I believe we're attempting a somewhat comprehensive TOD thread for noisy HLA's in EA82 and ER27 (XT6) engines.
***Simply put, I would replace the oil pump if you have TOD.
I've solved every case of TOD with a brand new oil pump (once I figured it out, after years of monkeying with other things that were temporary or had varying results). themoneypit (member here), Austin (forum administrator of www.subaruxt.com), and others have had the same experience - new pump solved the issue. I wouldn't be surprised if they spec'd out just fine since I've never seen these cars have issues or notable wear/problems, but that's speculation and in any event the success rate speaks for itself regardless of the cause.
Another 2 cases of replacing oil pump solving TOD:
I'm sure it's happened but I haven't seen it nor have I heard anyone say "I installed a brand new pump and it's still ticking".
4 step approach to diagnosis/repair:
1. Determine if this is likely oil supply related or HLA failure - See (*NOTE HLA Failure below)
2. Reseal the oil pump. Replace the mickey mouse gasket and oring (ER27 does not have that oring), shaft seal, and dabs of sealant on the very outer pump housing at 6 oclock and 12 oclock where it meets the mating surface of the two block halves.
3. In the cases where that doesn’t work, a new oil pump has always fixed it for me.
*** If you are not time rich or you get annoyed doing a job twice, skip step 1, at this point it makes sense to me given how many oil pump replacements I've seen necessary.
4. GD suggests that replacing the cam carrier (cam case/cam tower) orings can also fix some instances of TOD. Earlier EA82’s (85 and 86 I believe) came with plain rubber orings which are inferior for this application. The later EA82’s and all ER27’s come with a metal reinforced oring at that location. Other than Subaru I’ve only seen them available at www.thepartsbin.com , though I’m sure other places have them. Just make sure they are the metal reinforced variety.
GD's discussion on these orings and other HLA nuances:
Oil/Treatments and TOD:
Changing the oil or playing with oil viscosity or treatments is not the answer though covers up the symptoms for a bit, though possibly by inducing wear to the HLA's. GD covers the mechanisms involved in that in the thread linked above. Given the cause is likely still present (oil pump or orings), this is likely a band aid and not a great long-term solution. TOD is highly variable and as such a lot of results are anecdotal like changing oil weights, etc.
*NOTE - HLA failure:
If the TOD is isolated to one HLA then that HLA is likely failed and needs replaced. No amount of oil treatment or oil pump maintenance is going to help. The only time I've seen this is on HLA's with blown headgaskets that were run for an extended period of time (localized overheating, speculation). So I guess I haven't solved "every" TOD with a new oil pump, but every case that wasn't due to a blown headgasket/seized HLA. A good ear or mechanics stethoscope will isolate where one (or two) bad HLA's reside. Pulling the valve cover you can even see them if they're seized, you'll visually see a gap at various points of the cam lobe travel. Passengers side is far less messy to get access to and check that way. It's been a few years since I've seen one like this so my description isn't fresh, but I recall being able to identify the seized HLA's without disassembling anything - just pull the valve cover.
Mizpah engineering sells rebuilt HLA’s or will rebuild yours. Very economical, only a few bucks each. If you’re going into the valve train it’s not a bad idea to just get a complete set they’re so inexpensive. http://www.mizpahpre...com/pricing.htm
I have never been able to successfully pump up every single HLA's in a bag of oil like the FSM says, so I've just installed them as is and assumed they pump up on the vehicle and have never had a problem doing that.
There is also mention that some HLA’s need shimmed, I haven't done that
or found that thread yet but will edit it in if someone else does.
Edited by grossgary, 18 April 2013 - 12:44 AM.