Broken bolt in thermostat housing: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Dec. 7, 2011 1:30 p.m. ArthurDent Reader

Last night I thought I'd like to get some heat into my Micra by replacing the thermostat. Easy right? Well it was until one of the bolt heads broke off. I made a quick attempt at drilling into bolt to get an extractor in but the way it snapped off keeps the drill bit moving to one side or the other. Ugh. Now the threads are probably messed up too. Now two of three bolts have nothing behind them I could have just drilled out the whole and put a bolt in and a nut on the other side but not this hole. Argh. What are my options now? I can take to a mechanic I guess and pay a bunch of money for it to be put right. Given I only paid $160 for the car I'd rather not. Seems mental to give up on the car over something like this too. I rather like it too. Someone suggested I put in the other two bolts and then JB weld all around the housing. I'm skeptical as JB has never actually fixed anything for me yet. No doubt the new thermostat will last the rest of the lifetime of the car. I can put the two bolts in and pour coolant in but it bubbles out around where the third bolt should be without the engine running. Ideas?

This is what it looked like before I started messing with it.

As a bonus found a dead bird - I had to pull the radiator and hopefully fix the broken bolt in the thermostat housing and found the remains of a dead bird in there. Not much left.

is it mocking me? With all the dirt on there the valve cover spells out SSA which when turned backwards is ASS. Yes it gave me a little chuckle but perhaps I am easily amused.
Dec. 7, 2011 1:52 p.m. Don49 Reader

You can try center punching the bolt and then use a 1/8" drill bit to create a pilot hole. This should allow you to then use progresively larger drills and then an easy out or if the threads are buggered, helicoil it.
Dec. 7, 2011 2:42 p.m. Curmudgeon SuperDork

Okay, so the busted part is like half the bolt left in the hole, right? If so, it's going to be a time consuming little booger but not impossible. Soak it in PB Blaster or etc for a day or so, then use a small punch and a hammer to tap the broken part away from the threads it's stuck to, i.e. toward the hole you drilled. Once you open up a small gap, squirt PB etc back in the hole and leave it for a while. Then see if you can tap the broken piece out in a counterclockwise direction with the hammer and punch. It should evantually move, when it does put the punch down and get the needle noses, keep working it in that CCW direction. It will eventually start to thread out. Once it's out you can assess whether the hole will need a HeliCoil or similar.

If that fails, from your picture it looks like the bottom half of the t-stat housing bolts to the end of the head. Sometimes that kind of stuff is amazingly cheap new. Or you can take just the housing off and see if a machine shop can get the busted piece out.
Dec. 7, 2011 4:05 p.m. Streetwiseguy Dork

How sharp are you with a welder? I can probably get it out in 15 minutes or so, but that involves a tow to Saskatoon...Call around and see if you can find somebody local that knows about welding a nut on the broken stud and removing it. Don't worry too much about the threads, you will chase them straight when you screw the remains out. What you don't want to do is get frustrated and drill out the side of the stud into the aluminum.
Dec. 7, 2011 4:14 p.m. TRoglodyte HalfDork

Flag down a tool truck and get a set of left hand drill bits. work with the smallest bit to get rhe center back where you want it. As Curmudgeon said ,Patience is your friend.It took years for it to rust in there, it will take time to remove it.
Dec. 13, 2011 12:17 a.m. ArthurDent Reader

Too far down the hole for me to attempt welding. It wasn't rusty - bolt head just came off.

Well I got the bolt out. Messed up the treads really nicely :(

Drilled out a bit and used a tap and die set to create new threads. It promptly broken the tool and messed up the hole further. :(

I swear this car is trying to kill itself. Argh. I don't know what the hell to do now.
Dec. 13, 2011 8:20 a.m. TRoglodyte HalfDork

Tap broke in the hole?
Dec. 13, 2011 8:59 a.m. ArthurDent Reader

I got it out but messed up the threads (again).
Dec. 13, 2011 9:22 a.m. Curmudgeon SuperDork

Ow. Okay, a fix: go to the 1932 Datsun thread page 6 and look at how ditchdigger made his threaded insert.

http://grassrootsmotorsports.com/forum/off-topic-discussion/my-datsun-build/18604/...

You'd need to adjust for the size bolt you will need, of course. Another thought: there are 'stepped' studs out there, they have a large thread on one end and a smaller one on the other.

http://www.034motorsport.com/hardware-fittings-hoses-metric-hardware-step-stud-8mm...

That might do what you need.
Dec. 13, 2011 10:02 a.m. 44Dwarf Dork

You can find stepped studs at the local hardware store in the "mid west fastener" boxes
Dec. 13, 2011 2:49 p.m. TRoglodyte HalfDork

Is it open around the bottom? use some aviation gasket sealer ,two bolts and a hose clamp around the whole housing? Drill through and use a nut?
Dec. 13, 2011 3:44 p.m. ArthurDent Reader

Funny you say that - two out of three bolts are open at the back and I had that exact thought. I suspect you can guess which hole is not open at the back ...
Dec. 16, 2011 10:43 a.m. ArthurDent Reader

I gave up and took to a mechanic. He fixed it for a $100 so not too bad I guess. Funny thing is the new thermostat didn't even fix my no heat problem - just had to flush the heater core. Ugh.

So I feel a little bit like a failure but my car is now drivable again. First time I've visited a mechanic for something other than tires or mandatory safety inspection in almost a decade so can't really complain.

Thanks everyone for all the suggestions.
Dec. 16, 2011 11:34 a.m. TRoglodyte HalfDork

How did he fix it? $100 sounds like a steal. I find the price of aggravation very hard to quantify.