Today I got a coolant change done on my 987.1 boxster 2.7 manual 5-speed.I've got an independent ex Porsche technician with his own garage a few miles away. Really really nice guy and very supportive and helpful.

I bought 25ltrs of coolant premix ready for the change after reading that the system took 22ltrs. We were also changing the water pump and thermostat at the same time.

I had bought two bottles of Wynn's coolant flush (the correct amount for the size of the system). We sucked a bit of coolant out and put the Wynn's in, ran it for 10 minutes as per the instructions.

One of the guys opened up the pipes at the front near the front suspension and also the rear pipes near to where the water pump is were opened up as well. My friend estimated approximately 15 to 17ltrs came out in total.

Fitted the thermostat and water pump, connected the hoses back up and started to manually fill the cooling system. My technician friend opened the bleed valve round by where the roof folds, and we even tilted the car nose down a bit as well.

Run the engine blowers on half, temperature on full.

But.. when we'd filled it.. I still had about 15ltrs of new coolant in the bottles unused..

We went under the car and squeezing some pipes my friend pointed out the gurgling noise indicating the was air in the system.

So either (assuming my friend was right on his estimation of I was removing about 17ltrs) either there is approximately 8ltrs worth of air still in the system... OR ... The estimation of what we removed is incorrect.. and approximately 10ltrs of the old coolant (and coolant flush) was still in there when we filled it up.

So my friend said that I'd probably find that when I checked the coolant level over the coming week or two, that I would end up putting in between 5 and 8ltrs, as the air gradually made its way out of the system through normal driving.

We only did the job today.. but I've been driving it most of the day since and it's only taken about 100ml.

Obviously it's not been a full day yet.. but I have to confess to being concerned... Because I ordinarily monitor through the OBD and an app on my phone, The coolant temperature anyway.. and it's warming up a lot faster than normal which indicates air in the system.

I just don't want to overheat the car but I'm also still a bit concerned that we left a shed load of old coolant (and flush) In the system.. and the flush is caustic, only meant to be used temporarily for flushing. My friend did make the point that even if there was some left in it would be heavily diluted based on the fact that we removed a lot of coolant and topped up with new.

My friend said that he has never needed to use a vacuum or pressure system to do a coolant change in all his years working on cars and his time with Porsche.. and I don't at all want to undermine his experience.. but I'm just wondering what the best thing to do is

Sorry for the length of the message but.. I'd welcome any thoughts...


Many thanks