F250 compression #s

[boscoe99]

Leak down test done, 100 psi imput and holding 100 psi, all cylinders, I pulled the flywheel and all the pointers are lined up, I am scratching my head, my next thought is finding the head casting numbers to see if they are correct, I want to give you guys a Monday morning laugh though! while performing a leakdown test you really should not have a 24" breaker bar still attached to the flywheel bolt! it will swing around LOL! someone did mention that earlier on, some things you have to learn the hard way.

Now consider if it was a four foot long propeller blade with a piston having a five inch diameter! Folks can and have gotten hurt doing a differential pressure test if things get out of hand.

[formula29]

For sure, I am lucky I only gouged the port cowling, and didn't knock my teeth out! where would the part # be on the heads? under the valve cover?

[zenoahphobic]

Leak down test done, 100 psi imput and holding 100 psi, all cylinders, I pulled the flywheel and all the pointers are lined up, I am scratching my head, my next thought is finding the head casting numbers to see if they are correct, I want to give you guys a Monday morning laugh though! while performing a leakdown test you really should not have a 24" breaker bar still attached to the flywheel bolt! it will swing around LOL! someone did mention that earlier on, some things you have to learn the hard way.

From my previous posting, you can see that I had a feeling the leak down test will show up nothing.
What to do next? I think you are heading in the right direction.

[formula29]

process of elimination, according to the warranty work only the crankcase's were replaced, but who knows. I am going to try and verify the heads match, after that I think I'm done.

[99yam40]

I guess you were still using the HF gauge,
did you listen for any air leaking at the different places?

it would be nice if someone with other F250s would post what they get when running compression tests.

hopefully someone knows where the head #s are located

[boscoe99]

From my previous posting, you can see that I had a feeling the leak down test will show up nothing.
What to do next? I think you are heading in the right direction.

I thought the leak down test was the cats meow. The be all and end all to solving problems.

For having 900 hours, a leak down test showing 0% loss of air is quite remarkable.

What is the objective? Is there a problem with the motor?

[boscoe99]

I guess you were still using the HF gauge,
did you listen for any air leaking at the different places?

With 100 psi on the output gauge there would be no leakage. Nothing to hear.

[99yam40]

With 100 psi on the output gauge there would be no leakage. Nothing to hear.

he said before that the output gauge did not work, that is why I asked if he was still using the bad gauge.


Bosco do you know where the # s on heads are located?

[formula29]

900 hrs on the motor total, I am guessing half that on the new crank case based upon when it was replaced, just a guess, obviously the problem I am chasing is the 25# difference between cylinder banks, its not right, I know Yamaha doesn't produce a given # for what the compression should be but what do they generally have when new? 195? or 170?

[99yam40]

I thought the leak down test was the cats meow. The be all and end all to solving problems.

For having 900 hours, a leak down test showing 0% loss of air is quite remarkable.

What is the objective? Is there a problem with the motor?

he started this thread to find out if it was normal for one bank to be lower compression.

[formula29]

he said before that the output gauge did not work, that is why I asked if he was still using the bad gauge.


Bosco do you know where the # s on heads are located?

I replaced the secondary gauge with another off of a air regulator that I had, sometimes we have to make do with what we have laying around on the farm, anyway it works fine now,

[TownsendsFJR1300]

To clarify, you have 100 PSI going in (gauge on the left) and ALL cylinders are showing 100PSI on the gauge next to it(showing the sealing of all internal parts of the cylinder)? IE, absolutely no leak down at all??

[boscoe99]

he said before that the output gauge did not work, that is why I asked if he was still using the bad gauge.

Bosco do you know where the # s on heads are located?

Part numbers are not on 99% of Yam parts. There might be the engine prefix on the head (6P2) and then best that can be found is a head variation number such as 00, 01, 02, 03.

[formula29]

Correct, I connect the gauge with 0 psi, increase pressure up to 100 psi and both needles rise together and hold at 100 psi, I have also checked the gauge without it connected to the engine without andy backpressure and the secondary only reads about 70 psi

[formula29]

I'm pretty sure the only thing left at this point is either it has a 225 head or head gasket for some reason.