Yesterday, when I started the Tundra, it made a squealing sound for about 8 seconds. It sounded like it was coming from under the truck as opposed to the engine. The squealing gradually faded and things went back to normal. It scared me in fact. Then I started thinking it sounded like something that was not getting oil immediately.
Thanks for your replies. The thing is that the sound came from under the truck. Tranny area if I had to guess. Belt noises would come from the engine bay.
I'll see if it does it again. The cold has something to do with it for sure.
My 2000 tundra a made a squeal sound ealry in the mornings it was the belt a new one would fix that. Look at your belt for any were depending on miles on your truck might be time for a new one !
I remember long time ago in 2003 my belt was making a squealing noise.. then I took it to my cousin who is a mechanic. He diagnosed it as an lubriciated bearing in a pulley and fixed that. All disappeared when that pulley's bearing was lubed.
If it is that cold, plug your truck in every night and see if that makes a difference. I plug mine in up here in Alaska and I dont even get the cold knock on startup. Itll be -20 and she purrs like a kitten....
I think what we are all hearing on these cold start ups is the secondary air injection system compressing air to send into the exhaust for emissions on start up. Even on a warm day if you listen you can hear the high pitched squeal this system makes until it kicks off. For some reason in really cold weather the air pumps are really damn noisy.
The knocking sound is most likely also thanks to the emissions related programming in the VVT which phases the exhaust cam to open sooner and stay open longer on cold starts to allow more heat to reach the catalytic converters to heat them up. Until the emissions system registers adequate temp the exhaust valve timing will be defaulted to this. What you are hearing is the exhaust valves opening while a little bit of combustion is still taking place. Sounds kind of like a diesel until the cats are sufficiently warmed up. On a warm day it takes virtually no time at all for the cats to warm up enough so you would never notice it.
Coaldragger, sounds like a very viable option to what's happening but I know someone with a Ford that sounded like a diesel. They had the engine rebuilt under warranty and it purrs like a kitten at 5*, as it was tonight. My truck sounded like a brand new 6.4 diesel when I started mine up.
Oh yeah, the Ford has VVT as well as cats. I just wonder why Toyota couldn't get us an engine that sounds like a diesel.
Honestly, I'm not joking around - mine REALLY sounds like a 6.4. I know that b/c I test drove a 6.4 three weeks ago.
-rockstate
What model of Ford truck has variable valve timing on both intake and exhaust valves? None that I know of. As far as I know the valve timing can only be adjusted independently on a DOHC motor. The Ford SOHC engine will not have the ability to have as wide a range of adjustment, and most likely can't operate with the exhaust valves opening as early as they do on a 5.7L Toyota with dual VVT-i and dual overhead cams. If this were attempted on the Ford with only the single overhead cam the engine would probably run very rough, if at all, because the intake valves would be completey out of synch with the ignition and fuel injection.
Keep in mind Toyota is the first manufacturer to use dual variable valve timing on a truck motor, but the technology has been used by other makers to boost engine performance and flexibility. BMW, Porsche, Lexus (Toyota) all use it for those reasons and all of those are DOHC motors instead of SOHC motors for a reason. If the wide range of adjustment could be accomplished with only one camshaft per cylinder bank those companies would be using SOHC engines. Too bad a SOHC cam layout can't accomplish those things because having fewer moving parts would reduce costs, reduce complexity, reduce parasitic power losses due to friction,.... well you get the picture.
Last edited by Coal Dragger; 12-22-2008 at 03:26 AM.
I managed to record the sound this morning. It didn't last as long as the other day, but you'll hear what I'm talking about. It doesn't sound like a belt to me, but more mechanical.
Squeal at startup
Re: Squeal at startup
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