Blow by: How much is too much?

ShaqDiesel · **Posted:** Sat Jan 02, 2016 12:33 am

After installing the HDS Model 001 Thermostat, I've noticed there has been a significant increase in the blow by put off by my engine (I'm running the elephant hose mod so I can see the vapor coming out). Since the HDS thermostat makes the engine run at a higher temperature, I'm assuming the oil is becoming less viscous and resulting in more blow by.

Question #1: How much blow by is too much? Currently, I'm seeing a constant stream of vapor/smoke come out of the CCV/Elephant Hose (when at full operating temperature). When stopped at a stop light, smoke will plume up at a constant rate from underneath the vehicle. It's hard to judge exactly how much is coming out, but it is very noticeable to me and other drivers around me.

Note: In the summertime (prior to the HDS install), the CRD would reach similar temperatures in hot weather. In this case, there was significantly less blow by.

Question #2: What is the common source of blow by on these engines? Does it occur at the valve level, or is it blow by of the piston rings?

Question #3: Is there a cure, or a way to lessen blow by on these engines?

Thank you guys/gals for your input.

flash7210 · **Posted:** Sat Jan 02, 2016 8:33 am

Blow-by is compression/combustion gasses leaking past the rings.
Diesel engines have higher compression and therefore more blowby than a gas engine.
Add a turbocharger and cylinder pressures increase even more, creating more blowby.

Unless you want to tear down the engine, re-hone the cylinders, and re-ring the pistons, there is really nothing you can do about it. This is why things like Provent were invented.
Lots of information out there on the internet about why you should use a crankcase catch can.

Most of what you see coming out of your EHM is oil vapor. More heat creates more vapor. Hence why your hotter running engine seems to have more fumes coming out of the EHM.
Catch cans like the Provent were designed to condense those vapors and contain the oil, preventing it from going back into your intake or dripping onto the ground.

olypopper · **Posted:** Sat Jan 02, 2016 2:03 pm

Blow by is a natural occurrence and no need to read too deep into saying it needs new rings or internal engine work.

Road draft tubes on real diesels like Cummins 5.9BTA's were used for years until a cleaner route was mandated by govt regulations. As mentioned, a provent would solve your oil vapor issue.

ShaqDiesel · **Posted:** Sat Jan 02, 2016 2:30 pm

Thanks for the information guys. Have a Happy New Year!

WWDiesel · **Posted:** Sat Jan 02, 2016 2:57 pm

To educate yourself and anyone else interested, read the following thread; it explains in detail as to the why the little 2.8 CRD engine has so much vapor comming out of the CCV puck and why you should NOT be running the elephant hose mod and should be running a Provent or similar type coalescing type filter / separator... :wink:

http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=80491&hilit
Any questions just ask...

Blow by: How much is too much?

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