After reading Zenseeker's previa maint page and seeing the thread on here for 97 s/c head gasket replacement summary with parts (http://www.toyotavantech.com/forum/s...mmary-W-part-s) by Klisterkicker


"-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"

I believe this has to do with the "black flakes in coolant lines", which I've seen on toyotanation's forum after they got it from the yahoo group.

cleaning_out_tee.jpgcoolingtubeventilation.jpg

I was at a Toyota/Lexus/Scion salvage yard this morning getting those roof garnishes from a previa they posted for parts on craigslist. I started to snap pictures of the van taken part for myself and remembered to try and look for this tube.

Low and behold:

IMG_3572[1].jpg

I saw the tube and even the BLACK FLAKES coming out of it!

I mentioned this issue to the shop and it was kinda brushed off as the guy said that people on the internet"dont really know and just speculate". I planned on check out this issue anyway and do the inline filter, but reading and seeing it just convinced me this might have been the issue with my van.