TR2/3/3A How to check for cylinder-to-cylinder head gasket leak

[RedTR3]

Will a simple compression test do it?

Thanks, Tim

 

[Geo Hahn]

Possibly, be sure to have the throttle plates wide open.

A leak down test might tell you more.

What makes you think this is happening? Seems like it could occur between 1 & 2 or 3 & 4 but those are pretty stout sections of gasket.

 

[RedTR3]

Possibly, be sure to have the throttle plates wide open.

A leak down test might tell you more.

What makes you think this is happening? Seems like it could occur between 1 & 2 or 3 & 4 but those are pretty stout sections of gasket.

George,

Yes, I am working through solving the intermittent misfire issues I am having (posted about a month ago). I still have a lot of things on the forum's suggested list to work on but I am just thinking of the next step.... in case I finish the "list" without solving the problem.

 

[TR3driver]

If the leak is small enough to not show up in a compression test, most likely it also won't cause a misfire. You can actually have a pretty bad leak (significantly lower compression reading) and still have the cylinder run.

But it's definitely worth running a compression test.

 

[svtmikey]

Leak test would be the best way as Geo Hahn said earlier.
pressurize one cylinder, with piston and valves position properly and you most likely will hear an air hissing noise out of the spark plug hole on the other cylinder.
If it is bad enough to cause a misfire from low compression you should.
I guess if you run a compression test and have low compression wet and dry in side by side cylinders, that might also point to it as well.
But the gaskets are pretty "stout" as mentioned earlier

Mikey

 

[Deleted member 8987]

Just start with a compression test, dry, then wet, which gives you a baseline.
I keep a sheet of paper in the back of my shop manual with compressions by date, and valve lash by date.

You have an issue with guides not allowing valve to seat sometimes, spring, cam, leakdown won't tell you issues with rotation based compression.
Been doing this what, hobbyist and professional almost 50 years, leakdown is last if the compression testS show an issue you want to pursue.
Only time I ever saw anyone start with leakdown was an air cooled VW guy who worked for me in about 1980. I just let him do it his way.
Generally he would end up doing a compression test anyway.
Worst part is folks who pull ONE plug, test that hole, put it back in, pull the next plug, and so on.
First, the engine does not spin freely enough, and head gasket leaks between cylinders will be much harder to locate.

 

[dklawson]

When we got our Spitfire as a non-running project its 1300 never ran right no matter how much tuning and tinkering I tried. I started with the compression test and found low values of about 95 PSI on all cylinders with very little spread between them. After chasing this for a while I did the leak down test. Immediately problems were apparent. There was leakage into the block, into the water jacket, and into the intake. The only place I didn't appear to have a leak was into the exhaust. Each cylinder had its own leak path and none were "good". That engine is still wrapped up in plastic sheeting with oily rags in the cylinder head ports. I will rebuild it someday but it was quicker in this case to put in a different engine and find the source of the leaks later. My point is... sometimes the leak down test will reveal things that do not show up in a compression test.

 

[Deleted member 8987]

When we got our Spitfire as a non-running project its 1300 never ran right no matter how much tuning and tinkering I tried. I started with the compression test and found low values of about 95 PSI on all cylinders with very little spread between them. After chasing this for a while I did the leak down test. Immediately problems were apparent. There was leakage into the block, into the water jacket, and into the intake. The only place I didn't appear to have a leak was into the exhaust. Each cylinder had its own leak path and none were "good". That engine is still wrapped up in plastic sheeting with oily rags in the cylinder head ports. I will rebuild it someday but it was quicker in this case to put in a different engine and find the source of the leaks later. My point is... sometimes the leak down test will reveal things that do not show up in a compression test.

That's what I said. But you start with compression. 95 pounds tells you something right there. It's shot.
THEN you go deeper.
Leakdown is good, but get your numbers first.