97 s/c Head gasket replacement summary W/ part #s

Hello there everyone,
:dedhrs:I know this post is probably beating an old thread to death, but I know there are many others who will need the info and thought it would be helpful to have it all in one place:
97 S/C alltrac previa w/ 180,000 mi. head gasket seeping (tested and confirmed, still running great. Started w/ temp spikes at idle after long drives fyi.)
Spoke w/ Sammay in Seattle. His opinion (gold:clap:) was that the bottom half of these engines were solid and that if it were his, he'd replace the head gasket and not do a JDM swap. I considered driving it to him, but its over 10 hr away and I'd have to spend at least 1 night yada yada yada.
Had a hard time finding someone who WANTED to take this on (for obvious reasons) but found a shop about an hour away who specializes in Toyota head gaskets. He'd at least done it before and actually wanted my 12+ hours of work (such an imposition on so many :wall:).

While the engine is out I'm going to take care of some other things. I've listed the parts for this job as well as their OEM #'s to save the next Joe some time.
I'd love some feedback on anything I'm missing or should consider also doing.
I'm also adding a summary of some of the do's and don'ts and helpful tips I've found (none are mine, thanks to their writers!). I'd really love some input here.
Thanks everyone!:wave1:

Total = @ $1000 at Toyota Parts Factory

Head parts
VALVE GRIND GASKET KIT - 1997 Toyota Previa (0411276080) $229 @ Toyota parts factory

? 90910-02187 (was)9091002091 Head Bolt Set (10)
16261-76030 HOSE, WATER BY-PASS
16264-76011 HOSE, WATER BY-PASS, NO.2 was 16264-76010
16267-76010 HOSE, WATER BY-PASS, NO.3
16281-76010 HOSE, WATER BY-PASS, NO.4
99555-10100 HOSE, WATER BY-PASS, NO.6
87245-95D31 hose, water (heater)
90460-28001 Heater hose clamp

Other parts
water pump assembly $65 @TPF 16100-79165-83
TPS 89452-22090 $75@TPF
Thermostat 90916-03120 and seal
Timing chain 1350675010 $120 @ TPF
guide plates 13507-76010 slipper plates13540-75020 13550-75010

12261-76010 PCV hose
12204-15022 PVC valve
90480-18001 PCV Grommet

SADS parts
04374-28011COUPLING KIT, EQUIPM $235 @ Toyota parts fact

FRONT BOLT 90119-10648 (3)
REAR BOLT 90101-08143 (3)
37919-28010 REAR WASHER (3)

Other relevant parts and numbers (not needed (yet) for me)
17173-76010 Exhaust manifold gasket
17177-76011 intake manifold gasket
16341-76010 Water manifold gasket
90099-14091 Distributor O-ring
90311-88003 Rear Seal
90105-10276 flex plate bolts (BOLT, WASHER BASED H)
90311-48014 Front seal
12255-76010 Oil breather gasket
15692-76010 Oil filter housing gasket (a little "8" shaped O-ring kinda thing)
90917-06039 exhaust header port rings (two of 'em)
12371-76041 INSULATOR, ENGINE MOUNTING, REAR NO.1
12372-76011 INSULATOR, ENGINE MOUNTING, REAR NO.2
12361-76042 right motor mount
12362-76012 left motor mount


Advice summary:

-the most common culprit to headgasket failure was a clogged return cooling line. He had mentioned that the majority of Previas he had worked on had crud in the cooling line that ran from the reservoir back to the engine... causing insufficient coolant flow.
- Supercharged Previas have a long ventilation tube which connects the oil filler neck under the driver's seat to the air tube connected to the mass air flow sensor. This ventilation tube is double walled with hot coolant flowing from the throttle body to the top of the outer part of the ventilation tube to under the Previa on the left side of engine and then connects to a hose on its way to the EGR(???). The inner part of this ventilation tube brings crankcase gasses to the air tube connecting the mass air flow sensor and throttle body. Black flakes will collect in the upper "T" where coolant enters this ventilation tube. This can clog the tube and lead to high idles when it's cold out since warm coolant isn't flowing through the throttle body. The solution is to clean out the black flakes and blow out any clogs from the bottom with compressed air. If this fails, you may need to replace the tube altogether or reroute your coolant lines. If you reroute your coolant lines, you may need to frequently clean out the ventilation tube with SeaFoam or other solvent safe for your engine. If once you unclog your coolant lines, you may wish to consider a in-line filter to protect your coolant system

- After removing the cams, the valve shim assy's must be removed or they will fall out while handling the head. It is very very important to keep these in order. Unless you plan on re-shimming and replacing, they must be reinstalled in the exact location they were taken from. I used a piece of cardboard to keep them in the correct order.
- I would wire-tie the sprocket to the chain so there's no chance of it moving from it's original location. Then when you separate the intake cam from the sprocket leave it sitting in the chain guides. On assembly, another thing worth mentioning is the chain tensioner. The tensioner has a lock feature that only allows it to extend. It should only extend when there's oil pressure, so it probably won't move, but just to be safe I would release the lock and push it back to it's retracted position. This can be a bit tricky if you're not removing the timing cover, but it can be done with a screwdriver and a little patience.
- Installing the rocker arm bar upside down
There is a flat spot ground into the back of the rocker bar. This flat spot needs to be facing down against the head when you put it back on. Failure to do this will result in over-stressing the rear mount area and will also create too much valve lash. The result is increased wear, decreased performance, and noisy valves.
- Mixing up push rods
Push rods, lifters, and rocker arms are all the same when new, but as they break-in they develop unique wear patterns. Because of this, after break-in they should always stay paired with the parts they were originally mated with. Swapping push rods around or flipping them upside down will make them go through this break-in process again. Depending on how similar the wear patterns may (or may not) be, mixing these up can cause excessive wear and likely lead to premature failure. Typically it's considered acceptable to throw a new part into the mix, but not a previously used one. You can avoid early failure by keeping things in order. A good way to do this is to flip a cardboard box upside down and poke 8 holes in the bottom. Make the holes in a straight line and mark what end is the front. As you take the push-rods out, start on one end and remove them in order. As you remove them poke them right side-up into the holes (in the order they came out).
- When the SADS is separated from the engine you should check the rubber bushings and replace the flex couplers if needed. Also check the engine mounts & replace if separated or torn.
Do not let sads shaft hang! Always support it!
USE THREAD LOCKERS when installing the bushing kits. the bushing bolts tends to back out for some reason. uh....

Good luck to the next guy! Hope this helped.:grpwave:

Quote:

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Originally Posted by klisterkicker

- Installing the rocker arm bar upside down
There is a flat spot ground into the back of the rocker bar. This flat spot needs to be facing down against the head when you put it back on. Failure to do this will result in over-stressing the rear mount area and will also create too much valve lash. The result is increased wear, decreased performance, and noisy valves.
- Mixing up push rods
Push rods, lifters, and rocker arms are all the same when new, but as they break-in they develop unique wear patterns. Because of this, after break-in they should always stay paired with the parts they were originally mated with. Swapping push rods around or flipping them upside down will make them go through this break-in process again. Depending on how similar the wear patterns may (or may not) be, mixing these up can cause excessive wear and likely lead to premature failure. Typically it's considered acceptable to throw a new part into the mix, but not a previously used one. You can avoid early failure by keeping things in order. A good way to do this is to flip a cardboard box upside down and poke 8 holes in the bottom. Make the holes in a straight line and mark what end is the front. As you take the push-rods out, start on one end and remove them in order. As you remove them poke them right side-up into the holes (in the order they came out).

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I recognize this as a copy/paste (my words) from another area of the forum. This advice does not apply to the Previa. Previas have overhead cams, therefore no lifters, rocker arm bar, no push-rods & no rocker arms. Tim

Quote:

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Originally Posted by timsrv

I recognize this as a copy/paste (my words) from another area of the forum. This advice does not apply to the Previa. Previas have overhead cams, therefore no lifters, rocker arm bar, no push-rods & no rocker arms. Tim

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Thanks Tim,
Sorry about this mis-cut. I think the majority of this post originated from your posts. They've been so helpful in sorting out my project options I knew someone would appreciate them all in one place.
Thanks again!:whs: is what you need to know.

No problem, I'm glad my ramblings are appreciated by some :wnk:. I give permission to all members to freely use my posts (copy/paste is okay), but I suspect not everybody is okay with that. Just to be safe, it's always better to use the [quote] feature. Not only does this give credit to the original poster, but it also provides a link to the original post (a left mouse click on the little blue arrow next to their name will take you there). Thanks for your contributions to our forum :yes:. Tim