Pressure test failure.

[Ryan_G]

So my engine failed the pressure test again. First it was the epoxy on my cases. I fixed that. Now the pressure is slowly coming out of the cooling line on the head.

I sprayed this engine with soapy water for an hour last night, and could not find anything. Finally after not being able to sleep, I got out of bed and put the engine in the bathtub. Tilted it and sure enough bubbles out of the brass fitting on the cylinder head.

Where do I go from here? What is causing this? Base gasket? oring?(Pretty sure the head went on nice) exhaust gasket?

This is a Yamaha 62t engine. All new gaskets. Sealed it for the leak down test between head pipe and exhaust manifold, and between carbs and intake manifold.

:scratchchin:

 

[stanton]

somewhere you got a leak into the cooling jackets. id start with base gasket

 

[SXRguyinMA]

X2, base or head gasket/oring is your issue

 

[Endo]

How did you seal the exhaust? If plate isn't stiff enough it can leak into the jacket.

 

[Ryan_G]

I used the Watcon leak down test kit. It is a set of solid rubber gaskets about 1/4 in. thick.
http://www.watcon.com/Catalog_Pages/Leak_Down_Test_Kit.htm

I guess I will tear it down again:thumbsdown:

I was sure to clean the surfaces very well. Then installed the gaskets dry. Should I try yamabond on the base gasket this time?

 

[Watcon]

Leak

The usual culprit is a warped cylinder deck or cylinder head...If you cant find the leak anywhere else, get a thick piece of glass, tape some high quality sandpaper on it, spray with WD-40 and carefully make some "figure 8" passes while holding the cylinder / head directly against the surface. (don't let it rock). The sanding will show the high or low spots almost immediately.

If you have access to a surface plate, that's even better..

 

[Ryan_G]

After tearing down and looking closer, I dont think the base gasket has anything to do with it. I dont think it touches any cooling jackets.

Ill try what you said Randy. Thanks

 

[SUPERTUNE]

The guys that are suggesting the BASE GASKET are working on too many Seadoo's, Yamaha superjet engines has nothing to do with water jackets at the base gasket!!!

 

[Ryan_G]

It was my cylinder deck surface. I did what randy said and taped some sand paper to a piece of glass. (My coffee table) Sprayed it with wd-40 and sanded it smooth. I used a black sharpie on the whole deck surface. This helped to show me the low points. After I found the low points, I sanded until they were gone.

Finished everything tonight. It started right up. :Banane01: Now its time to break it in and get it tuned.

 

[DAG]

I used a black sharpie on the whole deck surface. This helped to show me the low points. After I found the low points, I sanded until they were gone.

this is also how you edge a ski/snowboard
"the more you know :reporter:"