View Full Version : Trouble! I crossthreaded the lower thermostat bolt

08-20-2006, 11:07 AM
Really simple maintenance item, replacing the thermostat. Been runnin a touch warm and I did not know how old the thermostat was, I knew it was at least 5 years so be on the safe side said I and replace the old with the new.
All was well until I reassembled the housing connecting the two halves new gasket and blue sealant in place.
I started the bottom bolt and evidently my old fingers and eyes betrayed me because once I should have been at proper tightness the bolt spun on me. Not a happy camper.
So........ what do you all think, should I re-tap the hole and make it a bit bigger, not my first choice. How about a sleeve and back it off with a nut?
How about just leave well enough alone to begin with, too late.
I believe I will disassemble the whole enchilada and sit and stare for a day or two.
By the way, the wife is really unhappy, I just tightened up the new clutch after a 300 mile break in and boy does she feel great. The car that is.
In trouble again.

08-20-2006, 11:20 AM

Try re-tapping out the original thread original size and thread first. If that does not improve the thread try tapping out the original thread the same size but try coarse thread (Use coarse thread bolt). If that doesn't work your into heli-coil, filling, and or drilling using larger bolt.


08-20-2006, 11:30 AM
As Harry recommends, take the time to fix it correctly now, even if it means the heli-coil route. You will probably be sorry if you take a shortcut or at the worst, leave it alone.

08-20-2006, 03:55 PM
Winston: "Never time to do it correctly but always
time to fix it"

Do it right the first time my Grandma always said.

I am spending big $$$$ and months and months of my
time fixing/repairing/replacing things the PO did
not have the time to deal with.

Do it correctly and you have to do it only once!!
Take the time, you'll not regret it.

Geo Hahn
08-20-2006, 06:43 PM
Well, worst case is a new housing -- they come up on eBay regularly for modest money.

Has anyone tried a 'Thread Restorer' product? I think it is made by LocTite. The kit looks to be a 2-part mix and a release oil. Not cheap but makes some interesting claims re torque it can handle. Obviously you wouldn't use it for a critical component but that Tstat housing doesn't have to be cranked down real hard to seal up fine and an immediate visual check would confirm if it is okay.

This is the stuff --

https://shop.torresen.com/ships_store/ind...81668&frm=g (https://shop.torresen.com/ships_store/index.php?p=details&mfc=PERMATEX%20/%20LOCTITE&sku=81668&frm=g)

08-20-2006, 08:38 PM
On the TR6, one of the bolt holes goes all the way thru to an open space. If this is the case on the TR4, consider just using a bolt with a nut and lock washer that can be placed from the bottom? If this is not an option, you should definately retread with HeliCoil, or equivilant.


08-22-2006, 07:41 PM
Winston, I beleive I have one for the TR4A, I think it''s a two part peice, the front has the thermostat in it and the rear bolts to the head with a overflow type pipe attached to it. If all else fails give me a e-mail and I'm sure we can work something out. Wayne

08-23-2006, 11:16 AM
I sent you a PM.


08-23-2006, 02:16 PM
When I decided to replace the thermostat on my TR6 (I had no idea how old it was), the first bolt came off cleanly, but the second one snapped right off at the thermostat housing. Lucky for me, it was the one that goes all the way through, so I drilled it out, hoping that the crumbling pieces would fall out and leave a nice threaded hole. The bolt seemed to be fused to the housing, so after a little more drilling, now I have a nice long bolt with a nut and lock washer holding it on, just as TR6BILL described above. Whatever works is OK with me.

By the way, when I finally got it open, there was no thermostat. Now, there is.