vw trained Mechanic insists G40 Coolant is fine... is it?

[coupcoup]

I've 2018 4motion 150bhp I believe. The local mechanic has just done the timing belt and I asked him before he did it if he used the vw spec coolant etc. he say oh yes. so I went to pick it up today and he was just topping off the coolant. not with the vacuum I have to add, just by sitting it slightly uphill and running it till the fans kick in then topping it up. The coolant he says was G40 Coolant. G40. when id specifically asked him to use G13 0r12++. He said just top it up with tap water if it looks a little low. I said not distilled water? oh No he said just tap its fine. So I drove away thinking he must know best being a vw trained mechanic and all.

should I care what coolant is in this? Is it too late if it is the wrong kind? Do I have to flush the entire system to get the g40 out before I use g13 and how is that even possible?

looking for the G40 is fine replies....

F****** nightmare.

 

[DXX]

I couldn’t tell you if the coolants are compatible but adding tap water isn’t a good idea as it obviously contains inpurities.
You instructed him to use XXXX and he ignored it and used YYYY, I would say you have grounds to have it re-worked at the mech’s cost.

 

[drinfinity]

I can’t comment on the coolant with any authority, but the water depends on where you are. Distilled or deionised water is corrosive stuff - no minerals in it, so it will eat metals until it reaches a saturated concentration. G40 has buffers in it, so it will cope in a reasonable range. The phosphates will bind minerals to stop it sticking to the pipes. Tap water here in the north west is very soft, so not much carbonates to fur things up. Down south it will have big lumps in it.

Caveat - I did a summer job as a student on phosphate additives to reduce scale, but not specifically automotive, and it was a long time ago.

 

[coupcoup]

Yeah I think if I took it back to him with legitimate concerns he would change it. But I called anotger independent trained mechanic who also said g40 was fine. I’d prefer to not have to alter anything but I will if I risk damaging the engine.

I’ve a £1500 mile journey I’m about to do towing a caravan so the engine is going to be worked hard.

I can’t comment on the coolant with any authority, but the water depends on where you are. Distilled or deionised water is corrosive stuff - no minerals in it, so it will eat metals until it reaches a saturated concentration. G40 has buffers in it, so it will cope in a reasonable range. The phosphates will bind minerals to stop it sticking to the pipes. Tap water here in the north west is very soft, so not much carbonates to fur things up. Down south it will have big lumps in it.

Caveat - I did a summer job as a student on phosphate additives to reduce scale, but not specifically automotive, and it was a long time ago.

I spoke to another mechanic who seemed pretty confident that it would be ok. And I can’t argue with your science cause I know nothing about it. I know I have soft water here( good for making cheese apparently) so I’ll take a bottle on my next journey and hope it lasts for a couple years at least. Thanks for the reply