Recently since temperatures have gone up here in oregon I have been experiencing something a little bit of the ordinary. Within 15 minutes of driving in hot weather the engine will start to make a roaring sound while accelerating. It almost sounds like it could be the radiator fan but I'm not all the way sure. When in Neutural if I rev the engine a little the roaring sound rises as the Rpms do. Coolant temp gauge reads fine, oil is fine, everythings seems fine, but when the sound comes on performance decreases dramatically. Anybody have any ideas?

 

Could be the waterpump. The electric fans won't change with rpm. If the bearing is shot it will add load to the engine and that would effect performance. It is driven by the timing belt so change it Asap and put a new belt on if that turns out to be the problem. If the belt hasn't been done recently do the rollers and tensioner also.

Are you leaking any coolant.

When the car is cold open your coolant resevoir you should hear an air rush if not your leaking somewhere.

 

It is called a viscous fan/mechanical fan. It is completely normal. TRUST ME, it is NOT your water pump. Mechanical fans only engage when the engine is warming up and are tied to the engine speed. The faster the engine goes, the faster the fan goes.

 

I agree with the fan clutch diagonostic. It is designed to engage when the motor reaches certain temperature. It most likely is normal, but if you haven't noticed the same symptoms during previous hot weather, I would try replacing the fan clutch; however, it is about $150. Typically, they either work or don't work, and sounds like yours is working.

 

It just sounds so loud to be normal and not to mention the car begins to run like crap when it engages. It did not do this the previous summer, and the only big change that I can think of since then is a timing belt and water pump job along with a thermostat.

 

http://www.youtube.com/watch?v=jwO1KeyJ460


Fan clutches rob a lot of power from the engine causing loss of power. Generally when they fail, they stop working. When mine was failing it made a crunching noise. Maybe yours is bad.

 

There is no doubt that the fan clutch robs power, but it should not make your car run like "crap". You should just feel a slight decrease in performance. You may wanto to try replacing the clutch. Looks like you can get one for less than $100 if you do the install yourself.

 

What year, model and engine do you have?

I assumed you didn't have a mechanical fan (belt driven) and only had electric fans. That's what I have.

If you do, Jeffla and hxgaser are right the clutch could be bad and they are extemely loud if the clutch goes bad and they spin solid.

 

A/C on? Check the A/C Clutch too

 

Update
$60.00 New Fan Clutch
Replaced it myself saved myself $550.00 that a local shop wanted to charge me.
Problem fixed, power is back and no more air plane take off sound from a stop on those really hot days.