Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Leak Detector is a great idea but would like a self test feature.

I used the leak detector and based on a negative response, I limited the engine tear down to the lower intake manifold. Of course one wonders if the negative result is due to a bad test. It would be helpful to have a method to introduce combustion products into the coolant after the test to see a positive response from the test set-up. I found the tapered stopper somewhat difficult to keep in place but, expectedly, a universal tool will be a compromise. Since I do not know if a small leak to atmosphere would compromise test results, I used a motor driven vacuum pump to draw through the sample tube allowing me to use two hands to keep the stopper in place.