Hello all, one of the bolts broke off in my thermostat housing, I drilled through the center and tried everything to extract it. Got the housing off but the bolt is stuck in there. Nothing to grab onto its flush with the manifold. Anything I can do? It will not budge at all.

 

Penetrating oil, heat, tap with hammer, center punch, drill, extractor, remove busted extractor, drill progressively larger until you can chip the bolt threads out of the intake threads, helicoil, machine shop for thread repair. Lots of options.

 

You can try to mig weld a nut to the broken bolt.
The heat from the welding will help un-seize the bolt and the nut gives you something to put a wrench on to remove it.

 

+1 This works the best,.... Bolt is steel, intake is aluminum. I got 3 snapped exhaust manifold bolts out of the head in my truck using this method. Took a Small fraction of the time that trying to drill them out would have taken.

 

Well after drilling the bolt completely out, I didn't realize I went a bit to far and now there a drill hole through the thermostat bolt screw-in. But not through the manifold. I was hoping the new threads I just did would prevent any coolant from leaking. Made new threads and bolted it down and nothing was loose. But started the car and a small puddle gathers around the housing. Did I mess up my manifold?

 

Did you replace the water outlet? If not, it's probably because the old one is warped. It's chinesium garbage; replacement ones are cast iron. Get one, and paint it with marine primer and marine engine enamel.

When you change it out, use stainless bolts, and put the Loctite/Permatex automotive thread sealer on the bolt threads.

 

Thank you all for info. I took it apart and looked around and there was a groove in the new gasket I put on. Come to realize I didn't FULLY scrape the old gasket off of the thermostat housing... Right I felt kinda dumb about it but also glad cause it wasn't the new bolt hole or anything. I put a water pump/thermostat sealant I got from Napa and some thread sealant for the new bolts and it works! No leaks and she warms up fine now. On to the next problem to fix!

 

Sorry my response is late but welding a nut on is my first suggestion also. Always easier than trying to drill out and extract a broken off seized bolt. If the bolt turned at all during removal before breaking, then drilling and extracting is a good option.

Glad you got it fixed.

 

Hi,
Just broke both of mine and will trybgwtting them out later.
A question thou, what are the dimensions of the two bolts?

 

3/8"-18 if I remember right. Don't know the length, but that should be pretty easy to figure out. What I did and would suggest to others is to replace the bolts with studs and use flange-nuts to fasten the T-stat housing. I used stainless steel studs...