Misc Thread VI: Return of the Threadi

[tankinbeans]

I had it towed to a shop when it started cutting power and they're going to take off the valve cover. I didn't want to one of those f-knuckles who drives with a very audible noise to see "if it gets worse." When I went back over there it was glaringly obvious that they'd not read codes because it was unlocked.

P0304 pulled a misfire code and the P0442 is evap unless I'm mistaken. Could these be lifters causing the valve to stick open and not allowing proper compression? I'm still trying to learn and may be spitballing the wrong issues.

[theholycow]

Yeah, P0304 is cylinder 4 misfire (as you knew) and P0442 is "ignore me until the next emissions inspection, I'm an evap leak" (and if it's anything like my 2002 GMC then it's the evap vent valve solenoid, a $30 bolt-on part they they just couldn't seem to engineer/build well).

Wait, so how is he going to inspect the wrist pin via a removed valve cover? Somehow I missed that earlier. I remember having read it as he is going to remove the oil pan, which is how you would inspect the bottom end for a failed wrist pin.

Removing the valve cover would indeed let him get a look at the valves and those hydraulic lifters. I suspect he intends to look for a collapsed lifter. See this well-written explanation:
http://www.naxja.org/forum/showpost.php ... ostcount=3

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.

(Note that your car has hydraulic roller lifters, so the "go flat" explanation does not apply.)

Disclaimer: This is not an area of expertise for me; I had some vague memories of reading threads about problems like this and a moderate theoretical understanding of valve systems so I had to hit up the repair manual and google to formulate this post. If it was my car and I was struggling with this problem in my yard I'd be content, and likely successful, working on it from this angle with additional reading/googling and maybe some forum posting, but I could still be WAY off.

[tankinbeans]

The makes a lot of sense, Cow. Thank you for posting it. I confess I didn't really catch all of what he said correctly because I was hearing Scrooge McDuck hurling coin about in the back of my head. Could that stuck valve (if that's the issue) be the cause of the rhythmic ticking?

I really hope this is a straight forward fix because the car was running fine under a variety of conditions until it wasn't. Just 20 minutes before this I had been on the freeway at 70-75 with nary a symptom, but attempting a brisk acceleration event precipitated this whole mess.

[theholycow]

Looking in the manual it looks like most of the top end has to come apart. It's an excellent DIY project for someone with patience...maybe not an excellent project when you're paying a professional.

[tankinbeans]

Update: I called back today because I have loads of nervous energy. The advisor said that the rocker wasn't attached ama said that in all likelihood it is repairable. He said he wanted to check with the technician to verify.

$500 to fix.

[tankinbeans]

I guess the threads for the rocker were stripped and pulled right out. He said they're going to put some called a helicoil in amd drill out some new threads. No warranty, but $290. Said the proper repair would be a used head, but that's $2k.

[theholycow]

Might want to ask him to evaluate the lifters and other rockers, and what might have caused it to strip. I'm guessing the whole top end has to come apart, and if so then it might make sense to do some preemptive work while it's apart.

Helicoil is an acceptable repair for stripped threads.

$2k for a used head? Crikey. A used engine would cost less (including labor, which may be less for an engine replacement than a head).

[tankinbeans]

I did ask to make sure there isn't additional work coming due since the thing is going to be apart anyway. Figured why pay that labor twice when parts can just go in.

[tankinbeans]

Got Galadriel back and she seems to be working well. I asked what might have caused the issue and all I got was it's just a mechanical thing. Helpful that.

[AHTOXA]

Rode to work today. Was hot on the way home. That's all I got for today.

[watkins]

Today can go f*ck itself.

[wannabe]

its hot everywhere. it wasn't hot on the way to work, tony?

Was hot earlier. now it is storming. will probably be hot *and* humid later. i want the rain/storms to COOL things down, not make it hotter/humider....

[theholycow]

Today can go f*ck itself.

[tankinbeans]

Said hi to my great grandparents and Fudge at the cemetery today after the short, emphasis on short, little gathering. There's nothing quite like the cemetery liaison saying, "your 15 minutes are up, please proceed to your cars [read: go the fluff away]."

Oh and awkward family time with a bunch of people for whom I really couldn't give two flying shits at rolling donuts. I have an aunt and uncle, and a couple cousins that I really like, but the rest... If you weren't born to the daughters, you're less important.

[potownrob]

Said hi to my great grandparents and Fudge at the cemetery today after the short, emphasis on short, little gathering. There's nothing quite like the cemetery liaison saying, "your 15 minutes are up, please proceed to your cars [read: go the fluff away]."

now that's cold. i've never been to a cemetery here that did anything close to that. that's just downright disrespectful, if you ask me. there was one where we got the clue that they wanted us to go so they could bury the casket, but we had been there for a long time and they never told us to pack it up.

Oh and awkward family time with a bunch of people for whom I really couldn't give two flying shits at rolling donuts. I have an aunt and uncle, and a couple cousins that I really like, but the rest... If you weren't born to the daughters, you're less important.

that's just upsetting. you are painting a pretty portrait of your extended family here.