Strange sound from engine/ratteling noise

Hello all,
(sorry for the long first post, but want to give out as much info as I can)

I am new here, and have a question that I have never had an answer too. I have 2006 Tacoma Prerunner 4 cyc, 2 WD, 5 Speed Manuel trans, extended cab with about 67,000 +/- miles. (mouthfull there). Here is my question. I have noticed that when I start my truck in the morning (regardless if it is cold outside, or warm) I can hear a rattling noise under my hood. Sounds like like a spring is coming unraveled. It sounds like it is on the driver side, kind of behind the steering wheel. It only happens when the engine is cold I have noticed. I have taken it to the dealership to see if they can duplicate the problem, and of course with all dealerships they say they can not duplicate it or so they say. anyone else here had the same issue, or at least able to pin point where it is coming from? In addition I don't use my A/C at all, and dont hear anything from the cabin air filter either, so I dont think it has to do with that at all.

I am not a mechanic or anything. So, sorry if I dont explain it right.
I have never heard this sound before in any vehicle that I have owned. It only happens when I start the truck, and it is sitting at idle after the initial warm up. It will make the noise. Stop for a sec, then make it agin. I almost want to say it is the big fan that is on the engine block. The best way I can discribe it. For those of you who have ever had or used a badge holder that retracks. You know that when the spring inside breaks, it makes a very distinct unraveling noise. That is the kind of noise I am hearing. I have started the truck, hopped out, and listend to the engine from under the hood, and so has a friend of mine, we can't really hear it. However when I get in the cab you can hear it clear as day.

I also got under the truck to listen to see if the starter is the culprit, and yeeaahh no noise from there. I did try to record the engine with my phone, but the file is not supported. I can try again, and see what happens... After I thought about this for a while, I remeber that the mystery noise does seem to much worse durning the winter, and not as bad during the summer. Also when I was under the truck, I could hear the noise a little bit better from that angle, and seemed like it was coming from the front more. I did have my water pump replaced by the dealership as well last year, cause there was a leak. However that was when i took it in the first time, cause of the sound. I have checked all wires, shrouds/covers, and dont see anything that is loose, or out of place.

I plan on keeping the truck for a while, and to be honest i dont really know much about engines in detail. I understand the basic's ok, but not the detail. So, any help, and suggestions is much appreciated. I am checking things off as I go. Please help....

 

Could be the catalytic converter, I had a similar rattle that was due to stuff coming loose in the cat. It would go away at higher RPM's but was always there at the stop lights.

 

It may very well be that. I hate to ask, but where is the cat at? Also it only appears to happen when starting up the truck in the morning, or at anytime that the truck has had to sit for at least 4 hrs or more. So, when it starts it hit like 1,000 rpm (maybe a little lower) then the rpms come down to normal idle at like 400-600 ish, then at this point is when i hear this sound. I dont hear it after the warm up phase like when driving down the road, or sitting at a stop light. If you tell me where the cat is, I will get under the truck, and listen to it, and see if I hear anything, and get back to you on that. Any other thoughts you can think of??


Thanks.

 

Follow your exhaust towards your engine. You'll see 'em.

 

Ok. So, no dice on the cat's. It appears that I have two for my truck... No noise coming from them that I can tell. Any other thoughts?



Thanks.

 

Skid plate loose?

 

Last time I looked at the skid plate it looked secure, and felt that way as well, but I will check it out anyway to see if that my be it. I also check my heat shields as well that are around the firewall, and above the cat etc. I dont fell anything loos. I wont rule out the heat shield just yet. Just cause I did not hear it the other day, does not mean it wont happen again. In fact I heard the noise this morning when i started my truck, the only bad thing is i was running late for work this morning, and did not have the time to get the camera to record. Which really sucks, cause I was going to record it this morning just to see if it would. I think I will try to take random recordings untill I get the sound (provided I get my lazy butt out of bed on time LOL). The sound in general does not sound like it is low, but more like right behind the steering wheel. Then again the sound may seem like it is higher when sitting in the cab, and it very well may be lower.....


Thanks.

 

I have a similar issue that I have yet to figure out. I have an 06 PreRunner but mine is an automatic V6. On occasion, usually when it is a little cooler outside, when I start it up first thing in the morning there is a knocking type sound behind my dash on the driver side. I am used to the typical tick tick from these engines but this sounds deeper and loud enough to get my attention over the radio. It gets worse with acceleration but only lasts a few minutes each time it does it. Sub'd, hopefully we can figure this out!

 

I hope we can figure it out. The only difference between ours though, is mine is only at idle. When I rev the engine it goes away, but when the rpm's get down to normal idle the sound will come again. Once the truck is moving, and has warmed up I dont hear again. Until the morning when I start it up, or it has been sitting around not in the sun for a few hours.

Thanks.

 

Mine only did it once on the accel. I got the bright idea that maybe it just needed to warm up a bit so I went ahead and pulled out of the driveway and that's where it continuted. I only tried it once as I don't want to damage anything. If our sounds are similar but our engines are different I wonder if there is anything in the engine bay on the driver side that is the same on both trucks? Forgive my ignorance, I haven't looked under the hood on a 4 banger yet.

 

No worries. They should be pretty close I would think. Lets see then. Tell me if you see this. Open the hood, and look where you Master Break/Break fluid reservoir is at. This should be pretty much right behind the steering wheel. Now look along the firewall toward the passanger side or to the left, and you should see two hoses going into the cab, and should be surrounded by rubber grommets to cover the hole. If you see this, then I would say yes they are the same.

Speaking of those two hoses. I wounder if because, they are able to move (due to the bracket that is holding them up) if that is the problem. Thougts???


Thanks.

 

same problem for 2 years now. Search up on this topic. No answers what so ever for me. mine does it even when its warm now, and even while driving. annoys the heck out of me.

 

Well the skid plate is secure, and not moving or anything. So, that is off the list. I am still trying to record this sound, but it has not made the noise. Figures on the times I have the recorder, it makes no sound.... Man.. Any other thoughts though??


Thanks.

 

Same issue with mine, 2006 v6. Is worse when it's cold but does happen from time to time when it's warm as well. Typically only there when you first start the car and goes away as it warms up. Suspected heat shields but never pinpointed it. Searched the forums and it does seem fairly common but no one has come up with a one size fits all solution. Many are fixed by adjusting the air intake where it attaches to the fender/hood area on the passenger side but I never tried that, mine doesn't seem to make the noise from there. Hasn't gotten worse or better but the same... Guessing heat shield or something along that line as my last car had a similar issue on cool mornings where it would make the same type noise but couldn't hear too well in the engine bay, just barely in the cab and under the car but was equally hard to locate. Haven't messed with it for more than 6 months, but sub'd to this thread and figured I'd add my 2 cents

 

ec8,
Well I dont know if it is the heat sheilds or not, but the air intake connection might be it as well, but I am not sure. I do have the sound recorded, but just have not had a chance to upload the audio yet, but I will see about doing that here soon, so that everyone can hear. The other morning when I started the truck I heard the sound in the same usual spot, however it kind of seemed like it went from left to right, then back. So, it might be the heat sheilds, but I am not sure as I dont see any metal shields in the front of the bay. Now at the firewall the shields are cardboard, and not metal so kind of weird. I am also thinking that it might be the windshield wippers too. I had them going the other day when it was raining, and I could swear I heard the noise as they went up, and down. I will try, and see if it is coming from there. It would make sense, because the sound it right behind the steering wheel/ gauge cluster. Have you yourself checked off any possible things over time?


Thanks.

 

If it's a 4 cylinder it may well be the timing chain. They are tensioned by oil pressure so on a cold start it needs a bit of time to tension it up no big deal mine had 248K on it when I sold it still ran fine if it's rattling idling after it's warmed up that's not good. If it's a rattle that only lasts a second or two that would be my guess. If it persists try a lighter weight oil like maybe 10-30 in cold weather.

 

Played with the heat shields and didn't seem to make any difference. They weren't touching any pipes and the material felt non-metal, so may not make much noise even if touching/vibrating. Also messed around a little with the air intake, but doesn't seem loose at all and doesn't seem to make any difference when pressure is put on it from different directions. The wire bracket on the firewall area that holds the tube of wires seemed tight and unmoving/non vibrating, so I really don't know. It doesn't happen much as I'm in Florida and doesn't happen much, probably because it doesn't get cold much, but it does happen on occasion when it's warm. It's never been loud enough to be a real concern/bother and with the dozens of posts on TW about this it seems fairly common to all. The #1 fix seems to be the air intake, but some say it comes back... so clueless, but seems normal enough

 

mainah,
I am using 10-30 for my oil currently, and in fact come think, I have always used that. The noise starts out just after your start the truck. The rpms come down to like 800-1,000 then the noise comes. It will start for a for like 3-4 seconds, then go away. Then it will come back 2 seconds later, then go away. After the truck warms up completely or I drive it goes away, and does not come back. I wonder if changing the timing to one that is a bit small would take care of it?? Thoughts.....?????

ec8,
Yeah it seems to be a common thing, but I would say it is far from normal. Or at least I think so. I say this because, I used to have a 96 Ranger that had 126,000 miles on it, and I never heard this noise from that truck. In fact out of all the trucks I have been in I have never heard this sound at all, except for this truck. So, yeah I dont think it is normal. If it is though, that is pretty crappy of toyota to let this be, and not fix it.

Thanks.

 

Spring coming unsprung sound is your ABS self test. Its not supposed to do it until you start moving though.... so thats strange.

Does it only last for a second?



EDIT I just read a little more.... I'm really not sure dude.

 

KaosTsoc,
Wasn't suggesting it is normal for trucks in general, only that it is very common for our tacomas, based on the number of threads talking about this. It seems to be on both the 4 cylinder and 6 cylinder ones, so being an internal engine issue is fairly ruled out. My wife has the same 6 cylinder engine in her 4runner and I have never heard it there, thus again I don't think it's an internal engine issue, more likely a body/routing/vibration issue of some component between the engine and the body or something like that (air intake box, heat shields, etc). I've accepted it as "common" for our trucks - when it becomes very common it becomes the norm (not saying it should be), but would still love to hear what people find out causes it.