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Discussion Starter #1 (Edited)
I just bought an 04 Tacoma PreRunner V6 XtraCab with 109k a little over a week ago, and it has developed a nasty noise. I did a search, but could not come up with anything.

Basically, the engine makes more of a thumping noise when it's under load. If I start the truck up and idle it in park, it cannot be heard. If I put the truck in gear, it can be heard sometimes. If I put the truck in gear and turn the a/c on, it's VERY noticeable. It's not a rapping sound....more like a thump. Sounds like it may be coming from the front of the engine, around the timing cover or fan clutch. I used a stethoscope all over the thing to see if I could narrow it down. It resonated all over and could be heard when I placed the stethoscope on the oil pan and even on the intake. I had a mechanic listen to it at the oil change place today and he thought it sounded like a timing belt tensioner, which is a possibility. The noise seems to be inconsistent but it does match the RPMs if I rev the motor. When I put the stethoscope on the compressor it was really loud also, but b/c it still makes the noise when the a/c is off; I've ruled that out.

I put the recommended 5w30 oil in it, and it started doing this a day or 2 ago before I got the oil changed. I'm hoping this isn't a rod knock due to lack of maintenance or a wobbly harmonic balancer. I didn't notice any wobble.

Again, if it idles in park, it's quiet. Please tell me I don't have an $11k paperweight outside.
 

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Make sure the crank pulley key slot is lined up with key and bolt is tight. I have seen this happen. If the water pump has leaked at one time the old coolant can seize-up the pivot bolt on T-belt tensioner pulley.
 

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Discussion Starter #4
I was going to remove the accessory belts and check it today, but whoever last put that skid plate on torqued the bolts on so tight, I was boogering the heads up even using my large ratchet. I threw my tools down and just took it in to the dealer. They also think it's either the timing belt tensioner or fan clutch; needs a timing belt anyway (109k). $300 for the V6 timing belt. They are comparable to what the independent shops quoted me anyway, so I left it with them.
 

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Discussion Starter #6
They're putting it back together at the shop as we speak. The water pump was leaking badly, ugh, so now with t-belt service and water pump I'm about at $800. Then he tells me that thumping is my #1 bearing! Oh great! He said the master tech said something about this happening if the accessory belts are way overtorqued (not sure why b/c I didn't think you had to remove the crank bolt to change the belts, only loosen the tensioner bolt). Anyway, the master tech thinks it will be fine once he puts it back together and properly torques everything. What bothers me is the fact that if the bearing is making noise and banging around, isn't it scoring the crank, which in turn toasts the motor? He said with 109k I may need to run a little thicker oil in it anyway.

I really hope I don't have a truck with a trashed motor. I've had the thing 12 days! They are supposed to call me back shortly and let me know if the noise goes away. I hope so. I owe $7500 on an $11k truck. If the motor is blown; I have no idea what I'm going to do.

This is why I paid extra to take it to Toyota. If some jack leg mechanic got in there and overtorqued something and messed it up, then I don't want to take it to just any independent shop. I'm hoping I come out ok on this one.
 

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Discussion Starter #7
Well he called again and said now they have it back together, but it's still making noise! The "master tech" now says I have a bent pulley which needs to be replaced to see if it goes away. He just now sees this?

Wait back up...I brought this truck in to diangose a noise-was told it sounded like a t-belt tensioner; so in their great service drive diagnosis they go for the timing belt service; while in there, the water pump is leaking so they fix that. Now its back together with the belts torqued properly, and it's still making noise. They said if the puelly doesn't fix it, it's in the bottom end. Now wait, do they honestly think I'm paying them $1300 for all these parts they threw at it that did not correctly fix the problem? No sir. I used to write service; the shop eats that crap. So if this pulley doesn't fix it and I have a shot engine, there's going to be some hell breaking loose there.

Not to mention, if my motor is shot. What am I going to do with it? I owe $7500, it's worth about $11k. Put thicker oil in it and trade it? I should have never bought this truck. Apparently my problem is unique since no one else has chimed in saying it happened to them.
 

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I just checked out a used 2002 with 78K, did the same thing. No load idle, sounds OK.
Turn the AC on and put it in Drive, and there's a thump at engine RPM that I can feel in the gearshift.
In Neutral with AC, it's slight, but turning the steering against the stops makes it come back.
If it were just the accessories, then putting the trans in drive should not have made much difference.

Needless to say, I passed on that truck. They wanted $10.9K for it. Otherwise it was in perfect condition.
I'm sure that's why it was on the lot, the original owner dumped it when it started making that noise.
I still see the truck listed, been over a week now, no buyers.
 

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Well he called again and said now they have it back together, but it's still making noise! The "master tech" now says I have a bent pulley which needs to be replaced to see if it goes away. He just now sees this?

<...snip...>
Did you get any closure on this? What was the actual cause of the noise and how did the dealership respond?
 

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Discussion Starter #10 (Edited)
Did you get any closure on this? What was the actual cause of the noise and how did the dealership respond?
I picked the truck up today from the dealer. They tell me that someone overtightened the belts and put stress on the crank; now the crank is hitting the bearings. Basically said I need a motor. They pulled the pan and 1 or 2 bearings to show me...but honestly those bearings look really good for 109k. They only pulled the rod bearings; not the main...not sure why they didn't both for all 6. Take a look









I wasn't confident in this answer. I told them to put it back together and let's discuss this $1080 repair bill for a bunch of unnecessary crap put on a "bad" motor. After a lengthy and turned heated discussion with the service advisor, fixed ops mgr., and the 2 techs that looked at my car; he finally credited back $400 of the bill. My thoughts were "who sells and puts routine maintenance items on a car when I brought it in to diagnose a noise/problem?". They argued that they had to "try this" or "try that" to see if it fixed it (throwing parts at it).

I took the truck to a shadetree mechanic that does work on the side. He said it sounds like nothing and those bearings in the pics looked good. He said just drive the thing; maybe it's the a/c but he didn't know. I actually heard the noise while it was idling in park today. I asked if I should run oil thicker than 5W-30 anyway with that many miles and he said he probably would--not super thick but not 5W-30. He said it sounds rotational and that some of these engines just make noise. His buddy had a 3.4 4Runner that made all kinds of noise and he sold it with 190k running fine.

I dunno...I guess I'll drive it until it blows up. The seller said he would trade me out of it if there was an issue. Not sure what to do. I like the truck but I still owe $7500 on an $11300 truck....but I don't want to drive it if it's a ticking time bomb. I don't know if I like the "just drive it" theory either.

Any ideas? I don't see how a rubber belt can put so much stress on a steel crank to screw it up. I think the dealer has a bunch of idiots working there. Who knows---I Googled "Toyota 3.4 noise in gear" and came up with a few others that had the same issue with no resolution.
 

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I've never heard of a tight belt putting pressure on a rod bearing... Is it the rod bearing or the front main bearing that they suspect?

Now that you've got it apart this far, put it back together with some new bearings. Make an effort to get a new front main bearing in there; if any are vulnerable to over tightened belts then that's the one I would suspect. Bearings are free compared to the labor to take the engine apart, and if it's a bad bearing that will fix the noise, assuming the crank isn't too bad. You can check the bearing clearance using a plastigage. Your crank pins won't be perfectly round after that many miles, so get some calipers and try your best to measure with the plastigage at the smallest point (smallest diameter), that's where your largest clearance will be. If the clearance is bigger than the spec allows then that might indicate the source of your noise. Measure the front main bearing too, that's the only one I could imagine would be hurt by overly tight belts:

http://www.ehow.com/how_2142943_use-plastigage-measure-clearances.html

I'll bet your shop didn't use plastigage to check, or a torque wrench putting it together did they? Torque is critical on all of these bearings. That said, you must find the cause of the problem or it will reoccur. If it really is overly tight belts then that's an easy one to fix. Another cause could be lack of lubrication. Typical causes might be long oil change interval, clogged oil filter (no-name filter, not changed on schedule, etc..), wrong or cheap oil, a lot of time at high RPM (loan your truck to anyone recently?), or maybe an oil pump issue. You don't use a quickie-lube place to change your oil do you? They are notorious for not changing filters or getting the oil level right (too full can be very bad too because the oil will foam up)...

In the perfect world you rebuild or use a new long block. In the real world, unless you're rich, you put new bearings in it and see what the result is, and do your best to find and fix the cause. If they're telling you to get a long block anyway then you've got nothing to loose by replacing the bearings and seeing how that goes. I would take it somewhere else to have the work done though. I've got the official Toyota mechanics manual for this truck (available from your Toyota dealer, it comes in a couple volumes), I'll try to get some time to scan the pages that discuss the rod bearings and post it here for you. That manual is spectacular, I highly recommend picking one up if you do your own work.

In regards to oil; I've got a 1999 3.4L that I've run on Mobile synthetic 5-30 since I bought it new, oil changed at 4k miles using Toyota OEM oil filters. Now over 145k miles and lots of towing a boat, trailers and hauling motorcycles and the engine is still fine, so I don't think 5-30 oil is the problem at all. Of course it knows I'm typing this so it will probably blow up on the way home from work today. ;)
 

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Discussion Starter #12 (Edited)
Thanks for the advice. The shop didn't mention main bearings, only pulled 1 or 2 rod bearing caps to show me that minimal wear, which I thought wasn't bad. At that point, they weren't going to go further unless I kept throwing $ at it. I had a $1080 repair bill for a t-belt, water pump, fan clutch and pulley assembly (which were bent). I still had a noise and those bearings looked ok to me. From then on, I didn't believe or trust a thing they said. I had them put the truck back together.

Now I have this other guy that says, don't worry about it, drive it...and the dealer saying I have a wobbly crank. This is frustrating. I may wind up keeping it and just taking a risk driving it. I'm sick of dealing with buying/selling cars and dealing with repairs right now. Maybe I'll wind up trading it anyway.

They told me I can't just replace the bearings because the crank would probably destroy those too. So I say, "the crank is bent then?" and they say no. By then I just said "huh? ok forget it, put it back together and call me when it's done".
 

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I don't see how you bend a pulley without being in some sort of wreck.
Now it's possible the rubber in the harmonic balancer is breaking down and
the thing is off-center.. Possible. Since they've already loosened the crank bolt, you could replace it without too much trouble. While you're are it , might as well get a runout dial and see of the crack is bent or has lateral play.

I ran 5W20 Mobil1 in my truck, the pistons started slapping and when I drained the oil, it had the look of fine metal flake paint. I switched to Mobil-1 10W40 for older vehicles, it's quieted up a bit, but still rattles at high RPM with no load. It's been 5Kmi since then, it still runs good, but I am looking for a new truck.
 

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Discussion Starter #14
I like this truck but man, what a pain in the ass. It's worth around 11 grand and I owe 7500 on it. I just don't want to make payments on a truck with an engine that may be screwed. It runs great around town and on the interstate and the noise, of course, is only heard at idle. I'm sure this truck will probably run another 100k like this; just noisy.

I feel like trading it in but I'll just wind up in a more expensive vehicle with a higher payment. I already have a project car; this was intended to be a reliable DD. I will find a shadetree mechanic that will look at it/fix it cheap if it's not major; otherwise I may just trade it.
 

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Starman has an excellent point, it could be as simple as the harmonic balancer. Those things do go bad, and they can make cluckety noises when they go bad. That's a lot easier than replacing main bearings.

If you only hear it at idle then I wouldn't be surprised if it was something other than a main or rod bearing. If you take all the rock guards off the bottom of the truck, start it up and crawl down there can you get any idea for what general area the noise originates?
 

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Discussion Starter #16
Got another mechanic to look at it. Right off the bat he said, "yep, that's a bad main bearing; has a different sound than a rod bearing". Well I called the guy I bought it from and he said he'd trade me out of it into something else. We're both concerned about how to get rid of this thing now. I'm sure my $4200 down payment is up in smoke. I owe $7500 on this $11k truck so I'll be lucky to get payoff I'm sure.

I might just trade down to a $3k Corolla or Civic for now. I just want out of this thing at this point.
 

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Put another main bearing in and drive it a while! If it really went south due to overly tight belts then that's a super easy fix and you might get years and years of good service. :)
 

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You can get a short block for about $1k, installation might run $2k.
You've got all new parts on the front and if the valves weren't clicking, the heads are OK.
 

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Discussion Starter #19
It will need probably new main bearings, thrust washers, and possibly a crank. Forget it! The dealer is going to trade me out of it if I want. He said if it were him, he wouldn't be bothered with it (yeah right). I'm going to trade it for a 4 Runner. He has an 05 but there's a hairline split in the dash that bothers me. I'll see if he'll find me something at the auction and I'll get a powertrain warranty on it this time around. Drove the 05 V8 he had and loved it except for the cracked dash.
 

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Discussion Starter #20
Well i got fed up with the stupid thing, so I traded it in today for an 07 4 Runner SR5 4.0 V6 (this one has a timing chain rather than a belt at least).

My cousin is F&I at the dealer, got the truck for about $800 over what they had in it. I took a hit on my truck b/c it had a knocking engine but I still got 9 grand for it. (yes I told my cousin b/c he's family and wanted to be up front about it. He still got me a good deal). Got a 3/36 bumper to bumper extended warranty at my cousin's cost and gap insurance at dealer cost also. The dealer also offered a lifetime engine only warranty with purchase--so no engine problem worries this time.

Maybe I just got a bad truck--I don't know. I'm happy with this other vehicle though.
 
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