Repairing a Lego Duplo train engine

Reading time : 3 minutes
Published on 09 Mar 2021
Repairing a Lego Duplo train engine from Delux train set

This time, I will repair my daughter’s Lego Duplo train engine. It is from a Train Deluxe LegoDuplo 10508 set, but I found two issues.
First of all, the locomotive has to make “Tchou Tchou” sounds, but it remains silent. It is an advantage for my dad’s ears, but I like to fix everything.
Secondly, the locomotive is slipping and cannot climb the bridge hill properly.

Train engine teardown

Lego Duplo train engine
Lego Duplo train engine

Here is the train engine I disassembled.

Lego Duplo train engine bottom view with instructions to remove battery cover
Removing battery cover

The first step is to remove the battery cover. It can be extracted by removing the two indicated screws.

Lego Duplo train engine bottom view with instructions to remove bottom screws
Removing bottom screws

The three screws holding the red top part of the locomotive and the bottom part must now be removed.

Lego Duplo train engine bottom view with instructions to remove top cover
Push there to remove top cover

To remove the top cover, you will need to be patient. There are four plastic clips to remove.

  1. Insert two small flat screwdrivers between the red and black plastic part on the outside.
  2. Carefully lift the top cover.

The operation will have to be repeated twice, once for the front and once for the back.
I had a lot of trouble, the opening is not easy.
If by mistake you have broken one or more fasteners, do not panic. The screws underneath will still maintain the top cover correctly.

Here is a video that can help:

Lego Duplo train engine top view without top cover
Train engine without top cover

After a lot of patience, the top cover finally comes off.

Replacing the speaker

So we can move on to repairing the loudspeaker.

View of the Lego Duplo train engine broken loudspeaker
Broken loud speaker

I found that the speaker producing the sounds is broken, its small PCB is simply detached. It feels like a violent shock, like a locomotive flying through the room during an epic child war. 👿

Brand new loudspeaker that will be used as a replacement
Brand new loudspeaker

I was able to order a small loudspeaker on AliExpress for a few euros and it arrived few weeks after.

Repair of the engine gear

Gear part of the train engine. Screws to remove are indicated in orange
Remove those screws to open motor block

To repair the motor part, first remove the two screws indicated which are holding the gear unit in place.

Train engine removed from gear box
Train engine motor removed

To take out the motor, the two parts of the gear unit must be carefully separated, it is then possible to take out the motor.

Location where to add some glue to fix the output gear motor issue
Add glue there to attach back output gear to the motor shaft

In my case, I noticed that the plastic motor output gear was detached from the motor shaft. As soon as the slope to be climbed by the locomotive was too steep, the motor shaft was turning alone without its gear.
So I added some Cyanolite glue (super glue) at the indicated place and reassembled the gear.

View of the fixed motor part of the train engine
Fixed train engine and speaker

Now that everything is fixed, I have put everything back together.


Another small victory over the machine, this Duplo locomotive works perfectly again. My daughters are happy and can play again at the little railwayman.

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