stripped the external thermostat cap threads

[Kevin Taylor]

I stripped the external thermostat cap threads somehow.
Specifically the larger one with the larger spring that actually holds
the thermostat in place Seemed to be going on fine then halfway in
it would not tighten all the way down. When I went to
unscrew it I could hardly get it back out. Finally with a pipe wrench
and large long cheater pipe ......with two people it finally
busted loose. It destroyed the threads. Now I have filed everything
down smooth and cleaned it out again.
I'm thinking about welding the cap back on but wanted some opinions
from anyone. Any bad repercussions from doing this. Theoretically it
should work fine....Right?
Has this happened to anyone else. There must be some special German
tool for this cap. I was using a large screwdriver to get it started on then used a large steel washer ground down to fit the grove
for the final tighten it with a simple adjustable wrench. Worked fine on the smaller cap. I would have thought the smaller cap would have given me a harder time because that spring was actually stiffer.
I was pushing down constantly while turning. Did the parts cleaner fluid somehow weaken the threads?
Should I have oiled the threads when reassembling? I could not believe it was so destroyed when I got it back off. I was trying to be very careful on putting it in but it just got tighter and tighter to turn going in.

How did it cross thread on me? Thanks for your replies in advance.
K.T.

1973 911 E 2.4 MFI
1983 911 SC
1978 911 SC
1965 Devin "D" / 1967 912 Power Plant
1998 GMC Serra 4X4 Z71
John Deere LT166
Money Can Buy Happiness........Buy A Porsche......a

[rusnak]

time for a new thermostat, not repaired or rebuilt.

[Jim Sims]

Bare/clean aluminum threads gall (weld together), therefore they should always be coated with an anti-seize compound such as "Never Seize."

See below thread for image of a tool we made to match cap slot:

External Thermostat Screw Caps

No experience welding the alloy in these housing so I can't comment other than saying that it's a one-way operation.

[Kevin Taylor]

Well............ went ahead and had it welded on yesterday. Really looks good.
He did a nice job on the weld. Will try it and report back.

K.T.

1973 911 E 2.4 MFI
1983 911 SC
1978 911 SC
1965 Devin "D" / 1967 912 Power Plant
1998 GMC Serra 4X4 Z71
John Deere LT166
Money Can Buy Happiness........Buy A Porsche......a

[KTL]

I recall someone saying that excessive heat could be bad for the thermostat because of the wax components inside it. Do you think this is true, based on your findings when you disassembled the thermostat?