92stroker

'89 4runner v6

So, my truck wouldn't pass emissions, did a tune up (plugs/wires/cap/rotor/coolant sensor/timing/thermostat/tps) and it didn't improve. Hc's at idle and high rpm were 3x and 2x their respective limits, so obviously something was more than a little wrong.

Finally got around to doing a compression test and the number 3 cylinder has zero compression... damn needle didn't even twitch. The other 5 were pretty good, I think the minimum was 150psi, and the max was 170psi. Also, it took a while for each cylinder to get to it's peak compression, so I know the rings are worn.

Truck has 223,xxx miles on it, and was pretty beat when I got it a few years back.

Anyways... 0psi on number 3. What am I looking at hear? My initial suspicion was a head gasket. Then I found out that these v6's tend to burn up exhaust valves.

If I'm going to have to go through all the trouble of pulling the heads anyways, I think I'll probably just do a re-ring, and replace the bearings as well.

Found plenty of re-ring kits on ebay around $160, but I would still need timing components, and valves it they are the issue. I know those kits are probably chinese, but I paid $1900 for this turd, and don't really want to invest a lot more into it.

Oh, also, I would never replace the headgaskets without getting the heads milled, but what about the block? Can I get away with doing this in chassis?

What kits do you recommend? Does Toyota package an OEM kit?

Thanks for reading.

donomite49

first check valve clearance, if ok,
then you can do a leak down test, and listen for air in the intake or exhaust.
this will narrow it down to a leaking intake or exhaust valve, or blowby past the rings.
unless it's all three of the above

if it's a valve problem

you can just do a valve job till the bottom end goes.

scope103

If it's valve or head gasket, the drill is pretty much the same, so go ahead and take it off.

BUT: doing rings is a whole 'nother matter. So I think it's worth the effort to do as donomite49 suggests, with a leakdown test. If the rings aren't that bad I'd be tempted to leave them. And you can't really do a leakdown after the heads are off (though you will still visually inspect the cylinder walls).

I doubt you would need to mill the block (but get out your straight-edge anyway). You'll probably only need to "kiss" the heads.

Good luck!

92stroker

Thanks for the tips guys! I don't have a leak down tester, but I could just use the adapter from my compression tester and hook it directly to my air compressor, and just listen for air in the exhaust or intake... If I hear air in either, then the lack of compression would be related to the associated valve, which I'm guess is probably the exhaust valve, since it's a known issue on these things. Compression across all 6 was:

1 - 160
2 - 155
3 - 0
4 - 170
5 - 155
6 - 165

Let me ask you guys this:

Is the crankcase accessible in-chassis on these trucks? Is it possible to replace the rings and bearings without removing the block? If the ring turns out to be good, I'll most likely just do the valves and associated gaskets + timing since the belt will be removed anyways and I don't know the maintenance history, but I will do a full re-ring and replace the bearings if necessary, but will most likely end up doing the work in my dirt driveway which can be a PITA for an engine hoist.

blake.nemitz

why not unplug the injector on that cylinder and run it again, might pass

92stroker

Funny thing is, I already considered that, but since it's the number 3 on a 3vze, I can't access the injector plug without pulling the upper intake, at which point I might as well just do it right. It would be nice to have a decent truck, and I've done so much other work to it, I think it's worth it to me for it to run well... especially since it hasn't run right since I've owned it, and now I know why.

92stroker

Still wondering if anyone can tell me whether or not I can do the bottom end on a first gen 4runner v6 without pulling the motor?

donomite49

think you have to pull the front diff just to pull the pan.

92stroker

Ahhhh... thank you, that tells me quite a bit. Hmmm...

blake.nemitz

you technically could gut how are you going to hold the crack up line up the rods and put the bearings in with the girdle all hanging from the bottom with only two hands even using your feet to assist. not to mention taking off the rear main seal and flywheel to pull the crank which you cant to unless the tranny is gone then you might as well unbolt the mounts and pull it. and you CAN NOT pull the pistons out of the bottom have to go out on the top. good luck did you try un plugging the injector for that cylinder and running it at the emmisions place?

92stroker

Usually a couple jack stands under the counter weights of the crank hold it up in order to secure the mains, then torque it and drop the rods and pistons down from the top. Works pretty well on inline motors, but I've never done it on a V motor before. We call it a "farm rebuild," lol! The reason I asked, is I've encountered some vehicles that simple don't have the clearance underneath.

Had I an engine crane and stand, there would be no question as to how I would proceed, but I do not.

Anyways, I don't think I'm going to mess with the bottom end, it was just wishful thinking.

I started work last night, and after about 3.5 relatively trouble free hours, and working solo, I go the upper intake manifold, fuel rails/injectors, and lower intake manifold off.

My truck is disgusting, and really needed this anyways, so I'm trying to enjoy the work as best I can. I'm hoping I can drop the intake manifold, and other various components off at the machine shop to get cleaned when I drop off the heads. The lower intake manifold was literally a rats nest when I took the plenum off. I knew it was coming because I had it off once before and just didn't clean it, so this time I'm going to try and do a better job.

Beaker801

You can make your own leak down tester very easily. There are many YouTube videos showing you how. Basically it's :
> Air in > pressure regulator with gauge > flow reducer ≥ T with gauge > tube with spark plug male fitting + o ring.
I Made mine with spare parts from an old compressor.
Doing a leak down will give you definite results. At least as it pertains to compression or loss of it and where it's going.