Report 1997 Deville Overheating Leaking Pressure Tank in Engine Cooling Posted June 15, 2016 Hi Guys, Thanks Bruce you're right it's a balanced system, need to check each part. Yes, the cooling fans were out for about an hour, got the new relay & they're ok now. The surge tank has actual cracks in the plastic that are leaking steam, pressure, coolant. Definitely not holding pressure. That's why I was wondering if no pressure alone like leaving the pressure cap off & driving around in hot weather would cause overheating by itself. Thanks JD, yes, coolant leaking from overflow hose & tank. Tank has bad leak at both hose connects, plastic has failed. Going to test the system today for the head gasket leaking, hopefully it's not. The new tank comes next Monday, after that I will put in tank & new cap & pressure test to hold 16LBS is that correct? Just trying to keep her running good til I can get a newer one. Need it to be dependable for wife & kids. Wish I had joined this forum years ago!