Coleman Xtreme Mash Tun Lid Issue

I recently gave my old cooler mash tun away and built a new one. I decided to build the very popluar Coleman Xtreme Mash Tun.

The cooler lid closes tight, however once the mash begins, the lid does not close tight due to the heat (my guess?). Which leaves a gap that allows heat to escape.

I place a blanket over the cooler and have tried using a Rachet Strap to try to hold the cooler tight together. However, I'm still getting heat loss.

Are there any secrets or ways I can better insulate the lid to get a tighter fit once the cooler gets warm? Is this normal for the Coleman Xtreme? My last cooler was an Igloo and I didn't have this issue.

Any tips or guidance would be appreciated!

I, fortunately do not have this problem, but interested to see if others do. you are pre-heating the ton, right?

i have the extreme 70 quart. i noticed the same problem, the lid won't stay closed when heated. it stays shut when I put the probe inside to track the mash temp, the wire helps keep it closed.

first time i used it i had problem with keeping temp. a lot of headspace in a 17.5 gallon tun and only 5 gallons of strike water in there. so i just roll out a layer of heavy duty aluminum foil on the top and now only lose one degree

and brettwasbtd: GREATEST AVATAR EVER! HTTR!

I don't have this problem.

Can you see where the steam is escaping? You might be able to fashion a gasket of sorts from one of those silicon baking pans. I've seen them at various places relatively cheaply. Here's a lovely pink one from Target:

http://www.target.com/p/silicone-so...i_sku=10429004&ntclickid=-9150577755113508396