Radiator Leak

[Wilburt]

So I was driving today and noticed my engine temp light came on a few times. I read about the sensor going bad (98 Standard) and was going to order a new one today. So I didn't really worry about it. However, when I arrived at work I noticed coolant leaking from what appears the radiator cap. I still have enough coolant. What could cause this? I bought the bike from a dealer who stated all fluids were changed. I have put 1000 miles on and this is the first time it has happened.

[Bighead]

Just check the radiator cap to SE if it is on straight. Back the set screw out and take it off check for grit under it in the seal. Reinstall tighten set screw and run it a while and see if it still leaks.
Mine leaked once last year,I had put a chrome cover over the cap and it was tight so I had to push down on it hard to get it on and it broke the seal between the radiator and cap gasket took it off and put it back on and no more leak.

[Wilburt]

That could be it. I took the cap off about 200 miles ago to check and I guess I could have seated it wrong. Still make wonder why it waited until now to leak.

[Bighead]

Wilbur's next time just check the level in the overflow tank under the side cover. The only time the radiator cap needs to be removed is during a coolant change

[Wilburt]

Yeah, I didn't (probably still don't) know what I was doing. It was the first time I noticed the temp light come on. I went home and pulled the radiator cap before I knew to check the reservoir.

Anyway, I took your advice and I took the cap off and put it back on. I wasn't able to clean the bike before riding home so I couldn't tell if that fixed it. I did however notice when I got home a little hissing coming from that general area. I read in my manual that radiator caps can be tested. I don't have a way to do this at the house. Wonder if I could have a bad cap?

[Bighead]

Possible. Did you have a hard time when you took it off and put it back on the first time? It wouldn't be too difficult to crack the neck on the filler hole in the radiator. Doubtful but could have happened.

[R J]

My 1st question is:  did you loosen that little set screw in the cap before you removed it?

Post a picture of where it is bubbling.   Under the cap seal, on the tower of the radiator cap on the radiator.

Etc etc etc.

Only time I really saw one leak was when the cap was removed improperly and twisted the stem out of the radiator.    They forgot to loosen the little set screw.

[CoachDoc]

My radiator cap leaked once on my Valk because the cap itself was not fully tightened. I realized this when it cooled down and I could turn the cap clockwise another 1/4 turn to the fully closed position. Tightened it up until it was fully clockwise and never leaked since. My cap came with the bike minus the set screw, so maybe there is a functional reason for having that screw, not usually found on most radiator caps (automotively speaking).

[R J]

I changed the fluid in MGM when I had my 1st 5,000 miles and threw tha damn screw away.

239K+ miles later, it is still minus a screw and no leak.

I have advised people on this board to bend the securing portion of the cap down just a tad to make it fit better.

I told them if it was totally on and would rock a little bit, to bend that piece down for a snugger hold on the radiator stem. (That be cap area).

[Wilburt]

My 1st question is:  did you loosen that little set screw in the cap before you removed it?

Post a picture of where it is bubbling.   Under the cap seal, on the tower of the radiator cap on the radiator.

Etc etc etc.

Only time I really saw one leak was when the cap was removed improperly and twisted the stem out of the radiator.    They forgot to loosen the little set screw.

I did remove the set screw before taking it off. I finally started it in the garage and heated it up until the fan came on. Sure enough, it started to leak again. So I took the cap off, cleaned it again and re-seated. I heated it up until the fan came on again, no leak. Let it cool and heated it up until the fan came on once more to make sure, no leak. At this point I am a bit baffled. No sure how I installed it different?

I have advised people on this board to bend the securing portion of the cap down just a tad to make it fit better.

I told them if it was totally on and would rock a little bit, to bend that piece down for a snugger hold on the radiator stem. (That be cap area).

Mine does rock a bit. If it leaks again, I'll try that.

----------------

On the pic below. It is leaking on the right side (when looking at the pic), right above the small hose. Definitely coming from the cap or lack of seal between the cap and radiator.

[Bighead]

Glad it stopped Wilburt I see in your picture you have a Yellow and White(my second favorite color) post us a picture of that beauty

[Earl in Pensacola]

The OEM radiator caps do "wear-out" and sometimes in unexpected ways, like bending the "tabs" for a tighter fit, sometimes the rubber gasket is or has come loose or torn. I replaced my cap with a NEW OEM cap, problems stopped.

[Jess from VA]

Sometimes the lips on the radiator neck can get a bit tweaked/bent... pretty thin.  Like if the prior owner or shop tried taking the cap off without loosening the set screw.

If so, carefully straighten.  

[The emperor has no clothes]

My 1st question is:  did you loosen that little set screw in the cap before you removed it?

Post a picture of where it is bubbling.   Under the cap seal, on the tower of the radiator cap on the radiator.

Etc etc etc.

Only time I really saw one leak was when the cap was removed improperly and twisted the stem out of the radiator.    They forgot to loosen the little set screw.

I did remove the set screw before taking it off. I finally started it in the garage and heated it up until the fan came on. Sure enough, it started to leak again. So I took the cap off, cleaned it again and re-seated. I heated it up until the fan came on again, no leak. Let it cool and heated it up until the fan came on once more to make sure, no leak. At this point I am a bit baffled. No sure how I installed it different?

I have advised people on this board to bend the securing portion of the cap down just a tad to make it fit better.

I told them if it was totally on and would rock a little bit, to bend that piece down for a snugger hold on the radiator stem. (That be cap area).

Mine does rock a bit. If it leaks again, I'll try that.

----------------

On the pic below. It is leaking on the right side (when looking at the pic), right above the small hose. Definitely coming from the cap or lack of seal between the cap and radiator.

It probably leaked because you killed that poor bee (karma) Glad you got it to stop leaking, probably had a little gunk on the rubber seal.

[Wilburt]

Put 50 miles on today so far with no leak......

[Ricky-D]

The radiator cap has two seals.

One seals the radiator and maintains the pressure.

The other seals the cap so the recovery system works properly.

It would seem your recovery system seal was the one leaking.

A good thing to do is to insure the hose to the reservoir tank is clear.

Just take it loose and blow into it. You should be making bubbles in the

reservoir tank if it is clear.

Check everything and make sure you have a closed system.

You have only done one part, there could be more to do.

Don't skimp.

***

[pancho]

What Ricky-D said,,, the overfill tank line should be the first thing to check when the radiator cap leaks. There are a couple of places where it is prone to be pinched, and then, the pressure is going to go somewhere,,,  out the cap seal is the least damaging. Check as he said by removing the line at the radiator and blow through it making sure the overfill tank is bubbling. Check the level in the tank also to make sure it wasn't drained back into the cooling system to make up for what was lost.

Clean bike.

[Wilburt]

A good thing to do is to insure the hose to the reservoir tank is clear.

Just take it loose and blow into it. You should be making bubbles in the

reservoir tank if it is clear.

Check everything and make sure you have a closed system.

You have only done one part, there could be more to do.

Don't skimp.

***

I made sure I got bubbles. That is good. What/how to I check for a "closed system"