Well, figuring the thermostat hasn't been changed since my '78 280Z left the factory decades ago (and it hadn't), I took the task of pulling off the 30 min quick job...which has now turned into a multi-day project (since it's now parked/stuck at my buddies apartment instead of my driveway).

My problem: I took the upper part of the housing off after snapping one of the bolts (closest to the head) off. Other one was rusty as all hell, but I babied her out fine. So, I get the cover off and pull the thermostat, clean off the old gasket, yada yada, and then to the task of extracting the remainder of the other bolt. Well...I'm still on that task... after PB Blaster, vice grips (which has grinded the bolt into what looks like a rectangular object now), hammer and screwdriver, tapping, back and forth, brute force, jedi power, hopeful wishing...everything. I've got a small propane torch, but I'm kinda hesistant because it's so close to fuel lines :dead: so I'm lost. I'm tight on time as I need it back to the house (baby due any day now), but I'd like to prevent having to replace the entire housing and run the risk of breaking those bolts! Any other ideas that I haven't seen on the search engine? Thanks!

Ugh! Sounds like you are trying all the right things. Didn't see you mention trying an E-Z-Out, though.

You are right to be concerned about the actual T-Housing to Head bolts. If the Cover bolt sheared, then the Housing to Head bolts are likely in similar shape.

EZ Out huh...tell me more.

Originally posted by TrojanOreo

EZ Out huh...tell me more.

Well, the name doesn't "exactly" describe the process, but basically what you do is drill a hole through the center of the broken bolt (as large as possible without buggering the threads of the housing, then insert the EZ OUT "Screw Extracter" which has flutes that are reversed from the direction of the threads, and you carefully try to back out what is left of the bolt using lots of penetrating oil and care.

Link to a Craftsman Tool Page

Picture of an E Z Out (Screw Extracter) below

Sears also has a new type that looks like a broken drill bit with the spiral going counter clockwise. Use extreme care with the EZ out. Usually the new post will read -Broken ez out. Those are harder metal than a drill bit. My get you home fix would be drill the center of the broken bolt. Get a few sheet metal screws that almost fit the hole. use them to 'tap' a hole.The reason for changing screws is fresher cutting threads and less fatigue of the screws.Once tapped use a washer on the cover. I ran one like that for years. I did remove it finally by drilling a little into the broken bolt ,then put the drill on reverse and press hard for a while. A few times of that and to my surprise it backed out!!

Hey man, I feel your pain. I just went through the same thing.

I replaced my manifold with headers and had a stud that broke off.

I tried an EZout but after breaking 3 drill bits and 2 EZouts I ended up drilling the hole out and using a helicoil.

after that project I realized my thermostat housing was cracked. I went to the local Zcar graveyard and bought a used one.(only because I wanted to start my car that day)(wishfull thinking).

Well when I got the housing unit home, the threads on one side were striped. I drilled it out and used my 2nd helicoil. It worked like a charm.

Have you considered replacing the stat housing? I wouldn't even mess with that old crap. After 30 years, that's usually the way to go.

-OR-

I have seen several where the cover bolts were drilled all the way through and a nut put on the other end of a new longer bolt.

steve

Ok, tonight's adventure:

I got tired/pissed off at the bolt, so I snapped it off and drilled the rest out, or I figure a good 99.9% of it. Here's the tool I got to finish the job, but I'm not too sure how to go about using the tap. The directions were far from descriptive, so I'm hoping someone can help me figure out how this goes. Here's a pic of the tools that I bought (from AutoZone).

The red installation tool and thread I'm sure is self-explanatory, but the tap it tells me to "Tap thread carefull using correct procedures". What the heck is the correct procedure? Thanks again everyone!

Somewhere on the package or the tap itself it should tell you the size drill bit you will need to use to drill out the hole the bolt was previously stuck in. Then you use the tap to thread the now larger hole. Then you use the red handled tool to install the heli-coil (new threads) which should restore the hole to the proper original bolt size.

***To use the tap, you'll need a "Tap" handle (or wrench) not sure what it is properly called. Be careful to drill perfectly straight down and to use the tap straight up and down also.

EDIT: Oh yeah, Like MikeW says below, you need to use lots of oil while cutting threads, and you back out the tap every 2 or 3 turns to clear the metal flakes out of the tap and hole.

Originally posted by TrojanOreo

The red installation tool and thread I'm sure is self-explanatory, but the tap it tells me to "Tap thread carefull using correct procedures". What the heck is the correct procedure? Thanks again everyone!

Normally you just drill the proper sized hole and run the tap in. You use a cutting fluid which keeps things lubricated. There's usually some sort of handle to turn it with, however.

Thanks a million guys!! I'll hunt down that tap wrench and get on it. Hopefully I can wrap this up tomorrow night!

Bambiker explained it perfectly. Although the part you are tapping is aluminum and you probably wont need any oil. I tapped the exact same part. Before you tap make sure that tap and helicoil are metric. And make sure the helicoil is for the same size bolt you are using.

I know it seems dumb to mention but face it, when you are re-building a 30 year old car sometimes the brain doesn't catch up until you've done something dumb.

I'm gonna cry...

Drilled the hole, tapped the hole, inserted the thread. So at this point, I'm ecstatic. Put everything together, fill'er up and....pssss....leaking anti-freeze right by that bolt.... :tapemouth

So, I'm giving up. Going to get another thermo housing. But first, I've got to get her home. Soooo, I'm gonna tighten down the working bolt and JB Weld the rest, leave it a day or two, and slow roll it the 10 mile trip home. I'm taking no chances when I get the new thermo housing. (well, not new, but y'know) It's heading to the shop (I can't believe those words just came out my mouth) to get installed so I don't have to deal with any more busted bolts, especially on the head.

Such a bummer. :disappoin

EDIT: I was browsing the MSA catalog, they have one for $30. Not too bad considering it'll be new. Anyone bought one or anything mechanical from them? I've bought tons of cosmetic stuff from here already with no complaints (except of course, some of the prices) but figuring it'll cost close to that at the junkers, I'm thinking why not. Any input? Thanks for everyone's help through this!