Which Loctite threadlock to use?

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Pete Bags
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Which Loctite threadlock to use?

Postby Pete Bags » Tue Sep 15, 2020 5:06 pm

I recently started a thread about fitting a water temp sender gauge, and then another thread about my attempt that ended in failure - I'm now pleased to say this has now been successful fitted!

I 'borrowed' a few drops from a friend's Loctite 2400 threadlock bottle for the job, and decided I will buy some Loctite threadlock for myself - I will lock the thermostat housing nuts and heater tap valve nuts that seem to loosen themselves from time to time - but there a number of different Loctite threadlock products available, many which seem to do the same thing - eg Loctite 242, 243 and 2400. Any a few more. Which should I get?

Which Loctite threadlock numbers do you all use, and for which applications?

Many thanks!

Pete

les
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Re: Which Loctite threadlock to use?

Postby les » Tue Sep 15, 2020 5:29 pm

I don’t know the numbers but there are various strengths, ie medium, high, etc. I wouldn’t use the strong variety in fact I wouldn’t use any on the nuts you mention. In fact I would give the threads a smear of copper grease. It’s unusual for the nuts to come loose.
Last edited by les on Tue Sep 15, 2020 8:25 pm, edited 1 time in total.


philthehill
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Re: Which Loctite threadlock to use?

Postby philthehill » Tue Sep 15, 2020 6:12 pm

I use Loctite 243 Lock & Seal. It is a good all-round locking and sealing fluid.

https://www.ebay.co.uk/itm/10-ml-Thread ... Sw6xxe40uq

Loctite has a use by date so I would advise against purchasing large amounts. I always write date of purchase on the packaging.


geoberni
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Re: Which Loctite threadlock to use?

Postby geoberni » Tue Sep 15, 2020 7:47 pm

243 is a good medium strength threadlock.
When I was in the RAF we used loads of different numbers on different fixings and pity anyone who got the numbers mixed up. If you got it wrong you could either fail to lock a big bolt, or lock a small one so much you'd wreck it when it came to removal.

This is a good application chart for car use. 270 is for applications like Cylinder Head bolts.
LOCTITE Threadlocker Product Range_10_11.jpg
LOCTITE Threadlocker Product Range_10_11.jpg (612.3 KiB) Viewed 213 times
But these days the range is far wider, with tread locking pastes amongst other products.

I think you'll find a lot of Loctite products are typically 12 mth life from manufacture, but personally I think there's a fair bit of leeway on that.
For decades, the RAF supply system used to recall oils/lubricants/sealants etc where the manufacturers life had been reached, batch test them and extend the life if they were still fit for purpose.
It was not unusual to see Loctite that had been extended by 6 or 12 months; now if that was good enough for aircraft use....
I would say, if in doubt about a bottle that is over it's date, do your own sample test on a bolt/nut. :wink:
Basil the 1955 series II

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oliver90owner
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Re: Which Loctite threadlock to use?

Postby oliver90owner » Tue Sep 15, 2020 10:23 pm

As Les, I would use spring washers in those applications. Don’t think I’ve had them come loose on either item - ever.

Pete Bags
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Re: Which Loctite threadlock to use?

Postby Pete Bags » Wed Sep 16, 2020 11:05 am

Thanks all for your replies.

A couple of years ago I bought a replacement thermostat housing/cork gasket/bolts/nuts/washers kit from ESM - looking at the kit, it does not come with spring washers, and I wonder if that is why the nuts tended to come loose - combined with a squishy cork gasket.

I replaced my squished cork gasket with a new gasket after keen eyed @philthehill saw the photo of my failed water temp sender fitting (thanks Phill!) and that is why I want to use the Loctite, as I don't want the nuts to loosen again. Or should I replace the flat washers with sprung washers? Likewise on my heater tap valve. It sounds like @Les and @oliver90owner use sprung washers?

Kit from ESM
thermo.jpg
thermo.jpg (281.55 KiB) Viewed 160 times
Squished cork gasket
IMG_7958.jpg
IMG_7958.jpg (76.99 KiB) Viewed 160 times
New gasket in place
IMG_7993.jpg
IMG_7993.jpg (122.53 KiB) Viewed 160 times

philthehill
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Re: Which Loctite threadlock to use?

Postby philthehill » Wed Sep 16, 2020 11:27 am

You do not need to use Locktite on the thermostat studs/nuts - use spring washers between the flat washers and the nuts.
If you can find them - wide flat spring washers can be used without the flat washers.
https://www.ebay.co.uk/itm/UNF-IMPERIAL ... SwpLNX~jpw


les
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Re: Which Loctite threadlock to use?

Postby les » Wed Sep 16, 2020 11:45 am

I don’t use spring washers in this application, just plain ones but as Phil mentioned if you use want to use spring washers put the plain ones on first.


Pete Bags
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Re: Which Loctite threadlock to use?

Postby Pete Bags » Wed Sep 16, 2020 11:52 am

Thanks Phil and Les - it's so useful to learn from those more experienced than me.


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