A batch of CAT 349E excavators (including the 336E series) purchased from Shenzhen entered the market. After a period of use, these machines all suffered from derated power and could not operate normally. Even the so-called “experts” who claim they can fix anything were unable to resolve the emissions system issues.

As a result, most of these machines ended up being listed online at low prices, but no one bought them. Some were sold for just tens of thousands of yuan — and these are 50-ton class machines. Everyone knows there is no such thing as cheap and good.

The Repair Decision

One owner, with my support, decided to purchase a machine whose chassis at least looked decent and sent it to a professional repair shop. The goal: resolve the engine emissions derating issue and restore normal usability.

Initial Condition of the Machine

Upon inspection, the machine could no longer operate normally:

1. Emissions control system triggered derated power;

2. Multiple fault codes were active;

3. The machine travel deviated severely, unsafe to load/unload on flatbeds;

4. Hydraulic pumps were leaking severely and performing poorly;

5. Four hydraulic cylinders had severe leakage;

6. Emissions control system had been dismantled in multiple locations, impossible to restore fully;

7. Control systems and circuits had severe short-circuit damage.

After discussing with the client that the repaired machine must reach normal operating conditions, the repair began.

Repair Process

• Previous modifications on 320E series machines were all imported and properly modified, never encountering such chaotic alterations.

• Despite the difficulties, all necessary repairs were carried out step by step.

Findings during repair:

• Even the hydraulic cylinders were damaged. The piston rod’s large nut was loose and could not be removed.

  • Likely caused by press-fit assembly damage, which damaged the threads. After cutting the nut, piston damage was discovered.

  • Cylinder rods underwent brush plating and groove plating.

• Hydraulic pumps were rebuilt, polished, tested, adjusted, and resealed.

• Electronic control systems were modified and restored, removing fault codes.

• Burned wiring from short circuits was replaced and restored.

• Attempts were made to restore the parts of the emissions control system that should not have been removed.

Step by step, the machine’s performance was restored to the client’s requirements. Yesterday, the client happily tested and accepted the machine, which was then delivered.

Advice to Owners

• In Shenzhen, sellers dig holes but don’t bury them — buying a machine there is a gamble. The mainland environment is not ideal for these machines, so failure is almost inevitable.

• Most technicians will not follow CAT’s official procedures to restore the emissions control system because it costs tens of thousands.

• Improper repairs often cost nearly as much as official repairs without achieving expected results, leaving the machine unusable.

• Dealer capabilities vary; some refuse such projects because it’s not their own machine.

• This situation leads to loss of trust in dealer repair skills and machines left idle.

Conclusion:

Owners facing a 349E in this condition should not sell it cheaply. Low-price resale will not fetch fair value. Proper, official repair is much better — this machine still has a long service life if correctly restored.