CMUpike

Aiight, now i'm a little confused, and most likely, one of you techies can make this all make sense to me.

i've had that strange clanking/knocking problem as a few others on this site have. and as my mechanic diagnosed... it's most likely a crankshaft problem or main bearing problem.
A few others noted that it may be valve flutter? or something like that, but my mechanic says judging by the way it sounds, and by where the sound is coming from, it's probably not a valve problem.

so, just for kicks, i switched to a higher octane fuel today, and the noise went away for a while. also, a while back, when i switched to a heavier oil (10W30) the noise also went away for awhile.

so if this IS a crankshaft problem, why would switching the oil or fuel make it go away for a little bit at all? it doesn't make sense to me, so i figured maybe some of you smart ones out there can help me understand.

my other question is, i read on a recent post that to check to see if the crankshaft is wearing away part of the engine, you can take off some bottom part of the longblock to check for any wear and tear. however my mechanic said that in order to really see what kind of problem it is, he'd have to disassemble the entire engine. i trust the guy, as he's a family friend, but could he be wrong about this?

thanks in advance!

its2slo

you would have to remove the oil pan, and then you could check the bearing caps for end play with a feeler guage. or you could take the bearig caps off and inspect the bearings.

i would run 50 or even 60 weight oil and see if that quiets it down, you could get many more miles that way. 10/30 wont be enough and you could spin a bearing and damage the crank beyond repair. eventually it will need a rebuild, i think thats what your mechanic is getting at. but i dont know your miles, etc.

MTL_4runner

Could be from preignition or detonation?

Try using some very high octane gas like 93+ for a couple of tanks and add some octane booster to see if it quiets down. I can't hear the engine myself but I would check everything else before I tore into an engine Like he is talking about.

If you really do need a motor, look into a used one rather than a rebuild.....it will save you big $$$$$$$$
If mine goes (knock on wood) I will replace it with a later model 1999-2002 version....make sure to get everything from airbox to exhaust.

CMUpike

thanks for the help guys.

right now, i have a little over 110K miles. this noise has been occurring since christmas time.

the noise sounds like a ticking noise, sortof like if there were something stuck in one of the belts. when i switch gears (like from drive to park or reverse) the noise gets much faster and louder for a brief second. i wish i had faster internet connection, i'd take a video of it, and post it somewhere.

i'm just confused why those simple changes i did (oil and fuel) would have reduced the sound at all. even if it was temporary.

Babypig

could even be dirty injectors.

MTL_4runner

The ticking could be the valves out of adjustment.
The lifters are solid so you would need a feeler gage to check em.
You really should get a mechanics stethscope and see if you can isolate exactly where the noise is coming from......then look into the components in that area.

its2slo

well your miles seem low to lose bearings, did anything happen? a mechanic can pretty easilly diagnose a knocking rod, and when exactly it is occuring could tell him if it is a main bearing. if this guy is a reliable mechanic then it seems you could trust his judgement. the reason you need thicker oil is to compensate for the larger clearence between the journal and bearing, the thin stuff cant keep it lubricated anymore. another way to look at it is more cushion on the throw...the point is didnt he reccomend a thicker oil?

CMUpike

well, during christmas time, when he took a look at it, he put her up on the lift, and used a stethescope to locate the sound to above the oilpan. which he concluded that it was most likely a main bearing problem, or a warped crankshaft??? he stated then, that i should throw in a really heavy oil, and try to sell the truck immediately before the sound got worse (at that time, the sound only came if i switched gears (park/reverse/drive))

being the kind soul that i am i didn't have the heart to cheat someone into buying a "broken" 4runner. not only would that be bad business for the reputation of the truck itself, but i don't think i could bring myself to do that.

his next options were, that i should drive it until the sound gets really bad, then take it in. he can disassemble the whole thing, and send it to his friend's engine rebuilding shop. where they can clean everything out and maybe even do a port and polish type deal while they're at it. then they can fix the broken parts, and he can put everything back in.

he suggested this, because a *new* engine would be too expensive. he's not a big fan of swapping out salvaged engines, because they could be unreliable. and since this engine would be rebuilt and cleaned out, it would run "better than a new engine" according to him. he stated that this whole job would cost around 3500 give or take a few, and depending on what exact damage has been done.

he is a very reliable mechanic. he's friends with my dad, and has worked on all of our toyota cars for the past 10 years or so.

my dad has a 96 SR5 which he's lookin' to get rid of, if i knew what i was doing and had the tools, i'd swap his out. but it doesn't look like that's happening anytime soon.

oh well, thanks everyone for your input. i think i will switch to a heavier oil, and maybe try an even higher octane fuel. is there any specific oil that i should use? synthetic? i'm using 10W30. i really dont' know what the numbers mean, so i assume maybe 20W30 would be heavier? how heavy can i go?

Lucky

Try some 20W 50 oil, about as thick as you can get, maybe add in some STP oil treatment for good measure.

I've even heard of unscrupulous people putting in EP90 gearbox oil into the engine oil. You wouldn't want to run too long like that but EP90 is pretty gloopy when warm and really quietens down an engine.

From the ticking noise it could be small ends, piston slap, a broken ring, an oil pump problem. Not all of these would improve with thicker oil (thicker oil will normally quieten valve train and cranckshaft noise but not piston slap or ring problems.

I would agree with his point about rebuilt being better than new, if the basic structure of the engine is good, no cracks etc, you can do a lot of things to make a reconditioned engine better. Port and balance it, blueprint it, use the best quality aftermarket parts etc.

Factory engines are built to a cost and time constraint. When you do it yourself or get a reliable mechanic to do it, they can spend the time to use the best parts (some aftermarket parts are much better than factory) and also put some performance parts on it.

Good luck, hope it's not too expensive. I've just had to replace a cracked head on my Diesel Surf, over $1000 to do it and 16 hours of my time. Mind you I know the condition of the engine better now so there is a good bit of peace of mind now.

Cheers

its2slo

i think it would be tough to better toyota's quality control on engines they build. i wouldnt rule out atleast looking around for a used one if you are interested in saving money, plus time is on your side.

you can get a good low mileage 3.4 for around $1500 complete, with all accessories, injectors..everything! then its just what you pay to put it in.

i was fortunate enough to find one with only 5,070 miles on it locally, then i put it in myself. it was crazy to swap motors on a toyota with only 140k, but i had problems, took the cheapest solution, and wouldnt trade my "new" truck for anything!!

someday i might just find the time to rebuild my original 3.4, but that will be years from now when i win the lottery and can afford an ati pro charger and all the works