My car is a 2006 PT Cruiser, and it has a very loud sound when you drive the car on a speed beyond 120 km/h (70 m/h). this was there since i bought it. Does anyone know what is the reason behind this

probably just the fact that its a relatively cheaply/poorly made vehicle under that retro-styled body. its just a dodge neon with a different body slapped on it. that sound is the inferior engine trying not to die while keeping u up to speed. invest in a good vehicle... like a subaru impreza. still very inexpensive, but a lotttt more fun and a lot better quality. sorry for bashing ur car. i'm sure u like the look of it but... its cheap :/

Watch the RPM's because the higher you go the louder it gets

You don't mentioned which model you own, and what tipe of sound is, and where it comes from. If it has a Turbo engine the sound is caused for 2 reasons and both are normal: 1°. If the sound you mention sounds like a whistle, that is the Turbo doings its job. 2°. If the sound is too loud, it most be turbulence because the aerodynamic, remember that the PT has not a very aerodynamic design, the design is oriented to be retro. If your car has an atmospheric engine (no Turbo) the reason of the sound is just the second one, and is normal too. I have one PT Cruiser Turbo, and at 150km/h sound from engine is loud but nice, an the one that comes fron turbulence is too high.

it could be that your wheel alignment is out or that the CV Boots are in need of replacement

are you confident that the sound is coming from the engine. Reason being, the stock tires on those are not great and speed rating could be coming into play. In other words, some vehicle once you top 120km/h start to hum very loud but all 4 wheels make the same sound which can make it seem that it is an engine noise. do you feel vibration as well?

I'm not agree the PT was recently awarded by JD Power mainly because its overall quality, mechanical quality and functionlaty, it isn't the only award it has it has 10 more international awards, maybe you need to read more information and news before emiting an opinion, you're not impartial, here are some articles and the JD Power comparative table if you dont' believe it: http://www.jdpower.com/autos/ratings/quality-ratings-by-category/compact-multi-activity-vehicle http://www.ptcruizer.com/pt-cruiser/awards.html http://finance.yahoo.com/news/JD-Power-and-Associates-prnews-2924871841.html?x=0&.v=1

Yea I have a 2006 PT I've only had it for a month ,and i found out that the barrens were going out,I had too of the cenzers go out on i it,cruze control,go out and the tires made a loud high pich sound.so have them check out and maybe you'll start to elaminate some of your proublems wiht this crapy unsafe car.