The windshield washer fluid cap may seem like a small and insignificant part of your car, but it plays a crucial role. However, things like the windshield washer cap breaking or forgetting to put it back after refilling happens. This may lead you to wonder if you can drive without the windshield washer cap and what happens if you do.
What is a windshield washer fluid cap?
A washer fluid cap is a small plastic or rubber component on top of the windshield fluid reservoir, usually found in the engine bay but occasionally in the trunk. The washer fluid cap will usually have a picture of a windshield getting sprayed on it, not to be confused with any other caps like the brake fluid or power steering fluid cap.
Its purpose is to seal the opening of the reservoir to prevent the washer fluid from leaking out and stop dirt from getting in. The cap typically has a small tab or handle that can be lifted to allow for the addition of more fluid and then securely fastened to prevent spillage.
What happens if you drive without a windshield washer fluid cap?
Although the car will operate as usual, and so will the windshield washers (if you have washer fluid in it, of course!), the problem comes when the washer tank fills with dirt as debris that can now fall into the tank.
The washer fluid pump uses skinny tubes to push the washer fluid through, and they easily block or cause the motor to fail. Typically, this always happens when you need the most windshield washer fluid. Precisely the moment a big truck passes and splashes a dirty puddle all over the windshield, you know what I’m talking about.
To solve the problem, a new windshield washer pump is not that expensive to replace, but finding a blockage in the pipes that run from the tank to the washers for the back window is a bit of a pain. However, replacing them is not actually that difficult. The lines are connected using plastic joiners at intervals, and the hose pops on, and off them, so minimal tools are required. Sometimes you can be lucky enough that blockage appears at the spray nozzle. In that case, using a sewing pin and pushing it down the nozzle will usually clear the dirt.
As a side tip the nozzles blocking also happens a lot when refilling the washer tank from empty all the dirt at the bottom of the tank gathers at the nozzle.
Can you drive without a windshield washer fluid cap?
You can drive without a windshield washer cap; driving without one is perfectly safe, and the windshield washers will remain operational. Actually, on many cars where the washer fluid cap is a flimsy clip-on cap, they always tend to be hanging off anyway.
Although the cap is also there to stop the fluid from leaking out, there is minimal risk of the fluid pouring out of the tank because they usually have a filler neck. Even if yours doesn’t, they generally hold several liters, which you will struggle to empty by just driving around corners. It might empty if you’re going off-roading, but it’s still unlikely to ever completely empty.
The only problem with driving without the cap is the dirt that can get into the washer bottle and cause the washer pump to fail or a blockage in the pipes/spray nozzle. Therefore, it is better to use a temporary cover solution to avoid the headache of repairing the washer fluid system.
How to fix a missing washer fluid cap
Because the washer fluid isn’t held at any specific temperature or under pressure, you can use almost anything to cover the washer reservoir filler hole. A bottle cap, gaffa tape, aluminum foil, or a rubber glove spring to mind.
Your goal is to protect where the washer fluid cap was to stop dirt from getting into the washer bottle and the fluid from leaking out. Once covered, you may not even need to get a proper cap. Keep replacing the makeshift one after refilling the reservoir. However, I would recommend getting another adequate replacement.
Although driving without a windshield washer fluid cap is perfectly safe, it is much better to drive with it covered. Use anything you can get your hands on to cover the hole; this will stop the fluid from leaking or dirt getting in and causing a blockage.