A silver Vauxhall VX220 on track
← All guides

Cooling system flush

A thorough flush of the Turbo's cooling system with the thermostat removed, a hose connected to the header tank outlet, and the oil cooler and return pipe blanked off. Written by a track-car owner who had black residue in the header tank.

Applies to: VX220 and Speedster, TurboDifficulty: InvolvedTime: Not stated. A Saturday job

Parts

  • Cooling system flush product (The author used Wynn's, plus a dishwasher tablet)
  • Red antifreeze (About 2.7 litres, which the author says is just under 25% of the system)
  • Thermostat housing seal (The flat O ring. Don't forget to refit it.)

Tools

  • Container to catch coolant, and a bucket for the flush water
  • Four axle stands
  • 10 mm socket. A small electric screwdriver with extension bars made the bolts much quicker
  • Hose pipe, Jubilee clip, and a Mikalor clamp for the kitchen tap attachment
  • A cheap hose attachment of 32 to 35 mm diameter, to blank off the oil cooler hose
  • A large bolt, to blank off the small return pipe
  • Hot water from a tap, and a screwdriver
Old coolant is toxic. The author collected the worst of the coolant and flush water to dispose of properly rather than letting it run onto the ground. The engine and coolant will also be hot, and you are working with the car on axle stands, so make sure it is well supported.

This is one owner's flush procedure for a VX220 Turbo used on track. He had black residue appearing in his header tank, was "pretty confident" it wasn't the head gasket, and wanted a thorough clean before the season. The manual's method is to disconnect the return hose by the oil cooler and the radiator hose. He didn't want to take the front undertray off if he could avoid it, so he came up with this instead: remove the thermostat, disconnect the outlet of the oil cooler, and blank off the return pipe that leads to the thermostat. Then he pushed water through from the header tank outlet, through the engine, radiator and oil cooler, and out to the drain.

Help wanted
This is a single owner's method rather than a factory procedure, and it was posted the same week he did it, so we don't know whether the residue came back. He also asked whether the air still needs bleeding at the radiator afterwards, and nobody answered. If you have done this or know the correct bleeding procedure, please tell us. If black residue is a sign of something else, such as oil in the coolant, a flush won't cure it. Other owners' bleeding methods are in Changing the coolant and bleeding the system.

Send us details or photos →

Diagram of the cooling circuit: radiator, heater, engine, pump, oil cooler, header tank, thermostat and temperature sensor
The cooling circuit, in a diagram the author attached to his first post.
Labelled engine bay showing the header tank return pipe, the hose in the header tank outlet pipe, the charge cooler tank, throttle body, oil filter, thermostat housing and water injection top-up cap
The engine bay, labelled by the author: header tank return pipe, hose into the header tank outlet, charge cooler tank, thermostat housing and water injection top-up cap.

Preparation

  1. Get the car up to temperature first (about 87 degrees).
  2. Remove the header tank and give it a thorough clean. Take off the black bracket that the header tank and the charge cooler tank attach to, to give yourself more room.
  3. Remove two bolts from the rocker cover so you can pull the water injection top-up pipe out of the way.
  4. Put a container under the gearbox to catch the worst of the coolant.
  5. Remove the two 10 mm bolts holding the thermostat housing, and take out the thermostat and its rubber O ring. Bolt the housing back on (without the gasket).
  6. Put the car on four axle stands.

First flush

  1. Disconnect the outlet of the oil cooler. It is under the car, just where it leaves the back of the passenger sill. Collect the water that comes out.
  2. Push a hose pipe as far as it will go (about 4 inches) into the hose that is normally on the header tank outlet, which is the thermostat inlet, and hold it with a Jubilee clip.
  3. Blank off the hose from the oil cooler outlet (the other thermostat inlet, on the engine side of the cooler). The author used a cheap hose attachment of the right diameter, 32 to 35 mm, which just pushed in and didn't need clipping.
  4. Blank off the small pipe that returns to the top of the header tank. A large bolt will do.
  5. Run hot water from the kitchen tap through the system to help dislodge more debris. Collect the worst of the water for proper disposal and run the rest to a drain. You need a Mikalor clamp on the tap attachment to keep the hose on, and no kinks in the hose.
  6. Take the small bolt out of the return to the header tank and flush through that too.
  7. Reattach the oil cooler and fill the system with hot water until it flows well out of the small return pipe to the header tank.
A hose pushed into the header tank outlet hose in the engine bay
The hose pipe pushed into the header tank outlet hose.
A green hose attachment used as a blanking plug
The cheap hose attachment used to blank the oil cooler hose.
The blanking attachment fitted in the oil cooler hose
The attachment pushed into the oil cooler hose.
The oil cooler outlet labelled, at the back of the passenger sill
The oil cooler, at the back of the passenger sill, with the flow directions marked.
A hose attached to a kitchen tap over a sink
The hot water supply from the kitchen tap.
A Mikalor clamp on the tap attachment
A Mikalor clamp holding the hose on the tap attachment.
A hose running to a bucket on the ground
A hose and bucket from the job.

Chemical clean and second flush

  1. Disconnect the hose pipe, reattach the header tank and add the cooling system flush product, a dishwasher tablet and a bit more hot water.
  2. Run the car with the header tank cap off, so the air can purge, and with the heater on maximum. With the thermostat out it takes a while to get to temperature, but the hot water helps. When it reaches 87 degrees, stop the engine.
  3. Disconnect the oil cooler, header tank and so on again, as in the first flush, and flush it through really thoroughly.
A bottle of Wynn's cooling system flush
The cooling system flush the author used.

Refilling

  1. Reconnect the oil cooler and fill the system until it overflows from the small return pipe.
  2. Disconnect the hose pipe. Push the screwdriver end into that pipe, and put the bolt back in the small return pipe to the header tank. This temporarily seals the system so that you don't lose water when you take the thermostat cover off.
  3. Take off the thermostat cover and refit the thermostat. Don't forget the flat O ring.
  4. Reconnect everything.
  5. Put red antifreeze in the header tank up to halfway. The author got about 2.7 litres in, which he says is just under 25%.
  6. Run the car up to 90 degrees with the header tank cap off and the heater on.

The author finished by saying it felt like a thorough job, and that he would see whether the black residue returned after heavy track use. He didn't report back in the thread.

Sources & credit

Written up from these owners' original posts. Thanks to everyone who contributed.

Last updated 2026-10-15