Technical coolant level dropped

[Big Black Stilo]

my bravo was serviced not so long ago and it was a can let and waterpump change so the coolant was changed. Today topping up the screen wash i noticed the coolant was at the minimum level... well, just under the minimum line so it wa touching the bottom of it.
Having just dumped a bottle of water in the car and miles away from a tap. I had a quick check with a torch, no signs of leaks and there wasn't a sign of anything at all (unlike when the rad cracked and it was easy to spot)
I took the lid off the tank and there was no hiss, and it only took about two twists and it was off, when input it back on it took over 5 twists before it clicked and wouldn't go further, so I'm thinking the lid wasn't on tight enough and this could be how the coolant has been lost. I also checked the oil which is clean and water free. I couldn't check the thermostat and on the cambelt side there was no sign of coolant although the engine tray looked damp on that side (more like oil residue- nothing unusual for what you get round pulleys). as the was no tap where I was and with te tank fastened I drove to where the was water to top it up and it ran fine, no over heating, no warnings, no sign of leaks after running it. when inpulled up and checked it, the level was over maximum, but it was hot. (usual temp). I did my big shop and by the time that was done and I did some other errands the car had cooled to cold. on unscrewing the tank cap it hissed as pressure was released, something it didn't do when it was cold before.
I've topped it up, and although I expect coolant levels to rise when it's warm, I didn't expect that much when I checked it when hot. I'm going to keep a close eye on it, but is my theory about the tank cap not being 100% fastened a valid one?

 

[PROV]

I recently had a coolant dropping problem, and again mine was not long after a new waterpump was fitted, so I was suspicious of this. I did have pink water around the bottom of the cambelt (on the undertray), which also pointed to waterpump issue.

However, when they had it in it turned out to be a gasket somewhere further up (sorry can't be more specific), and the water was making its way down past the waterpump.

As to the cap not being on, I suppose this could have been the issue, was there any excessive moisture on the underside of the bonnet though?

 

[PROV]

Also just had a thought, could have been an airlock in the system after the change?

Monitor and if it doesnt drop again dont worry about it

 

[Tad-bravo]

Coolant loss is normal sometimes especially after a big service. It happened to me once long ago after a service but after I topped it up it never went down again.

 

[cardinalbiggles]

Coolant loss is normal sometimes especially after a big service. It happened to me once long ago after a service but after I topped it up it never went down again.

Its actually not normal, its the garage not doing the job properly.

If they drain the coolant they should run the car up to temperature and top up once the new coolant has made its way back into the system.

 

[Most Easterly Pandas]

Its actually not normal, its the garage not doing the job properly.

If they drain the coolant they should run the car up to temperature and top up once the new coolant has made its way back into the system.

:yeahthat:

 

[cardinalbiggles]

The coolant level drop happened days after I took my car back.

Its still not normal, its a closed system, there is nowhere the coolant should be going apart from circulating in the cooling system so if it did drop then you have a large problem somewhere.

 

[Tad-bravo]

Its still not normal, its a closed system, there is nowhere the coolant should be going apart from circulating in the cooling system so if it did drop then you have a large problem somewhere.

Actually my coolant loss wasn't explained, and since I wasn't over the mechanics shoulder I don't know why it happened but it never dropped again since.

As for it not being normal, slight coolant loss is very common because the coolant tank's cap lets off steam in certain conditions and sometimes you have to replace the cap to stop it from doing that too often.

 

[Most Easterly Pandas]

As for it not being normal, slight coolant loss is very common because the coolant tank's cap lets off steam in certain conditions and sometimes you have to replace the cap to stop it from doing that too often.

No it isn't unless there is a fault with the system / engine somewhere. Yes the cap has a pressure release valve, but under ever day circumstances this shouldn't operate.