Coolant Reservoir Cap Autozone (2024)

FAQs

Is a coolant reservoir cap necessary? ›

Over time, the coolant fluid reaches its boiling point, resulting in an increase in pressure within the system. To alleviate this pressure, the pressure cap plays a vital role.

If it has both a metal radiator cap and a plastic coolant reservoir cap, and you lost the plastic coolant reservoir cap, but still have the metal radiator cap properly installed, then yes, you can wrap the top of the coolant reservoir with aluminum foil and go buy a replacement. The plastic cap does not hold pressure.

Radiator cap sizes are not all the same.

in answer to the question - its perfectly fine to start, and run, and rive the car withou a rad cap - however the collant will boil at a lower temp, and will eventually overflow due to this boiling - so carry a bottle of fresh water to top up the system as you go along....

Conclusion: Never drive your car without coolant

If you discover that you are running low and there is no gas station nearby, then it is recommended that you should call for assistance. Do not continue to drive as you may end up permanently damaging your engine.

Yes, you can start a car with the radiator cap off. In fact, turning the engine on with the cap off can help remove air bubbles which is part of the process when topping up your radiator coolant level.

Without the cap, the steam bubbles push coolant out of the radiator neck in large “burps”. This lost coolant makes overheating worse and if not quickly shut off, the heads on the engine can warp, causing the head gaskets to leak.

The worst possible thing you can do is drive around with a dry engine. Without a liquid like a coolant or water, your engine will rapidly overheat and suffer serious damage as you drive. There are problems that can cause your radiator and other parts of your cooling system to leak.

No, a loose cap stops the system running at pressure, and the pressure helps the coolant to circulate. It also runs at a higher temperature as the system is under pressure.

If the cap can't maintain the correct pressure for your vehicle, the engine will start to overheat. An overheating engine could also be a symptom of air pockets within the cooling system. If the radiator cap doesn't have a good seal, air can make its way into the system, creating little pockets.

How long does a coolant reservoir cap last? ›

You don't have to replace the radiator cap often. Experts recommend replacing it every five years to prevent issues from popping up.

The cap regulates the maximum pressure, preventing damage to the hoses and radiator. After turning the engine off, the system cools and the coolant contracts significantly. The cap therefore has a return valve that admits air from the atmosphere or coolant from an expansion tank, if fitted.

Remove the cap completely. If the coolant level is low, add the correct coolant to the reservoir (not the radiator itself). You can use diluted coolant by itself, or a 50/50 mixture of concentrated coolant and distilled water. When coolant rises to the cold fill line, replace cap and tighten it until you feel it click.

If there was still coolant visible in the tank, no damage whatever will have occurred. The cap is there, not only to prevent dirt getting in, the liquid getting out but also to maintain the pressure above atmospheric, which means the coolant can exceed the normal boiling temperature.

Yes, you can start a car with the radiator cap off. In fact, turning the engine on with the cap off can help remove air bubbles which is part of the process when topping up your radiator coolant level.

If the coolant reservoir is overflowing, a bad radiator cap may be the culprit. When the cap is faulty, coolant can flow to the reservoir without releasing excess pressure, leading to a lack of necessary pressure in the radiator. This lack of pressure can cause the coolant tank to overflow.

So, unfortunately, it is not recommended to open the reservoir while the engine is hot. The engine does not need to be absolutely stone cold, however, you should wait until the system cools off and system pressure has dropped before opening.