After watching Ben's Garage on the tube, he showed a simple tester to make sure your coolant is still working. It is a syringe thing with floating plastic discs inside and costs less than £10.

The coolant in my car looks fresh and clear pink as new.

Now I have sucked up the fluid from the expansion tank filler cap and all the discs floated, which according to the guide means the coolant is bad. So before panicking, I did the test on a new bottle of concentrated coolant, and the same thing happened.

I may try on another bottle of coolant, but it does seem odd. Maybe the bad coolant disc is not relevant in the new modern coolants? Or maybe I am over concentrated, but is that a bad thing?

Any thoughts or ideas are welcome. Tom

Current Drive
2011 4.4 TDV8 Autobiography - Santorini Black - Ivory Leather

Previous Drives
2004 Model Vogue Td6 (Touchscreen) - Java Black - Parchment Leather
1994 RR Classic 3.9 V8 Soft dash - Niagara Grey - Grey Leather
1972 Series III SWB Safari - Green (Hand Painted) - Black Plastic

I've never found the bubble type of tester to be accurate. Better is a Refractometer type of tester. More expensive, I paid about £10.

David Range Rover 4.2 Supercharged 2006
Ford Focus EcoBoost 1.5 2017
MG TF 2003

Previous Cars of note
Land Rover Discovery 2
Jaguar Mk2 3.8 - Company car
MG Midget 1974 - Concours

What type of coolant is the tester for? you may be using the wrong one. As above, refractometer type are more accurate, cheap anything can be false economy though. My refractometer cost £38 and has passed calibration every six months for the last five years. One of the tech's bought a 'pound shop special' from one of the no-name tool vans, although it could be referenced to zero, it mis-reported by 10 degrees on first use.

3rd a refractor to look at the specific gravity of the coolant. 2015 Range Rover Autobiography 4.4 SDV8

Great feedback, will definitely look into a refractor based tester.

I will test the disc one against it which should be interesting. My thoughts are that the G30 modern coolants might be more effective than the older ones hence making the last disc rise. When I tested it just on tap water only the first disc went up which shows it sort of works, but as said here, the accuracy of the devices is important too. Tom

Current Drive
2011 4.4 TDV8 Autobiography - Santorini Black - Ivory Leather

Previous Drives
2004 Model Vogue Td6 (Touchscreen) - Java Black - Parchment Leather
1994 RR Classic 3.9 V8 Soft dash - Niagara Grey - Grey Leather
1972 Series III SWB Safari - Green (Hand Painted) - Black Plastic

If there is no evidence it's been changed recently I'd refresh it anyway whatever tests are available. 2012 TDV8 Vogue (L322)