Engine/Transmission (1998.5 - 2002) Manometer blow by test

[leathermaneod]

I know this has been covered many times on just about all the diesel forums out there, but I still have some questions I can't seem to find the answers to. Hopefully you guys can help me out. I'm sure some of you that read this have read some of my many other posts lately and are wondering if ill ever get some peace of mind. Im wondering the same thing at this point. Anyway, I want to perform the manometer test my self. I have all materials and have made the "T", but i still have a few questions. How much water do you put in the manometer? wouldn't the amount of water change the inches of water reading that you get because of its own weight? For instance, 8oz of water should rise higher than 16oz at the same pressure from the crank case. How is this test accurate without more details?? Also, the orifice is specified to be .221 of an inch. Everywhere I have read about this, the writer rounds up to 15/64 which is .2344 (presumably because that is a much more common drill size) but that is quite a bit bigger. Wouldn't that also make the test very inaccurate?

Thanks in advance guys!

 

[Bob4x4]

You have a dyno??

 

[leathermaneod]

No I don't, why?

 

[Bob4x4]

the test should be performed under a hi load; a dyno is the only way to make that happen correctly

 

[mwilson]

You can't duplicate the conditions needed for accurate manometer results unless the truck is strapped onto a dyno, there is no other way. Can't do it sitting still and there is no hill long enough either.

We do not have a dyno here and there occasions where we have to send various diesel powered big trucks to Portland for Dyno testing for that very reason. Sometimes it is required for warranty purposes. Especially if it is a condition that is rare or weird.

 

[leathermaneod]

So there is no other way to check the overall health of a Diesel engine than a manometer on a dyno? Wouldn't performing the test without a dyno at least give you some kind of reference? Also, I realize that blow by is higher under load, however aren't the numbers published by cummins and posted on this forum from a test done without a dyno by just reving the truck to the prescribed rpms? After just reving it should increase the blow by and as long as you have a base line from a new engine to compare your numbers against that should be good enough for most cases. Or am I totally misunderstanding?
Thanks guys just trying to get a solid answer on this blow by thing once and for all so I can determine if I need to be worried about my truck or not.

 

[Bob4x4]

Specs,are under 100% load