How to remove Grohe Sinfonia Faucet

I need to replace the cartridge in my Grohe 20.655 Sinfonia two-handle lavatory wideset. This requires removal of the cross handle 1 and cap 5 (see the diagram and parts list). It is straight forward to remove the cross handle. But I can't figure out how to remove the cap.

Grohe tech support recommended a strap wrench. I've tried, but the strap wrench keeps slipping because of the bell shape of the cap. As a last resort, I'd have to loosen the nut under the sink. But it is very crowded under the sink and I want to avoid this route. Any suggestions on how to unscrew the cap? Thanks.

Wrap it with black electrical tape and use a good pair of Channelock pliers. Removing the faucet would not help at all.

HJ - thanks, I'll try out the electrical tape and channel lock pliers.

Sorry, I didn't mean to remove the faucet but just the handle and cap. Thanks for correcting that.

Man I hate Grohe, heh. That escutcheon should unscrew. Hj's method will certainly give you a good grip, but you have to careful with how much squeezing force you apply. Another way to go is to wear gloves with a special rubber grip coating applied to the underside...that will allow your fingers to get a good grip if you can't get a rubber strap wrench on there.

Finally got the cap off by wrapping it in plenty of electrical tape and using channel lock pliers. I can see now why it was so hard to unscrew - the cartridge and the inside of the cap are heavily corroded. Now to the next challenge - despite removing the cap, I can't get the cartridge out. It's frozen inside the housing due to corrosion. Time to call Grohe for more warranty parts.

Basement_lurker - agree with your sentiment.