# Broken Thermostat Housing Bolts



## Mo_Heato (Apr 14, 2020)

So I was taking my thermostat housing off and I broke the two lower bolt heads off and I just wanted to know if it’s possible to drill them out even with one being at a weird angle.

Anyone got any good ideas or could help?


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## rogoman (Dec 16, 2004)

If the bolts are broken off flush with the thermostat housing, you'll have to drill them out. Here's a video clip:



how to repair drilled out bolts - Google Search



If you're unable to get in there with a drill, you'll have to remove the thermostat housing from the engine.

Sometimes bolt breakage goes beyond simple bolt extraction to where the bolt and threads must be completely drilled out. Damaged threads can sometimes be chased and cleaned up with a thread chaser or tap. When they're so badly damaged they cannot be cleaned up your only choice is to drill out and replace them with a Heli-Coil insert.


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## Mo_Heato (Apr 14, 2020)

Thankyou so much for replying and okay I will try. One bolt is easy to get to and the other is hard to see because the bolt is broken lower than flush but I have room.
Also if I end up having to take the whole housing out, then do I need to remove the Upper and lower Intake again?


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## rogoman (Dec 16, 2004)

It's been a long time ago since I looked at a 300ZX setup; trying to remember. IMO, you really shouldn't have to touch the intake system at all but take a good look how the housing is attached. If anybody else knows for sure, please chime in.


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## Mo_Heato (Apr 14, 2020)

Sweet Thankyou man 👌


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## smj999smj (Jan 1, 2006)

Knowing how those bolts are, I would imagine it's going to be a real PITA! The safest bet would be to remove the housing to get a better chance at drilling them out. The bad news is that you would have to remove the lower intake manifold and upper plenum because there is a pipe that runs under the lower intake manifold that bolt to the back of the thermostat housing. Worse case scenario, I do believe the part is still available as P/N 11061-02P01 (there's also a couple of gaskets that will be needed for the housing...plus those required for R&R the lower manifold to get at it). If your production date is prior to February, 1987, the original housing was discontinued and service filed to use the 11061-02P01 housing and 13049-42L00 water inlet (that's the part that covers the thermostat and connects to the radiator hose).


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