...snip...Certain engines that are more prone to dropping valve seats should be cold when undertaking this procedure. This will help reduce the amount of stress on engine components from temperature differences and expansion. However this also reduces the effectiveness of Seafoam, because carbon and other contaminants in the combustion chamber are best cleaned when hot.
Start the engine and locate the most accessible vacuum line. This is usually the brake booster line. Take the line off and put it up to the can of Seafoam.
The engine's vacuum will begin to draw the seafoam out of the can. While doing so the engine will want to stall, so reving the throttle is required. Usually this is easiest with a friend inside the car but can be done by using one hand to hold the bottle and hose and the other to rev the throttle body.
The engine may vibrate and shake during the intake but this is normal.
Seafoam can also be used by pouring small amounts into the cylinders while changing the spark plugs. However pouring too much can hydrolock the engine and cause damage. Usually no more than 20 ml is recommended per cylinder.
Once the entire can of Seafoam is empty the engine should be turned off and left to sit for 5 minutes. During this time Seafoam will soak into and weaken the carbon and oil deposits inside the cylinders.
Turn on the engine, which may require some extra throttle the first time. Once the engine is on, lots of thick white smoke will come out of the exhaust. This is normal, the smoke is the Seafoam along with deposits being burned out of the engine. The dirtier the engine the more smoke will come out, it serves as a good sign of the treatment working.
Typically new engines with less than 50,000 miles will barely smoke at all, and will not see as much of an improvement from the Seafoam engine treatment due to lack of deposits buildup.
Drive the car until all of the smoke is gone. If the white smoke dissapears and blue smoke begins to come out at the end, this is fine as it will dissapear in 5-10 minutes of driving. ...snip...