When & Why You Bleed the Lash Adjuster
Many misunderstand the term for bleeding the oil which there is no reason to do. It has to do with the wrongful assumption that the valve will hang open and hit the piston on start up if the lifters aren't bled of oil. Some will even tell you it's necessary during a cam swap. Whatever you saw or heard, throw it out the window. Lifters don't magically pump up without oil pressure, nor are there seals to blow or anything else to be of any concern. Even new or lifters manually pumped up will bleed down while you torque the cam caps due to the valve springs. I have never seen a valve hang open because the lifter didn't bleed fast enough but it's still good practice to turn the crank so none of the pistons are at TDC prior to installing cams.
When the cams are taken out allowing the spring loaded plunger to extend, air can get in the high pressure chamber. This causes a tapping sound which goes away with normal operation of the car. To avoid this you can choose to bleed the lifter (of air) as it's a good time to clean and check for defective lifters. The whole point of bleeding a lifter is to remove the air and pump it full of oil so that no air gets in during assembly.
How to Bleed the Lash Adjusters in car
With the car warmed up raise the engine speed to 3000rpm gradually(30 seconds) and then lower it in the same manner. Low/excessive oil levels can cause the air to mix in the oil and deteriorated oil to not allow the air to separate. Check the oil level and/or replace if necessary. If the ticking persist, stop the car and remove the valve cover. Press down over the rocker arm where the lifters are. If the rocker arm can be pushed all the way down, replace the lifter.
How to Bleed the Lash Adjuster
ball check valve at lifter base (body removed)
Immerse the lifter in clean diesel fuel. While lightly pushing the check valve open with an allen wrench, pump the plunger a few times to bleed the air out. With the plunger extended remove the allen wrench so that the lifter's high pressure chamber is full of fuel and no air. Keep it upright until installing. Press down on the plunger. If it's stiff and can't be pushed in, the lash adjuster is normal. If the plunger feels spongy, bleed the lifter and test again. If the plunger is soft and can be pushed in all the way, replace the lifter.