Hi, after having my 14 plate 1.6 TDCi repaired (water pump and thermostat) the coolant levels have dropped below minimum level. Is there warning light to tell you when this happens? Am I ok to top up with tap water or does it need to be de-ionised water?

The car will be back in for MOT in 4 weeks and they'll do a pressure test then, in the mean time I will monitor the coolant levels closely. 

Top up with ready mixed coolant or neat coolant and deionised water, yes

Just now, DaveT70 said:

Top up with ready mixed coolant or neat coolant and deionised water, yes

Thanks ... I have heard you shouldn't mix coolant brands/types ... is that true? (I only ask because I have no idea what coolant is in there, as the garage filled it).

Brands ok

Types no

Handbook will tell you spec

On 2/3/2025 at 12:20 PM, DaveT70 said:

Brands ok

Types no

Handbook will tell you spec

Cheers. How do I know if my car has a low coolant sensor/warning light? The level was waaay below minimum when i checked, but no warning light came on. Either it doesn't have a sensor, the sensor is broken, or the levels didn't get low enough to trigger it.

1 hour ago, hiace_drifter said:

Either it doesn't have a sensor, the sensor is broken, or the levels didn't get low enough to trigger it.

Most cars/engines do not have any form of level sensor for the coolant.

You probably don't have a sensor, most cars it's just a plastic expansion tank, if it's going down regularly then check under the bonnet more frequently.

After a long drive check under the hoses that meet the firewall under the bonnet, check the doorbell to see if it's wet, and obviously check under the engine/expansion tank and see if any hoses are spraying/leaking 

It's been back to the garage and pressure tested, and no leaks were found. They believe it was just an air bubble that had worked it's way through to the coolant tank. I'll keep checking the levels until I'm sure it has settled.