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Old August 3rd, 2015, 07:10 AM   #1
VaFish
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Head Gasket or Coolant Pipe Leak

Any educated guesses?

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Old August 3rd, 2015, 08:10 AM   #2
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follow it all the way back.. where is the origin ? maybe pop that valve cover off and see .. or drain the oil. need more info.
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Old August 3rd, 2015, 08:53 AM   #3
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From viewing the picture I'd say (90% sure) that it's a coolant pipe leak.

The EX250's cylinder head gaskets are very robust (if the cylinder head has never been removed from the engine and subsequently reinstalled). The only exception to this rule is if the engine has been severely overheated.

The coolant pipe junction to the cylinder head is a well known and common leak point. Just a minor weak-point in the design of what is otherwise a top-notch, high revving jewel of a small-displacement, flat-plane crankshaft, parallel twin engine.

This junction tends begin slowly weeping coolant after a valve adjustment procedure. This happens when the person doing the valve adjustment "man-handles" the coolant pipe while removing the valve cover. If you feel that you've disturbed the coolant pipe junction while doing the valve adjustment you have to carefully insure that the piping is fully re-seated and properly secured in the junction (and based on the age of your EX250's ('89 and '01) I'd say that it might be time to replace the junction O-ring with a new one).

Also, while looking at the picture of your bike's cylinder head I have to say it appears that the cylinder head's spark plug water drain port is plugged up with something (looks like tan-colored dirt in the picture). I had a similar experience with my Suzuki GSF400 when a mud-dauber wasp decided that my cylinder head spark plug drain ports would be a perfect place to store its eggs.
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Old August 3rd, 2015, 09:12 AM   #4
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Quote:
Originally Posted by greg737 View Post
From viewing the picture I'd say (90% sure) that it's a coolant pipe leak.

The EX250's cylinder head gaskets are very robust (if the cylinder head has never been removed from the engine and subsequently reinstalled). The only exception to this rule is if the engine has been severely overheated.

The coolant pipe junction to the cylinder head is a well known and common leak point. Just a minor weak-point in the design of what is otherwise a top-notch, high revving jewel of a small-displacement, flat-plane crankshaft, parallel twin engine.

This junction tends begin slowly weeping coolant after a valve adjustment procedure. This happens when the person doing the valve adjustment "man-handles" the coolant pipe while removing the valve cover. If you feel that you've disturbed the coolant pipe junction while doing the valve adjustment you have to carefully insure that the piping is fully re-seated and properly secured in the junction (and based on the age of your EX250's ('89 and '01) I'd say that it might be time to replace the junction O-ring with a new one).

Also, while looking at the picture of your bike's cylinder head I have to say it appears that the cylinder head's spark plug water drain port is plugged up with something (looks like tan-colored dirt in the picture). I had a similar experience with my Suzuki GSF400 when a mud-dauber wasp decided that my cylinder head spark plug drain ports would be a perfect place to store its eggs.
I haven't done a valve adjustment yet. Just got the bike legal on the road. Like many of these poor bikes it sat for a while. This is on the '01.

Just did an oil change, oil didn't look milky.

Didn't know there was a spark plug drain port. Just googled it and found a picture. I'd say yes mine if plugged with a mud dauber nest.

Oh well something else for the kid and I to tear apart and play with. These little bikes will be a fun Father Daughter project.
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Old August 3rd, 2015, 09:19 AM   #5
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Cleaning out the spark plug drain passage was a simple process.

I used a piece of plastic (a small zip-tie) to dig/pick out most of the blockage (a surprisingly strong mixture of tan-colored dirt and mud dauber spit) and then followed up with a spray of Simple Green to penetrate and soften what was left in the hole. Then I reamed the hole clean with a fuzzy wire pipe cleaner.
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Old August 3rd, 2015, 10:09 AM   #6
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I'm guessing coolant pipe. You really need to clean that thing well. Then glue it in with a new o ring and sealant like Honda bond.
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Old August 3rd, 2015, 10:38 AM   #7
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As long as your replacing that O-ring, do the other ones on the other coolant pipes as well, as a preventive maintenance.

Part #s 670 @ 2 each



& 670A @ 1 each



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Old June 21st, 2017, 09:55 AM   #8
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Quote:
Originally Posted by Racer x View Post
I'm guessing coolant pipe. You really need to clean that thing well. Then glue it in with a new o ring and sealant like Honda bond.
Reviving and old thread…
Regarding the coolant pipe at the back of the cylinder head cover:

When it is properly installed, is it normal for the pipe to still have a little play (~1mm back-and-forth at the top of the pipe) – or is this a sign that the o-ring is bad? I bumped mine when working on the bike; it moves a little bit now but I don’t know if that’s normal.

To remove the pipe & replace the o-ring, do you first have to remove the head cover? or can you just simply rotate the pipe and pull it out?

Thanks for any advice.
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Old June 21st, 2017, 10:17 AM   #9
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I realize this probably isn't the answer you're looking for, but if mine did that and wasn't leaking, I'd leave it alone.
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Old June 21st, 2017, 10:22 AM   #10
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I realize this probably isn't the answer you're looking for, but if mine did that and wasn't leaking, I'd leave it alone.
funny! if it ain't broke don't fix it
Right now the engine is sitting in a box in my garage so I've got a while until I know if it will leak....but there is no sign that it was leaking before...I'm guessing it's normal. If I could change the o-ring without removing the cylinder head I would go for it just to be on the safe side.
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Old June 21st, 2017, 12:31 PM   #11
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Quote:
Originally Posted by pickax View Post
funny! if it ain't broke don't fix it
Right now the engine is sitting in a box in my garage so I've got a while until I know if it will leak....but there is no sign that it was leaking before...I'm guessing it's normal. If I could change the o-ring without removing the cylinder head I would go for it just to be on the safe side.
If it's like the Ninja 500 I just finished working on, it is held in-place by 1 bolt to the valve cover or head, and comes right out.

They corrode pretty quickly, and since the engine is just sitting there it would be a good time to replace the o-ring. The o-ring is metric, so most hardware store parts aren't going to work. Possibly NAPA might have it.

Clean the tube and opening of corrosion, and apply a very thin layer of silicone plumbing grease (not adhesive) to the o-ring and opening before reassembly.

The 500 I just worked on had only 4000 mi on it, and the pipes didn't look that good.
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Old June 21st, 2017, 02:01 PM   #12
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Mine had play in it after I did my valve adjustment. Triple Jim is right. Just leave it alone lol I've been riding for 3k miles and I keep checking the coolant but it never seems to get any lower. Maybe I'm just lucky...
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Old June 21st, 2017, 02:26 PM   #13
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Here's what Ninja250.org says about it -

Leaking coolant pipe

After several valve adjustments, you could start to see a leak from the coolant pipe (the metal piece connected to the cylinder head). What does the coolant pipe leak have to do with the valve adjustment? You may rub the pipe a little each time you take off the cylinder head cover, as you try to wedge the cover out toward the right side of the bike. Putting the cover back rubs it a bit more. The rubbing might be enough to move the pipe ever so slightly side to side. This could be enough to allow a worn out O-ring to start leaking.
The O-ring alone is about $3 at Ron Ayers, or you can get one at a local hardware store. However, there is one that you can have for “free”. The oil filter comes with a small O-ring, which (at least in Fram filters, and should be in all of them) is the same size as the coolant pipe's O-ring. Since most people don't replace the small O-ring at every oil change, you can use one for this application, if needed.


Didn't realize the o-ring that came with with the oil filter was the same as the one on the coolant pipe. It's up to you - do it or leave it.

It's not a job that easily gets messed-up, so doing it doesn't involve a lot of risk. Just easier to do it now with the engine out IMO.
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Old June 21st, 2017, 02:33 PM   #14
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Originally Posted by jkv45 View Post
Here's what Ninja250.org says about it -

[I]Leaking coolant pipe

Didn't realize the o-ring that came with with the oil filter was the same as the one on the coolant pipe. It's up to you - do it or leave it.

It's not a job that easily gets messed-up, so doing it doesn't involve a lot of risk. Just easier to do it now with the engine out IMO.
Very helpful info (thanks to all)!!! I confirmed that the oil filter o-ring and the coolant pipe o-ring are the same P/N (#670 in the diagram posted earlier in this thread). I've got one of those o-rings already, brand new. I'm going to pull, clean, and replace it now rather than chance it and kick myself later.
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Old June 22nd, 2017, 03:04 AM   #15
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Quote:
Originally Posted by pickax View Post
Reviving and old thread…
Regarding the coolant pipe at the back of the cylinder head cover:

When it is properly installed, is it normal for the pipe to still have a little play (~1mm back-and-forth at the top of the pipe) – or is this a sign that the o-ring is bad? I bumped mine when working on the bike; it moves a little bit now but I don’t know if that’s normal.

To remove the pipe & replace the o-ring, do you first have to remove the head cover? or can you just simply rotate the pipe and pull it out?

Thanks for any advice.
Mine wiggles a-little and doesn't leak. The "O" ring must give a-little.

Bill
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