loud squeal from engine area when ICE speeds up above idle; noise when car stopped in Park or moving

My 2004 Prius makes a loud, consistent SQUEALING NOISE from the engine compartment, only when I increase the ICE RPMs a little by stepping on and holding down the gas pedal. Car is in Park and not moving (it also happens when car is driving, and ICE revs above idle). It sounds like either something rubbing, a bad bearing, or a vacuum leak. I looked everywhere. I removed the serpentine belt and the noise still happened when the ICE is sped up, so it's not an idler bearing, the waterpump, the belt, or anything driven by the belt. I changed the engine oil. The transaxle oil looks dark red but clear. Someone said it may be the MG1 or MG2 bearings. Others say vacuum leak. It is really loud and sounds like it's from everywhere -- engine and transaxle and electric motor and inverter. It does not happen when the ICE is off, or idling. Any suggestions would be great.

 

Re: loud squeal from engine area when ICE speeds up above idle; noise when car stopped in Park or mo

thanks for everyone's replies. I drove the car today, paying more attention to the noise. It does NOT happen in stealth mode. It does not happen when the ICE idling. It DOES NOT seem to happen when the ICE is increasing from an idle speed (such as when I floor the pedal to accelerate the car) but it DOES happen when the ICE is HOLDING AT A HIGHER RPM or SLOWING DOWN IT'S SPEED. It is a high pitched squeal. I am starting to think it's a vacuum leak from the engine or some vacuum device, rather than a bad bearing. For the most part, while I'm cruising on the highway, I don't hear it. I hear it most when I'm driving around town, and the noise happens when the ICE is slowing down from a faster speed. I hear it when I'm in Park and I step on the gas pedal to speed up the ICE. The noise will continue constantly when I hold the gas pedal half way down to keep the ICE spinning at above idle. Anyone know what to look for that only leaks vacuum when the ICE is above idle or slowing down? I may try tightening the intake manifold and throttle body bolts tomorrow. I can't find any loose vacuum lines, but there are so many.

 

Re: loud squeal from engine area when ICE speeds up above idle; noise when car stopped in Park or mo

Anyone have the vacuum diagram for the engine compartment?

 

Re: loud squeal from engine area when ICE speeds up above idle; noise when car stopped in Park or mo

Forgot to say, car has 19k miles (2004 Prius), and was in a front end accident. I replaced the hood, fenders, inverter, inverter pump, left front brake line, brake fluid reservoir, radiator, radiator fans, air bags, seatbelts. I bought it after the accident, and don't know if the seller replaced other things. Also, what does fresh ATF-WS look like? My fluid is dark red, and non transparent. I put some into a plastic bottle and you can only see light through it if you slosh it around inside the bottle so that only a thin layer is on the bottle. I am wondering if worn trans fluid can cause the noise, but I'd like someone to tell me this noise has nothing to do with the transaxle (based on it happening when car is stopped).

 

Re: loud squeal from engine area when ICE speeds up above idle; noise when car stopped in Park or mo

Loud Squeal Problem Solved - just wanted to close this issue in case someone later on has a similar problem. The loud squeal from the ICE area was caused by tiny cracks in the intake manifold mounting flange, which were caused by the front end accident which pushed the radiator fan into the Throttle body, cracking only the Throttle position motor casing. Enough force to crack the intake manifold flange at 2 of the mounting bolts, which allowed vacuum to escape at the flange/cylinder head interface while the ICE was running only at certain speeds and conditions (highest vacuum level, I guess). Thanks for everyone's help, advice. Special thanks to Patrick Wong.

 

Re: loud squeal from engine area when ICE speeds up above idle; noise when car stopped in Park or mo

Hi Patrick, thanks for the inquiry. I took some photos of the intake manifold overall, just to document what things looked like so I can refer to photos during reassy. I didn't take any close up photos of the cracks in the intake manifold, because they were barely perceptible and my cell phone camera does not take good macro photos. Basically, the front end accident applied a downward force against the intake manifold, which stressed the manifold mounting flanges near the bolts. There were microcracks in the flanges between the bolts, not through any intake runners. But because the cracks went all the way through the flange, the bolts no longer applied uniform clamping pressure across the flange between bolts. Result was air leaking loudly into runners under certain engine loading conditions - drove me nuts to find this. I used silicone sealant on both sides of the intake gasket (cleaned all head, gasket and manifold surfaces first) and larger washers under the intake bolts to distribute the clamping force better; problem solved. The throttle body was also damaged during the accident; I bought a used one from car-parts.com for about $50. The prices from carparts.com are great but sometimes you get junky parts.

 

Re: loud squeal from engine area when ICE speeds up above idle; noise when car stopped in Park or mo

I got most of the parts to repair my Prius from www.car-parts.com really cheaply. The used throttle body was about $50. For the intake manifold, I simply used a 1/8-inch thick washer under each mounting flange bolt, near the cracks, as the cracks were not conducive to the intake runners; they were just in the flanges which caused loss of clamping pressure at the intake gasket. Works like a charm. I took some photos but can't see the cracks in them, sorry.