Hi Gang,

I have a 99 4Runner Ltd w. 75,000 km on it. I live near Vancouver, so the tempature in the late fall mornings has been +5 to -3 C.

On start from cold, I have noticed a "whistling" noise from the front end on light acceleration. No sound during cruise. It goes away after a few minutes.

Anyone know why? And thanks.....

Bruce

 

I know my 99 makes a bit of a roar for about the first minute when starting up cold. It then goes away. You may be hearing a whistle from the truck's own systematic process of warming up. I wouldn't worry too much about it, probably just something in the intake making it whistle. You might check your intake mani gaskets and TB gasket if you're hearing it at high rpm after it's warmed up. Otherwise, doesn't sound like too much of a problem. Of course, the coldest start i've had mine in is about 30 degrees F.

 

I'd put my money on a loose or slipping belt. When they are that cold, they don't get as much grip as usual on the pulley. Once the engine heats them up, then grip like usual and don't "squeak". If you want to find out, try spraying some belt dressing on them and see if the whistle goes away. You can buy belt dressing at most auto parts stores or you can even try some hairspray.

 

Thanks to you both for the ideas.

B