How to Pressure Test a Radiator Cap | YourMechanic Advice

How to Pressure Test a Radiator Cap

As the coolant in your cooling system increases in temperature, the pressure in the system increases as well. Normal operating temperature of a cooling system is around 220 degrees Fahrenheit and the boiling point of water is 212 degrees Fahrenheit.

By increasing the pressure in the cooling system, the boiling point of the coolant is increased to 245 degrees Fahrenheit at 8 PSI. Cooling system pressures are controlled by the radiator cap. Radiator caps hold pressures between 6-16 PSI for most automotive systems.

Most cooling system pressure test kits come complete with everything you will need to pressure test most vehicles. This includes testing radiator caps as well. In order to pressure test the cooling systems of multiple makes and models of cars, adapters are required for each manufacturer.

Part 1 of 1: Pressure testing the radiator cap

Material Needed

radiator cap and neck with cap being removed

Step 1: Make sure the cooling system is not hot. Carefully touch a radiator hose to see if it is hot.

  • Warning: Extreme pressure and heat are at play. Do not attempt to remove the radiator cap while the motor is hot.

Step 2: Remove the radiator cap. Once the motor has cooled down enough to touch a radiator hose without it burning you, you can now remove the radiator cap.

  • Warning: There could still be hot pressurized coolant in the system so be sure to pay attention and be careful.

  • Tip: Place a catch pan under the radiator to catch any coolant that may come out when you remove the radiator cap.

cooling system pressure tester with radiator cap adapter

Step 3: Attach the radiator cap to the pressure tester adapter. The cap will fit onto the pressure tester adapter in the same way it twists onto the radiator neck.

Step 4: Attach the adapter with the installed cap onto the pressure tester.

Step 5: Pump the pressure tester handle until the pressure builds to the specification written on the radiator cap. It should not rapidly lose pressure, but it is normal to lose a little.

  • Tip: The radiator cap should be able to hold most of the max pressure for up to five minutes. You don’t need to wait five minutes, though. A slow loss is normal but a rapid loss is a problem. This takes a little bit of judgment on your part.

installing the radiator cap

Step 6: Install the old cap. Do this if it is still good.

Step 7: Buy a new radiator cap from the auto parts store. Make sure you know the year, make, model, and engine size before you head to the parts store.

It is often helpful to bring the old radiator cap with you.

  • Tip: It is a good practice to bring the old parts with you to buy the new parts. By bringing the old parts, you can be sure you are leaving with the correct parts. Many parts also require a core or an extra charge will be added to the price of the part.

Radiator caps are an essential part of the cooling system that many discount, keeping the cooling system in balance. If you would like one of YourMechanic’s professional technicians to pressure test your radiator cap for you, book an appointment today and one of our mobile mechanics will test it for you at your home or office.


Next Step

Schedule Pressure Test Radiator Cap

The most popular service booked by readers of this article is Pressure Test Radiator Cap. YourMechanic’s technicians bring the dealership to you by performing this job at your home or office 7-days a week between 7AM-9PM. We currently cover over 2,000 cities and have 100k+ 5-star reviews... LEARN MORE

SEE PRICING & SCHEDULING

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Recent Pressure Test Radiator Cap reviews

Excellent Rating


YourMechanic Pressure Test Radiator Cap Service

Average Rating

5/5

Number of Reviews

24

Rating Summary
24
0
0
0
0
24
0
0
0
0

Patrick

31 years of experience
369 reviews
Patrick
31 years of experience
Honda Civic - Pressure Test Radiator Cap - Las Vegas, Nevada
I am extremely happy with Patrick and I hope that if I need a mechanic again, that I can request Patrick for any future repairs.
Subaru Legacy - Inspection / Diagnostics - Las Vegas, Nevada

Robert

11 years of experience
76 reviews
Robert
11 years of experience
Dodge Ram 1500 Van - Pressure Test Radiator Cap - San Jose, California
From the beginning, I knew just from looking at Robert, that he would exceed expectations and I was not wrong! My suspension diagnostic revealed stripped wheel barrings. It was the source of my driving problems including knocking noises. Thank you Robert for your thorough and patient diagnostic and recommendations to the problems. I recommend knowledgeable, professional Robert for your vehicle needs and will be doing by my word also.
Nissan Altima - Pressure Test Radiator Cap - Alviso, California
Nice, knowledge. Very convenient.

Todd

25 years of experience
95 reviews
Todd
25 years of experience
GMC Sierra 1500 - Pressure Test Radiator Cap - Newport News, Virginia
Todd was early for my appointment !! That is a good thing !! Todd was very professional and knowledgeable !! He took the time to show me what my issue was !! I have scheduled Todd to return and make the necessary repair !! I am extremely happy with the experience. Thanks Todd

David

35 years of experience
195 reviews
David
35 years of experience
Toyota Corolla - Pressure Test Radiator Cap - Los Angeles, California
What a great service this is! David M. showed up on-time, was friendly and professional, explained what he was going to do, and completed the three services items in just one hour.

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

Related articles

How to Replace a Car Radiator
Car radiators remove heat from coolant after it's cycled through the car engine. Cars overheat and damage is caused without a functioning radiator.
How a Car's Cooling System Works
Have Have you ever considered the thousands of times explosions occur in your engine? If you're like most people, that thought never enters your mind. Every time a spark plug fires, the fuel and air mixture in that cylinder blows...
How Does a Radiator Keep an Engine Cool?
Car radiators cool off your engine and prevent your engine from overheating. Coolant absorbs engine heat and dissipates it through the radiator.

Related questions

What can be causing my van to leak coolant?

Hi there. Check the coolant hoses and see if any hose are loose. If they are loose, then they will need tightened up. Check the coolant reservoir and see if it has a crack or loose hose to it. If...

The heat isn't working in my 1995 GMC

Hi there. The symptoms you're describing (especially the soft radiator hose) along with the fact your heater is not working may be caused by restrictions in the coolant line such as an air bubble. This could have happened when you...

I have replaced radiator watepump ect still running hot

If you did not replace the thermostat then you should replace it and then refill the system after bleeding out all the air in the system. Check to make sure the fans come on when the temperature goes up. If...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com