Jump to content

07 WR450f dripping coolant out of overflow hose

Recommended Posts

My 07 is dripping coolant out of the overflow hose.  The overflow reservoir is nowhere near full - maybe 10% or 15% full.

I'm struggling to understand how this is possible..  Isn't the point of the overflow reservoir to catch any excess coolant from the radiators?  If the reservoir isn't full, how could it overflow too??

Share this post


Link to post
Share on other sites

In theory, what you've described could be possible if the inlet/outlet lines are mistakenly inverted on the reservoir.

 

Edited by mlatour

Share this post


Link to post
Share on other sites

Well, I checked my coolant today, and my expansion tank was completely empty, and my rads were about 1-2" low.  

I do not see any leaks.. Any idea where my coolant could be going?

I haven't replaced the cap in a long time, but I see Yamaha wants $35 for a replacement.  Yikes!

Share this post


Link to post
Share on other sites
7 hours ago, THE KRAN said:

Any cap that fits will do.

1.6 bar or higher

You should be replacing it every year or so

Thanks Krannie. I believe the current one says 1.1, which is roughly 16 psi. 1.6 bar is roughly 23psi.

Does that mean I have a cap that's too low? 

Share this post


Link to post
Share on other sites
On Thursday, September 07, 2017 at 8:08 AM, THE KRAN said:

 

You should be replacing it every year or so

WTF...have never replced a cap even on 20yr old bikes as they never give trouble

 

To the OP...coolant in tank gets splash around and it empties itself

Coolant expands when bike is hot, goes to expansion tank and gets splashed out. When bike cools there is none to get sucked back in which results in water level being about an inch below fillwr neck on the rad.

Expansion tank is meant to be empty as the norm.

  • Like 1

Share this post


Link to post
Share on other sites
20 hours ago, GuyGraham said:

WTF...have never replced a cap even on 20yr old bikes as they never give trouble

 

To the OP...coolant in tank gets splash around and it empties itself

Coolant expands when bike is hot, goes to expansion tank and gets splashed out. When bike cools there is none to get sucked back in which results in water level being about an inch below fillwr neck on the rad.

Expansion tank is meant to be empty as the norm.

I have never ever had an empty expansion tank.  It expands and flows back as it cools.  That is the point.

I have replaced a couple of caps - unfortunately after they have failed causing major repairs.

Share this post


Link to post
Share on other sites
20 hours ago, GuyGraham said:

WTF...have never replced a cap even on 20yr old bikes as they never give trouble

 

To the OP...coolant in tank gets splash around and it empties itself

Coolant expands when bike is hot, goes to expansion tank and gets splashed out. When bike cools there is none to get sucked back in which results in water level being about an inch below fillwr neck on the rad.

Expansion tank is meant to be empty as the norm.

Where does the coolant splash out of the expansion tank? 

Share this post


Link to post
Share on other sites

I tried running mine, as per my road bikes, with coolant in at about half level but after a couple of hare n hounds races it would be empty, presumably loss through the overflow.

I would also try to keep the rads topped up to the top but they always 'emptied' to about 1" below the filler neck, but then no more, again presumably due to expansion of the water into the header tank and then lost as above, so that when it cooled down there was none to suck back in.

 

My current WR250 2016 has no header thank, if I top it off, when I next check it its about 1" down but then never gets any lower

 

HTH

Share this post


Link to post
Share on other sites
On 9/13/2017 at 10:12 AM, jamesm113 said:

Where does the coolant splash out of the expansion tank? 

I have had coolant loss from the pinkish radiator overflow hose that goes to overflow tank. They get brittle over the years and get a small crack and can loose your radiator fluid as it goes back and forh.

For the record I have never replaced a radiator cap on a motorcycle. 

Share this post


Link to post
Share on other sites
2 hours ago, stevethe said:

I have had coolant loss from the pinkish radiator overflow hose that goes to overflow tank. They get brittle over the years and get a small crack and can loose your radiator fluid as it goes back and forh.

For the record I have never replaced a radiator cap on a motorcycle. 

Yes, but how many radiators  have you replaced......

Share this post


Link to post
Share on other sites

I tend to buy second hand older bikes as bush beaters.  The cap is largely over looked as a service item.  I went through 3 head gaskets on my Aprilia Pegasso before diagnosing the cap as the problem - that bike was bought new with a defective cap.  The agents replaced two head gaskets under warrantee, I replaced the third and found the cap to be the culprit.

The purpose of the cap is two fold:

1.  Discharging excess fluid as the pressure builds to protect the radiator cores and hoses.

2.  Equalising the pressure as the fluid cools and a vacuum forms in the radiator - sucking back fluid. 

If any of the two functions are impaired, you will loose fluid.  Either because it is not sucking in, or because you loose it to the atmosphere in the form of a leak.  The net result is air in the radiator that encourages boiling and thereby doing in the radiator in the form of oxidisation or too much pressure in the system - yes, I have replaced radiators - or blowing the head gasket when the air gets stuck in the head cooling passages causing uneven heating and the aluminium flexing - yep, replaced head gaskets too.  

Attached is a photo of my WR's cap I replaced when I finished my rebuild.  I You can clearly see the cracks in the seal where my thumb is.  This cap hadn't leaked yet, but would have eventually.

20170916_054858.jpg

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×