[ROVERNET - UK] p6b- stripped thread on thermostat housing

rogerdm at iprimus.com.au rogerdm at iprimus.com.au
Mon Sep 20 00:55:52 BST 2004

We have all done it either on the thermostat or the water pump.  If you are
going to drill out the old bolt then geting the drill exactly square is very
important, and having a look at my car it will be difficult in situ and I
would be taking out the inlet manifold.  Before drilling out the bolt have
you considered an "easy out".  You drill a hole approx 3/4 of the diameter
of the bolt and screw in an easy out which has a left hand "thread".  As
you tighten anti clockwise, hopefully the broken bolt will unscrew.  BUT
you must have the best quality easy outs and use the correct drill size.
AND you must use plenty of penatrating oil and give its lots of time to soak
in.  Assuming you can get the housing square consider drilling right down
the centre of the bolt and into the chamber between the end of the bolt and
the end of the hole.  Get precise measurements of the hole and the length
of bolt and perhaps another netter can give you these measurements sooner
than I can   The point is that such a hole enables you to squirt penetrating
oil into the chamber so it can work both ends of the bolt.  If this technique
fails you can still drill out the bolt and re tap it.  You can use a re threading
kit called helicoil that will insert a thread into the new thread with an
internal diameter of the original bolt.  This is the technique used to repair
spark plug holes.  Sometimes you can get left hand starting taps which have
the same effect as easy outs, and they sometimes remove the bolt before starting
to cut the new thread.  Assuming you are brilliantly successful consider
using threaded rod with a nut to bolt up the housing.  This means you can
get the housing off in the future with studs protruding from the housing
that need not come out if you replace the thermostat in the future.  In fact
if such problems are suspected then it is beter to drill of the head of the
bolt, remove the hosing and then have an exposed bolt to grip with a locking
vice grip and visually see whether it is unscrewing or breaking as it is
gently turned.  This allows the soaking in pentrating oil trick before the
bolt is broken.  Why not take off the manifold and see if you can set it
up in a drill press.  Use a top quality centre punch and a small drill to
make sure you are drilling down the middle.
Good luck and no bad language likely to offend our delicate ears        
>-- Original Message --
>From: "Peter Mitchell" <peterm at arach.net.au>
>To: "Rovernet" <rovernet at lyris.ccdata.com>
>Date: Sun, 19 Sep 2004 20:02:56 +0800
>Subject: [ROVERNET - UK] p6b- stripped thread on thermostat housing
>Reply-To: rovernet at lyris.ccdata.com
>Hi Rovernetters
>Today I changed the thermostat on my P6B 1976, as the engine has been taking
>forever to warm up.  Despite my best efforts, I stripped a thread when
>replacing the bolts on the thermostat housing.
>I have a tap to re-thread the hole a size larger to take bigger diameter
>bolts.  As a rooky Rover owner my questions are please Netters:
>Access is going to be a problem - should I remove the distributor to get
>clear shot at retapping the thread by hand?  Or would I be best to take
>the inlet manifold entirely?
>Please forgive the lack of knowledge displayed and your responses will be
>genuinely appreciated.  We are hosting the National Rove, a get together
>Rovers from all over Australia, next week, and my car may not be leaving
>garage at this stage.
>Kind regards
>Peter Mitchell
>Perth Western Australia
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>rovernet at lyris.ccdata.com
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