Thread: Td5 Blowby, Okay or too much?

Originally Posted by LeakinOil

Well good news in that when I rev the engine up it makes quite a significant difference, the smoke from the fill cap pretty much all but disappears

This might not be such good news though cos as @onebob mentioned it shows that the DCV is open while it should close with revs. Unfortunately i dont know what harm can cause excessive depression in the crankcase but it seems that the DCV on your's is not working as it should. I dont think that the smoke seen in your first video has vanished just that it was less sucction from the intake due to your catch can


Crankcase emission DCV.jpg

Originally Posted by sierrafery

This might not be such good news though cos as @onebob mentioned shows that the DCV is open while it should close with revs. Unfortunately i dont know what harm can cause excessive depression in the crankcase but it seems that the DCV on your's is not working as it should. I dont think that the smoke seen in your first video has vanished just that it was less sucction from the intake due to your catch can


Crankcase emission DCV.jpg

The plot thickens then it would seem. Might put a new DCV in as they’re not expensive and re check everything

That would be a good move cos the DCV can be stuck in a middle position so it mixes up the whole ventilation process. I'm not an oil expert and dont want any debate about oils but you saw how my engine is running and after many experiments and study i ended up using oil which is dedicated for EUI/PD engines cos that's what the Td5 is (Comma PD Plus 5W40 which was changed about 1000km ago)

Originally Posted by onebob

.... indicating that your depression control valve is open

Not necessarily , more likely rings are sealing better when revving creating less blow by

Originally Posted by sierrafery

This might not be such good news though cos as @onebob mentioned it shows that the DCV is open while it should close with revs. Unfortunately i dont know what harm can cause excessive depression in the crankcase but it seems that the DCV on your's is not working as it should. I dont think that the smoke seen in your first video has vanished just that it was less sucction from the intake due to your catch can

The DCV will usually close under revs because of the above reason ,it , when working keeps a natural balance between positive / negative pressures

Originally Posted by LeakinOil

Should I try it with breather disconnected then?

yes ,by isolating the DCV it will give you an indication of the general state of the engine , which I guess is all you wanted to know, just block the DCV intake and outlet on rocker cover but only with oil cap loose or off for the test

Originally Posted by discorevy

Not necessarily , more likely rings are sealing better when revving creating less blow by



The DCV will usually close under revs because of the above reason ,it , when working keeps a natural balance between positive / negative pressures



yes ,by isolating the DCV it will give you an indication of the general state of the engine , which I guess is all you wanted to know, just block the DCV intake and outlet on rocker cover but only with oil cap loose or off for the test

Yep just wanting to get an idea of general health of the engine as when I took it in for an unrelated electrical diagnosis the mechanic was saying the crank pressure was a bit high.
As it only takes 5 minutes I’ll recheck with the breather blocked and oil cap off while revving.

What catch can are you using?

Originally Posted by Tombie

What catch can are you using?

Using the flashlube catch can

That catch can has its own depression valve.
Just replace the one in the intake to the turbo with a 90 degree brass elbow.