It finally happened. At 18 months our Britax Marathon 70-G3 Convertible Car Seat became a hotbed of spilled milk, baby farts, Cheerios, and juice. It needed to be cleaned. If you’ve ever wondered how to clean a Britax Marathon, hopefully this works for you.

I put off cleaning it for a couple of weeks as we’d been mostly ferrying Maggie around in my car, but it became a thing recently where I placed her in and pulled her out and there was a sticky separating sound, so it was time.

Cleaning the fabric and padding once it’s off is easy: wash cold/cold, little or no tumble/agitation, I air dried but if you’re considering a dryer, remember that hot air drying destroys velcro. Do not wash the belts or buckles. We’ll talk about all belt materials in a minute.

Wipe the plastic seat off with a paper towel and mild detergent or water to remove the hot mess of Cheerios you’ve somehow accumulated through the fabric.

Unfortunately, taking all the stuff off and putting it back on is not easy. I’m here to help with some pictures and how I did it.

Warning: this will take a while

not quite a warning: all pictures below the text

How to clean a Britax Marathon car seat

Removing the pieces

1. Remove the car seat from the car
2. Turn the seat around, get this stuck in your head
3. Remove the shoulder straps from the metal hook (you’ll need to squish them)
4. Pull the shoulder straps out the front of the car seat
5. Remove the piece of fabric that is behind your baby’s head and back. This is on the center slider and is secured by two stretchy loops
6. Empty the pouch of anything that’s in it
7. Notice that the main body of the car seat covering has two plastic clips up top and two down below that keep the seat in place. These pop out with next to no force
8. To remove the crotch strap, feel under the seat and you’ll feel the metal on the other side the prevents it from moving. I managed to rotate the strap by about 90 degrees and slide the fastening buckle up. You’ll get it when you do it but it’s impossible to photograph and a bit difficult for me to explain
9. Once the strap is removed, you need to turn the metal buckle about 45 degrees and slide it through the thing that’s holding the strap. You’ll need to pull and poke to get it through, but it’s not terribly hard. This will free up the crotch fabric for washing
10. At this point you should be able to remove the main body of the car seat covering
11. remove the foam butt pad

Washing the parts

Wash all the stuff you removed on delicate / cold / cold. Little or low agitation. No bleach unless you want everything solid white.

Do not wash any buckle or strap. Washing the straps in theory can destroy them. I’m skipping out on commentary on whether this is the case or not as I don’t have any evidence one way or the other. Just repeating what I was told to never do.

Wipe down the plastic main seat with some mild soapy water.

If you washed everything, squeeze the remaining water out of the butt pad, air dry the remainder.

Putting the Britax Marathon back together

• Place butt cushion in appropriate location
• Re-make the crotch strap, but do not insert it into the plastic seat base
• Place main car seat body loosely over everything
• Re-inset crotch strap in appropriate location (through cover, through car seat, into latching area)
• Replace sliding back seat cloth. Secure with the two pieces of stretchy fabric loops
• Secure the main cloth seat body to plastic body using the four plastic connectors, pull side fabric over areas it needs to be
• Place should straps back in appropriate holes. Make absolutely sure they’re not rotated around weirdly. They should look flat
• Reconnect should straps to metal hook, keep in mind first one goes on easy, second you’ll have to scrunch up a little bit
• Fluff out everything – you should be done
• Place baby in car seat, adjust belts and straps while you’re inside as it’s easier to do here than it is in the car
• Take baby out of car seat, place baby in hands of other parent or crib, place car seat properly in car, return to baby, celebrate accomplishments

Cleaning the belt and buckles

Surface clean the belts with water and nothing else if possible. Bring soapy stuff into the equation only if really needed. Make sure the belt buckles are cleaned and cleared of Cheerio debris. You might need alcohol and q-tips.

The Britax marathon cleaning pictures

How long did cleaning the Britax Marathon take?

It took 11 minutes to disassemble the car seat. I had to double-wash the car seat as the soap didn’t get out of it the first time, so an hour there. Two hours sun time. About 20 minutes to re-assemble as that part was harder.

So figure half an hour of work to clean it, but five or so hours of it being out of commision.

Did I help?

Bottom right of every page is a donate link (right above the defunct Amazon wishlist.) Donations there go indirectly into making things dirty so I can write more cleaning articles. Or they buy me and the missus a bottle of wine. Who knows. Maybe I’ll just blow it on crack.

Did I err?

As at the current rate of needing to be cleaned it will be 2017, if I got anything wrong in how to clean a Britax Marathon car seat, let me know and I’ll correct it. Also if any of the Marathon seats are different a heads-up would be appreciated.