When, and how often, should I replace the radiator cap?

When, and how often, should I replace the radiator cap?

Should I replace the radiator cap at intervals or when the gasket is broken?

I only only replace mine when there is a problem. If you want to replace yours prophylactically, I suppose once every 100,000 miles would be a good interval.

Radiator caps can be checked. Every cooling system pressure tester I know of has an adaptor to check radiator caps.


Where would I check it? The local mechanic?

It might be cheaper to replace it than check it.

Are you sure this is worth worrying about? Are you experiencing some kind of problem, or is this an OCD thing?

I read in “Auto Repair for Dummies” that drivers should keep a spare radiator cap in their vehicle just in case the one in use stops functioning. It made me question if my old radiator cap is about to blow. I could be worrying about nothing.

It won’t blow, it would start leaking or rather not holding pressure and you loose coolant. Rarely an emergency if you are in the habit of checking under the hood once a week. My Caravan’s cap decided to go last week at 106KM, so 100KM sounds about right. I noticed some whitish dried stuff around the cap after the coolant had dried.

I never had to replace a radiator cap … been driving for over 50 years.

If you’re serious about maintenance, as many here are, you should get in the habit of inspecting the radiator cap weekly and replacing it monthly, without fail. That would also be a good time to shoot some graphite into all of your door locks. If you don’t own a steam cleaner, please for the love of God get one. Your engine should be steam-blasted monthly.

Carrying a spare isn’t such a bad idea. I carry a spare gas cap. Frankly, you are more likely to need a spare fuel cap than you are to need a spare radiator cap, but if it brings you peace of mind, I don’t see any reason not to carry a spare radiator cap.

These things are very cheap to buy. If you’re worried just go buy two. Replace your current one and throw the other in the trunk. You’ll probably be out all of $15 after that.

If there is something strange about your cap that makes it expensive (unlikely) then you might think about actually having it tested.

The only times in over 40 years that I’ve ever replaced a radiattor cap is when I’ve replaced a radiator. Yes, they can be tested, but they’re so cheap that it isn’t worth the time unless you’re trying to troubleshoot a cooling problem.

There’s no cause to change them as preventative maintenence. However you should routinely monitor the level and condition of your coolant, replace it (either drain and refill or flush the system with hosewater and refill) every three or four years, and keep an eye out for signs of radiator corrsion, leakage of the radiator or pump or any part of the system, and keep the engine in generally good working order. Correct problems as you find them and you’ll be far more likely to get many happy years out of the radiator cap.

very funny hey what?

ME too…I’ve replaced radiators…and usually just put on the old cap because the new radiator didn’t come with a new cap…NEVER EVER replaced one with well over 1 million miles of driving.

As a maintenance and reliability specialist, I always try to optimize equipment “uptime” at the lowest cost. Radiator caps used to be checked, but since labor is getting more and more expensive, they are normally replaced.

When my vehicles go in for service which includes the cooling system I request the caps be replaced. If the cooling system is acting up for some reason before its servicing date, the cap should be checked as a normal diagnostic procedure.

Similarly, when you buy new tires, buy new valves and valve caps at the same time.

The lowest long term ownership cost should always be your goal.

I guess I didn’t have to replace mine, but last time I had a problem with my cooling system, I replaced the radiator cap as a first step, just because it was cheap. It wasn’t the radiator cap that was the problem though. I guess it might not be a bad idea to put the old one in the trunk with the spare gas cap.

new valves and stems if they are the rubber ones, yes. Newer cars they have steel stems with the sensors built into them…$$$ to replace.

Yes, unfortunately this is an “improvement” that just adds to the cost of reliable operation.

I used to drive old cars in the 70s and 80s. If coolant started to disappear, I used to buy a 7.5 PSI cap with the lever release on top. Sometimes it would stop a leak, sometimes not. That policy probably cost me only $500 in engine repair. About the same as the four radiators would have cost. You win some…

The only one I had to replace was riveted together and was blowing some steam right through the grommet-style rivet. That was on a 1987 Plymouth Horizon which had zero power but would never quit running.

I replaced quite a few of them working at the dealership. I always tested the cap when pressure testing a cooling system. You’d be surprised how many of them dont hold the pressure they are rated for.