Rear Cylinder Coolant Leak?? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 10 (permalink) Old 11-29-2015, 03:32 PM Thread Starter
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Rear Cylinder Coolant Leak??

Hey Guys,

Ive got a really persistent coolant leak and its driving me nuts.
Its coming from where the metal tube for the coolant connects
to the rear cylinder, as pictured below:



I undid the bolt holding the tubing and replaced the gasket, but
unfortunately it is still leaking out. I used an O-Ring from a variety pack I had in the garage, figured an O-ring is an O-ring right?

Is there something special about the stock O-ring that will stop
the leak or is there something I am missing here? Any ideas?

Thanks guys


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post #2 of 10 (permalink) Old 11-29-2015, 04:47 PM
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Have you checked to see that the tube itself isn't cracked? Could it be running down the hose from higher up?

Does it leak immediately when you put it together? Or does it take some time for it to start leaking? If it takes time, your oring may not be AF friendly.

Just some thoughts.

Jon

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post #3 of 10 (permalink) Old 11-29-2015, 05:26 PM
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Make sure there's no corrosion buildup in the head, and the pipe is clean (and not cracked or pitted through) Steel pipe on the aluminum head causes corrosion there.

The o-ring is metric size, but I was able to use a 5/8" o-ring on mine. Also can help to coat the tube/o-ring with grease.

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post #4 of 10 (permalink) Old 11-30-2015, 09:28 AM
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I had a leak there also and used a Metric from HF (I don't remember the size maybe a 14mm?) and added red Permatex at the bottom, under the o-ring. when I installed it. I wiped up the excess after it was in, hooked up the hose and waited overnight to add coolant. So far so good.

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post #5 of 10 (permalink) Old 11-30-2015, 09:47 AM
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Is that the o-ring I'm seeing at the top of the hole? Two o-rings? (between the alum. head and the hold down bracket on the pipe) Tried zooming the pic but still not sure.

The o-ring should be seated near the bottom of the steel pipe and ends up near the bottom of the hole once seated.

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Last edited by Spockster; 11-30-2015 at 09:51 AM.
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post #6 of 10 (permalink) Old 11-30-2015, 09:59 AM
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Looks that way to me as well. The o-ring does not appear to be seated correctly at all.

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post #7 of 10 (permalink) Old 11-30-2015, 06:24 PM Thread Starter
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Hey guys,

I appreciate all the feedback. Update:

1) Yes, there are O-Rings visible at the top of the tubing. After replacing the O-Ring, and still having a leak, I removed the tubing and put some extra O-Rings at the top in an effort to help stop the leak.

2) I was able to fix the leak today. I used the advice stated here and grabbed a 3/8 O-Ring and set it on the tubing in the correct spot. The O-ring I had installed before was too small, and thats why it was leaking. I did still leave one extra O-ring at the top because I am paranoid.

Thanks!!

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post #8 of 10 (permalink) Old 11-30-2015, 06:32 PM
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Cool!

Actually, that second o-ring might keep corrosion from happening so easy, keeping water and dirt out of the hole. It will still corrode, but slower maybe.

3/8" sounds kinda small.

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post #9 of 10 (permalink) Old 11-30-2015, 07:09 PM Thread Starter
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Quote:
Originally Posted by Spockster View Post
3/8" sounds kinda small.
D`oh. I meant to say 5/8". That one did the trick.

Believe the one I had on there was 3/8", still let the coolant leak out.

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post #10 of 10 (permalink) Old 11-30-2015, 07:51 PM
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Quote:
Originally Posted by MadKat View Post
D`oh. I meant to say 5/8". That one did the trick.

Believe the one I had on there was 3/8", still let the coolant leak out.
I caught that in your other thread, 5/8.

The 3/8 thinned out when it stretched, made it easier to leak.

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__________________________________________________ ____________
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