Changing the coolant and bleeding the system

This collects what owners said in several threads. It is not a factory procedure. For draining and refilling after a radiator job, see Radiator replacement, which has a bleed method. For a deep clean of a Turbo system, see Cooling system flush.

Do you need to change it at all?

• If you have the standard orange Vauxhall coolant, there is no need to change it unless you are working on something in the system. If you change the radiator, you can leave the header tank cap on and retain most of the coolant.
• If you only topped up with water, test what is in there first. If the long-life coolant is fairly young, a full drain probably isn't worth it.
• One owner changes his as soon as it loses its clear, see-through look. That is one owner's rule.

Which coolant

• Put back what is in there. Red should go back in if red is what you have. It is a different kind of coolant from the other colours, and the one you want is pink, not blue (OAT). Owners call the factory coolant red, pink and orange, and the threads don't explain whether these are the same product.
• Genuine GM coolant from a Vauxhall dealer was the most recommended. It is sold as a long-life coolant: one dealer quoted a 5-year product in 1 litre bottles, and another owner says there is a 10-year one in 5 litre bottles.
• Blue coolant was used by two owners, who topped up what was already in there. The threads don't say whether mixing the types matters, and a question about it went unanswered.
• Water Wetter. One owner calls it snake oil. Another used it and says it keeps things a few degrees cooler on track. A third uses a car on track without it.
• Storage. An opened, sealed bottle is fine according to one owner. Another was told by GM to discard it after 6 months open.

How much does it hold

The owners' figures don't agree, and the answer depends on how you count it.

• 12 litres for the NA is the figure most owners give, and one had read 12 too. One says it is 6 litres of coolant and 6 of water, 50/50.
• 6 litres: this is what two owners got out when they changed their radiators, and a handbook seen in Halfords also said 6 for the NA. A lubricant site gave 6.8.
• Turbo: 13.2 litres. Others don't say which engine: one had heard 13, and another says about 10 and that his Pro-Alloy supercharger charge cooler set-up holds about 5 litres.

You can't get it all out. The block retains a few litres, as do the pipes running down the chassis, and the system is never entirely empty. One owner has never got anywhere near 12 litres in after draining, or after changing the front radiator pipes and the radiator. Another changed a radiator and water pump on a flat surface and had to add 6 litres, and a third put in 6 litres after a radiator change. So after a drain, owners typically needed about 6 litres, and nobody gives a reliable total for the whole system.

Mix quantities. One owner normally puts in about 3 litres of antifreeze and the rest tap water. That is concentrate, and ready-mixed needs no water added. 5 litres of ready-mixed is enough for a radiator job, because you will struggle to fully empty it. Another mix was half 10-year GM coolant and half distilled water, and the advice is not to use alcohol.

Neat coolant instead of water? Not recommended. It has much lower thermal capacity, because coolant is water based and has corrosion inhibitors, and waterless coolant was called snake oil.

Topping up a weak mix without a full drain

This is a common need after topping up with water. Test with a cheap tester, remove some of what is in the header tank and replace it with new coolant, run the car for a few days, then do the same again, until it reads medium strength. Another version is to syphon out what is in the header tank, top up with neat antifreeze, run the car around for a couple of days, then test again, and repeat if needed. A big syringe works. One owner sucked air out through a hose and ended up tasting the coolant, so don't do that.

Draining and refilling

1. Drain. One owner emptied the system by taking off a water pipe. The method of draining at the radiator hose is in the radiator guide. If you are only changing the front radiator, jack the front of the car up quite high, so you only lose two or three litres. One owner concluded from the amount that stays in that flush products are a bad idea. That is his opinion.
2. Optional flush. One owner rinsed the radiator, matrix and engine with a hose pipe, and then thought the new mix looked a bit weak because of the water left in. Another rinsed with a garden hose, then ran the engine until the pump circulated, with the return to the header tank disconnected, and topped up with neat antifreeze as the level dropped. All the antifreeze you need goes in before the concentrate gets back to the header tank. Then bleed with the three bleed valves. Don't do it in December, because the water on the ground freezes straight away.
3. Refill with the 50/50 mix, slowly. One owner refilled from completely empty without trouble, and his level hasn't moved since. He used the expansion tank to make sure it went in in one go.
4. Bleed, as below.

Bleeding the air out

Where the valves are. There are three. One is on the passenger side behind the headlight, for the front part, and another is on the passenger side in the engine compartment, which you will probably need for a full flush. The one behind the headlight is known to be a bit weak, so be careful with it. That was the description for the NA, and the Turbo is assumed to be similar. One owner used the Exige hose, which has a more accessible bleed valve.

What owners did:

• Cap off and let it purge. After a radiator change, take the pressure cap off, let the engine idle until it blows a lot out of the filler, keep filling and then recap. One owner says it worked wonders, and guesses steam was replacing the air as it warmed up.
• Bleed valves and then the airlock. After filling and bleeding with the valves, one owner found once the engine was hot that coolant wasn't going through the radiator because of a big air lock in the top hose. He took the little hose off the expansion tank and sucked the air out.
• Park on a slope. Several threads suggest having the end of the car with the bleed nipples higher. One owner was told to raise the rear when bleeding. Another opened all the nipples and topped up, and it took ages.
• Pressurise it (the Vauxhall method). Step 10 of the Vauxhall method applies 1.0 to 1.5 bar to the system with tool KM-471, which one owner found expensive, so he built his own, see below. The rest of the Vauxhall method isn't in the thread, only a link to a PDF.

A home-made pressure cap

One owner cut away the valve in a standard cap, removed the rubber seal but kept most of the black section, drilled a hole in the yellow cap, and fitted a tyre valve cut from a bicycle inner tube. He turned his compressor down to about 1.5 bar, filled the header tank, put the cap on, applied pressure, and opened the engine bleed valve and then the radiator valve. He waited until all the bubbles had gone and the coolant ran clear, shut them off, topped up, and started the engine, and got circulation into the header tank straight away. A few air pockets were left in the radiator and it "just needs to be driven", and the process may need improving. He wasn't sure the modification was reversible. Nobody else in the thread tried it.

Checking it afterwards

• One owner changed his radiator, put in 6 litres and bled it. After about 10 minutes at around 90 degrees the whole radiator was hot, including the inlet pipe.
• Run it through a full thermal cycle so the fan comes on and goes off, because it is better to find a problem under control, and it pushes the system past 100 degrees to test the hose clips at full pressure. The fan comes on at 106 on the NA, and took about 10 minutes at idle. If it hasn't come on by 106, turn it off and diagnose the fan.
• Another owner disagrees with just switching off. He says to take it for a drive first, so there is airflow instead of hot coolant sitting still.
• One car idled for 15 to 20 minutes and hovered around 92, with a maximum of 94. The owner turned it off and connected the fan straight to the battery to check it, and it worked. There is no easy way to check the thermostat without reaching the required temperature, so watch the gauge in standing traffic instead.