Leak down test fail

[Boyd12]

I am doing a leak down test on a 951 and it leaks at the cylinder head studs. Any idea what could cause this?

 

[mikidymac]

Did you use the correct stud o-rings and a good quality head gasket?

 

[Boyd12]

Did you use the correct stud o-rings and a good quality head gasket?

I did. I also used Copper Spray Gasket. I tried a cheap Chinese gasket for gits and shiggles and it didn't seal at all. I find it odd it seals everywhere but at the studs.

 

[Boyd12]

Is it possible the erosion where the temp sensor is located could be causing the leak? I have three head and they are pretty similar in erosion in certain areas.

 

[mikidymac]

No, that should not cause it, head looks good.

How is the cylinder deck surface?

 

[Boyd12]

A machine shop decked the cylinder a while back. I put a straight edge to both and find no issues. I checked the torque wrenches and they are accurate. It makes no sense.

 

[mikidymac]

The only thing I can think of is the stud o-rings.

 

[Boyd12]

The only thing I can think of is the stud o-rings

If the head gasket is sealing properly, the o-rings should not come into play. I thought they were for vibration. I had one engine where they used Three Bond 1211 on the head gasket. I dont know if that was a good idea.

 

[JC-SUPERJET]

Did you follow the proper cross-torquing Procedure and two-stage Torque sequence as specified in the Service Manual?

To what Torque did you set the Nuts on each Torque Stage?

Were the Studs completely screwed all the way into the Crankcase and snug before installing the Cylinder Head?

 

[Boyd12]

Thank you for your assistance!
"Did you follow the proper cross-torquing Procedure and two-stage Torque sequence as specified in the Service Manual?" I did.

"To what Torque did you set the Nuts on each Torque Stage?" 11lbs/25lbs. I checked the torque wrenches and they are accurate.

"Were the Studs completely screwed all the way into the Crankcase and snug before installing the Cylinder Head?" They were.

 

[Poormanracing]

Stud rings are for vibration and to seal moisture from getting down the studs.never use sealant on head gaskets.the coating on the head gasket itself is used to help seal it also.clean surface ane reaply then try it

 

[Boyd12]

So this is not good? Lol!

 

[Poormanracing]

Nope

 

[Boyd12]

Nope

This was done by "a professional aftermarket high performance shop". I think they used Three Bond on the head gasket. It didnt seal.

 

[Poormanracing]

I don't get it been at this a long time built many dirt bike motors drag sled motors fast jet ski motors etc.no matter what sealant you use none of it works on gaskets.some guys argue it's all they use.but none of it sticks to cast aluminum.no matter how clean it is it always has trace amount of oils.nothing is better than a OEM gasket and a flat surface.to each there own.but out of the thousands of cyl heads I have taken off and put on not once have I needed sealant

 

[Boyd12]

Do you work on engines for a living or is it a hobby?

 

[Poormanracing]

Professional I own a jet ski and snowmobile repair shop in mass

 

[Boyd12]

That is hard work!

 

[Poormanracing]

The work isn't hard been doing skis for over 30 years and started working on sleds and dirt bikes at age 6 I enjoy doing what I do.the hard part is starting out with nothing no plans or real inside knowledge of running a business.the dealer I worked for list the franchise floated from Mariner to Mariner got fed up found a garage moved to a bigger garage and trying to keep it together.lol

 

[Boyd12]

By hard I mean there is a lot to it. I was a parts manager, service advisor, and service director. Dealing with all of the variables/headaches etc throughout the day was not easy. When I had good techs, I enjoyed it!

 

[Poormanracing]

The hardest part is parts.i deal with alot of the older model machines.the old days of going on the parts catologs and getting a certain part are long gone as far as sea Doo goes.some models it takes hours just to find a 30 dollar part

 

[Boyd12]

Agreed. If they offered degrees for searching for parts, I would have a PhD and I dont work on these full time!

 

[Boyd12]

Update:
I have two cylinders and two heads.
I tested:
Head 1 on cylinder 1
Head 1 on cylinder 2
Head 2 on cylinder1
Head 2 on cylinder 2.
I used WSM head gaskets (Copper Spray Gasket used in some cases) and both torque wrenches are reading correctly. On the last test I torqued to 30lbs. In ALL circumstances, the head leaks like this. My straight edge shows the cylinder, and the head are straight, the torque wrenches are correct, and the gaskets are good. This defies the laws of physics. Any thoughts?

 

[Boyd12]

I just torqued the head again and increased torque to 30lbs. The head leaks slightly by one bolt, there are bubbles on five nuts. It is better, but not right.

 

[Poormanracing]

Your head is either pitted from corrosion or the cyl is leaking.dont use sealant on the gasket either.