My RRS has a strange coolant leak, that only occurs around the Coolant Expansion tank, and only when I put my foot down.

I have taken it to a well respected specialist locally who replaced the water pump due to a leak, I had it back and put my foot down and noticed steam coming from the front left. They pressure tested the system and it did not leak, but each time I put my foot down it leaks under pressure I guess somewhere around the coolant expansion tank.

I replaced the tank with a new one today, just took it for a spin, put my foot down and the same thing.

Anyone experience the same?.

Thanks,
David.

Is it only under load? Can you have someone rev the engine while you look? Is it just steam, liquid dripping, liquid spraying or all of the above? Have you tried with the expansion tank cap off? Just throwing ideas at you. 2019 5.0 SC SVA (Current)
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Thanks, it's only under load when I put my foot down, steam out of the uk nearside front bonnet. Open the bonnet and there's coolant spray around the expansion tank area.

I replaced the expansion tank yesterday and the same happened on a test drive. The Indie did the water pump and replaced a hose then pressure tested ok. I had the cap off for 20 minutes when replacing the expansion tank yesterday.

Was it bled properly as these are bad for getting air locks

That's a good question, I am hoping it is this and the Undue mentioned it did have an airlock. What's the best way to bleed these beasts?.

Have a quick search on here it should be explained

So after bleeding the system I still have a leak. It only happens when warm and when putting my foot down and seems to come out of the coolant return pipe or connector?, on top of the nearside of the engine. I replaced the original clip with a jubilee this morning thinking it was the clip, but maybe there is a rubber seal in the plastic connector, or it is leaking from the plastic connector going into the supercharger? - see pic...thanks.

Pic below

Just to respond to my own message, I still have a coolant leak to my dismay, however, thought I would post back to advise I was sorely mistaken thinking the pipe clip I replaced was a coolant pipe. After tracing the pipe further, it was a pipe that went into the intake in the front of the engine.

Ah well, back to the drawing board on the leak...