Old construction machines overheating is becoming more common as summer approaches. Everyone in the villages and workshops has their own trick for this — it’s an old movie line: older folks have all heard it! I’m retired now and not trying to steal other mechanics’ work, but I want to offer a few suggestions to colleagues about how to solve high-temperature problems. If you want to listen, great; if not, there’s a wall in front of you — I’m not saying go bang your head on it, and I won’t pay your hospital bills.

Some colleagues use a few “folk” or makeshift methods to treat engine overheating. Sometimes they work — you get lucky. Other times they don’t work at all and parts money is wasted. Out of concern for fellow mechanics, here are several suggestions:

1) Blocking the “small circulation” line (bypass)

This trick is used on engines that have poor circulation and whose thermostat someone already removed. I suspect the person who taught them learned on old Jiefang or old Yellow River trucks — they were used to taking thermostats out frequently. Long ago, thermostats used an charge to control opening temperature and were prone to failure, so many machines had their thermostats removed. Especially in very cold northern regions in winter, if the large-circulation never opens the radiator can freeze — even with louvers and insulation blankets, the radiator can be damaged. Back when radiators were copper-tubed, shops had radiator repair teams that could remove and fix broken coolant tubes (soldered parts). Now radiators are aluminum and need TIG/argon-arc welding — you can’t easily pull out single tubes.

So this trick (blocking the bypass) lowers water temperature but it doesn’t fix the extra wear caused by cold circulation. That’s treating the symptom, not the disease. Experts point out that 90% of engine wear happens during cold starts — that’s why standby engines (e.g., for fire pumps) are kept within a temperature range or electrically heated (glow plugs/heaters). If you properly check and restore the thermostat, you’ll solve the cold-start extra wear problem — that’s not trivial. If engine overheating is due to other causes, blocking the small circulation won’t help (for example: slipping fan belt, clogged radiator, etc.).

2) Removing the engine cover/hood

Some mechanics simply remove the engine cover when the engine overheats — in real life some machines are used with the hood open. Opening the hood can help because the issue is often hot air recirculating inside the engine bay or poor intake airflow. If you then follow up and repair the actual cause (air leak, blocked intake, etc.), job done.

3) Adding extra fans

Some colleagues add an electric fan to the AC condenser (or otherwise “add fans”) to try to stop the engine from overheating when the A/C is on. The idea is to increase air flow through the condenser and thus reduce condenser temperature. The intention is good, but the effect can be bad: in the example photo (not shown here) the added condenser nearly blocks two-thirds of the original engine radiator, creating a major airflow obstruction — will engine temp drop? No. If opening the A/C always raises engine temperature on your machine, check: is the fan slipping? Is the radiator clogged?

Designers calculate the required airflow, pressure and velocity at the factory — adding improvised cooling bits is often counterproductive. For a rough figure: a construction-machine cooling fan drive typically consumes about 5–8% of the engine’s gross power. Unlike road vehicles which benefit from ram air, construction machines have almost no ram-air advantage, so they need larger cooling capacity. Two small electric fans of a few dozen watts each are not going to replace that.

Practical examples and correct approach

• Case 1: If the water pump flow is insufficient — check it. Is the thermostat stuck? Is the radiator blocked inside or out? Do targeted repairs.

• Case 2: Check for hot-air re-circulation faults and fix the leak(s).

• Case 3: Check whether intake/airflow passages are blocked or restricted. I have seen owners apply lots of sealant at the ram-air inlet and never fix the root cause.

So: inspect carefully and diagnose the root cause; don’t randomly try “this or that” and hope. Some machine issues are complex, others are solved by a single correct action. I’ve done on-site repairs many times; this is just advice for colleagues.