dang. That'll be a bugger. Good luck!

 

I was able to get the broken extractor out with a carbide tip drill. I'm going to have to use a helical thread insert, as the original threads are completely shot. I ordered a kit from Mcmaster-Carr, so I will get it done next week.

All this for a simple thermostat replacement... at least the thermostat was actually bad (leaking)