Generator radiator and cooling system repair
In this climate the cooling system decides whether a set carries its rating. Everything else can be right and a blocked core will still shut the set down on high temperature at the worst possible moment.
Do not open a radiator cap or header tank on a hot system, and never add cold water to a hot engine. Put the controller in Stop and isolate the starting battery before hands go near a belt or fan — some sets restart automatically. Manifolds, turbochargers and exhausts stay hot long after shutdown. And two findings on this page are stop-the-set findings rather than diagnoses to repeat: coolant in the oil or oil in the coolant, and a cracked or damaged fan blade — a shed blade is dangerous.
The real design case
Why a Gulf summer is the condition that matters
A generator's rating assumes it can reject its heat to the surrounding air. Manufacturers publish ratings against reference conditions, and every degree of ambient above those conditions eats into the margin. In a Sharjah August the air arriving at the core is already close to the limit the radiator was sized around — which leaves almost nothing in hand for the things that go wrong.
- A core partly blocked with dust, airborne sand and fibres
- Fins bent or flattened, so air passes over the core instead of through it
- A plant room that recirculates its own hot discharge air back into the intake
- A slipping or worn fan belt, or a viscous fan drive not locking up
- Coolant that has lost its inhibitor and its heat-transfer properties
- Scale and sediment inside the core and the block
Any one of those is survivable in a temperate winter
Two of them together, in July, at rated load, is a shutdown. That is why radiator core cleaning in the UAE is a maintenance task rather than an occasional repair — and why a set that has "always been fine" fails in its first genuinely hot week carrying genuine load. The corollary is worth saying plainly: a set that trips on high temperature is very often not a set with an engine problem. It is a set whose cooling capacity has quietly fallen below what the ambient demands. Establishing which of those you have is a measurement, and it is a cheap one.
Find your symptom
Faults we are called to
| Symptom | Where it usually is |
|---|---|
| High temperature shutdown under load, fine off-load | Core blockage, airflow restriction, or a plant room recirculating hot air |
| Temperature climbs steadily from the moment it starts | Thermostat stuck closed, water pump failure, or a badly airlocked system after a coolant change |
| Coolant loss with no visible leak | An internal leak — head gasket, cracked head, failed liner seal, or an oil cooler leaking into the oil |
| Coolant in the oil, or oil in the coolant | An internal path between the two circuits. Stop the set. |
| Header tank pressurising, or coolant pushed out of the overflow | Combustion gas entering the coolant, or a failed pressure cap |
| Wet floor under the radiator | Core leak, hose, clamp, water pump seal, or a corroded header tank seam |
| Fan noise, vibration, or a cracked blade | Fan hub bearing, drive, or a blade that has been struck. Stop the set — a shed blade is dangerous |
| Belt squeal, belt dust, or repeated belt failure | Tension, alignment, or a seizing pump or idler pulley |
| Charge air temperature high on a turbocharged set | Charge air cooler blocked externally, or leaking internally |
| Rust-coloured or oily coolant | Inhibitor exhausted, contamination, or the wrong coolant added at some point |
Wider symptom diagnosis is on diesel generator repair, and the informational companion to this page is why a generator overheats.
The core itself
What we do to a radiator
- Clean it properly, from the right sideExternal cleaning is done from the discharge side back through the core, so debris comes out the way it went in rather than being driven deeper. Cores loaded with sand and fibre need chemical cleaning and rinsing, not a quick blast with an airline. A core "cleaned" with a pressure washer at close range often arrives here with its fins flattened — a different fault with the same symptom.
- Flush and clean it internallyScale, sediment and old inhibitor residue reduce heat transfer inside the tubes. A system flush is part of any serious cooling repair — there is little point fitting a clean core to a block full of sediment.
- Pressure test itA radiator is pressure tested to find leaks rather than to confirm them. A weep that only appears hot and under pressure is exactly the leak a visual inspection misses.
- Repair it where it can be repairedTube leaks, header seams, tank-to-core joints, mounting feet and brackets. Tanks and mounting hardware are also fabrication and lathe work, and that sits in our own machine shop rather than at a subcontractor.
- Re-core it where repair is finishedWhen a core has too many blocked or leaking tubes, or corrosion has thinned it generally, a repair is a delaying tactic. Re-coring puts a new core into the existing tanks and mountings and keeps the radiator's exact fit — which on an older or unusual set matters more than it sounds, because the alternative is finding a replacement that no longer exists in any catalogue.
- Straighten the finsWhere airflow has been lost to physical damage rather than to dirt.
Not just the radiator
The rest of the cooling system
Run on plain water or exhausted inhibitor, they pit through the liner wall — and then the job is an overhaul rather than a coolant change.
Where the expensive failures start
Coolant is a specification, not a colour
The most expensive cooling failures we see did not start with the radiator. They started with someone topping up with water, or with whatever coolant was in the store, on an engine whose manufacturer specified something else.
- Use the coolant type the engine manufacturer specifies for that engine
- Mix it to the correct concentration rather than by eye
- Do not mix incompatible coolant technologies in the same system
- Check the inhibitor level at service rather than assuming it
- On a wet-liner engine, treat the supplemental additive level as a maintenance item with a consequence attached
We record what went in, by specification, at every visit — see generator maintenance and preventive servicing.
Physical, not commercial
Repair, re-core or replace — and how we decide
Radiators are one of the clearest cases of the repair-versus-replace argument on this whole site, because the deciding factors are checkable rather than a matter of opinion.
Clean and repair
When the core is structurally sound, the tube leaks are few and localised, and the tanks and seams are good.
Re-core
When the core is generally corroded, has many blocked or leaking tubes, or has been repaired repeatedly. Tanks, mountings and connections are retained, so the radiator still fits the set exactly.
Replace
When the tanks or the frame are beyond saving, or when a new radiator is genuinely available for that set and the arithmetic favours it.
What the check actually is
How many tubes are affected, whether the core walls have thinned, whether the header seams will hold pressure, and whether the assembly still fits its mountings.
On older sets, re-coring is often the only route back into service
Where nobody stocks a replacement any more, re-coring exists as an option because we build to the existing tanks rather than shopping for a part number. Send us a photograph of the radiator, the set's data plate and the position it sits in, and we will tell you which of the three is likely before anything is removed.
Under load, not at idle
Proving the fix
A cooling repair is proved under load. The honest test is to run the set at load, in present ambient conditions, and watch the coolant and charge air temperatures stabilise rather than climb. Where the set's own load is not available or not sufficient, that means a load bank test with temperatures recorded at each step.
If the set still runs hot with a clean core, a proved thermostat and a working pump, the problem has moved off the radiator and onto the installation — the plant room's ability to bring cool air in and get hot air away. That is an airflow question, dealt with under installation and commissioning.
- On site
External core cleaning, flushing, thermostat, pump, hose and belt work — done where the set stands.
- In the workshop
Chemical cleaning of a heavily fouled core, pressure testing, repair and re-coring, with the radiator removed and returned.
- Behind both
Tanks, mountings and brackets are fabrication and lathe work, done in our own machine shop rather than sent out.
Common questions
Cooling repairs, answered
How often should a generator radiator be cleaned in the UAE?
More often than the engine manual assumes, because the manual was not written for this air. Cores in dusty industrial areas, near construction, or on coastal sites load up quickly, and the cost of core cleaning is trivial against the cost of a set that derates or trips at rated load in August. It is a routine service item here, checked at every visit.
Can a leaking generator radiator be repaired, or does it need replacing?
Usually repaired or re-cored. A small number of tube leaks in a sound core is a repair. A generally corroded core with many affected tubes is a re-core, keeping the original tanks and mountings so the fit is unchanged. Replacement is the answer when the tanks or frame are finished, or when a new unit is genuinely available and works out better.
My generator only overheats when it is loaded. Why?
Because off-load the engine makes a fraction of the heat it makes at rating, so a cooling system at half capacity copes. Load it and the deficit appears. That pattern points at the cooling system or the installation airflow rather than at the engine, and it is the reason cooling faults are so often diagnosed on load rather than in a plant room at idle.
Do you clean radiators on site, or does the set have to come to you?
External core cleaning, flushing, thermostat, pump, hose and belt work are done at your site. Chemical cleaning of a heavily fouled core, pressure testing, repair and re-coring are done at the workshop in Industrial Area 15, with the radiator removed and returned.
The coolant keeps disappearing but there is no leak on the floor.
Then it is going somewhere internal, or leaving as vapour. The candidates are a head gasket, a cracked head, a failed liner seal, an oil cooler leaking into the oil, or a pressure cap that is not holding the system pressure. A pressure test and a check for combustion gas in the coolant separate them. Do not keep topping it up and hoping.
Before you phone
Two ways to start
Set tripping on high temperature
- Call or WhatsApp +971 50 767 9050
- Tell us what the temperature does off-load
- And what it does under load
- And how long it takes to get there
Radiator to be assessed
- Email jacob@abradiesel.com
- Photographs of the core and the header tanks
- The set's data plate
- The position the radiator sits in
We will tell you whether it is a clean, a repair or a re-core. The rest of what we do on a genset is on generator repair and service.
Set shutting down on high temperature?
Call or WhatsApp. Tell us what the temperature does off-load and under load, and how long it takes to get there. Do not open a hot system while you wait. Open 7 days, 07:00–20:00.