OHC valve lash adjuster bleeding?

[NickB]

Does anyone know how hydraulic lash adjusters bleed the air out of themselves? The type i'm specifially asking about in this case reside in the head. The rocker arm sits between the lash adjuster and the valve stem, with the cam pushing down on it. Chrysler 2.2 and the Mitsubishi 4G63 are two examples that come to mind.

I know that there is a ball and sproing check valve inside, and that pushing a small wire down the hole inteh top will unseat the ball, allowing you to compress the lifter. I had to do this today as i put in a new set of cams in my 4G63. After 10 minutes of idling at 1500 rpm the liters were still ticking.

Any insight into this?

 

[ivymike]

HLAs constantly leak around the edges of the piston (this is a necessary part of their function) and I would expect air bubbles to escape via this path if the piston is facing up. If the piston isn't up, I'm not sure how air bubbles could get out, because the body is usually a single solid piece.

 

[Chumley]

Many hydraulic valve lifters have specific storage and installation instructions for the the lifters to allow them to initially bleed down properly prior to initial engine start. I'm not familiar with your specific engine but did you check the factory service manual for any installation specifics?

Usually after the oil gets good and hot and up to full pressure for several minutes at normal operating rpm's they self bleed. I've not found it to be the case but others have reported that an oil change with a new oil filter and multi weight oil tends to quiet them down a little faster after replacement. The viscosity of fresh multi weight oils
tends to be at its lowest point when new so that would make sense.

It's kind of funny but in my water cooled inline 4/5 cylinder VW's and Audis with hyrdraulic lifters, I can tell with great accuracy if the oil is below full by any amount depending how much the lifters clatter on cold start.

This is for VW's so it may not apply but there is an interesting discussion on hydraulic lifters here:

http://www.bostonengine.com/articles.html

Chumley

 

[NickB]

The oil has about 20 minutes of run time on it. I just finished putting the motor together and in the car a week ago when my cams came in.

The FSM says to bleed them down by poking them as i did. It also says it can take up to 10 minutes at 4000rpm to quiet them down.

Yes, the piston does face up, just as it does in every other adjuster i've seen.

I'll just keep waiting, it should go away.

 

[ivymike]

Well, I've never seen an upside down one either, but I didn't want to make any assumptions.

In regard to the statement "An air-bound lifter may expand as the engine heats up, and thereby prevent a valve from closing. " in the article @ bostonengines.com, I disagree. I have difficulty imagining a scenario where you could trap enough air in a lifter to open the valve at all, much less force it open. Comments?

 

[Chumley]

Ivymike:

Some of the VW engines are boxter style where the lifters are horizontal if that helps makes any sense. In the inline OHC I4/5, V6 and V8 VW/Audi engines the lifter is upside down and runs directly on the camshaft between the cam lobe and the valve stem. They don't use rocker arms at all. Over the years, I'm slowly convincing myself that if you don't use a quality OEM oil filter with a good anti drain back valve and your oil level is less than full, over a few days time, the oil in the galleries up to the cylinder head drains back to the pan. Then when you fire the engine, the lifters get a good initial shot of air from the empty galleries instead of oil causing them to clatter a while longer on start up, especially if they have a few miles on them and have a tendency to leak down anyway. It seems to make a difference where the engine stops also because when certain valves remain open with continuous compression though the lifter, those seem to clatter even longer but usually shut up within ten seconds or so.

NickB:

Some of my factory service manuals actually say that its normal for the lifters to clatter for up to 2 minutes before they are considered "a problem" as long as they eventually quiet down. In due time, yours probably will too. Good luck!


Chumley

 

[ivymike]

Well an upside-down lifter without any bleed features at the top end of the high pressure chamber will almost certainly have some amount of trouble if the HPC fills up with air. As far as I can tell, the air will result in a substantially more flexible (compressible) HLA, and extremely poor valvetrain behavior. I still hold that there is no way it will hold the valves open as a result of the expansion of such air. I suppose it would be possible, if the valvetrain control got bad enough, for the lifters to "pump up" (with oil), resulting in a no-seat condition (or things that go bump in the chamber). I would expect that moderate levels of air would be entrained in the oil and removed rather quickly, so I'm not sure that the above scenario is plausible.

 

[Chumley]

From my both my Audi and VW factory service manuals for I4/5 engines with hydraulic lifters:


----------------------------------------------------------
| "CAUTION
|
| Hydraulic lifters are to be stored upside down.
| After replacing lifters DO NOT (in bold) start
| engine for approx. 30 minutes to allow lifters
| to bleed down."
----------------------------------------------------------

I learned long ago, when Audi makes statements like above, the people who ignore them usually spend a little more time under the hood and they eventually find out exactly why Audi wrote it. All the dummies like me never really know for sure. We prefer to "drive" around guessing until curiosity gets the best of us. Then we just "drive" over and ask the other guys who usually, by then, know for sure!

Have a good day!

Chumley

 

[carnage]

in my truck if I have run low on oil I find that no amount of idleing will quiet down the valvetrain, I have to drive it (3000 rpm) and it slowly goes away.

 

[comnean]

Hy,
I have long time experience with two hydraulic lifters type. One is GM type (+rocker arm) and one is VW type (cams are contact directly with upper surface of lifters)
For first case the low and the high oil pressure circuit are inside the lifter and in many case this are noisy if the engine is not runing for several months!
For the other type only the high oil pressure circuit are indide the lifter and if the bore in cyl.head are weared you can put inside OK. lifters but this come noisy in short time because lower pressure oil circuit that is between lifter and external bore surface can't make carring function.
All lifters are packed in work position and are filled with specialy oil. If you clean lifters is wery important to fill the high pressure circuit with oil.
sorry for english language.

 

[NickB]

The Mitsubishi FSM says to do the same thing, but submerged in Diesel fuel instead. I didn't have any diesel handy, so i just did it dry. In any case, the lifters have bled nicely. The valvetrain is nice and quiet now.

On a side note, i took the car for it's first full throttle rip tonight.... *drool* it's gonna be a monster!!!