Coolant liquid

I need to refill or replace the coolant. (It�s a strange Green colour) It�s dropped just below the Min level.

  1. Its obviously not water. What is it and where can I buy it from?
  2. Do I just top up the level to read max?
  3. If I do top it up should the engine be warm or cold?
  4. Is it better to just bleed the system and replace the lot?
  5. What�s the best way to bleed the system

Hope you can help

Thanks Aaron

Aaron, this green stuff is called antifreeze. You can just top up with water but not too often as you shouldn’t weaken the mixture. Someone will be along in moment and tell you which type it should be.
Top up when cold.
Remember that it will find its own level after driving and when hot. If the level just changed suddenly do you have any leaks from anywhere? radiator hose, radiator end plates etc
If the antifreeze hasn’t been changed since new it is probably a good idea to do it.


your fluid is only green because it has been mixed with blue, as it was the original fluorescent yellow one.

I had tried to find this yellow one but couldn’t and decided to use what Lotus is using currently, the fluorescent pink one (Havoline OAT), you can get it from Rover.
If it’s ony a bit you need no problem on topping it up with clean, fresh water (you will only dilute it slightly and possibly bring down its boiling temp, but by a fraction of a degree) but not to the max, but to the mid line.
Engine cold of course, do not attempt to open with engine hot.
If you fear that there is an airlock n the system, proceed to bleed, but normaly it’s self bleeding, so no need.

If you really want to, like in the case of replacing the whole fluid for OAT (when you need to drain completely the existing fluid, refill with clean water, redrain and do again as they are not compatible), then you will have to bleed.

The procedure is long(ish) and I typed it sometime ago (do a search) but the bleeding points are at the left of the radiator (need thin arm to get there, near the left light) and to the left of the head, a screw on a black steel pipe.
You need to pressurize the system, I use EZ bleed, from Halfords (uses the air pressure from a tyre).

It’s also well described in the manual.
Let me know if you couldn’t find it (I’m in a bit of a rush now).


i’d go with Uldis advice and drain the whole lot out… flush it with clean water and replace it with OAT… then you know what is in there and it will be as recommended.

If it’s any help the green stuff is Unipart 4 year antifreeze. Uldis your yellow stuff is Uniparts 2 year antifreeze. For those of you who’d like a lovely yellowy green coloured coolant - you can get the three year stuff. This range was the recommended coolant by Lotus, certainly on the S1 at least. The only place I’ve found it is at Partco, although obviously once I’d found it I stopped looking any further
I think that it should only be filled to the minimum mark on the expansion bottle when the engine is cold and should ideally be 50% coolant 50% water.
I find the best way to drain the system is to take the bottom hose off the just before it disappears into the left chassis rail but it’s quite messy so I am open to suggestions. To bleed the system I think you’re meant to pressurize it with a fancy tool, but I just run the engine and keep opening both the bleed valves on the top hose and on the left hand radiator hose until the paranoia leaves me…or until you get a constant dribble of coolant.

NB The year refers to the recommended maximum length of time between replacement.

NB The year refers to the recommended maximum length of time between replacement.

Darn, I thought it was the vintage - hic!


Thanks Guys

Looks like a job for the weekend…

Doh! Is there any such thing as an IDG proof posting

Thanks for the rapped knuckles Ian, maybe I did over-simplify that a little.

Doh! Is there any such thing as an IDG proof posting

No, I’ll take the mick out of anything!

Oh hang, it’s anti-freeze that has the vintage!


I thought not.

Hope to see you out and about at the AMOC races again this year Ian.