How much should I apply to the threads on a hydraulic fitting? It says 3/4 of a thread but I don’t know how much that really is...

Loctite 592 has a ribbon style nozzle, wide slot for discharge. The correct method is to hold the end of the nozzle up against the side of the fitting, so the width of the slot opening is across a few threads. As you squeeze the tube gently and dispense the sealant into the root of the threads, slide the nozzle around the fitting in order to go ¾ of the way around the tube. Feel free to go 360° around if you wish. That’s a little excess material but won’t really hurt. You end up with sealant in the root of the treads only, which is enough. Hope that helps.

Is the "activator" necessary or will the sealant work without it?

While the manufacturer recommends cleaning with their cleaner (that just happens to be a primer and activator) I have used the 592 thread sealant and even the 518 gasket maker with other cleaners such as vm&p naphtha (that is not a primer or activator) with excellent results. A primer is recommended when both surfaces are considered "inactive". The Loctite primer defines what this is.

How strong is the thread locker? Can fittings be removed?

This is not thread locker. This is thread sealant (like pipe dope). You will be able to remove the fittings.

I have a brass engine coolant temperature gauge leaking. Do i have to drain the coolant before using and let dry completely?

The fitting must be clean and dry prior to applying the 592, and it should be allowed to cure for at least 24 hours (preferably 72) before adding the coolant back into the system. Any other questions, please reach out to our technical team at 1-800-LOCTITE

ASIN	B0002KKTH2
Best Sellers Rank	#138,291 in Car & Motorbike ( See Top 100 in Car & Motorbike ) #135 in Fillers, Adhesives & Sealants
Brand	Loctite
Brand Name	Loctite
Colour	off-white
Compatible Material	Glass, Metal, Plastic, Rubber
Container Type	Tube
Customer Reviews	4.7 out of 5 stars 327 Reviews
Full Cure Time	24 Hours
Global Trade Identification Number	00079340373976
Item Form	Liquid
Item Package Quantity	1
Item Type Name	LOCTITE PST 592 Thread Sealant for Automotive: Low-Pressure, High-Viscosity, Anaerobic, Prevents Galling \| Opaque, Off-White, 50 ml Tube (PN: 483630)
Manufacturer	Loctite
Material	Anaerobic
Material Type	Anaerobic
Model	37397
Other Special Features of the Product	Prevents Galling, Anaerobic
Special Feature	Prevents Galling, Anaerobic
Specific Uses For Product	Fleet and plant maintenance.
UPC	079340373976
Unit Count	1.69 Milliliters
Viscosity	high
Volume	50 Millilitres
Water Resistance Level	Water Resistant

Loctite 37397 592 Thread Sealant (50-Mililiter Tube)

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