Hi All, 

Purchased this lovely Focus ST-line MK4 and know it uses a Timing chain for the engine, but a wet belt for the oil pump, it has 66K on the clock and a majority main dealer service history.

Should I do a preemptive wet belt and timing chain replacement or hold on until it's next service in 2026?

 

10 years is the maximum belt life.

Many would recommend changing it when it is 8 years old.

Right, so if my maths is right, it's got another year of life before it's due to changed?

Has anyone got experience of the oil pump wet belt failing? I guess it isn't as catastrophic a as the timing belt failing.

Is it simply the case that when the belt fails the oil pressure light comes on, the driver stops the engine, and after the belt is changed no lasting damage is caused?

Once the oil pressure light is illuminated / warning message is shown, and the driver is able to switch off the engine it is usually already too late. When the oil pressure light is illuminated / warning message is shown you literally have seconds before the engine starts developing catastrophic damage due to oil starvation.


There are very few situations that the driver is actually able to switch off the engine in time to prevent damage.

When driving on a motorway or main road you just cannot switch off the engine immediately. You have to come to a save stop first before you are able to switch off the engine. The time to come to a save stop is usually enough to develop engine damage. 

The only situations I can think of that the driver is actually able to switch off the engine immediately is when the vehicle is stationary. For example, when stuck in traffic or when waiting for a traffic light or railroad crossings.

3 hours ago, JW1982 said:

Once the oil pressure light is illuminated / warning message is shown, and the driver is able to switch off the engine it is usually already too late. When the oil pressure light is illuminated / warning message is shown you literally have seconds before the engine starts developing catastrophic damage due to oil starvation.


There are very few situations that the driver is actually able to switch off the engine in time to prevent damage.

When driving on a motorway or main road you just cannot switch off the engine immediately. You have to come to a save stop first before you are able to switch off the engine. The time to come to a save stop is usually enough to develop engine damage. 

The only situations I can think of that the driver is actually able to switch off the engine immediately is when the vehicle is stationary. For example, when stuck in traffic or when waiting for a traffic light or railroad crossings.

You can hold the power button to turn off the engine while driving, but it's not advisable as you'll quickly lose brake pressure.

8 hours ago, alexp999 said:

You can hold the power button to turn off the engine while driving, but it's not advisable as you'll quickly lose brake pressure.

I'd be a lot more worried that the electrically operated steering lock would engage, with total loss of control.

13 hours ago, unofix said:

I'd be a lot more worried that the electrically operated steering lock would engage, with total loss of control.

Fairly sure the steering lock doesn't engage until it loses the fob signal from inside?

Easy enough to test next time you're in car.

The steering lock does not engage while the vehicle is moving.

The electric power steering however does no longer work after the engine has been switched off. This makes steering extremely hard (even harder than a non-functioning conventional hydraulic power steering). Because of this I do not recommend to switch off the engine while the car is still moving 

1 minute ago, JW1982 said:

The steering lock does not engage while the vehicle is moving.

The electric power steering however does no longer work after the engine has been switched off. This makes steering extremely hard (even harder than a non-functioning conventional hydraulic power steering). Because of this I do not recommend to switch off the engine while the car is still moving 

My power steering failed when the battery died on my car, I have driven it without power steering.

It's not too bad at speed but almost impossible at manouvering speeds, especially with the ST's short rack and 235 tyres.

Electric PAS wouldn't work on my Golf after the battery died.

That's on 205/55/16s and I still couldn't move the wheel stationary to turn out of the parking space.

Luckily it only needed driving a few feet forward for the ABS sensors to pick up motion then the ePAS kicked in again.  I'd never have been able to get it out of the space otherwise.  Much heavier than a knackered hydraulic system as Wilco says.

On 7/14/2025 at 9:49 AM, TomsFocus said:

Fairly sure the steering lock doesn't engage until it loses the fob signal from inside?

Kept meaning to come back and update this thread.

Using my 2019 Focus 'Automatic' as a test, I took it on a private farm track and drove at 20 mph and pressed the power button to see what happens. The answer (on my car at least) is nothing happens.

No amount of pressing the power button or even holding it in causes anything to happen. The engine does not switch off, and the car keeps driving.

9 minutes ago, unofix said:

Kept meaning to come back and update this thread.

Using my 2019 Focus 'Automatic' as a test, I took it on a private farm track and drove at 20 mph and pressed the power button to see what happens. The answer (on my car at least) is nothing happens.

No amount of pressing the power button or even holding it in causes anything to happen. The engine does not switch off, and the car keeps driving.

It's in my manual. My mum had to use this feature on her Kuga when an ABS wheel speed sensor failed, she lost speedo and the car couldn't "see" that the car was stationary, even when she had stopped.

1 minute ago, alexp999 said:

It's in my manual.

Give it a try 👍

Perhaps it is different on a manual car, but I can assure you on my 2019 Focus diesel, pressing the power button did not turn off the engine.

That's concerning tbh.  So if you get wetbelt rattle on the motorway there's no chance of stopping in time.

Also concerning that the handbook states the airbag circuit is only live with ignition on.  Surely that should have some battery backup for use in the event of an electrical failure which causes a crash because you can't steer or brake effectively.

 

54 minutes ago, TomsFocus said:

That's concerning tbh.  So if you get wetbelt rattle on the motorway there's no chance of stopping in time.

I don't suppose there's much chance anyway - "when it's gone it's gone" as the supermarkets say. 

The Fiesta handbook says the same sort of thing, though:

Stopping the Engine - Stopping the Engine When Your Vehicle is Moving - Manual Transmission, Vehicles With: Push Button Start

STOPPING THE ENGINE WHEN YOUR VEHICLE IS MOVING - MANUAL TRANSMISSION, VEHICLES WITH: PUSH BUTTON START



WARNING:  Switching off the engine when your vehicle is still moving results in a significant decrease in braking assistance. Higher effort is required to apply the brakes and to stop your vehicle. A significant decrease in steering assistance could also occur. The steering does not lock, but higher effort could be required to steer your vehicle. When you switch the ignition off, some electrical circuits, for example airbags, also turn off. If you unintentionally switch the ignition off, shift into neutral (N) and restart the engine.

1. Press and hold the push button ignition switch until the engine stops, or press it three times within two seconds.

1. Shift into neutral and use the brakes to bring your vehicle to a safe stop.

1. Apply the parking brake. 

 

 

 

Stopping the Engine - Stopping the Engine When Your Vehicle is Moving - Automatic Transmission, Vehicles With: Push Button Start

STOPPING THE ENGINE WHEN YOUR VEHICLE IS MOVING - AUTOMATIC TRANSMISSION, VEHICLES WITH: PUSH BUTTON START



WARNING:  Switching off the engine when your vehicle is still moving results in a significant decrease in braking assistance. Higher effort is required to apply the brakes and to stop your vehicle. A significant decrease in steering assistance could also occur. The steering does not lock, but higher effort could be required to steer your vehicle. When you switch the ignition off, some electrical circuits, for example airbags, also turn off. If you unintentionally switch the ignition off, shift into neutral (N) and restart the engine.

 

Only in case of emergency, do the following:

1. Press and hold the push button ignition switch until the engine stops, or press it three times within two seconds.

1. Shift into neutral (N) and use the brakes to safely bring your vehicle to a complete stop.

1. Shift into park (P).

1. Apply the parking brake.

Fiesta Owner's Manua

My belt was toothless at 5years 90k mark. Oil pressure light came on. Nothing catastrophic happened I guess but chaning it isn’t exactly a quick job. Expensive mainly due to labour costs.