Bests & Worsts Reviews from Amazon

Here's the scenario: 2003 Nissan Altima 2.5 liter, 175K miles on it. Symptoms: Losing coolant, about 8oz a day, but no external leaks. Had a problem with heat going back to last winter - there is no heat when the engine is at idle, the engine has to be around 2K revolutions or higher to get heat from the heater core. This is because there is combustion gas constantly leaking into the coolant system creating a vapor lock in the heater core. Engine has occasional misfires in cylinder 3, I believe caused by coolant leaking into that cylinder. If the radiator is running under pressure the engine sputters and struggles to run at times - I believe because an over-pressurized coolant system is forcing some coolant into the engine. Setting the radiator cap so the radiator doesn't pressurize, the engine runs fine. Replaced both thermostats (yes there are two for some reason) and made no difference. Given those circumstances I was very certain there was a head gasket issue. Because of the high mileage I didn't want the expense of doing a head job, so decided to give Blue Devil a try. I followed the instructions on the bottle to the letter with these exceptions: (1). Idled the engine with the Blue Devil mixture in it for 80 minutes, not 50 as the instructions state. After letting the engine cool overnight and starting it, it was rough getting it going and it sputtered a bit at first. This led me to believe that the mixture may have bled into a cylinder while under pressure and the car not running. So: (2). I drove the car for 3 days, about 200 miles, with the mixture still in radiator and thermostats out, to give the pure mixture more time to seal any leaks. (3). After 3 days driving I drained the coolant down, keeping the liquid, put the thermostats back in, then added enough anti-freeze for a 50/50 mix. Topped up with the Blue Devil/water mix and bled air out of the system.. It's now been over 2 weeks since I used the Blue Devil, I've driven about 1500 miles including a day trip of around 400 miles. Engine runs great, there are no misfires, no loss of coolant, no excess pressure and there is ample heat from the heater core with the car at idle. So at this point, problem is 100% fixed. Blue Devil did the job as advertised and I'm a happy customer so far. This is supposed to be a permanent repair so real proof will be how it holds up over time, including the upcoming winter. I'm hoping to get 2 to 3 more years from the car, until the car I just purchased for my wife is paid off and I can afford to replace this one. I will update this review as time passes so keep tuned, but so far, so good! **UPDATE** - October 3 2016, going on 2 months and over 4K miles driving after using the product. Car continues to run great, no indications of any head gasket issues. I've driven the car on 2 trips, one 350 miles and one 750 miles at speeds up to 80mph. No problems and am getting better gas mileage on the trips than ever, 31 to 32 mpg highway. **UPDATE 2** - January 5, 2017 - it's now been 10K miles since using the product. Still no issues at all, no coolant leaks or loss, no air or combustion gasses getting into the coolant system. Prior to the Blue Devil repair, air/combustion gas would be trapped in the heater core meaning no heat inside the car unless RPM's were very high. Now there is no problem with heat, even at idle the heat blows strong. I'm sure results of using the Blue Devil Gasket Sealer may vary depending on the type and extent of damage to the head gasket, but in my case it has resulted in an effective and very cost-efficient repair. **UPDATE** - August 21, 2017. It's been one year, 21,500 miles and I've had no problems with the car at all. Running great, no coolant or head gasket leak. **UPDATE** - July 13, 2018. 212,000 miles on the car, 37,000 miles and 2 years since I added Blue Devil. Still no issues, not losing any coolant, car runs great. 2 years of driving this car on a 60 mile/day work commute plus personal driving miles. **UPDATE** - July 5, 2019. 233,000 miles on the car, almost 3 years and 58K miles since Blue Devil was added. A few weeks ago I noticed my coolant level was slowly dropping. No external leaks so it has to be internal. I've wrapped a paper clip around the internal radiator cap seal so no pressure builds in the cooling system, coolant level is now stable. There is no evidence of combustion gases in the coolant, however there may be issues developing, I will monitor closely. *Sep 8, 2018 - turns out a small bypass hose to the throttle body had a slow leak that dripped onto the transaxle housing and collected in a small area that evaporated before it dripped to the ground. The leak got worse and I noticed it, replaced the hose and now there's no coolant loss, so no internal leaks. Engine is still running good.