I'm currently changing a lot of parts on my N18 Cooper S, including converting to silicone coolant lines. I've also fitted an aluminium crossover pipe and a new thermostat housing.

Is there a way of removing as much of the old coolant as possible. So I can change to a different brands etc of coolant.

I've removed the following items, but I'm convinced there is plenty of coolant still in the engine.
- Coolant lines
- Thermostat housing
- Crossover pipe
- Expansion tank

The radiator hasn't been removed from the car, but has had a good shake when removing the old pipes.

 

You shouldn't have to worry about it. As long as you're following the Mini spec, any small amount left in there should mix fine with the new stuff. Zerex G48 is a blue BMW/Mini HOAT coolant and is pretty easy to find, I'd suggest just getting that.

(I hope you're not trying to switch to that Evans waterless crap...)

 

@airbusA346
The other option is drain coolant as much as you can, put back together and drive 25Km or so and then drain the mixed coolant again in order to completely get rid of the old coolant. From that point, you’ll have 100% silicone coolant in your system.

 

One way is to fill the system with tap water. Then run the engine until up to temperature. Ideally to the point the radiator fans come on. You want the hot coolant circulating with as much force and flow as possible.

Back on your driveway after the engine has cooled to where it is safe to open the cooling system remove the cap and open all the drain valves and drain the water/residual coolant blend out of the engine.

If you are switching to an anti-freeze that is incompatible with what was in the engine before you probably should repeat this fill with water run the engine then drain process again at least one more time and to be doubly sure maybe a 3rd time. I've never had to thoroughly remove old coolant. The tiny bit left in the engine was of no consequence when refilling the system with the same anti-freeze/water blend.

Be aware if you switch to a different anti-freeze if you ever take the car in for anything a helpful tech might top up the coolant level with what he expects to be in the cooling system and contaminate the cooling system.

Might add if the engine cooling system was neglected for the first flush it might be advisable to use a flush additive. These can help loosen/remove the stuff that collects in a neglected cooling system. After using this stuff then one or more refills with plain water and run the engine then drain operations might be called for. The instructions on the flush fluid container should cover this.

 

I had looked at the Waterless stuff, but have seen that temperature can run higher than standard.

Cheers... I want to remove as much of the old coolant, because I'm not 100% sure what was used last time.

Is there a technique I am missing when trying to empty the coolant? In all the videos I have watched it showed the lower radiator hose being split where the plastic pipe joiner is. I did this and about 2-3 litres came out. As far as I am aware the N18 holds 5.2 litres.

 

The factory service manual might cover how to completely drain the cooling system. But most of the time a car's cooling system doesn't need to be completely drained and all old coolant removed.

Also more and more cooling systems can no longer be filled by gravity alone. They require a vacuum lift system. Because of this layout they don't completely drain by gravity.

I'm reluctant to disturb hoses to remove coolant. Even using drain valves is a bit worrying. They remain unused for a long time. And exposed to the same (probably) poor cooling system fluid. Then they are loosened and the fluid drains out. The drain plug is tightened but it can seep a bit. I don't recall if any of the times I had a cooling system drained and refilled if the tech had to replace any drain valves due to leaking or just to be "safe".

But I would seriously consider replacing any drain valves as a preventative measure if any were opened to drain the cooling system.

A drain removing as much as possible then refilling with water and running the engine to temperature for a while then draining and repeating until the water comes out clear ensures all the old coolant is gone.

 

You can try using compressed air and jury-rig a fitting on one end of the open lower drain hose, on some cars that can help remove additional coolant. Don't go too high on pressure.

As noted above, a vacuum fill tool is a big help in avoiding air bubbles when refiling. If you have one you can also close up the system after draining, pump it down with the tool, and then drain again. That often gets additional coolant out that's hiding as well.

 

Hi,

I flushed my N18 with 2 rounds of distilled water after replacing the thermostat. There was still a bit of color in after the 2nd flush but I decided to stop there. A third flush might get all the old coolant out.

Where did you get the metal crossover pipe from?

cheers
MacMini34

 

It's from MotorTek in Italy.


If you are going to contact them/order. It is best to do it via Facebook Messenger or WhatsApp.

EDIT: Why won't the forum just display the hyperlink to Facebook?

 

Had a go at doing the first flush today.

- Heater Temp: 'HI'
- Heater Speed: Low
- Engine at a combination of idling and 2-3k RPM

It took about 1.5 hours for it to reach 106°C and the bottom hose to get heat into it when the thermostat finally opened.

No air was coming out of the bleed screw on the thermostat housing and the expansion tank cap was off for a good chunk of the time.

Surely it shouldn't take that long? Well I hope it doesn't because I still need to get the remains of the old coolant and radiator/coolant system cleaner out of it.

 

Idling the engine can take a long time to get to the point the coolant is hot enough to trigger the radiator fan on. Have to admit I wouldn't have thought it would take 1.5 hours to reach 106C.

The heater on might have worked to slow heat build up some. But I don't think it would account for all the time required. Was the A/C on? If the A/C is on this has the radiator fan running all the time.

My SOP is to when I want the coolant up to temperature and in a reasonable amount of time is to drive the car in town traffic. With the A/C off. Driving is nothing fancy or wild and crazy. Just the normal city traffic: Stop and go, idling at a stop light now and then will in my experience with a number of cars get the coolant to 212F and above but also the oil hot up to 238F. (Might mention too that in the case of both fluid temperatures the temperatures drop rather quickly when I leave city streets for the freeway.)

 

A/C was off for the whole time and the heater was producing hot air pretty much straight away (all instructions I've seen say to have the heater on full heat/low speed).

Unfortunately the car isn't in a driveable state at the moment (various components not fitted).

 

Well that you can't drive the car makes this a more difficult task.

I can tell you with other cars to refill the cooling system after a drain and a cooling system that really needs a vacuum lift to refill properly the alternative is to fill the system then start the engine and run it at elevated RPMs until the coolant level drops. Let the system cool to where it is safe to open the cooling system then top up the level put the cap back on and operate the engine at an elevated RPM again. And repeat this until the coolant level no longer drops.

For elevated RPMs I no longer have the factory manuals for these cars and I don't want to trust my memory to offer a number but I recall the RPMs were high enough I thought the process bordered on engine abuse and I would never had done it that way. Fortunately all cooling services were done at the dealer and the service department had a proper vacuum lift system.

So you have to make do.

 

Would the vacuum lift system (like what are on Amazon) do the job? Would they be able to pull any of the coolant from the engine block?

 

Not sure how completely a vacuum lift system can empty a cooling system. I've only observed them when the cooling system has been drained and the tech is ready to fill the cooling system. The system pulls the cooling system down to a very low pressure. Low enough the coolant hoses collapse. Then the vacuum is shut off and the valve to the reservoir filled with fresh coolant is opened. The reservoir is open to atmosphere and the pressure difference pushes coolant into the cooling system.

Did a quick search and all vacuum lift systems mention filling the system. None mention being able to use the system to evacuate the coolant.

The thing is you could use one to quickly fill the cooling system with water then of course you are faced with operating the engine to get the coolant hot enough to open the T-stat and circulate the hot coolant.

 

Hi airbusA346 (is that your other ride?),

Took look at their Facebook page - at least I could see it as I won't Facebook myself. They didn't have pricing although a number of people had asked. Do you mind telling us what the cross over pipe cost? Their works looks very nice. But having done mine a while back I'm really hoping not to have to do it again or for a long while, or something. Barry the Cooper hasn't had too many miles added since the thermostat repair.

Some mentioned filling with water and driving for a while. Isn't there a risk of the water boiling? My Scantool says I'm at 102˚C once up to temp. How pressurized is the system?

cheers
MacMini34

 

You're never going to get ALL the old coolant out - there will always be little pockets of old coolant in the block and other passages. Best you will ever get is to dilute the old coolant with new. Anything more than two drain and fill sessions is over kill.

I have a vacuum tool for coolant filling, and it doesn't get all the old stuff out. It will collapse all the hoses and get most of the stuff out, but its main purpose is for filling.

 

ttt.... Interesting topic.



.

 

With a cooling system able to hold pressure the water shouldn't boil. You don't have to get the coolant temperature pegged just hot enough to cause the t-stat to open and let the water flow through the system. A WAG would be this would happen at something less than 102C probably closer to 90C.

 

in the 2nd gen engines, the thermostat is electronically controlled. At rest and unpowered, the thermostat is open. When you start the car, the thermostat is energized and closes. Then, the ECU will control the thermostat to a temperature target. It is not a simple “open-closed” control.

 

The T-stat should still open up as the engine runs and builds heat. The electronically controlled T-stat is just to try to avoid big swings in engine coolant temperature that an old style T-stat can cause.

Have to say the few times I have put a new and used old style T-stat in a pan of water on the stove and bring the water to a boil the T-stats just don't suddenly spring open at some point. The opening is dampened so some extent.

 

Are you switching up to NPG type of coolant ?

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Presumably, a wet shop vacuum would get all the old coolant, rust & debris out, wouldn't it?

 

Not all. Some.

To me the best way is to drain as much of the old stuff as is reasonably possible. Fill the cooling system with water. Run the engine enough to get the T-stat to open and water to circulate. After a bit shut off the engine and let it cool to where it is safe to open the cooling system to drain the water (with some residual coolant) out.

If circumstances call for a pretty clean cooling system before refilling with the final blend of anti-freeze and water repeat the above process until the water comes out looking free of any anti-freeze. Sure it will have some tiny bit of the old anti-freeze present. Even if you do this 100 times a close enough analysis will find some molecules of the old anti-freeze present in the water.

The coolant doesn't "hide". The system is designed so there are no stagnant areas for coolant to collect. It is just a matter of running water (with the T-stat open) through the cooling system to remove enough residual coolant that the amount left in the engine doesn't matter.

 

The Bentley manual states to turn the car on not started open the heater to full before adding coolant?
presently I have yet to hook up the battery I was just going to fill until I could start engine.
Replacing with mini coolant same same, system was emptied during oil filter housing fix.

do you need to turn on ignition to refill coolant?