skybox

i'm new to toyotas but i have been using this forum to learn about my new truck. its a 92 sr5. anyway the motor was rebuilt about 30,000 miles ago before i owned the truck so i'm not sure what parts were replaced during the rebuild.
The problem i have is after the truck has warmed up to normal operating temp, and driven around the block a few times i can start to hear a nasty rattle when i give it some gas. it doesn't matter weather i'm in drive, park, neutral. the rattle seems to go away as soon as the engine stops accelerating or revving up. i've gone over it with a stethascope but can't really isolate exactly where its coming from, but generally its coming from somewhere around the power steering or AC compressor. a mechanic friend thinks that it might have something to do with the timing belt tensioner which is close to that area as well, but he doesn't really know toyotas that well.
Does anyone have a past experience that is similar or any ideas? i read a couple threads on engine noises that turned out to be a bad rod bearing.
I don't think it is detonation, i checked my timing and actually needed to advance it a couple degrees to get it where my book says it should be. if it were a rod bearing shouldn't i have been able to really hear it on the oil pan?
Is my timing belt tensioner hydraulic or a spring type? What is the advantage of a hydraulic tensioner vs the spring type? If my tensioner has failed what kind of symptoms should i expect?

thanks guys.

DeathCougar

iTrader: (23)

92 can be either style, depending on what the production date is (assuming no one has ever changed the engine)

Up to 4/92 is spring style, from 5/92 is hydraulic tensioner.

The easiest way to see if its an out accessory is to remove the belts. You will be able to run the truck long enough to determine if its any of those. Rod bearings should be pretty obvious, but you might have to take it to a shop if you don't know what it sounds like.

skybox

hey thanks for the idea, it never occured to me to take belts off the PS and AC.

My friend told me that if it is a rod bearing then i should be able to hear it the loudest on the oil pan because it is the closest thing to the crankshaft. Is that an acurate assumption?

There was a sound recording of a bad rod but i never could get the thing to play on one of the posts in this forum. If anyone can send a link to a bad rod bearing and how to identify it by the sound it makes i'd like to check it out.

skybox

hey thanks for the idea, it never occured to me to take belts off the PS and AC.

My friend told me that if it is a rod bearing then i should be able to hear it the loudest on the oil pan because it is the closest thing to the crankshaft. Is that an acurate assumption?

There was a sound recording of a bad rod but i never could get the thing to play on one of the posts in this forum. If anyone can send a link to a bad rod bearing and how to identify it by the sound it makes i'd like to check it out.

Kiroshu

If you can get a video it would be alot better to tell. Does the sound increase in pitch with RPMS? Or is it constant. Does it matter if the truck is moving down the road or can you hear it parked and reving. Assuming the motor was rebuilt "correctly" 30k ago i would not imagine a rod bearing how ever it is possible... did the motor come with a warranty? If you think its a rob bearing pull the spark plug wires off one at a time and see if the noise goes away. If it does its a rod bearing on that cyl. Possible a pulley on the front is wobbling or messed up. Crank pulley wobbling? Generally tensioners on these trucks don't have that kind of throbbing noises.... Check the oil too how much you got and does it have coolant in the oil...

skybox

i'll try pulling spark plug wire also and listening for a change. The noise is not always present. you can only hear it after a few things have taken place.
1. the engine needs to warm up
2. then throttle needs to be actuated or the truck driven for a few minutes.
3. you can only hear it when you blip the throttle and the engine is revving up. after the engine catches back up to the throttle position i don't hear it anymore.
4. If i produce the sound by revving it up and then let engine idle untouched for a few minutes then try revving engine up again i need to do it a few times before the sound will come back.
5. I can set my park brake and drive around at less than 2000 rpm and hear it constantly, wich makes me think road noise muffles the sound and i don't hear it all the time.
I checked my timing a couple of days ago and needed to advance the timing a couple degrees but the problem was present before i touched timing. I wonder if i should just try retarding the timing back to 0 and see what happens in case its a knock issue. Also i wonder if i may have accidently used the number 5 cylinder instead of the number 1 to check/advance my timing after looking in a haynes manual. I don't know if it would even run? Can anyone confirm?

DeathCougar

iTrader: (23)

Firing order is 1-2-3-4-5-6 I believe, so I don;t think its possible to time it to #5 cylinder

yotabiff

I thought I had a





You might check the top idler/bearing on the timing belt,I thought I had had a rod going but it was the the idler making the noise

xwing777

wrist pin maybe?

skybox

here is the update.
I took the wires off the dist. one at a time to see if the sound would go away. unfortunately i didn't realize that when i laid the wire next to the terminal it was still making contact and arcing across and thus still firing. i realized this after i got to about the fifth cylinder and saw the actual arc happening so went back to number 1 and redid it making sure to keep the wire clear of the terminal on dist. The knocking went away and came back as soon as a replugged it in on the number 1 cylinder. So all i can say is oh crap. now what. Is it really a rod bearing or something else. could it just be a noisy lifter or a valve that isn't adjusted quite right.

What is wrist pin?

keep chiming in with all your advice guys its very helpful. Thanks kiroshu for that trouble shooting technique. I never would have known to do it.

xwing777

A wrist pin is what connects the rod to the piston. If it is this it can run for years or go the next day.

BTW. This page may help you finding out exactly what it is:
http://remanufactured.com/Engine_Noi...gnosis_101.htm

Kiroshu

Well it could be a wrist pin but its prob a spun rod bearing. I would highly advise you to quit driving it as you don't want to cause any more damage to the crank shaft if it is a spun bearing. Either way its internal. Whats the mileage on that engine? (Xwing777) "IF" it is the wrist pin then yes you could prob run it for a long time and have not issue for while until it possibley seized to the connecting rod and broke it(not likely but possible). But if its a rod bearing which it prob is quit driving unless you just really really have too.... but not a good idea... You may want to look for another truck or rebuild the motor or get another one...

skybox

at this point i'm thinking of just driving it to see if it gets worse. it has done this since i bought it and previous owner says it has for a long time as well, but its hard to get a good straight answer out of the guy but thats a whole different story. I"m thinking if it lasts and just happens to sound this way when accelerating then thats what i have to deal with and if it just quits on me then i'm thinking of getting a JDM used engine or maybe a rebuild from toyotacarparts.com.

does anyone have a thought on a good rebuild or used engine supplier or someone better than what i've been looking at on the internet?


the motor was rebuilt at around 157,000 miles on the odo or so back in 2000. it now has around 188,000 on the odo. I have the paper work from Jones Automotive Engines our of spokane who did the rebuild and a local shop in missoula installed the engine as well as all the other recommended new parts so this rebuild obviously wasn't very good as it only has around 30,000 miles on it.