Something is Cycling next to firewall
 

2001 Montero, 3.5l. There is a pump (I'm guessing) next to the firewall that is cycling for maybe 2 seconds every 10 to 15 seconds. It is a black cylinder, maybe 4-5 inches in diameter with a nut molded into the top. It is located right up next to the brake fluid reservoir.


Could someone tell what it is please.


Thanks,
Greg

The black metal cylinder is brake accumulator. The cycling sound you are hearing is most likely from the ABS brake booster motor trying to build up pressure (and unable to maintain it). This is purely a guess - but I think your brake accumulator had failed. Does it happen more when you press the brake pedal? It will be making a nasty sound...
Take a look at this diagram. It will be part labeled #2

COMPONENTS ON DASH PANEL.. Fits: 2001 Mitsubishi Montero Limited 3.5L V6 Automatic | Savannah Mitsubishi

Thanks Hunter. Now that I know what it is called, I did a search on here for "accumulator" and found everything I needed.


Thanks,
Greg

Replacing it is very easy. Put some rags just under the area where it bolts into the brake master cylinder (to catch brake fluid that will drip out). Turn off the engine and press brake pedal about 20-30 times (to relieve all the accumulated pressure). Unscrew the old accumulator and screw in the new one. Top off the brake fluid if needed. Done...