Dan, I read somewhere (probably in one of my automotive training course textbooks) that pressure in the block and heads reaches 90 psi when the thermostat is closed and engine RPMs are high. Therefore pressure from a municipal water system should not be a problem. Pete in PA From: therichardsonfamily@xxxxxxxxxxx Subject: IML: colling system pressure? Date: Tue, 20 Feb 2007 20:35:23 +0000 Reply-To: mailing-list@xxxxxxxxxxxxxxxx Here's a question for Dave, but others may have some insight as well. My '67, 440 cid (Imperial engine) has newly replaced freeze plugs, and a lot of casting sand and junk in the cooling system. Prior to doing a closed system flushing with "Cascade", I want to get most of the garbage out using a garden hose on the lower radiator hose, thereby avoiding the redone radiator. We all know 15-18 psi is what a radiator cap opens at. However, my garden hose may be as high as 25 to 30+ psi. Can the head gaskets, etc. and inside of the engine take that kind of pressure? Does anyone know what pressure exists inside the block? Or would I be wiser (with this old , tired engine) to just throw an old radiator on and do a closed system flush? Any other drawbacks to my open system flush? Thanks for any input. Dan Richardson 300L Family Heirloom ----------------- http://www.imperialclub.com ----------------- This message was sent to you by the Imperial Mailing List. Please reply to mailing-list@xxxxxxxxxxxxxxxx and your response will be shared with everyone. Private messages (and attachments) for the Administrators should be sent to webmaster@xxxxxxxxxxxxxxxx To UN-SUBSCRIBE, go to http://imperialclub.com/unsubscribe.htm