Putting Humpty together again! (Previa content)

I got into a weird Previa lust a year or so ago and started hunting for blown motor egg shaped beasts to quiet my demented challenge dreams. I found one locally, bought it and dragged it home. I gutted the interior, filled it with parts, crawled around under it, measured everything-then bought a much nicer one (also with a blown motor). We then moved which necessitated a bit of a fleet downsize. Egg number two survived the cut. Now many months later we are sort of moved in, the Egg has made it into the garage, and life has told me I need a functioning Previa instead of a hopeless challenge distraction.

Humpty is a 1996 AWD Previa SC (supercharged). He has 200k miles and a blown head gasket. I have lots of dreams of increased boost, VIP treatment, etc..., but the reality is he will probably be a DD rat that I frequently stuff with armies of children or piles of greasy parts.

Reporting my progress to you guys makes me get more done, so here goes:

Humpty:

The cordless impact I bought after much deliberation in an earlier thread. Lets see how she does!

there isn't one of those around every corner is there

If you didn't know, Previa's have their engines under the front seats. Toyota took a big 4 cylinder, tilted it onto its side, fixed the oiling issues, and plopped it under the front seats. Great for handling, horrible for repairs. I decided to take the "easy" route to Previa headgasket replacement and do the job with the engine in the car.

There's an engine under there somewhere!

OK-there it is!

So the Ryobi will take off lug nuts just fine......but it might be a bit much for crusty 10mm heat shield bolts:

Hrmmmm...Braided steel brake lines on an Egg? Knowing Humpty's prior life story would be interesting.

Well the bubbling coolant reservoir and the steamy exhaust were really good signs of a blown head gasket, but the drain plug nails it:

I got excited when draining the oil because my 5 gallon oil container just barely squeezed under the drain hole if you tilted it a tiny bit.

Lol-maybe I shouldn't have trusted the "wedge to fit" method of securing my catch jug:

I haven't made that big of a mess working on a car in 20 years.

belteshazzar wrote: there isn't one of those around every corner is there

Not around here. It took me months to get my first one. Trying to get one with my challenge budget constraints (sub $500) made it more difficult.

Nice! Ive always liked the Previa. It will probably be my next dd. I also like to go the vip treatment but rubber band sidewalls is not practical for a dd. Id lower it for sure and grab better rims from other toyota/lexus and maybe even some fords. Google images of other Previas show some pretty cool rides.

Following this. Just what I need, another van to get interested in. That dashboard is something else.

After cleaning up the giant oil slick I got to the fun parts. To do a head removal with the engine in the van, you remove the motor mounts and lower the engine a few inches. Unfortunately you are limited to about two inches because of all the attached stuff and the oil filter housing that conflicts with a factory welded on crossmember. That two inches only comes after you remove the passenger motor mount by wedging an open end wrench between the mount and the head oil drain tube, somehow breaking loose the large nut with the slop of an open end, 1/16" of a turn available, and interference preventing you from using anything longer than a short wrench. The "ship in a bottle" approach was off to a good start.

After the motor mounts you remove some heat shields, the egr tubes, the distributor, the exhaust manifold, a coolant junction, and the intake manifold. The intake manifold again made me re-think the wisdom of leaving the engine in the car.

My hands and forearms had sharp things above and below and I had to use a box wrench with 1/4 turn available to remove the upper intake braces. The process took a long time and hurt. Please don't point out that the brackets were easily accessible by using the access hole under the drivers seat. If my forearms and hands find that out they might actually bludgeon me for putting them through that. I question the wisdom of working on a car while rushed and fatigued.

failboat wrote: Following this. Just what I need, another van to get interested in. That dashboard is something else.

They are really cool and drive pretty well. But if anyone is truly interested in one I would suggest looking up the offset frontal crash videos, they were a bit scary. I will be getting rid of the sewn in seatbelt overlap Toyota loved during that era. The overlap slowed your deceleration as it tore, but you traveled a long way. In this case-right into the path of the steering column as it headed towards the roof.

Still time to add boost!

Though the name, if I remember my nursery rhyme right, could be sort of unfortunate...

I have to confess I am playing catch up a bit. I have been working on this a little at a time over the last month or so. I occasionally got lazy with the camera so I skipped some of the progress. Progress was also depressingly slow so I didn't feel like it was worth posting. I actually got some free time today so I made pretty good progress and decided to start a build thread.

I spent a looong time looking for the "lower intake manifold support bracket" The "upper intake manifold support brackets" were on the upper intake (assuming upper meant throttle body end because the whole intake is parallel to the ground). It turns out the directions meant lower intake manifold support bracket, not lower intake manifold support bracket. It is right under the upper intake manifold support brackets, just heading towards the transmission instead of the block and you access it from under the van. Oh well, it will make sense if I buy another one some day?

So tonight I got the head off!!!!!!!!

The cylinders, pistons, and valves show an amazing lack of steam cleaning for as bad as the head gasket seemed.

There is definite evidence of compression and coolant travel on the cam gear end (cylinder 1). It looks like the compression and coolant may have actually made it in to the timing chain area. It also looks like there may have been compression/coolant passage combining on cylinders 3 and 4! Next stop-machine shop!

Osterkraut wrote: Still time to add boost! Though the name, if I remember my nursery rhyme right, could be sort of unfortunate...

The wisdom of the web claims Japanese tuners pushed this motor to 400hp. The wisdom of the web never quite reveals how this was done, just that it was supposedly so.

Okay...I'll ask. Why not just drop the engine? I ask out of ignorance.

dyintorace wrote: Okay...I'll ask. Why not just drop the engine? I ask out of ignorance.

Because doing it this way is "easier".

Ah. That makes sense!

dyintorace wrote: Okay...I'll ask. Why not just drop the engine? I ask out of ignorance.

The reality is that dropping the engine requires removal of many many more parts.

Parts I didn't have to remove/do that dropping the engine would require:
1) front driveshaft
2) rear driveshaft
3) 2 transmission cooler lines
4) Speedometer cable
5) transmission mount
6) 1000 wire connectors (possibly exaggerating)
7) fuel lines
8) Supplementary accessory driveshaft
9) intake tubing
10) starter wiring
11) several ground wires
12) throttle cable/cruise control cable, etc...
13) drain transmission
etc...

I am sure I am missing a few. In the real reality, a lot of the problems I had were due to lack of room to get a good angle on a part. I am not sure leaving the engine in really saves any time or makes it any easier. I chose the engine in method because I didn't have to remove so much stuff, dropping the engine and transmission alone would be tough, and I don't really have anywhere in my overcrowded garage to work on it if I could get it down. I wish I had taken more pictures because good directions would have saved me quite a bit of time.

Previas have always interested me, it's a shame we didnt get one with sliders on both sides.

m4ff3w wrote: Previas have always interested me, it's a shame we didnt get one with sliders on both sides.

The only reason I tell you this is because you are a glutton for punishment: the American and Japanese ones have the sliding doors on opposite sides.

oh-and if you are willing to give up 6 vertical inches of the driver and passenger inner lower seat bolsters you can totally fit an lsx under a Previa.

MrJoshua wrote: oh-and if you are willing to give up 6 vertical inches of the driver and passenger inner lower seat bolsters you can totally fit an lsx under a Previa.

Maybe a boxer engine? Less "cutting" ...i guess

driver109x wrote:

MrJoshua wrote: oh-and if you are willing to give up 6 vertical inches of the driver and passenger inner lower seat bolsters you can totally fit an lsx under a Previa.

Maybe a boxer engine? Less "cutting" ...i guess

The problem with most "Boxer" engines is they put them in regular engine bays. That means they put the intake, the accesories, the turbos, etc... on top to the engine and make it just as tall as any "vertically" configured engine. Now a Previa does have all of its accessory drive components up under the hood so If I could find a boxer motor with a low profile intake I might be set! But not on this one-this one needs to actually drive instead of be an entertaining brainstorming/parts collection exercise.

You said this is an AWD vehicle but from the pics it appears that the front wheels are in front of the engine so how does this system work?

When you said that I got strange dreams of an AWD Locost.

Wiki said this (all things that if enough reliable power could be made might make this a good Locost donor. Many builders like the front spindles.)

"It featured a unique mid-engined platform, where the inline four cylinder gasoline-powered engine was installed almost flat (at a 75-degree angle), beneath the front seats. Installing the engine in this configuration allowed moderately easy access to the spark plugs, which were located underneath a panel on the upper left-side of the vehicle, after removing the front passenger seat, the carpet, and an access panel. All engine-driven accessories, such as the alternator, power steering pump, air conditioning compressor, and radiator fan, are accessible from the front hood, driven off the front of the engine by an accessory driveshaft, and is known as the Supplemental Accessory Drive System, or "SADS." This allows for even front/rear weight distribution, which benefits ride quality and handling. However, it also prevents the installation of a larger engine, while the cost could not be relayed by sharing the platform with other vehicles."

Wiki says it came with a 4 speed auto or 5 speed. I'm betting 5 speeds are scarcer than

Wiki also says engines were: 2.4 L 2TZ-FE I4 2.4 L 2TZ-FZE I4 supercharged 2.2 L 3C-T I4 diesel 2.2 L 3C-TE I4 diesel

135 - 160 hp won't really set the world on fire, and that was considered one of the bigger problems of the van in the marketplace.

"The supercharged engine is different from the normally aspirated engine, owing to a slight decrease in compression ratio. The supercharger is engaged on-demand by an electromagnetic clutch, based on input from the engine management system computer (the Engine Control Unit, or ECU)."

I'd feel sorry for the threadjack, but after all this is GRM and wacky ideas are considered the norm on here.

carguy123 wrote: You said this is an AWD vehicle but from the pics it appears that the front wheels are in front of the engine so how does this system work?

The engine is indeed behind the front wheels. The AWD system works more like a truck AWD/4WD system with the power going through the transmission into a transfer case which then powers a normal driveshaft to the rear and a driveshaft to the front that powers the front wheels through a front differential. Contrast this with most transverse transmission AWD vehicles that have basically a FWD transmission with a rear output shaft that is connected to the rear wheels through either a viscous or clutch based coupling. Usually the transverse transmission based ones are FWD biased while the longitudinal transmission based ones are RWD biased.

The big problem with AWD Locosts is the engine is behind the front wheels so most systems won't fit. I'm going to have to try to find a pic of the set up.

Too bad it doesn't come with an optional M134 Minigun