How important is replacing your radiator cap at coolant change?

[OilPatch197]

Yeah. That is the question, I've only bought one type of cap, and that is the octagon style that is easier to grip.

Other than that I don't change my cap at coolant changes. I usually get a new cap when I buy the truck, and never buy another.

 

[Shran]

There's really no reason to replace it unless your cooling system won't hold pressure, or if the cap is damaged. In that case, it's a good place to start.

 

[northranger]

+1

 

[Mark_88]

You can get it pressure tested at a rad shop...if you're losing fluid check the hoses cause they're more likely to need replacing more often than the cap...and check the drain cock because they can start leaking...

I usually leave a piece of cardboard under my truck when I want to check for leaks...the driveway is too wet to notice anything half the time...

 

[kunar]

i've had caps that leaked before. its surprisingly hard to trace back to the cap. if its in decent shape though, i wouldn't worry about it.

 

[Wicked_Sludge]

caps are cheap...too cheap to ignore. i replace mine every few years when i flush the cooling system.

people dont realize how many items the radiator cap is actually responsable for. it doesnt just seal the top of the radiator. it has to hold pressure (the right amount of pressure), vacuum, and be water-tight. it spends its days soaking in a corrosive chemical bath, and it can cause quite a few different and often hard to diagnose cooling system problems.

 

[LearjetMinako]

I only replace them when they need to be. If the seal is damaged or has engraves in it, its time to replace it. My Ranger rad cap is okay, but the Blazer's rad cap is in not so nice condition (Dex-cool is the worst).

 

[thegoat4]

Radiator caps are cheap crap and go bad frequently. If you can get yours tested, do so at least once a year. IMHO, it's more important to check it when it's getting into the hot part of the year than the cold. If you somehow do not have any way to check your cap, replace it annually.

A bad radiator cap can cause coolant loss, running hot, water pump failures, cracked heads, poor mileage, and can even damage the block.

An expensive cap is $15.

 

[Mutant Pony]

I wouldn't worry about getting a cap tested, If there is ANY question, replace it. I have a cap tester at home and one at work. I've seen caps thirty years old that were fine. I've also seen caps with 20,000 miles, less than a year old, that were junk.
It's cheap insurance that is usually overlooked.

 

[shadetree]

Radiator caps are cheap crap and go bad frequently.

I haven't found that to be the case. Quality caps last a long time.

A bad radiator cap can cause water pump failures,

How does that happen???Shady

 

[thegoat4]

I haven't found that to be the case. Quality caps last a long time.

How does that happen???Shady

I've seen lots of rad cap failures. Some fresh from the factory.

Water pump failures can be caused by cavitation eroding the impeller. Cavitation will occur at high water temps with no cooling jacket pressure, or just low cooling jacket pressure. The suction side of the water pump (and back side of the vanes) will have the lowest pressure in the entire cooling system.

I have not torn into too many automotive water pumps, so maybe it's not as big an issue, but the diesel engines will happily eat impellers and backing plates all day long. The problem is compounded by weak or old antifreeze--or rather, part of what antifreeze does is prevent cavitation damage and bad antifreeze can't do that.

 

[Mark_88]

Actually, I meant to have the cooling system pressure tested...not the cap...if there is a leak the pressure test will tell you where it is...if it's not the cap...it's a hose, clamp, or water pump...or, in the worst case, a leak in the head gasket or a cracked block...

 

[clarkperez2334]

Radiator cap is a big NO NO NO ordinary cap. It is not only for covering.. it also plays a vital role in our engine which we must not taken for granted. We should once in a while check our rad cap. And if possible replace it every 2 years... Don't wait for your mechanic to tell you -> hey! you need a new alternator radiator cap now. well this was based on my experience

One morning, i checked my radiator, removed the cap and i noticed that my rad cap looks like rats have been chewing on it. The moisture from the steam is escaping caused by a bad radiator cap... it went bad.. spent lot of $$$ to fixed it... not only the cap was damaged but also some other parts...

and i had hard time looking for a compatible cap for my radiator... i tried the Futaba brand... that's what my mechanic suggested..

 

[TheTopher]

After almost two years resting in our archives this thread is BACK FROM THE GRAVE, BABY!


Lets throw it a party, you bring the beers bud!

 

[adsm08]

What's an "alternator radiator cap"?

Is that like an alternator flush? Out with the old voltage, in with the new.