What is a "collapsed lifter"?

black89xj · Aug 30, 2006

This is probably best for the OEM tech forum but, I saw a posting there on something called a "collapsed lifter". I cant imagine what it is, and from the thread, didnt glean anything.

Any of you gurus like John explain this?

hards91xj · Aug 30, 2006

When a lifter won`t open the intake or exhaust valve .

5-90 · Aug 30, 2006

Lifters, in most OHV engines, are hydraulic (there are "solid" lifters - they're just pieces of metal, and require frequent adjustments.)

Hydraulic lifters have an oil cavity, a plunger, and a valve in them (usually, the plunger going over the hole in the body does the valving.)

In old solid-lifter setups, it was necessary to adjust "valve lash," or operating clearance for the lifter. This was done betwen the valve tip and the rocker arm tip, and could range anywhere from .005" to .015". Instructions were different for each engine - many were adjusted "cold," but some were adjusted "hot", some while running, ...

Anyhow, a hydraulic lifter displaces the operating clearance - rather than being between the rocker and the valve tip (which just translated to a slight clearance everywhere...) it is meant to be entirely within the lifter. The plunger has somewhere around .030"-.035" of travel, which is supposed to allow for lash adjustment at all temperatures (lash reduces as materials expand at operating temperaure...)

The valve lifter is "pumped up" by engine oil pressure, and this has the side effect of pumping oil up to lubricate the top end (via the pushrod -which is why most of them are hollow.)

Now, a valve lifter can fail in a small number of ways:

"Go Flat" - a lifter is made with a very slight "crown" on the foot - it complements a sidewise taper on the cam lobe, and is meant to rotate the lifter in normal operation. A lifter that's "gone flat" has lost that crown or has somehow been restricted in rotation, which rapidly results in losing that crown and the cam lobe WILL wear a groove (about a cam lobe wide...) in the lifter foot. Oops. Can also be caused by crud, grit, or a burr in the lifter bore, preventing the lifter from rotating. (This does not apply to roller lifters - just "flat" tappets and "mushrooms.")

"Go Solid" - a lifter that has "gone solid" has the plunger held at full uptravel - usually, this is caused by sludge or contamination. Pennzoil has cause a great number of "solid" lifters, in my experience - so will infrequent oil changes... This is a reference to old "solid" lifters - they didn't have moving parts. (Does not apply to solid tappets)

"Collapse" - a lifter that has "collapsed" is suddenly unable to retain oil pressure needed to self-adjust the lash out of its operating train. Simply put, the plunger goes to the bottom of the travel and stays there - this is usually caused by wear of the plunger in the body/bore. A slight leakdown is normal (that's how oil gets pumped up to the top end,) but excessive leakdown will make it sound like an old "solid-tappet" engine. Or maybe a Diesel. (Does not apply to solid tappets)

A quick check - the typical "flat" tappet doesn't have a flat foot - there's a very slight crown there, it corresponds to a circle that's about 30" in radius. Therefore, you can check the "crown" simply by putting the lifter foot on a flat surface (I have a glass that I use - not a surface plate, but it works) or putting two lifters "foot-to-foot" and trying to rock them around. You should be able to rock the lifters - if you can't, they're probably made truly flat and should be exchanged.

Make sense now?

5-90

black89xj · Aug 30, 2006

5-90 said:
Lifters, in most OHV engines, are hydraulic (there are "solid" lifters - they're just pieces of metal, and require frequent adjustments.)

Hydraulic lifters have an oil cavity, a plunger, and a valve in them (usually, the plunger going over the hole in the body does the valving.)

In old solid-lifter setups, it was necessary to adjust "valve lash," or operating clearance for the lifter. This was done betwen the valve tip and the rocker arm tip, and could range anywhere from .005" to .015". Instructions were different for each engine - many were adjusted "cold," but some were adjusted "hot", some while running, ...

Anyhow, a hydraulic lifter displaces the operating clearance - rather than being between the rocker and the valve tip (which just translated to a slight clearance everywhere...) it is meant to be entirely within the lifter. The plunger has somewhere around .030"-.035" of travel, which is supposed to allow for lash adjustment at all temperatures (lash reduces as materials expand at operating temperaure...)

The valve lifter is "pumped up" by engine oil pressure, and this has the side effect of pumping oil up to lubricate the top end (via the pushrod -which is why most of them are hollow.)

Now, a valve lifter can fail in a small number of ways:

"Go Flat" - a lifter is made with a very slight "crown" on the foot - it complements a sidewise taper on the cam lobe, and is meant to rotate the lifter in normal operation. A lifter that's "gone flat" has lost that crown or has somehow been restricted in rotation, which rapidly results in losing that crown and the cam lobe WILL wear a groove (about a cam lobe wide...) in the lifter foot. Oops. Can also be caused by crud, grit, or a burr in the lifter bore, preventing the lifter from rotating. (This does not apply to roller lifters - just "flat" tappets and "mushrooms.")

"Go Solid" - a lifter that has "gone solid" has the plunger held at full uptravel - usually, this is caused by sludge or contamination. Pennzoil has cause a great number of "solid" lifters, in my experience - so will infrequent oil changes... This is a reference to old "solid" lifters - they didn't have moving parts. (Does not apply to solid tappets)

"Collapse" - a lifter that has "collapsed" is suddenly unable to retain oil pressure needed to self-adjust the lash out of its operating train. Simply put, the plunger goes to the bottom of the travel and stays there - this is usually caused by wear of the plunger in the body/bore. A slight leakdown is normal (that's how oil gets pumped up to the top end,) but excessive leakdown will make it sound like an old "solid-tappet" engine. Or maybe a Diesel. (Does not apply to solid tappets)

A quick check - the typical "flat" tappet doesn't have a flat foot - there's a very slight crown there, it corresponds to a circle that's about 30" in radius. Therefore, you can check the "crown" simply by putting the lifter foot on a flat surface (I have a glass that I use - not a surface plate, but it works) or putting two lifters "foot-to-foot" and trying to rock them around. You should be able to rock the lifters - if you can't, they're probably made truly flat and should be exchanged.

Make sense now?

5-90

Yup....makes perfect sense now, and esp after looking at the diagram of a hydraulic lifter in my Chiltons manual. The only real experience I have with lifters are the "solid" ones used in my old MGB. Had to adjust the valve lash every so often. Fun! I always wondered how "Hydraulic" lifters worked...now, I do.

Thanks!

--Karl

anodyne33 · Aug 30, 2006

Can I go a bit off topic and take this space to thank 5-90 for his (from what I've seen so far) frightening contributions to this site? That was the most detailed description of the possible lifer failures you'll probably ever find on the internet!

53guy · Aug 7, 2010

If I may revive this old thread, 5-90, what would the oiling characteristics be of these lifters in their failed conditions? As in, if I were to have the engine running and the valve cover off, would a failed lifter still be pumping oil to the top? How would you identify the failed lifter without disassembling the whole engine? Is it possible to determine if there is a failed lifter by looking at pushrod's/rockers? If a lifter were to collapse or go solid, therefore no longer taking up the lash/clearance, would the lack constant contact cause damage to the cam? Thanks for your awesome descriptions as well, invaluable really.

5-90 · Aug 7, 2010

53guy said:
If I may revive this old thread, 5-90, what would the oiling characteristics be of these lifters in their failed conditions? As in, if I were to have the engine running and the valve cover off, would a failed lifter still be pumping oil to the top? How would you identify the failed lifter without disassembling the whole engine? Is it possible to determine if there is a failed lifter by looking at pushrod's/rockers? If a lifter were to collapse or go solid, therefore no longer taking up the lash/clearance, would the lack constant contact cause damage to the cam? Thanks for your awesome descriptions as well, invaluable really.

It could still pump oil up to the top of the head - but it would be reduced.

The easiest way to find it would be to note a power loss in the engine, then go over it with a mechanic's stethoscope (ten dollars very well spent!) A collapsed lifter won't "pump up" and remove lash from a particular valve, and you'll note increased noise in a general location in the head. Once you note that (you'll hear it most in the valve cover,) go down to the passenger side of the block where the lifter gallery is, and you'll hear it there. It's much easier to isolate the particular lifter from the block.

(Side note - I even find my medical stethoscope useful for finding body creaks, loose panels, and suchlike; since I can use it to "focus" my hearing in a particular area. This is also why sometimes you'll see me looking for something small during the day using a flashlight - using it as a spotlight will allow me to "focus" my vision on a particular area more, which can also be very useful. The latter is a psychological trick, but one that has helped me considerably over the years.)

Edit - it is easier to locate a collapsed lifter - or one that has "gone solid" - on an inline engine, since the lifter gallery is at the side of the block (and not in the intake valley, where you can't get a bead on anything specific - except in certain engines that have an open intake manifold...)

orange · Aug 7, 2010

Another handy trick to narrow down the location of sounds is to use a length of say one inch i.d. hose or tubing about three feet long. Hold one end to ear and point other end at sound.

For example, a wind leak on a window, sweep the end of the tube around the edge of the window, a couple of inches from it, and find the loudest point. Works on bearing and knocking, and squeeking sounds, etc.

Regards,
Orange

What is a "collapsed lifter"?

black89xj

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hards91xj

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5-90

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black89xj

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anodyne33

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53guy

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5-90

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orange

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