Thread: 300 tdi blow by... theories

blow by is almost always ring or piston related.

if your lucky its just a couple of dodgy rings

a leak down test would reveal (mostly) all.

Originally Posted by roverrescue

so i ducked round to my local rover mech to get a serp belt to shut up the squeek squeeek after all the rain we had... changing it over in his driveway and he notices a bit too much oil on top of the rocker cover (I havent opened bonnet since last oil change bout 4000km ago)... he says, bit too much blow by eh? Anyway new belt on and turn it over and sure enough blow by is as you would say excessive... cap bouncing away when loosely in place...

Sooooo shoot me some of your theories, ask some questions...

Ive started pulling it to sort and will let you know...

Steve

Check your Crankcase Ventilation, I dont know how they work on a 300TDi but I would check any hoses, breathers or connections to make sure their not coked up or blocked, make sure your oil level is correct and not overfilled, before you pull your engine down, Regards Frank.

Steve

How many K, Do you have any oil consumption?

Crankcase Ventilation is via a tube into the suction side of the Turbo. I remember JC telling me to mod the baffle in mine because eventually the oil stream scrubbed off the engine will have a detrimental effect on the compression turbine.

I'll be interested in the answers you recieve as I've starting to see an issue with mine which I'll elaborate on in due course.

Sticking rings, they could be stuck in the ring grooves and not expanding fully onto the cyl. walls-what oil do you use and how often changed? Hopefully no broken ones

-185k or there abouts - ex forestry then farmers truck so wouldve been flogged
- no significant oil use
-10k changes using Castrol Diesel 15w40
-no blockages i could determine to crank case ventilation
-"leak down test" is that a compression test then sit and wait for specified leak down time???

steve

a leak down test is when you apply compressed air to a cylinder via the glowplug/injector hole in the head (in the case of diesels in a petrol use the spark plug hole) and listen to various locations (inlet tract, exhaust, radiator and the crank case) for air bypassing the seals of the engines combustion chamber.

Originally Posted by Blknight.aus

a leak down test is when you apply compressed air to a cylinder via the glowplug/injector hole in the head (in the case of diesels in a petrol use the spark plug hole) and listen to various locations (inlet tract, exhaust, radiator and the crank case) for air bypassing the seals of the engines combustion chamber.

you apply 100psi of compressed air to the cylinder.
The losses are expressed as a %, eg, if the gauge reads 95 psi, that's 5% leakage (which was always our maximum allowed in race engines, a road engine should be Ok up to around 10%)

As Dave says, you are also able to see if the leakages are via the rings or valves, by just listening to where the air is going.
Obviously, if the gauge reads 60psi and you can hear the air whistling back through the crankcase, the rings aren't seating on that cylinder.