McLaren 720S Suspension Accumulators: Gas Loss, Pump Cycling and Bellows

A rhythmic pump sound from a McLaren 720S can lead an owner straight to the idea of a failing pump. McLaren's own diagnostic guidance describes another possibility: gas-pressure loss in a suspension accumulator can make the hydraulic system repeatedly adjust its pressure, producing a cycling pump sound and synchronized valve-block clicking.[47] Understanding that relationship is useful before any expensive component is named as the cause.

The accumulator changes how the hydraulic system behaves

The important distinction is between the component making the sound and the condition making it work differently. In the documented situation, the pump and valve block are responding to pressure behavior in the suspension circuit. McLaren explicitly cautions against assuming that either noisy component is faulty before the diagnostic checks are completed.[47]

For the owner, this means “the pump is noisy” is a useful observation. “The pump needs replacing” is a conclusion that still needs evidence. A repeating sound also deserves attention when there is no dashboard warning: the manufacturer describes the concern with or without a suspension message.[47]

The timing matters. Tell the service team whether the sound is new, whether it is intermittent, and whether you noticed a suspension message at the same time. If a recording already exists, share it. There is no reason to reproduce the condition deliberately or operate the car simply to capture a better clip.

The metal-bellows update has a defined scope

McLaren's June 2022 service information covers a metal-bellows accumulator retrofit for 720S Coupe and Spider vehicles built before May 2021. It describes improved longevity compared with the earlier membrane design and states that later production received the updated accumulators.[46]

The bulletin also treats the retrofit as a coordinated change involving the accumulator set and vehicle software. It does not permit mixing the earlier membrane and newer metal-bellows designs on one vehicle.[46] A parts description alone therefore cannot establish that a previous conversion was complete.

If you are discussing an update, ask the specialist to explain what is currently installed and how the proposed work fits the car's build information. An invoice saying “suspension work” leaves that question open. Conversely, the age of the car does not establish that it still carries its original components.

Condition monitoring is the supported care approach

These documents do not establish an owner replacement interval. They also do not promise that an update will eliminate every future suspension concern. The useful preventive habit is to take a changed sound or warning seriously enough to have its cause assessed, rather than waiting for several unrelated symptoms to accumulate.

Keep that conversation focused on the hydraulic concern. A warning, a noise and a proposed retrofit are three different pieces of information. A clear assessment should connect them, explaining which finding supports the repair and which observations remain unexplained. That is especially helpful when planning seasonal use and deciding what needs attention before the next outing.

Werke Autosport's diagnostics and programming information is a starting point for discussing the concern and confirming the appropriate assessment scope for your 720S. Share the build information and any previous accumulator work when you make contact.

Sources

Back to blog