The FSM procedure for replacing the CDI glow plugs specifies using a pair of cylindrical brushes, 6mm and 10mm. So I got a set of brushes. What about also using compressed air to dislodge the carbon? Any downside to that?

__________________
14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 178k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 75k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Why would you want to blow dislodged bits of carbon deeper into your engine?

Use a shop vac to remove the bits instead.

__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now

I don't have a suitable vacuum.

Won't dislodged carbon fall into the engine when using the brushes? Why would that matter...won't it just get blown out the exhaust?

__________________
14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 178k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 75k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

You can use compressed air to pull a vacuum, just blow air through a tee with both ends open. The tee side will pull a vacuum:

__________________
$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

Bucket Head 5 gal. 1.75-Peak HP Wet Dry Vac-BH0100 - The Home Depot

For $20 plus tax, you can't go wrong.

__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now

Thanks for the tips/recommendations. But as to the fate of carbon that drops down into engine....it just gets blown out the exhaust, right?

__________________
14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 178k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 75k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

AFTER it gets dragged up and down the cylinder walls. Usually causes no problem when it's loose but using compressed air can force it into any gaps of the rings, valve seats, etc.

Your car, your money.

__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now

Thanks for the clarification....makes sense just to stick with the brushes like MB recommends.

__________________
14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 178k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 75k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Put this on your Xmas/wish list.

https://www.shopvac.com/product/shop-vac-5-gallon-4-0-peak-hp-hardware-wet-dry-wall-mount-vac-catnum:3942300

Handy to have and it's one of those things you wonder how you did without. Keep an eye out for specials. I picked mine up for $39.95 at Ace Hardware during one of their spring special savings deals.

__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now

This is another good method if you have compressed air. If you tie wrap a breathable cloth bag to the discharge port you can capture the carbon.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

why not just isolate the starter solenoid wiring and turn the engine over by hot wiring the starter (like you do on a compression test on these engines)

Any carbon, dust, tools etc will be shoved out of those holes with super high pressure from the cylinders.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)