Automatic gearbox specialists
Having a transmission cooler issue?
Overheating, burnt fluid, or milky oil. A cooler fault cooks the gearbox from the outside in.
- Gearbox temperature warning or a burnt smell after a run?
- Pink milky fluid on the dipstick?
- An automatic that only plays up when towing or in traffic?
The transmission cooler dumps heat from automatic fluid. When it blocks or leaks, the gearbox cooks or the oil turns milky. Cooler diagnosis is part of automatic work at Service4Service.
Milky ATF is coolant in the oil. Do not keep driving. You can wreck the unit in a short run.
8am - 5.30pm Mon-Fri
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What is a transmission cooler?
A transmission cooler is a heat exchanger for automatic transmission fluid. Many sit in the radiator. Some are a separate radiator in the airflow. Hot oil from the automatic gearbox goes out, cooler oil comes back.
A blocked cooler raises temperature. A leaking one mixes coolant and oil. Either way the gearbox oil pump and packs suffer.
Towing, traffic and a skipped automatic gearbox service all push the cooler harder.
An overheating automatic can fail in one journey
Heat varnishs the valve body and glazes the packs. Milky oil from a cooler leak is worse. Stop, do not motorway it home, and call.
Cooler symptoms people search
If any of these sound like your car, do not wait for it to fail on the road.
Overheat warning
The oil cannot dump heat.
Burnt smell after a hill or a tow
The cooler is overloaded or blocked.
Milky pink fluid
Coolant in the ATF. Stop.
Mayonnaise on the dipstick
Same leak, further along.
Fine on a short trip, awful in traffic
Heat soak.
Wet around cooler pipes
An external leak. Level will fall.
How a transmission cooler works
Hot ATF leaves the gearbox, passes the cooler, and returns. A gearbox filter does not replace this job. Both are needed.
A radiator-stack cooler that fails internally dumps coolant into the gearbox. That is an emergency, not a top-up.
Hot oil leaves the unit
The cooler dumps heat.
A block or a leak starts
Temperature climbs, or oil turns milky.
The gearbox cooks
Slip, limp, then no Drive. It only gets worse.
Cooler work we do
We inspect fluid, temperature data and the cooler circuit, then repair leaks or advise when the gearbox has already been cooked.
- Fluid condition and temperature diagnosis
- Cooler and pipe inspection
- Contamination checks
- Collection when it should not be driven
Oil that looks milky, or a gearbox that runs hot?
That is not a later job. That is automatic gearbox repair now. Call before the unit is cooked.
Why this work comes to Service4Service
- Automatic and dual-clutch work is core work, not a sideline
- Diagnosis before parts
- Collection when the car should not be driven
- 12 months or 12,000 miles on parts and labour
Guarantee and payment
Repairs are backed by a 12 month or 12,000 mile warranty on parts and labour. See Payment Options for ways to pay.
Sometimes an external cooler can be. A radiator stack that has mixed coolant and ATF usually needs replacement, and the gearbox needs assessing.
On a tow car it can. It will not save a unit that is already slipping.
It is the usual cause. We confirm before we strip.
Many wet-clutch dual-clutch boxes do.
No.
No. Heat is how automatics die on the last few miles.
Related guides
Do not drive an overheating automatic home
If the oil is milky, burnt or the temperature warning is on, tell us. Cooler faults are how good gearboxes get cooked.
