Leaking radiator

[mrcasual666]

I'm pretty sure I'm seriously screwed here. Total noob.
I bought a 1992 K75S a month ago, and everything seemed to be running fine. I took it on a longish ride last weekend (300 miles) and I was riding pretty hard, keeping the rpm between 4000 and 7000 for about 2 hours. A few days later I was riding in traffic and noticed the smell of burning coolant. When I parked, it was dumping a ton of coolant.
I thought it was just a hot day in traffic, so I took it out again the next day. Same thing. Turns out, at some point in there, I had burned off about a half engine's worth of oil, and subsequently most of the coolant.
Ok, I topped off the coolant in the overflow reservoir (later realized that was a mistake) and filled the oil up to 3/4 full. Then drove upstate another 150 miles. Still burning coolant... Towards the last 20 miles,  the temp light came on. That night I realized I had to refill coolant at the reservoir under the gas tank. Did that...
Now I turned on the engine to run it, and total bummer: I realized that the coolant was leaking from the middle of the radiator grill. Pretty sure that was the case the whole time.
Am I screwed? Does this indicate a broken radiator? That's gonna be expensive, no?
A little help please.

Pete
Brooklyn, NY
1992 BMW K75S, 48000 miles

[frankenduck]

I'd take the fairing off and see if it's the radiator or a hose leaking.  Replacing a radiator (or hose) is pretty easy.

PM me if you need parts.

[mrcasual666]

Thanks, I'm gonna check tomorrow without the fairing.
It did occur to me that I overfilled the radiator (straight up to the cap!) so I wonder if the big coolant dump was from the relief valve. Does the excess coolant get released at the radiator cap? It could have spilled out and run down to the back of the radiator and leaked through...
Will update...

Pete

[frankenduck]

You never know until you get the bodywork off.

If you get it hot enough for the cap to blow then it will blow to the coolant reservoir.

If a few cases fans have been known to come loose and drill a hole in the raidator so when you say it's dripping from the middle of the radiator that might be it.  Or it could be the filler hose. :dunno

[mrcasual666]

Update: I took the fairing off and gas tank, to get a better look. Visibility was still pretty poor, but it didn't seem like there was coolant on any of the hoses. Also, the spot where the coolant leaks appears to be directly opposite the center of the fan. At this point, I'm thinking you may be right about the fan (it seemed a bit wobbly, although I'm not sure how tight it would normally be).
I guess the next step is to take the radiator off and get a better look at the back side.
Whomp whomp.

[mrcasual666]

Solution: As suspected, the plastic fan blades had come loose from the spindle and punctured the radiator.

I took the radiator to a repair shop, where they told me they would use "aluminum welds." It basically looked like a sloppy epoxy fix job. I repaired the fan with JB Weld.

While the tank and radiator were off, I replaced all the external fuel hoses, the air filter hose, and all the water hoses. I reattached the radiator assembly, filled it up, ran it to let the air bubbles out, then reattached the tank.

I rode 400 miles this weekend, and no radiator problems yet. Thanks for the help!

[GasStation]

You never know until you get the bodywork off.

If you get it hot enough for the cap to blow then it will blow to the coolant reservoir.

If a few cases fans have been known to come loose and drill a hole in the raidator so when you say it's dripping from the middle of the radiator that might be it.  Or it could be the filler hose. :dunno

I am impressed by your clairvoyance...so how does the fan helicopter itself off its centre spindle? 

[frankenduck]

I am impressed by your clairvoyance...so how does the fan helicopter itself off its centre spindle? 

It does happen occasionally but not often enough to worry about until it happens to you. :deal:

[GasStation]

Hello Frankenduck,

The phenomenom of the radiator fan flying off into the radiator has occurred to a rider in another Forum; right smack in the centre (or so) of the radiator. So how does the fan actually move forward into the radiator? He even has a pretty good picture to show and tell.

[robleyd]

So how does the fan actually move forward into the radiator?

It's a propellor pushing air back at lots of revs; if it cuts loose from the drive spindle you have to figure that it is going to push itself forward and chew into the radiator until it runs out of energy :-)

[GasStation]

Hello Robleyd,

I've never taken the fan/radiator off my K75S, so I guess my question can be rephrased by: What item(s) fail that cause the fan blade assembly to tractor forward into the radiator?

[frankenduck]

Though it does happen occasionally its not all that common so I wouldn't worry about it if I were you.