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Discussion Starter #1 (Edited)
So the Subaru dealer (technically it was on the Mazda lot next door, but same company nonetheless) sold me a '07 B9 (140k miles) with a compromised head gasket... I'm sure they knew something about it because they let me walk off the lot thinking I ripped them off, but the joke's on them because I'm going to replace those HGs myself, as opposed to the ~$3,000 they quoted me (incidentally, the purchase price + $3,000 would still put me under the Edmunds appraisal value, so I'm still feeling good).

I've been studying the FSM profusely, and even though you can replace HGs on an EJ25 without pulling the engine, it doesn't look like this is even a possibility with the H6 in the Beca... so out it will come.

This won't be the first time I've pulled an engine, but it will be my first time breaking heads off a Subaru. Here is my work plan so far:

UPDATED JOB LIST (2-24-14):
1) Replace HGs.
2) Have shop machine heads and inspect valves. Deck block if out of tolerance.
3) Replace rocker (valve cover) & spark plug gaskets.
4) Replace throttle body gasket.
5) Replace intake and exhaust manifold gaskets.
6) Inspect and replace any worn, soft, and/or corroded hoses & pipes.
7) Replace spark plugs & serpentine.
8) Inspect (replace if necessary) timing chain, water pump & tensioners.
9) Replace oil pan gasket and block oil seal (oil cooler gasket replaced Feb 2014).
10) Replace water pump gasket.
11) Replace EGR pipe gasket.
12) Replace fuel injector seals & o-rings.
13) Replace PCV valve.

What else should I look for and/or consider replacing so long as I have the engine out? EGR gasket? Injector seals? Oil pump? The engine runs beautifully (except for exhaust in the coolant), so I don't want to replace something that should last forever (provided it doesn't show any sign of failure).

Also, can anyone provide insight on the flywheel stopper (Subaru part#
49827720)... the FSM says to install it just before the engine is separated from the transmission; I presume it's to keep everything aligned for reinstallation, but $200 for a small piece that resembles angle iron seems a bit pricy? Any alternatives or workarounds?

If I can get my son to cooperate, I will post pictures and a walkthrough once it's finished (sometime mid to late March).
 

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please post your walk through and step by step. I may need to do that someday and no one here has posted on this procedure to my knowledge
 

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I never heard of a Tribeca needing a head gasket. I have a lot of consumer experience on the Subaru out backs called Gen2.

I and a friend just finished putting an OEM shortblock in a Subaru out back because I had a leaky head gasket ( second time fix..first was at 60,000 and now a 94,000). 2 rods went bad at when head leaked..came all of a sudden. So I just spent well over 4,000 on an engine on a 2002 Subaru.

my 2000 out back blew the headgasket at about 110,000 and now I think its going again at 170,000.based on antifreeze consumption
 

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Just out of curiosity where did you get the information about the timing chain replacement interval? My service manual from Subaru does not have it as a recommendation and I have been told that the timing change is not a routine service part.
 

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There is no interval for the timing chain replacement in all subby's H6 engines. There are plastic timing guides in there that wear, but I have never seen recommended replacement interval, just people saying if you are in the timing cover, replace the guides while you are there.
 

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I never heard of a Tribeca needing a head gasket. I have a lot of consumer experience on the Subaru out backs called Gen2.

I and a friend just finished putting an OEM shortblock in a Subaru out back because I had a leaky head gasket ( second time fix..first was at 60,000 and now a 94,000). 2 rods went bad at when head leaked..came all of a sudden. So I just spent well over 4,000 on an engine on a 2002 Subaru.

my 2000 out back blew the headgasket at about 110,000 and now I think its going again at 170,000.based on antifreeze consumption
It can happen if it was overheated at some point, usually because coolant level wasn't monitored.
 

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Discussion Starter #9
I never heard of a Tribeca needing a head gasket. I have a lot of consumer experience on the Subaru out backs called Gen2.

I and a friend just finished putting an OEM shortblock in a Subaru out back because I had a leaky head gasket ( second time fix..first was at 60,000 and now a 94,000). 2 rods went bad at when head leaked..came all of a sudden. So I just spent well over 4,000 on an engine on a 2002 Subaru.

my 2000 out back blew the headgasket at about 110,000 and now I think its going again at 170,000.based on antifreeze consumption
On the OB board, I too have seen the chatter about HG issues with the H6 being a rarity, but I don't think they're any less common when compared to any other automobile, especially - as tdelker noted - since O/H can blow the HG on any car.

IMO, the EJ25 has completely distorted Subaru owners' perception of what is commonplace when it comes to HG issues.

There is no interval for the timing chain replacement in all subby's H6 engines. There are plastic timing guides in there that wear, but I have never seen recommended replacement interval, just people saying if you are in the timing cover, replace the guides while you are there.
Page PM-4 in the FSM recommends replacement of the "Camshaft Drive Belt" at 105 months / 105,000 miles. I simply assumed they meant the timing chain, and whoever copied/pasted the schedule simply forgot to edit for the H6; however, perhaps they forgot to delete that line entirely, too. But since I'm in there, I'll definitely replace the guides.
 

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Discussion Starter #11
Timing belt for the 2.5 is at 105k miles. There is a star on that scheduling excepting the H6 because it has a chain.
You're right. I was looking at the 2006MY FSM somewhere online... I downloaded the 2007MY FSM from SOA's website this weekend, and the line item for the camshaft drive belt on the schedule was eliminated completely. (Such is only one of the many subtle - though somewhat material - differences I've found between the 2006 and 2007 FSMs just over the past 48 hours.)

Verdict: I have yet to go through the Technician Reference Booklet for chain-driven engines, but as of now I'm planning on replacing the guides, sprocket shafts and bolts (interior bolts, not the cover bolts)... no plans to do anything with the tensioners or sprockets unless a visual inspection dictates otherwise.
 

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Discussion Starter #12 (Edited)
D-Day is a few days away: engine is being pulled this Saturday. After consulting the OB folks (grossgary and Glennda5id, in particular), here is my updated job list:

REPLACE:
1) Head gaskets (machining of heads/deck TBD)
2) Water pump
3) All timing guides and tensioners (nine in total) + six bolts holding the center guide, and guides b/t LH & RH camshafts (per FSM).
4) Water pump
5) Cylinder head washers (bolts are not TTY, so they will be reused if undamaged)
6) Misc gaskets & seals, including: throttle body, intake manifold, exhaust manifold, fuel injectors, timing covers, cylinder block, crankshaft, oil control valve.
7) Spark plugs.
8) V-belt idler bolts, bearings & plates.
9) Lower oil pan gasket (liquid RTV)
10) Hose clips (only those being disconnected)

INSPECTED (but not being replaced unless necessary)
1) Timing chains
2) Valves: leakdown and clearances
3) Water pipes
4) Oil and ATF cooler hoses/lines.
5) Timing idler bolts/shafts
6) Leakdown & valve clearances
7) Pan magnets
8) Engine Mounts

TBD - STILL RESEARCHING:
1) Replace outer timing cover's OEM socket bolts with hex bolts.
2) Valve seals

NOT BEING ADDRESSED
1) Block components, including pistons, bearings, & crankshaft.
2) Radiator hoses & T-stat (replaced Jan 2014)
3) V-belt (still within spec) and tensioner.

OTHER:
1) Reboot front axle inners (both are leaking, outer boots are fine)
2) Flush ATF & change filter
3) Flush radiator
4) Change front & rear differential fluid
5) Change oil and coolant (duh!)
6) Vacuum test

NOTES:
1) All parts being replaced are OEM.
2) After much reading on the topic over the past two months, I've decided the HGs are being installed as-is. Not going the copper spray route.
 

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Good luck!

When flushing the ATF, the line at the bottom of the cooler is the SUPPLY, not the return as I expected. Fluid came gushing out of the line coming from the filter in the fender area, I thought it went from filter to top of cooler and would come out of the bottom of the cooler.

Just FYI...
 

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Discussion Starter #14 (Edited)
That was fun.

I am not going to post a detailed walk-through or step-by-step since there are already multiple threads about tearing down an H6 on the OB forum - they've said it much better than I ever would be able to anyway. However, I will share the general process along with some tips, notes, and tricks - Tribeca-specific and otherwise - from my experience. I'm going to go multi-post format here, because some of my thoughts might (read: will) get wordy... accordingly, it may take me a few days (or weeks) to get everything up.

But first, a disclaimer:

I am not a professional mechanic, I have neither been trained nor ever taken a class in auto repair, and I have never worked inside an engine beyond the rocker cover or - for that matter - even pulled a Subaru engine before I undertook this project. I'm not even a shadetree mechanic... I'm a YouTube mechanic. Accordingly, what I'm about to share is a matter of my amateur opinion and experience and should not be construed as any sort of advice, recommendation or professional diagnosis. With that said...
 

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Discussion Starter #15 (Edited)
Basic overview of my process:

***NOTE: "Total work time" does not include extra time to pick up parts/tools, or time lost to my own "screw-ups." It does include time to bag, label, and/or clean parts.****

Saturday afternoon/evening:
) Seafoam trifecta - gastank, intake, oil. Drove ~25 miles to get some engine degreaser and then to the car wash.
) Park the car, pull the fuel pump fuse, wait for engine to kill, drain fluids. Reinstall ATF and gear oil plugs.
) Raise hood to vertical position (move the hydraulic lifter to the lower position on the hood), D/C & remove battery
) Remove all plastic covers & undercovers.
) D/C fuel line and evaporator hoses.
) Remove vacuum hoses, intake air duct & filter
) D/C throttle coolant lines, PCV hoses, manifold pressure sensor harness.
) Remove intake manifold.
) Unclip & remove the front bumper and the foam absorber, put in a safe place away from curious children.
) D/C the hood latch and remove the radiator stay (t-shaped assembly running above and down between the radiator and v-belt)
) Disconnect hoses from radiator (coolant and ATF lines), drain additional coolant.
) D/C the radiator from the condenser, remove the radiator.
) Remove v-belt (optional: remove idlers if replacing)
) Remove electrical connections, grounds, etc.
- "Main": three harnesses on the rear lifting eye.
- Power steering pump, alternator, AC compressor
- Engine grounds (one near starter, two underneath near exhaust manifolds)

[My total work time: approx. 4-5 hours]

Sunday afternoon/evening:
) Dismount (but do not D/C hoses) the PS pump from the engine block. Secure with reservoir tank to side of engine bay.
) Remove the alternator.
) Dismount (but do not D/C hoses) the AC compressor and suspend from ceiling as far out of the way without bending/kinking the hoses.
) Remove two top bolts on vacuum pump bracket.
) D/C heater hoses (I found it easiest to D/C at the engine rather than the firewall).
) Raise car on jack stands.
) D/C front exhaust pipe from rear pipe (may need to cut bolts if seized/corroded, save the springs). D/C oxygen sensors (four)
) Remove bolts mounting pipe to chassis hanger, but do not remove from hanger yet.
) D/C exhaust manifold from heads. Remove front exhaust from hanger. Put front exhaust in safe place away from curious children.
) Remove two lower bolts on vacuum pump bracket and remove.
) OPTIONAL - If rebooting axles, remove axles at or before this point.
) Remove lower transmission/engine mounting bolts (four) and nuts (two).
) Remove nuts from engine mounts.
) Remove jack stands and lower car.
) Remove cover from crankshaft pulley.
) Remove timing hole plug and D/C flywheel from torque converter (four bolts), use 22mm socket & breaker bar to rotate crankshaft until next bolt appears.
) D/C pitch stopper from transmission (does not need to be D/C'd from firewall)
) Remove the starter. OPTIONAL - If use the torque converter "stopper", install in starter hole.

[Total work time: 2-3 hours]

Monday afternoon:
) Support transmission with jack... do not raise engine/transmission yet.
) D/C upper transmission/engine mounting bolts (four), note their original location.
) Attach chains/leveler from hoist to engine. (I used the AC compressor mounting bracket and the rear lifting eye.) Lift engine slightly (<1") to put load on chains, leveling so both chains have no slack.
) Raise transmission with jack, about 1-2 inches. Engine will raise with transmission at this point. Raise hoist to just barely put load on chains (without raising engine further).
) Break engine free from transmission. There are two guide pins at the 3-o'clock and 9-o'clock positions on the transmission housing on which the engine will probably stick. Use putty knives/screwdrivers and a small rubber mallet to gently (I cannot overemphasize this enough) pry the engine from the transmission. Penetrating oil is your friend if it's stuck... spray the pins, inside the bolt holes on the sides, inside the timing hole cover, along the mating seam near the pins, etc. Take your time because you don't want to screw this up... it took me 20-30 minutes of work plus another 20-30 minutes of waiting for oil to penetrate to separate the two.
) Slide engine horizontally towards condenser until it clears the lower studs. Raise the engine to put more load on hoist if necessary. Watch that your torque converter doesn't come out with the engine.
) Make sure everything to the engine has been D/C'd
) Raise engine slowly, moving hoses, PS pump, AC compressor and electrical cords out of the way as you lift.
) Mount on 1/2 ton engine stand using the OEM bolts (different bolts and/or add'l washers may be necessary depending on your engine stand). OPTIONAL - If you're going to remove the flywheel and/or replace the rear oil seal, do so before mounting if using an engine stand.
) Spray timing cover guide pins with penetrating oil. (suggestion in restrospect... I did not actually do this)

[Total work time: 3-4 hours]

Tuesday:
) Removed crank pulley *
) Removed front timing cover. **
) Removed timing chain assembly (including guides, tensioners, idlers, etc.)
) Removed cam sprockets *
) Removed oil pump ***
) Removed water pump
) Removed oil pipes (head to lower engine).
) Removed upper engine water pipe and hoses.
) Removed rocker covers, cam caps & bearings, cams and valve buckets/shims.
) OPTIONAL - This would be a good time to do an initial leakdown test if one hasn't been done already. If significant leakage can be heard from the intake or exhaust ports, you may wish to consider a valve job.
) Removed heads.
) Removed oil cooler and lower water pipe.

[Total work time: 3-4 hours]

* Lost about 1.5 hours designing & "fabricating" my universal crank/cam sprocket stopper
** Lost 0.5 hours removing stripped hex head cover bolt (fortunately, only one stripped)
*** Lost about 2.0 hours because the hex heads on bolts 1-4 stripped and had to be drilled out.

Wednesday:
) Removed oil solenoid valves & cam position sensors from heads
) Removed old gasket material from heads (did not remove the half-circle plugs)
) Heads machined
) De-glaze pistons, clean up residual carbon, mineral deposits, etc.
) Scrape and cleaned block mating surface.
) Removed lower oil pan, replace pickup tube o-rings, removed old gasket material.
) Reinstalled heads and removed carbon & cleaned cam chamber
) OPTIONAL - This would be a good time to perform another leakdown test. If results are comparable to the first test and you have significant leakage, then either the HG isn't installed properly and/or you have bad valve seats or rings.

(Couldn't go any further since new rear timing cover arrived Thurs morning)

[Total work time 3-4 hours]

Thursday:
) Installed new rear timing cover with new o-rings & waterpump gasket (paper-type).
) Reinstalled oil pump (rotors and cover plate) ****
) Installed new water pump & o-rings (2)
) Reinstalled buckets, shims, lifters, cams, bearings, caps
) Checked valve clearances *****
) Cleaned and reinstalled rocker covers
) Sanded (as necessary), primed and repainted upper engine water pipe and lower oil cooler water pipe.

[Total work time: 4-5 hours]

**** New hex bolts (#1-4) wouldn’t arrive until Friday. Everything else installed fine.
***** Lost about 1.5 hours because I did not keep my buckets and shims in order and had to remove/reinstall the cams twice to ascertain the original positions.

Friday:
) Cleaned & reinstalled lower oil pan. Reinstall drain plug (with new gasket).
) Cleaned and reinstalled oil solenoids (w/ new gaskets) & cam position sensors to heads.
) Cleaned EGR port (the MY07 doesn’t have a EGR, just a cover plate over where it would be installed on the head) and reinstalled cover plate with new metal gasket.[/B]
) Installed remaining hex head bolts in oil pump cover ******
) Reinstalled cam sprockets, idlers and timing chains w/ new guides, levers, and tensioners
) Installed new spark plugs, reinstalled and reconnected coil packs.
) Removed crank pulley oil seal.
) Cleaned and reinstalled outer timing cover w/ new oil seal.
) Cleaned and greased (di-electric) all electrical harnesses/connectors.
) Reinstalled upper and lower water pipes & hoses.
) Cleaned and replaced o-rings on oil cap and dipstick.
) Cleaned filters and reinstalled oil pipes w/ new metal gaskets (between pipe and engine).

[Total work time: 5-6 hours]

****** Lost about an hour because one of the hex bolts was backordered and had to go to Ace Hardware.

Saturday:
) Removed & cleaned fuel injectors and connections
) Reinstalled fuel injectors/rails with new o-rings and seals. Reconnected injector wiring harnesses (fuel injectors, oil controls, and cam position sensors).
) Reinstalled crank pulley
) Reinstalled engine, connected main harness and knock sensors.
) Reinstalled vacuum pump & starter
) OPTIONAL - Reinstall axles, if removed/rebooted.
) Removed old gasket material on exhaust pipe. Repaired (welded) broken hanger bracket. Reinstalled exhaust with new gasket, bolts and nuts (springs reused). Used two 3” c-clamps to mate front exhaust pipe to rear exhaust and tightened bolts with c-clamps still in place.
) Reconnect oxygen sensors.
) Removed throttle body from intake manifold, cleaned (removed carbon) throttle plate, reinstalled body to intake with new gasket.
) Cleaned and reinstalled intake manifold w/ new gasket.
) Reconnected fuel hoses & piping
) Reinstalled fuel rail covers.
) Reconnected all vacuum hoses, PCV hoses, heater hoses, engine electrical connectors & grounds. Installed new vacuum pressure sensor filter on front of intake.
) Reinstalled PS pump (and reservoir), alternator & AC compressor. Reconnect harnesses and zip tie to fuel rail cover.
) Flushed and reinstalled radiator and drain/bleeder plugs
) Cleaned & reinstalled overflow bottle.

[Total work time: 8-9 hours]

Sunday:
) Reinstalled v-belt idlers and v-belt. Reinstalled crank pulley cover w/ new o-ring.
) Reinstalled radiator stay, reconnected upper, lower & ATF hoses, installed new gasket on thermostat.
) Reinstall hood latch, reconnect radiator fan connections.
) OPTIONAL - If changing the ATF filter, do it now (before the bumper is reinstalled). Installed new clips on hoses where ATF was leaking
) Reinstalled front bumper, upper and lower radiator covers
) Reinstall air filter housing & intake duct. Reconnect MAF sensor.
) Move hydraulic lifter to original position.
) Double check all plugs, hoses, clips, harnesses, and connections
) Fill oil, ATF, coolant, PS fluid and gear oil.
) Check for leaks. Triple check all hoses, clips, harnesses and connections.
) Reinstall battery.
) Crank engine twice for 10-15 seconds (to begin oil circulation)
) Reinstalled fuel pump fuse.
) Poured a beer, said a prayer, and fired it up.

[Total work time: 4-5 hours]

At the point where you are content that everything is back together & you have no leaks, reinstall the lower engine cover.
 

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Discussion Starter #16 (Edited)
These are the websites I found most informative and useful in preparing and executing the project:

http://www.subaruoutback.org/forums/99-do-yourself-illustrated-guides/33809-engine-removal-thread.html

http://www.subaruoutback.org/forums/88-head-gasket-issues/26887-h6-head-gasket-replacement.html

http://www.subaruoutback.org/forums/110-gen-2-2000-2004/31558-3-0-h6-timing-chain-guide-discussion.html

http://www.subaruoutback.org/forums/110-gen-2-2000-2004/38498-h6-head-gasket-replacement.html

[The moral of the story from the last two is if you're going in to do the chains, go all the way to the head gaskets. I couldn't agree more.]

This was entirely a solo job... I had zero help; I’m not saying this to brag but to merely provide perspective on the time commitment involved. Total project took me just over a week (Saturday to the following Sunday). I estimate my total "wrenching" time was about 40-45 hours. I probably spent another 10 hours running back and forth for parts/tools, getting the heads machined, in-project research, breaks, etc.

You can change the head gaskets without pulling the engine, but I wouldn't recommend it. It seems counter-intuitive, but especially if you haven't worked on the H6 (or any engine, for that matter) before, you're going to want to pull the engine. So much easier to clean things up, check flatness on the block, put things together, understand how it works, etc. (not to mention that being able to invert the engine made replacing the oil pan gasket a snap). Disconnecting everything and pulling the engine took about 8-9 hours of work; replacing it was probably a couple hours less – keep in mind, this was the first time I had ever did this on a Subaru… a good 25% of the time pulling the engine was me meticulously identifying, bagging, labelling and photographing parts. If you’ve pulled an engine before and/or are less OCD than I am, you could probably pull the engine in under 5 hours. Putting the engine back in was about the same... the time I saved not having to label/bag/photo was consumed by checking, double-checking, and setting my torque wrenches.

In any event, the extra two project days to pull the engine were well worth it.
 

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Discussion Starter #17 (Edited)
I ran a 10 oz. of Seafoam through my oil for about 25 miles before starting. The oil I drained was the thickest, sludgiest muck I have ever seen despite being only 4,000 miles removed from my last oil change. But boy, did it ever clean up the interior oil passages/chambers.

Seafoaming through the intake on the 3.0R is a bit different than the earlier H6s. Follow the hose to the PCV valve (there are two hoses off the LH head, the rear one is the one to follow) and disconnect from the head. Rotate the hose up so that it sticks up above the engine. Take an old baby bottle (or a new one you'll never use again), fill with 6 oz. of SF, start the engine, and squeeze the bottle. You just need to get the stream close enough to the hose, the suction will take care of the rest.

The timing chain was in excellent condition. Most of the guides were visibly worn, but still had several years of life in them (at least, if not better, shape than "salvage" quality). I'm glad I changed all of the guides & tensioners, but if I was on a more limited budget, I would have been perfectly content leaving all of the timing components alone finding them in the condition they were in.

If you are doing the timing chains/components only, don’t pull the engine. Just remove the bumper and radiator/condenser, and you’ll have clear access to the timing cover. You might even be able to rotate the condenser out if you don’t want to evac your A/C system.

Follow the FSM when reassembling the timing components... it's much less confusing the the technicians reference booklet. Basically, unload the pistons by setting the crank sprocket triangle mark to the 9-o'clock position, key grooves on both exhaust cams to 12-o'clock, LH intake cam to the 75 degree position (about 2:30), and RH intake cam to the 50 degree position (about 1:45). Move piston #1 to TDC by rotating the cam sprocket triangle clockwise to 12-o'clock. Align your chains, install the tensioners and guides, and when everything is set, pull the tensioner pins.
 

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Discussion Starter #18 (Edited)
As suspected, the heads were warped. Spec tolerance is .020 mm... I found several areas above .050 and one spot that was nearly .100 (~.004", which is what was cut). The block was in much better shape: while there is no flatness spec in the FSM (only a "standard height" spec of 202mm), I was generally referring to the head tolerance of .020 when checking the block, but since I only found a couple spots that barely even hit .020, I did not deck the block.

Notice the faint-orangish areas on the mating surface, particularly outside the 7-o'clock coolant passage on cylinders 1 & 3 (RH, right & center)... that's your Subaru Coolant Conditioner, folks.

If it's recommended for your vehicle, use the SCC... my HG leak was internal, but in taking the thing apart, if not for the SCC, I would have had external HG leaks in more than one spot. The SCC did exactly what it was supposed to do on those external leaks and even kept the internal leak from being much worse. I noticed some scaling and mineral deposits in some places, but I couldn’t find any restrictions - from the SCC or otherwise - anywhere throughout the cooling system. SCC isn't going to kill your radiator or anything else; there's no downside and it's only a couple bucks a bottle. End soapbox
 

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Discussion Starter #19 (Edited)
There are two "guide" pins that hold the outer chain cover to the block. The pins are not aluminum and the corrosion made taking the cover off a real chore. I wish I had sprayed those pins with PB blaster or Deep Creep the night before, otherwise, I probably wouldn't have had to buy a new rear chain cover.

Yep... I killed my rear chain cover. First, when removing the outer cover, I broke off a little tab prying it off just above the RH tensioner lever. I was being extremely careful, but aluminum doesn't bend, it breaks... and after losing patience, I pried too hard in the wrong spot. I figured I could probably just weld that tab back on somehow and use some extra gasket material, but I crushed the water pump threads trying to remove the pump anyway, so I just decided to replace the thing entirely.

Which brings me to the water pump. I wish I hadn’t used the "thread an 8mm screw" method prescribed by the FSM to remove a stuck water pump... if it is really stuck, you'll end up crushing the threads on rear cover that hold the water pump bolts. Instead, thread the screws until just tight, and use a slide hammer or anything else that does not use the chain cover as leverage to pull the water pump out of the housing.
 

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Discussion Starter #20 (Edited)
There are three classifications to the rear chain cover that corresponds with the three classifications of oil pump rotors, 'A', 'B' and 'C' each which have tolerance ranges of about .013 mm. An A cover has the deepest housing for the rotors and C has the shallowest; likewise, A rotors are the thickest and C rotors are the thinnest. While FHI did this, I have no clue. The tolerances for A/B and B/C overlap, so you could mix a C cover with B rotors and still be in spec (which is what I had to do since I had B cover and rotors, but a B cover to match my rotors and C rotors to match a new cover were both backordered at least a week), but not always. I presume the problem is that if your rotor is too thick for the cover depth, it can bind (or grind) between the rear cover and oil pump cover; if the rotor is too thin, you can lose oil pressure. FSM says the clearance between the cover depth and rotor thickness should not exceed .020. I was fortunate to be in that "overlap" range where my clearance was barely .020... but from the time I ordered the cover until the time it arrived, I was worried about the possibility of having to wait a couple of weeks to put my engine back together or taking my chances having the rotors shred the inside of the pump housing.

Bolts 1-4 on the oil pump are hex socket bolts that are supposed to be 5mm, but every 5mm hex head I tried felt loose and 5.5mm was too big. I ended up stripping three of the four and ended up having to drill them out. Obviously, the socket itself contributed, but the real problem was that the bolts were installed well beyond the 4.7 ft-lb torque spec. The longer of the two bolts was on backorder at the dealership, so I just went to Ace Hardware locally and bought an M6x35x1.0pitch socket bolt; it was a perfect fit.
 

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