Hi Scotty, I have a 2005 Toyota Sequoia with 287,000 miles. It runs great, and has no engine codes. The Sequoia overheats slowly to about 235-240 degrees. It’s ok at slow speeds, but heats up on the highway. It does cool down at slower speeds. There are no visible coolant leaks, and no white smoke /steam from the tailpipe. I’ve replaced the thermostat, temperature sensor, did a head gasket leak test, with the blue liquid never turning yellow/green. It loses about a pint of coolant after 60-80 miles. When I pressure tested the coolant system to the recommended 13 lbs, the needle decreases about 2 pounds in 5 minutes. Could I have a small head gasket leak just enough not to cause the typical head gasket leak symptoms? Should I use a can of Bars Heat Gasket Repair as you have recommended? Thanks.
When they do that you want to perform the combustion gas leak test while you have somebody in the car and holding the rpms at around 2000 rpms to get those pistons really pumping any ((possibly)) leaking combustion gasses into the cooling system (through a potential tiny head gasket leak) like it seems to be doing at highway speeds. (Make sure the thermostat is open while doing the test)
If you find it is a head gasket leak, and with 287K miles, nobody would blame you for trying a "leak seal" product.
And with a tiny leak you may have success. Try Steel Seal
