Truck:
1994 F150 4X4
4.9L (300 6cyl)
Manual
no A/C
170K Miles


I have a squeal that started a number of years ago. The squeal would only happen when it was below 20F. The occurrence of this noise has recently increased to all the time after the engine has warmed up.

The noise only happens when the engine is not under a load. As soon as a load is applied, the noise goes away. The pitch of the squeal does not change in relation to the RPM of the engine.

I have replaced the belt, idler pulley and the alternator.

My best guess is that it is some sort of vacuum leak or the smog pump.

At this point I might just let the squeal happen until the offender fails thus confirming what the problem truly is. But in effort to save my hearing, has anyone else had this problem and what was your solution?

Thanks
ER

 

Get a 3' section of garden hose, or a mechanic's stethoscope with the probe removed, and pinpoint the noise.

 

Thanks Steve, I will try it.

 

I I bought a stethoscope and probed all the parts associated with the belt. The squeal was not to be heard. I narrowed the location of the squeal to the intake manifold. I did not see any cracks. I then removed vacuum lines one by one to see if the squeal would stop, it did not.

Any ideas?


ER

 

Did you plug the vacuum lines when you removed them? How do your brakes feel when driving? I'm guessing brake vacuum booster.

 

When I took a vacuum line off, I would plug each end independently. No change on the squeal.

Brakes work fine.

 

Squeal if you take the belt off?

Adrianspeeder

 

Did you remove the probe & use the open tube of the stethoscope?