Troubleshooting a Leaking Hot Melt Module

Hot melt equipment is designed for precision, but productivity can quickly suffer when a module starts leaking adhesive. If glue seeps from your applicator’s nozzle even when the system pressure is low, you may be dealing with a simple but correctable issue: spring tension.

In this case, the hot melt adhesive module is leaking glue due to the spring tension not being high enough.

How to Adjust Spring Tension on a KEYSTONE Applicator

At APPLIED Adhesives, our KEYSTONE hot melt glue modules — part of our trusted proprietary parts brand — are built for reliable, trouble-free operation in your hot melt adhesive applications. These air-open/spring-close assemblies are engineered to meet the rigorous demands of your production environment.

But even the best components occasionally need fine-tuning.

Below is a complete walkthrough explaining how to diagnose and resolve glue leakage caused by incorrect spring tension. Watch our expert technician show you how it’s done in our troubleshooting video, or read the step-by-step instructions.

Safety First

Before servicing any adhesive dispensing equipment:

  • Always wear appropriate personal protective equipment (PPE). Hot melt components and adhesive may still be heated!
  • Power down and unplug the equipment. Before performing any maintenance, make sure everything is shut off.
  • Grab the right tools. You’ll need a standard X-head screwdriver. Do not use a power screwdriver or drill.

Step-by-Step: Adjusting the Spring Tension

  1. Locate the Spring Tension Adjustment Slot:At the top of the KEYSTONE module, you’ll find a slotted section designed to allow spring tension adjustments. The spring tension is preset at the factory to work with most adhesive materials. However, if your module is leaking from the nozzle, a slight adjustment may be required to suit your specific adhesive formulation.
  2. Loosen the Retaining Nut: Use your screwdriver to turn the retaining nut counter-clockwise.
  3. Tighten the Adjustment Screw: Turn the adjustment screw clockwise until it bottoms out. Be sure not to overtighten.
  4. Back the Screw Out by 3½ Turns: Once you’ve backed the adjustment screw out by three and a half full turns, re-tighten the retaining nut securely.

Verify the Fix of The Hot Melt Module

Once your system is powered back on, observe the module operation. You should now see the module fully close as air pressure approaches 0 psi.

If you’re still seeing adhesive leaks from the discharge port, and you’ve already flushed the dispensing system, follow these steps:

  • Loosen the retaining nut again.
  • Tighten the adjustment screw clockwise in ¼ turn increments until the leak stops.
  • Re-secure the retaining nut.

Note: This adjustment will not impact adhesive flow rate.

Adhesive Equipment: Back in Action

With the spring tension dialed in, your KEYSTONE module should now be running clean, efficient, and leak-free, just as it was designed to. If you’re still experiencing issues, our factory-trained field technicians are always here to help you troubleshoot and optimize your dispensing system.

At APPLIED Adhesives, we don’t just supply equipment and parts — we deliver full-service and custom adhesive solutions designed to keep your lines running at peak performance.

Need help with hot melt adhesives, equipment, parts, or service?
Reach out today. We’re ready to support your process with the right expertise, right when and where you need it.