How to prevent moisture in distributor cap Nov 22, 2010 路 Fortunately, there are ways to keep the inside of the distributor cap dry. Spray it down regularly with WD-40; especially at times of the year when it’s very humid or cold and damp. If the distributor cap screws down, remove the screws. The key factor is the dew point in the atmosphere. Once fitted run one length of rubber pipe from one side of the distributor cap to a constant vacuum port on the engine. . If it’s held in place by clips, use the screwdriver to open them. Remove the coil wire from the distributor cap and follow this with the spark plug wires, marking which wire goes where on the cap. Cleaning caps would scrape off the corrosion build up then immersed the cap in vinegar for a few days then sprayed out with brake clean and blast of compressed air. Jul 20, 2018 路 Water in the cap solution using the what i call the distributor diaper found on factory dizzys in the last years of the dizzys helped a lot. This modification means that there is a constant flow of fresh (dry) air through the distributor cap. Aug 25, 2020 路 In coastal areas or areas with very high RH you might consider drilling a hole in the top of the caps and running a vacuum line to the caps, but it would be essential to use a sprung non return valve such as those used in modern PCV systems to prevent fuel vapours from being drawn into the distributor where there is a source of ignition. Hoping that condensation issues stays between the bag and outside of the cap. Jul 1, 2014 路 Moisture can get inside of the distributor cap no matter how tightly it has been sealed. Feb 6, 2024 路 I was told WD-40 spray the inside and outside of the cap and rotor helps this issue. My thought is once I replace this cap and rotor again I would place a plastic bag over distributor to help alleviate condensation issues inside the cap. If there is moisture in your distributor cap you’re going to have problems starting your car. Step 1 - Access. Then run a length of rubber vacuum hose from the other side of the distributor cap to the inside of the vehicle. Fortunately, there are ways to keep the inside of the distributor cap dry.