Combustion engines heat up the longer they are on. If you run them dry, they will go from blue, to green, to yellow, to red, then explode. Each level they move up means they move quicker. If they are adequately cooled, they should never go beyond yellow.
There are two issues you could be having, one being you might not be pumping enough water. Generally, and this isn't a hard rule, I find I like to have 4 redstone engines on a pump for each full-run combustion engine. Not exactly sure where tin engines fall in relation to redstone engines as far as power.
The other issue is you might not have enough room in your pipes. If you are using stone/cobblestone waterproof pipes, you might not have enough actual liquid in those lines to reach all of the engines. If you were using gold waterproof you'd have a lot more space for liquid in a single pipe, but then again, I don't know what a waterproof teleport pipe has for space in it either, or if it simply just jumps it to the next pipe without taking on the properties of a pipe itself.
Make sense? Probably not, that shit was terribly written.