Hydraulic lifters

[Volhv]

I am having a hard time figuring out if my lifters are good, or bad.
After reading several threads, and the write up on this site Bennington Motorsports I have become more confused.

So as I understand it, there are no non-metalic parts, therefore mechanical failure is the only way they can break. I am soaking one of them in Butanone, aka MEK. It's a really good solvent for dissolving gum, and solidified oil. The stuff that oozed out of the small side hole when the lifter was submersed, turned the solvent dark brown.
A good sign. This was a lifter that would easily be depressed, it would spring back, but It would never stiffen when in oil, even when injected with a syringe. Hopefully it will now work properly. There was also an other lifter that showed the same symptoms. The other 6, are super stiff and the piston will not budge. Perhaps the MEK treatment will free them up.

Since my lifters don't pump up from soft, are both groups bad?
Sorry for the rambling. Any help is appreciated,

Cheers.

[rmcdonnell]

I'd like to know if a thorough cleaning might bring bad lifters back to life. I thought the arrangement was self sealing, where once the oil was pumped in under great pressure, it closed a valve and became virtually incompressible. If MEK helps yours out let me know, I have a couple I can drop in the ultrasonic cleaner
cheers
Rissole

[John_AZ]

The superstiff are the ones to keep.

Discussion---conclusion by Britwrench--pro mechanic.
http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/375469-question-about-lifters.html

Try to buy good used INA OEM lifters. The later INA lifters have been known to fail.

NOTE: the lifters should remain in the same bore removed. Per Porsche.

GL
John

[Volhv]

The main question we need to ask is "WHY"

They can be BAD when...

they are STIFF
-the piston may be gummed up, and unable to operate
-they would be pretty much solid lifters, and it would defeat the purpose of them being self adjusting/dampening, and they would not make any noise from mechanical rattling, but that does not necessarily mean they are good.

they are SOFT
-they may be gummed up in a way they will not allow them to fill with oil (oil hole blocked)
-chattering would be evident

Hopefully my assumptions are right, and a good cleaning can revive them. I can only see two things that would cause a "clean" lifter to be bad. Broken spring or wear between the piston adjacent walls.

I will see if the one I cleaned internally with MEK stiffens after being filled with oil.
Stay tuned for results.....

[9FF]

"...they are STIFF
-the piston may be gummed up, and unable to operate
-they would be pretty much solid lifters..."

Your assumptions are wrong.
Hydraulic lifters are designed to act like solid lifters when the engine is at operating temperature, they are not a damping devise. Think about it like this:

On a solid lifter engine you have to adjust the lifter clearance on a cold engine. This is so that when the engine is up to normal operating temperature the clearance is gone. Problem with this is there is always some lifter noise on cold starts that disappears after a few miles. Other problem is the cold gap clearance will go out of adjustment over time due to being "tapped" when cold and that is why you have to adjust the lifter gap occasionally on solid lifter engines.

The hydraulic lifter resolves the two problems with the solid lifter by:

1. A mechanical spring that allows the lifter to make contact (no gap) when it is cold but also move as the engine warms up. So no cold start tapping.

2. Oil entering the lifter as it gets hotter and thinner through the pump action of the spring making the spring action disappear and in effect making it a solid lifter (you cannot compress oil or any liquid).

So, you get the best of both worlds, a relatively noise free cold start and a solid lifter when the engine is up to temperature.

Therefore it is almost impossible to diagnose a failed lifter with it out of the car. It may compress or may not, filled with oil or without and either way it may or may not be bad.

Installed in the car they are easy to diagnose. Listen with a long screwdriver to your ear on the cam cover above each lifter in turn when idleing and the engine is cold. There should be no "tapping" noise, mark the cam cover for the ones that are noisy. When the engine is at operating temperature (fans come on), check them again.

If it was noisy cold and and quite when hot your lifter spring is worn. If it was quite cold but noisy when hot your oil hole may be blocked.

Either way the best course of action is to replace the offending lifter next time the cam cover comes off. Messing around with syringes or cleaning fluids may or may not work so why bother. Its not like these are nla or very expensive items to replace. Most of the expense/time is in removing the cam cover.

Sorry for the long post but this lifter thing keeps coming up and imo it's one of the better features of our cars and an easy fix - replace it if it's bad!

[Volhv]

Nothing more reliable than an operational test. I agree.
Unfortunately I have the cam tower off. I don't remember any lifter noise last time the engine was run. I guess I'm fine, but preventative maintenance (while you're in there), is always recommended.