How to Install Rinse-Aid Dispenser Cap WP8558307 in a Whirlpool Dishwasher
Quick answer: Open the Whirlpool dishwasher door and twist or pry the old cap off the rinse-aid port on the inner door panel. Wipe the port, fill the reservoir to the mark, then press cap WP8558307 onto the port and turn it until it locks. Run a cycle and confirm no rinse aid weeps around the cap.
The rinse-aid dispenser cap WP8558307 closes the rinse-agent reservoir built into the inner door of a Whirlpool dishwasher. It keeps the liquid inside the dispenser until the final rinse, when a small metered dose is released. When the cap cracks, loses its seal or the locking tabs wear, rinse aid drains out during the wash, the reservoir empties in a couple of cycles and dishes come out spotted. A missing cap also lets wash water into the dispenser and dilutes what is left.
Our fitment data lists this cap for 950 models, mainly Whirlpool and Kenmore dishwashers such as 66516299402, GU2451XTST1 and GU2600XTPT6. It is one of the easiest dishwasher repairs there is: no tools, no wiring and no need to remove the door panel. This guide covers how to remove a worn or stuck cap without damaging the port, how to seat the new one so it actually seals, and what to look for on the next cycle. A short video exists for this repair as well.
See part details and every compatible model: WP8558307
- Let the door cool if a cycle just finished; the inner panel and any rinse aid residue can be hot.
- Rinse aid is a detergent, so keep it off skin and out of eyes, and wipe up drips before they run onto the floor.
- Do not force a stuck cap with a metal screwdriver; a cracked dispenser port means replacing the whole dispenser, which is a much bigger job.
Tools and Parts You Need
- Clean cloth or paper towel
- Rinse aid to refill the reservoir
- Flashlight to inspect the port
- Small flat plastic tool if the old cap is stuck
- Coin or large flat screwdriver on cap styles with a slot
Step-by-Step Installation
- Open the door and find the dispenser Open the dishwasher door fully. The rinse-aid reservoir sits on the inner door panel next to the detergent cup, with a round cap marked for rinse aid.
- Remove the old cap Turn the cap counterclockwise a quarter to half turn and lift it out. If it is a pry-off style, slide a plastic tool under the edge and lever gently. If the cap is broken, pick out any pieces left in the port.
- Inspect and clean the port Shine a light into the opening. Wipe dried rinse aid from the port rim and the threads or tabs with a damp cloth, and check for cracks in the port itself.
- Fill the reservoir Pour rinse aid slowly into the port until the level reaches the full indicator. Wipe away any spill on the door so it does not foam during the next wash.
- Check the new cap Compare WP8558307 to the port. The gasket or sealing lip on the underside should be intact and the locking tabs should match the slots on the port.
- Seat and lock the cap Press the cap onto the port so the tabs enter their slots, then turn it clockwise until it stops. It should sit flush with the door panel and not lift when you pull on it lightly.
- Run a cycle and check Close the door and run a normal wash. Afterward, open the door and look for rinse aid weeping around the cap or a sudden drop in the level indicator.
Fit Checks Before You Call the Job Done
- The cap turns and locks without forcing and sits flush with the inner door panel.
- The cap does not lift off when pulled lightly by hand.
- No rinse aid appears around the cap rim after a full cycle.
- The level indicator drops slowly over many cycles rather than emptying in one or two.
- Dishes come out without spots, which shows the dispenser is dosing normally.
Common Mistakes to Avoid
Overfilling the reservoir Rinse aid above the fill line spills into the tub during the wash and causes heavy foaming. Stop at the mark and wipe up the excess.
Cross-locking the cap If the tabs are not in their slots when you turn the cap, it sits crooked and leaks. Press it down first, then turn.
Reusing a cap with a hardened gasket An old gasket looks fine but no longer seals. Fit the new WP8558307 rather than swapping caps between machines.
Prying with metal tools A screwdriver tip cracks the plastic port. Use a plastic trim tool or a coin in the slot only.
Leaving residue in the port Dried rinse aid on the sealing surface stops the cap from seating flat. Clean the rim before fitting the cap.
Troubleshooting After Installation
Rinse aid runs out after one or two cycles The cap is not locked or its gasket is not seated. Remove it, clean the rim, and refit, making sure it turns fully to the stop.
Foam or suds in the tub Rinse aid spilled during filling or the reservoir was overfilled. Wipe the door, run a rinse cycle to clear the suds, and fill only to the mark.
Dishes still come out spotted Confirm the reservoir has rinse aid and the dispenser setting is not on its lowest dose. If the level never drops, the dispenser itself may be blocked or faulty.
Cap will not lock Check that the port tabs are not broken and that no old cap fragment is in the slots. If the port is damaged, the dispenser assembly needs replacing.
Care Tips After the Repair
- Top up rinse aid when the indicator shows low rather than letting it run dry.
- Wipe the cap and port rim each time you refill so residue does not build up on the seal.
- Remove the cap and rinse it under warm water every few months.
- Adjust the dispenser dose setting if you see spotting or streaking rather than overfilling.
Compatible Models (Sample)
This part is listed for 950 Whirlpool models in our fitment data. Always confirm your exact model number on the appliance's rating plate.
Repair Difficulty and Time
Difficulty: Easy. Typical time: 5 to 10 minutes.
Frequently Asked Questions
Which dishwashers use rinse-aid dispenser cap WP8558307?
Our fitment data lists it for 950 models, mainly Whirlpool and Kenmore units such as 66516294400, 66516479300 and GU2451XTST1. Check the model label on the door edge to confirm.
Do I have to remove the door panel to change the cap?
No. The cap is fitted from the inside of the open door. The dispenser body stays in place.
Why does the rinse aid empty so quickly?
Almost always because the cap is missing, cracked or not locked. Rinse aid then washes out during the main cycle instead of being dosed in the final rinse.
Can I run the dishwasher without the cap while I wait for the part?
You can, but leave the reservoir empty. Water will get in and any rinse aid inside will wash out immediately and cause foaming.
Final Checklist
- Door cool and fully open
- Old cap and any broken fragments removed from the port
- Port rim and tabs cleaned and inspected for cracks
- Reservoir filled to the indicator, not above
- Cap WP8558307 pressed on and turned to the stop
- Cap flush and secure when pulled lightly
- Cycle run with no weeping around the cap