Hydraulic lifters and how to test 'em better?

[rabbitman]

Thought I'd start a new thread since my problems have changed a couple times.
Here's the old one: http://www.vwdiesel.net/forum/index.php?topic=30534.45

So I flattened all of my lifters and installed them, the cam and t-belt. They all squished a little bit without opening valves. I turned the crank with a wrench and it felt nice with compression on all cylinders which is better than ever before.

The engine started real easy and ran perfect, I idled it for 10-15 minutes 'til it was mostly hot and then shut it down.

Next I pulled the valve cover and pushed on each lifter with my finger, they all squish like when I installed 'em meaning they haven't filled with oil at all.

In the bentley for testing lifters it says "with a hot engine like after driving 20-30 minutes push on each lifter and if it depresses more than .1mm (.004") replace it" (not word for word....). Granted, I didn't drive it at all or get it all the way hot, but I thought they would've filled partway especially with the cold thick oil.

I couldn't hear any lifter ticking with it running.

So now I'm wondering if the lifters are junk after all and now they're empty instead of too full.

[rabbitman]

Ok now I'm confused, I just cranked it over without starting it and the lifters all pumped right up to where I couldn't compress 'em at all. After a minute or two of sitting they started loosing pressure and I could squish 'em a tiny bit.

Even the ones that weren't compressed by the cam started flattening after sitting.

I might just be worried about nothing but these crazy lifters have me all mixed up. With solid lifters you can slide a feeler gauge in and know how much gap there is. With these goofy things I can't fit any feeler gauge without compressing the lifter and sliding the feeler in, even then it squeezes the feeler gauge tight for a little while.

What is normal?

[ORCoaster]

http://www.ehow.com/how-does_5006538_hydraulic-valve-lifters-work.html

[smutts]

Don't panic.
If you bolt the cam down with pumped full tappets, with the engine at TDC, then panic.
If it sounds good, then they are ok.
If there is air in them, they will tick like hell and  it will take about 20 miles or so for the bubbles to shake out.
Hydraulics are cool.

[bajacalal]

http://www.ehow.com/how-does_5006538_hydraulic-valve-lifters-work.html

All engines have hydraulic valve lifters in one form or another.

[rabbitman]

http://www.ehow.com/how-does_5006538_hydraulic-valve-lifters-work.html

All engines have hydraulic valve lifters in one form or another.

Yeah some people are ignorant.........

[R.O.R-2.0]

Ok now I'm confused, I just cranked it over without starting it and the lifters all pumped right up to where I couldn't compress 'em at all. After a minute or two of sitting they started loosing pressure and I could squish 'em a tiny bit.

Even the ones that weren't compressed by the cam started flattening after sitting.

I might just be worried about nothing but these crazy lifters have me all mixed up. With solid lifters you can slide a feeler gauge in and know how much gap there is. With these goofy things I can't fit any feeler gauge without compressing the lifter and sliding the feeler in, even then it squeezes the feeler gauge tight for a little while.

What is normal?

that is, indeed normal.. they have a spring inside them, to keep them in constant contact with the cam..

the valve lash is slightly more at idle with hydro lifters.. then you rev the engine up, oil pressure comes up, and the valve lash is tighter because of the increased pressure inside the lifter..

[libbydiesel]

R.O.R. it sounds like you are saying that the amount of lash is dependent on the oil pressure.  That is not the case with properly functioning hydraulic lifters.  There is a valve in the lifter that allows a certain set amount of lash and once that lash is achieved the valve is closed and the lifter becomes solidly filled with fluid.  The lifter needs to have a good flow of oil but will function properly and maintain a constant lash down to virtually zero pressure.  There are cases where extremely high abnormal oil pressure (stuck pressure relief valve) can cause the lifters to over-extend, but under the entire range of normal oil pressure with properly functioning lifters, the valve lash will remain constant both at idle and at the highest pressures seen.

[R.O.R-2.0]

R.O.R. it sounds like you are saying that the amount of lash is dependent on the oil pressure.  That is not the case with properly functioning hydraulic lifters.  There is a valve in the lifter that allows a certain set amount of lash and once that lash is achieved the valve is closed and the lifter becomes solidly filled with fluid.  The lifter needs to have a good flow of oil but will function properly and maintain a constant lash down to virtually zero pressure.  There are cases where extremely high abnormal oil pressure (stuck pressure relief valve) can cause the lifters to over-extend, but under the entire range of normal oil pressure with properly functioning lifters, the valve lash will remain constant both at idle and at the highest pressures seen.

nah dude, oil pressure (and engine RPM) has alot to do with it too..

someone will chime in and confirm what i said..

and if the valve lift was static across the RPM and oil pressure range, then why does everyone say that solid lifter engines have more grunt?

[rabbitman]

I read somewhere that as the lifter goes up and down the check valve lifts off it's seat due to it's inertia and lets the lifters readjust. So every cycle they have a chance to bleed excessive pressure off. Also makes sense that if the pressure is way too high it would counter act the bleed-off and extend too far.

[rabbitman]

So this nonstarting issue is rearing it's ugly head again.

Here's the deal, when flattened the lifters DON'T hold any valves open, when I first flattened the lifters and reinstalled 'em I could hear ALL four cylinders working properly.

Since then though the engine never likes to start, even when it has just been ran it takes a bit of cranking to get it to fire up. And during that cranking I can hear that not all cylinders are developing full compression........and the longer I crank it the worse it gets.

So I'm looking at new lifters, cheapest I can find are $9.11 each. Anyone know of a cheaper place?

While I'm waiting on the new lifters I thought I'd take the head off and shorten the valves stems so I can KNOW that it isn't the problem anymore.

[R.O.R-2.0]

So this nonstarting issue is rearing it's ugly head again.

Here's the deal, when flattened the lifters DON'T hold any valves open, when I first flattened the lifters and reinstalled 'em I could hear ALL four cylinders working properly.

Since then though the engine never likes to start, even when it has just been ran it takes a bit of cranking to get it to fire up. And during that cranking I can hear that not all cylinders are developing full compression........and the longer I crank it the worse it gets.

So I'm looking at new lifters, cheapest I can find are $9.11 each. Anyone know of a cheaper place?

While I'm waiting on the new lifters I thought I'd take the head off and shorten the valves stems so I can KNOW that it isn't the problem anymore.

why not just MEASURE first, rather than shorten the valves, and put it back together, to figure out that you shortened them too much, and now its a clattery *** all the time?

i would check/measure before i machined anything..

[smutts]

To be honest, I'm doubting that the lifters/ tappets are the problem.

Sticking valves would also cause the same hassles,

Sticking could be caused by:-
  A slightly bent valve,
  Poor oil getting cooked into coke & tar on the exhaust valve,
  Wrong valve stem seals not allowing enough lubrication?
  Engine shop reamed the valve guides too tight?
  Engine shop reamed the exhaust valves too loose? If it is a turbo setup, and the exhaust valve guides are loose & the seals poor,
  that would be a blow torch of hot gasses going one way meeting lube oil in the guide, coke and tar again.
  Engine shop used crappy guides?

Apologies if it wasn't an engine shop.

Just keep looking and thinking, 

[rabbitman]

I've measured them and and all exhaust valves where AT the limit and only one intake valve was good, the rest where way out of spec so over the weekend I pulled the head and ground the stems down so I KNOW they're good, got them all at least .020" within spec.

One cylinder has always had "in spec valves" and when it's not wanting to start it will always fire on one cylinder so I think this'll fix it.

I also took apart the lifters and cleaned 'em out with gas and made sure nothing was gunked up inside.

Drove it today and so far so good but last time after flattening the lifters it took a bit of driving to start acting up again.

We'll see..........

[smutts]

  I was wrong again!

Sounds like you got some of those chewing gum valves like I had on my Peugeot, apparently detonation on gasser/ petrol engines with large inlet valves can tulip the inlet valve heads due to the overloading, I don't know if there is a diesel equivalent.

Congratulations on nailing the problem.