One of the rear tyres on my Punto is losing tyre pressure. I took the car into National Tyre Services. They put the wheel under water and we could not see any bubbles. They removed the tyre, put sealant(black) around the rim, put the tyre back on with a new valve.Balanced it. NO Charge.
two days later it has lost 2.5 psi. Any suggestions?

2.5psi is not a lot of pressure. Is your car constantly losing air??? Or does it just drop a couple psi then stop?

Simple things like cold weather and hot weather can easily give some variations in psi by 1 or 2 psi and this may be your problem. If it is losing air and eventually becomes flat then it's a faulty tyre or air valve and I'd get it re-checked. Somewhere else if the place you took it previous didn't notice it when they had it.

NE1L Thanks for you fast reply.It loses about 2.5psi over a couple of days and then another 2.5 over another couple of days then it appears to stop. I have only just began to monitor it because I was using a meter in bars but a 0.1 bar drop is probably within the accuracy of the meter.I will monitor it over the next few days. By the way the other tyres do not lose pressure over the same time period..

It could be something as simple as weather etc causing the air to contract or expand within the tyre giving slight changes everytime you check. But if it's a standard drop everytime then it would suggest a puncture or something as you'd expect at some point to catch it when the pressure was increasing slightly after a drive or during a warm day.

I'd get it checked again at another place and see what they think. After all you got it checked and balanced free last time so no extra pay out

tyre pressure can vary by as much as 4psi between cold and hot (been driving ) tyres so make sure you check both times first in morning or somting.