Broken Radiator Cap

asrock · June 2, 2015

Hi Guys, Yesterday when I removed the radiator cap, I found that the inner middle part (sorry I don’t know the exact name of this part, is it the pressure release valve?) is missing from the cap

It’s probably fallen inside of the radiator, but I can’t reach it or see it. I don’t know if this part is only rubber or has some metal parts. I replaced the cap with a new one. Will this fallen part do any harm to the radiator? Is it safe to drive with this thing inside the radiator? I have attached a pic of the old cap. Please advise me.

The Don · June 2, 2015

If it has actually fallen inside the radiator, its a little too big to actually go through any of the cores so probably still stuck inside the top tank. If you go to a radiator repair place they can get it out by removing the top tank and then pasting it back on again. Its probably not going to do much damage but the above is probably a good idea if it doesn't cost too much.

Its very unusual for it to break inside the radiator as the spring seals the entry into the overflow tank and it moves by pressure. So even if it got detached it won't fall in. What might have happened is the cap was broken by somebody who took the cap off like during service and then didn't tell you about it.

Davy · June 2, 2015

Agree with The Don. It's unlikely that the valve and spring mechanism would have fallen inside.

If you're certain that it has fallen inside somehow, you can try this:

Get hold of a strong magnet. Hold it outside the radiator top tank and move it slowly towards the middle. If the spring mechanism has fallen inside, it should still be inside the top tank and should follow the magnet until it comes out.

asrock · June 2, 2015

Thanks guys for the answers. But it’s not the entire middle part that has gotten detached. It’s the small middle part. The spring and the rest of the assembly is still attached to the cap. Please see my photos of the old cap, the thing is I dont know the missing part is rubber or metal.

The Don · June 2, 2015

Its rubber Asrock. Its basically supposed to seal the opening which you pour coolant through so that when the engine warms up, all the water does not flow into the overflow tank due to increased pressure.

Rumesh88 · June 2, 2015

The "middle part" indicated in your picture consists of both a rubber part and a stainless steel part (a stud riveted to the top metal cap but made free to move when you rotate the top part). Rubber part cannot fall into the radiator for it is larger than the radiator cap bottom seating. The metal part, if get detached from top cap still cannot fall into the tank for there is a rubber part below blocking the opening. Unless something very freaky (something beyond our imagination) has happened it is impossible for the metal part or the rubber part to fall into the radiator.

Davy · June 2, 2015

I believe the radiator cap in question is not the common "big head" type. This one has the spring in centre chamber of the cap, secured by a metal ring. While parts of the "big head" type caps are highly unlikely to fall into the radiator, this one looks like it can. According to OP's photos, I assume the metal ring broke off somehow, resulting in the plastic head, spring and the ring to separate (and perhaps fall into the radiator).

asrock · June 2, 2015

No Rumesh, it’s not the whole assembly, just the small middle part that is supposed to be in that hole. Those photos are of the actual cap, you can see the rivet mark inside the hole but the part that is supposed to be there no longer is. As it’s a small part it can easily fall into the radiator neck?

I think the incident is something like this: http://acurazine.com/forums/second-generation-tl-1999-2003-98/bad-radiator-cap-823310/ though my temp gauge never went up. Like Don said if its only rubber do I need to worry about it? But seems like there is a spring too.

asrock · June 2, 2015

On 6/2/2015 at 1:31 PM, Davy said:
I believe the radiator cap in question is not the common "big head" type. This one has the spring in centre chamber of the cap, secured by a metal ring. While parts of the "big head" type caps are highly unlikely to fall into the radiator, this one looks like it can. According to OP's photos, I assume the metal ring broke off somehow, resulting in the plastic head, spring and the ring to separate (and perhaps fall into the radiator).

Spot on Davy. So what should I do?

The Don · June 2, 2015

So its the cap thats missing.

To be honest to service the whole radiator only cost me 2000 about 5 years ago. I suggest you do that, as they will take both the top and bottom tanks off, service the radiator and put the tanks back on.

Even if the cap has fallen in I don't think there is much possibility of it travelling further afield as the openings in the cores are tiny compared to the cap.

tiv · June 2, 2015

On 6/2/2015 at 8:58 AM, The Don said:
If it has actually fallen inside the radiator, its a little too big to actually go through any of the cores so probably still stuck inside the top tank. If you go to a radiator repair place they can get it out by removing the top tank and then pasting it back on again. Its probably not going to do much damage but the above is probably a good idea if it doesn't cost too much.
Its very unusual for it to break inside the radiator as the spring seals the entry into the overflow tank and it moves by pressure. So even if it got detached it won't fall in. What might have happened is the cap was broken by somebody who took the cap off like during service and then didn't tell you about it.

As Don said your best bet is to take it to a radiator joint, take the top part apart and remove the bits or whatever that is there. While you are at it, you can flush the radiator / cooling system and change the coolant as well, these bits might come out during manual flushing if you can channel running water from the outlet and let it pour via the cap or inlet.

Davy · June 2, 2015

I think you can drain the coolant, take the radiator off and turn it up side down. Give it a good shake and the lodged parts should come out through the top tank hose inlet or the same way it fell in (through the filler neck).

You can also try filling it with water (while the radiator is still up side down and both the filler and top tank inlets closed off) through the bottom tank hose inlet. Then after the entire radiator is filled, release the top tank inlet. The plastic will probably be flushed out with the water.

Edited June 2, 2015 by Davy

asrock · June 2, 2015

Thanks Davy, Don and Tiv, I just need to know if this has to be done immediately? Is it ok if I wait till the next service to do a radiator service? Also I found this on another site:

Quote
"The bits that fall into the radiator won't cause any problems so don't lose sleep over it. It won't corrode and it won't migrate thru the engine. None of the bits are big enough to pass through the cooling channels so it will just bobble around in the upper tank for eternity. The coolant path is from the engine, to the upper radiator tank, thru the radiator, to the lower hose, to the water pump, to the engine." http://my.is/forums/f87/radiator-cap-broken-pieces-547913/

Edited June 2, 2015 by asrock

The Don · June 2, 2015

On 6/2/2015 at 2:11 PM, asrock said:
Thanks Davy, Don and Tiv, I just need to know if this has to be done immediately? Is it ok if I wait till the next service to do a radiator service? Also I found this on another site:

If you are going to do it, whats the point of waiting? Normal service stations cannot perform what we have advised as it will most certainly require you to remove the radiator (even Davy's DIY suggestion).

asrock · June 2, 2015

It’s just that I'm in Kandy at the moment and has planned some up country trips over the weekend. I rather to do this job in Colombo. Any good radiator joint that you guys recommend?

The Don · June 2, 2015

On 6/2/2015 at 4:00 PM, asrock said:
It’s just that I'm in Kandy at the moment and has planned some up country trips over the weekend. I rather to do this job in Colombo. Any good radiator joint that you guys recommend?

Any of them should be able to manage this. The one I go to is just off Nawala Road accross the road from the place the old sand lorries used to park.

asrock · June 3, 2015

On 6/2/2015 at 4:45 PM, The Don said:
Any of them should be able to manage this. The one I go to is just off Nawala Road accross the road from the place the old sand lorries used to park.

ok will do. thanks!