Numbchux

so I just bought this '87 turbo 4runner that's in awesome shape, except for the knock. it's a long story, but the short version is, I bought it from a guy who origionally salvaged the truck many years ago, and then sold it to his sister in law.

24k miles ago, it got a new head, and turbo. and complete rebuild from the shortblock up. all by the guy from whom I bought the truck. (I say this because I know he's a damn good mechanic, and the chances of something going wrong from his work are slim).

less than 1k miles ago, the owners boyfriend offered to change her oil for her. we don't know exactly what happenned from there, if he forgot to fill it, or filled it which too much/little....but within ~500 miles it developed this knock. it's coming from the back of the motor, and is pretty pronounced. throughout the rpm range while cold, but it goes away in the mid range (about 3k rpms) when it warms up a bit. although I haven't let it run long enough to really get it up to operating temp.

as I was backing it off the trailer, I couldn't help chuckle because it sounded so much like a diesel.

anyway, I'm assuming it's something bottom end. main, or hopefully rod bearing. how possible would it be to replace these with the motor in the car. I don't have a hoist, the trucks parked on a gravel slab, nor do I have a good place to put the motor while I worked on it (it'd have to be carried down ~15 stairs to get to the house, then ~10 more down to the basement. I don't have a garage).

I've got a haynes manual, which explains in detail how to get the oil pan off with the engine in the truck. and I crawled under there to take a look...and I can do that. I downloaded a pdf FSM of an '85 from pavementsucks.com. and it explains rod bearing removal...and I think I can handle that aswell...but it says to remove the main bearings you have to remove the crank....

is there a way I could do this without removing the crank? is it maybe possible to remove the timing chain, and get a little play in the crank from the front to slide the main bearings out? is there a way to check them without removing them...

I'm an experience subaru guy. only work I wouldn't do myself is tranny work (never needed to anyway). I've done an engine swap, etc. but this is my first yota...so I'm still learning.

dcg9381

I thought you couldn't get the pan off the IFS trucks w/o lifting the motor a bit? (I don't actually know for sure - someone else can answer)

If it's a rod bearing, you can get to that pretty easily w/o any major work, just get the pan off, set the motor so your cylinder is at the bottom of it's stroke, unbolt the rod, push it up just a tad, and remove the bearings.

I've pulled pistons by removing the head, unbolting the rods and pushing them up.


Note, most of the cars I've seen that develop a rod knock actually have some damage/wear to the crank. Replacing the rod bearing is a bit of a band-aid that usually doesn't last too terribly long. It might be OK if the crank is in good shape, but I haven't run into the condition of rod knock + crank surface in good shape. You might get 10k miles out of it.. depends on the shape of the crank.


These photos may or may not help you understand the config of the motor:

Numbchux

those do help! thanks!!

I understand that usually a rod knock means crank damage. but because this rig developed it so quickly, and hasn't been run much since, I'm hoping it's just a bearing...if I get the bearings replaced, and it comes back before too long, I'll bring it down to my parents' place where there's a garage and a concrete floor...and swap it out.


according to the haynes manual (no bible...I know), once the front diff is out, the pan can be dropped pretty easily. even anyway, it would be possible for me to lift it a bit, but a huge pain in my situation to pull the motor completely.


any idea if the main bearings can be removed? I don't want to go to all this trouble, and only replace the rod bearings...

dcg9381

I think you can get the pan out by removing the front diff... I think that's a pain, however.. I've never done it on IFS.

Main bearings (top side) can't be removed without pulling the transmission, front cover, timing chain - pretty serious motor disassembly.

fthertime666

Are you sure he didnt damage the knock sensor or wire to it? They are in the same location as the oil filter. The oil filter can be a pain to change if you are not well prepared.

Numbchux

no, I'm not sure....but that wouldn't cause a knock...would it?

ovrrdrive

The front diff will definitely have to come out to do this kind of work in the truck.

I have a 3"BL on my truck and had to jack the motor all the way up until it hit the body to pull my pan. Without the BL I never would have gotten it out. If I were you I'd either drop the diff or go ahead and pull the motor.


As for the type of work you are wanting to do, just how long do you want this truck to run after you do it?

6 months?

6 years?

Putting a band aid on the problem like that probably won't give it an extreme amount of longevity...

Numbchux

I understand that this may only be a band-aid. I may be new to toyotas, but not to the internal combustion engine....

a band-aid is the only prayer this thing has at running in the next 6-months or more.

so spare me the lecture. I just wanted to know if the main bearings could be done with the motor in the truck. and pretty much got my answer.

fthertime666

It could cause a knock. When the knock sensor senses a knock (from preignition) it should retard the timing to prevent this. If its fubar then it cant
do its job. I believe its pretty important on the 22rte because of the forced
induction. Have you tried running high octane fuel thru it? One of you turbo
guys chime in if I am mistaken. Im still learning myself.

Numbchux

hmmm...interesting. I'll check into that. I have not tried fuel, I just bought the truck and it came with a full tank...I'm not even sure what octane is in it or how old it is.....I believe a call to the PO is in order.

thanks for the ideas, though!!!

dcg9381

This has nothing to do with a rod knock...
Rod knock != detonation. (rod knock is not equal to detonation)

If the knock sensor is disconnected, I believe the ECU will retard timing all the time.

fthertime666

preignition=detonation... basically the fuel is igniting too soon, ie before TDC
This happens when... a. glowing spot in combustion chamber ignites fuel...or
b. fuel spontaneously combusts because of heat from compression (like a diesel)

ovrrdrive

So, I try to help and offer advice and you act like a damned smartass?!?

Wow, that's just great...

Oh and please point out my lecture... I must have missed it.

Numbchux

I appreciate the advice. but I already said that despite the chance of this only being a temporary fix. it's pretty much my only option at this stage. I say it was a lecture, because you brought up things I had already addressed, and options that, well, aren't.

if you've got something new and helpful, great. if you want to send me the cash to build a garage and buy an engine hoist, awesome. but you have done neither..



so, I took a quick look on my way out today, and it appears that the knock sensor is connected (right under the oil filter right?). the truck doesn't have A/C [anymore], so getting to/seeing that side of the motor is pretty easy.

also, if there was a problem with the sensor, wouldn't it throw a CEL? the couple times that I have started the truck, the light did not come on.

Numbchux

bump...