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keithluneau

2014 FC 450 losing coolant

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I just purchased a used bike, it's a 2014 Husqvarna FC 450. No issues during the test ride, but of course as soon as I get it home and start riding it, about 10 minutes in I smelled coolant... lol Yay!

It's pushing coolant out of the overflow on the radiator. It's not running hot. The first thing I did was changed the radiator cap which didn't help. I put a new cap on with a temp. gauge just to be sure, it's definitely not getting hot. If I start the bike ice cold after sitting all night, within 30 seconds of idling (water temp still below 100ºF) it's already dripping. A quick blip of throttle pushes a quick stream of liquid from the hose. If I remove the cap with the bike ice cold, and start it, the water level slowly rises up and out of the radiator. When I shut it off, there's a quick gurgle of air up and out of the coolant, and the coolant settles back down to normal levels again. I'm 99.99999% sure it's combustion gasses getting from the cylinder into the water.

Is it safe to assume it's the head gasket? I've ordered a top end gasket set and will tear it down when they get here. I've owned many bikes over the years and do my own work, but this is the first KTM/Husky I've had here. Are there any known problems with this particular bike that I should look for, anything else that might cause these symptoms that I'm not aware of? Worst case might be a crack somewhere in the head or cylinder? If it comes to that I'll replace what I need to, I'm just hoping it's nothing that major and a gasket change will have it fixed up. I paid pretty much fair market value for the bike and don't want to start dumping a ton of cash into it to get what I thought I was already getting... lol

Thanks for your time and help!

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Most likely the head gasket. Could also be a cracked cylinder so we will hope for a bad gasket. While head is off check for warping on a flat surface like a glass plate. Use feeler gauges. 

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Thanks for the reply! I'm hoping that when I pull the head off there will be obvious signs of the head gasket leaking... lol If not I'll be sure to check everything over as best I can, including checking for warps. If there's a crack in the cylinder, would I be able to see it with a visual inspection? I guess worst case if I put it back together and run it and it's not fixed, I'll know to find someone who can check for cracks or whatever next time... lol Hoping for the best, but mentally prepared for the worst! I should know something by the end of the week of all goes as planned, I'll report back when I do.

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As far as seeing a crack it depends on where it is located but most likely not. Good luck. Please let us know what you find. 

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7 hours ago, keithluneau said:

Thanks for the reply! I'm hoping that when I pull the head off there will be obvious signs of the head gasket leaking... lol If not I'll be sure to check everything over as best I can, including checking for warps. If there's a crack in the cylinder, would I be able to see it with a visual inspection? I guess worst case if I put it back together and run it and it's not fixed, I'll know to find someone who can check for cracks or whatever next time... lol Hoping for the best, but mentally prepared for the worst! I should know something by the end of the week of all goes as planned, I'll report back when I do.

Generally you'll see any concerning areas once you pull it apart.  That being said if the gasket and/or head isn't obvious where it's leaking from then you might have to resort to a more extreme LPI (Liquid Penetrant) inspection on the cylinder & head.  However, that type of inspection is generally costly and difficult to locate someone to do it for you.

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Posted (edited)

So a bit of an update...

I talked to the guys at KTM Parts Pro, their service manager said that he's only seen one or two cases after a lifetime in the industry where there was an actual cracked head/cylinder, and suggested I check the surfaces on both for warps. He even offered to check them for me on their lapping table if I sent them in. I pulled the top end apart, and didn't see any obvious signs where it had been leaking, and couldn't see any cracks anywhere. I couldn't see any warps with a straight edge. I had it checked out locally and there did seem to be a low spot on both the cylinder and head in the same spot around one of the water passages. We re-surfaced it to be sure, and put it back together with a new gasket. Sadly, no change, same symptoms as before. lol There's something I'm missing!

At this point I'm about two clicks (and $1300) away from ordering everything new from the bottom end up and rebuilding it, make sure I get the culprit this time... 😉 At least it will all be fresh with 0 hours, right now I'm not sure how many hours is on it. (previous owner said he put 7 hours, not sure before that) The bore and piston both look great though, and no signs of wear anywhere in the head.

Will report back later, hopefully with a good ending eventually. lol Thanks for the tips so far!

Edited by keithluneau

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Posted (edited)

I realize someone else checked the cylinder and head and resurfaced but the proper way to check for low spots is on a flat surface (glass plate) with feeler gauges. The service manual has the tolerances. Was it checked this way after resurfacing? Can’t check with a straight edge. Would hate for you to do an entire rebuild and have the same problem 

Edited by willbilly

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I wasn't there while they did it, dropped it off and picked it up later. I did give him a PDF of the service manual though. He's a competent engine builder that's done work for me previously and been in business with a good reputation for years. I trust his work... lol

I'd expect the new parts to be flat and ready to go from the factory. I too would hate to build it all up new and still have the same problem. I really don't see how anything below the cylinder would give these symptoms though. Any leaks with the water passages down there would be mixing water in the oil no?

Either way, parts are ordered and on the way. I'll find out soon! lol

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21 hours ago, keithluneau said:

Any leaks with the water passages down there would be mixing water in the oil no?

That’s correct. At least you will have an extra head and cylinder!

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A bit of a follow-up:

The new parts arrived during the week. Yesterday I pulled the engine apart again, still couldn't find anything wrong. No visible cracks anywhere or signs of leaking, no warps that I can see with glass/feeler gauge. So I rebuilt it with the new parts. Piston, rings, wrist pin, clips, cylinder, head, valve guides are all new. Of course I used all new gaskets and valve seals. I re-used the cam and valves from the old head. Oil jets/nozzles as well. I've got almost an hour of easy run-in on it breaking it in, but so far there's no issues with leaks inside or out of the engine. Radiator is holding pressure when warm too. Finally! lol

I'm still very curious as to what the problem is with the old parts though. Logic tells me there has to be a small crack somewhere, likely in the head, but there's no way I can say for sure without having it tested. Is there anywhere in the US that does that sort of thing for a reasonable cost? I haven't even looked around yet, I'm not sure if it's common or a costly process. If it's worth it, I'll have them checked out so I can at least know for sure what the issue was, and maybe end up with some good spare parts if I can rule out the culprit.

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Go talk to any of the aircraft maintenance hangars near you.  Ask them if they've got an "LPI guy", or someone qualified to perform a "liquid penetrant inspection."

If you're curious, LPI is a non-destructive test.  Essentially the tech applies a special glow-in-the-dark die to the metal and allows it to penetrate the surface.  After a certain amount of time they wipe off the die, then shine a UV light at the surface in a very dark shop.   If there's any cracks or casting flaws the die will remain making them glow.  It's a very cool trade, however they charge a LOT of money to do it because the products they use aren't cheap.

Warning, don't handle the head afterwords with your bare hands.. EVERYTHING you touch or that head touches afterwords will glow in the dark for a VERY long time. haha

Edited by zibbit u2

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