I have a 2005 Trailblazer with 311K miles that has developed a minor head gasket problem. I'm having to add some coolant about every 1,000 miles. Note: The radiator was replaced about 10K miles ago. My question is which brand and type of Head Gasket Sealer would you recommend? (know that the treatment cannot involve removing the thermostat as it's a thermostat housing). Also, before anyone jumps in with "get it fixed with a new gasket"...please remember that it's 17 years old with 311K miles and worth about $800. Just need it to last long enough until this supply chain mess is over and dealers actually have an inventory of new vehicles.

 

Depending on how bad the leak is, a sealer might not work. They are also usually on temporary, but they might last about a year if the leak isn't to bad. I only used them once and used Barr's Head Seal. It worked for almost a year.