Coolant leak on a Aprilia SR GT 125 2026

Cracked hose / loose clamp

Diagnosis confirmed: a coolant leak caused by a cracked/porous hose or a loose clamp. The cooling circuit connects the engine to the radiator through rubber hoses, held on with clamps. Heat, pressure, and age cause the rubber to harden, crack, and split (often at the ends or bends), and clamps loosen over time: coolant leaks out, the level drops, and the engine risks overheating. The approach: find the hose or clamp responsible, replace the cracked hose (or retighten/replace the clamp), then top up the level and bleed the air out of the circuit. This is an accessible, intermediate-level job. Safety: work with a COLD engine -- never open a pressurized hot circuit (risk of scalding hot coolant spraying out). Risk level: moderate. On cost: a coolant hose runs roughly 10 to 40 euros depending on the model, a clamp just a few euros, plus coolant itself (8 to 20 euros). Important: bleeding the air out is the tricky part -- a trapped air pocket can mimic overheating; follow the procedure (bleed screw, warming up with the cap open under supervision, topping up gradually). Use a coolant that matches and is compatible with what's already in the system. After the job, keep an eye on temperature and level on your first ride. If the leak turns out to be coming from somewhere else (radiator, water pump), keep investigating. This tool helps you understand what's going on -- it doesn't replace a certified mechanic.

How to make the repair yourself

🟡 Intermediate level: a few basic tools and a bit of method are all you need. Work with a cold engine, take your time, and don't hesitate to stop the moment you're unsure.

1. 1Engine completely COLD (several hours), find the leak: follow the coolant hoses and look for the cracked/porous hose or the loose clamp (traces of colored coolant, whitish or colored deposits).
2. 2Place a container under the area, open the circuit (bleed screw or lower hose) to drop the level below the repair point, and collect the coolant cleanly.
3. 3If it's just a loose clamp on an otherwise healthy hose: retighten it properly (without crushing the rubber) and retest. Replace a rusted or worn-out clamp with a new one.
4. 4If the hose is cracked/hardened: loosen both its clamps, remove it (some coolant will drip out), and clean the fittings it mounts onto.
5. 5Fit the new hose (correct shape/length), pushed fully onto the fittings, and secure new or good-condition clamps at both ends, in the right position.
6. 6Close the bleed screw if you'd opened it, then refill the circuit with a compatible, matching coolant, filled slowly to the top.
7. 7Bleed the air out: open the bleed screw if there is one, start the engine and let it warm up with the cap open (under supervision), topping up as bubbles escape until it stabilizes, then close everything up.
8. 8Check for leaks while warm, confirm the fan kicks in and the temperature stays normal. Recheck the level cold the next day and keep an eye on it during your first ride.