What Was Happening
An iMac came in from a Putney SW15 customer who could not get it past the startup screen. The machine powered on, chimed, and then hung on the grey spinning wheel indefinitely. Safe mode boot also failed, and attempts to access macOS Recovery showed the internal drive was not visible in Disk Utility.
The customer had been using the iMac for work and had files they needed to access urgently. Whether those files could be recovered was the primary concern.
Our Diagnosis
We ran SMART diagnostic tools against the internal drive. The results showed multiple critical errors and the drive was not mountable via Disk Utility, confirming the drive had failed. Despite the complete boot failure, a data recovery attempt before fitting a replacement drive found that the majority of the user’s files were in sectors of the drive that could still be read.
This is the typical picture for a hard drive that has failed in a way that prevents booting but has not yet failed completely at the sector level — the file system is compromised but much of the data is still physically present on the disk.
How We Fixed It
We carried out a recovery pass on the original drive, extracting available files from the readable sectors. The majority of the customer’s documents, photos, and key application settings were recovered successfully.
A replacement hard drive was then fitted. iMac hard drive replacement requires removing the display glass and screen assembly — this is a procedure that requires care and the correct tooling to avoid damaging the adhesive and glass. macOS was reinstalled from Recovery, and the recovered data was transferred to the new installation.
The Result
The iMac was returned to the Putney customer the following day booting normally into a clean macOS installation, with recovered data accessible. Drive replacement was carried out at our Putney workshop — no journey to a distant service centre was needed.
Why This Happens on iMac Models
All-in-one iMac models from this era use laptop-format 3.5-inch hard drives in a sealed chassis with limited airflow around the storage bay. These drives operate at higher temperatures than desktop drives and accumulate wear faster as a result. iMac models that have been running the same hard drive for five or more years are at significant risk of drive failure. The sealed chassis also means the only practical warning signs are performance degradation and SMART errors, which many users miss because they are not in the habit of checking.
Prevention Tips
- Enable Time Machine and back up to an external drive connected to the iMac — Time Machine runs automatically and means a drive failure results in minimal data loss
- Run a SMART health check on the iMac drive annually using a tool such as DriveDx; SMART errors appear before complete failure and give time to plan a replacement
- Ensure the iMac has adequate ventilation — avoid placing it in an enclosed unit or against a wall with no space behind it
- Consider a proactive SSD replacement on any iMac that is still running its original spinning drive and is in regular use
- If the iMac starts taking noticeably longer to boot or applications take much longer to open than they used to, investigate the drive health before waiting for a complete failure
Local Help in Putney SW15
We provide iMac hard drive replacement and data recovery at our Putney SW15 workshop. Same-day and next-day turnaround is available for most iMac storage repairs.
Related Services
- Data Recovery — recovery from failing and failed drives on Mac and PC
- Data Recovery in Putney — local service covering SW15
More Case Studies
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- MacBook Air Hard Drive Replacement in Streatham SW16 — failing HDD replaced with SSD on a MacBook Air
- Asus N56VM hard-drive replacement and data recovery in Battersea — laptop storage failure and rebuild on a Windows machine