Strange noise @ >3000RPM

[loonatic]

I have recently noticed that the exhaust noise becomes much loader/rougher as I reach 3000RPM and then as the revs drop back down it makes another odd noise kinda like it's blowing ?

It's not easy to describe...you need to hear it really.

Apart from that everything seems to still be fine with no loss of power.

I started noticing it shortly after I changed the cam belt.

Any ideas ?

Cheers, Lee

[STMO123]

Vibration? Exhaust baffles on their way out?

If you need to replace use genuine Vx

[Gwilym]

Can't really give you any sensible advice but welcome to the forum.

[STMO123]

Cant really see how it could have anything to do with belt change, except may have changed resonance a bit. Exhaust was prob on its way anyway.

[Markjay]

Hi and welcome.

Model year, engine type, mileage? Any modifications (not typical on Omegas...)?

Did you check for stored fault codes?

Who/where did the camblet change, was the tensioner changed as well, and which make of kit was used (e.g. original Vauxhall).

My first thought would be as above i.e. the exhaust is blowing and not related to cambelt change though.

[TheBoy]

was a proper cam locking/timing kit used when cambelt done? If not, do it again with right equipment immediately!

As said, were tensioners done as well?

[loonatic]

Firstly...thanks for all the replys

Right...it's a W/2000 3.0 MV6 estate with just under 60k on the clock.

I only bought it 2 months ago and it had a full service shortly after I bought it.

The cam belt was changed by my local friendly mechanic...can check about what he used...what difference does it make ?

I was thinking exhaust and had a quick look at the tail end and there does seem to be some corrosion where the tail pipes meet the backbox...can't really see the rest.

If a new exhaust is in order...what sort of price are they ? and what about aftermarket stainless pipes ?

Cheers, Lee

[TheBoy]

The cam belt was changed by my local friendly mechanic...can check about what he used...what difference does it make ?

Most mechanics think you can change the belt without any extra tools, as you can with most cars. GM V6 units must use the cam timing kit. If he didn't use one, get it done again immediately.

Did he simply change the belt, or did he change the belt along with tensioners and rollers? If he just did the belt, get it done again properly immediately (with tensioners).

[TheBoy]

I was thinking exhaust and had a quick look at the tail end and there does seem to be some corrosion where the tail pipes meet the backbox...can't really see the rest.

If a new exhaust is in order...what sort of price are they ? and what about aftermarket stainless pipes ?

Cheers, Lee

There are a few posts with prices - generally you are looking at £80 + VAT each for centre sections and same again for backbox on Trade Club. Probably looking at £130+VAT for each retail. Forgetting Stainless for the moment, don't fit pattern exhausts, they sound crap and are noisy.

Stainless always seem to be noisier, but not with the crap sound of pattern steel exhausts...

I'm sure members here can recommend stainless makers, if thats what you want

[loonatic]

The cam belt was changed by my local friendly mechanic...can check about what he used...what difference does it make ?

Most mechanics think you can change the belt without any extra tools, as you can with most cars. GM V6 units must use the cam timing kit. If he didn't use one, get it done again immediately.

Did he simply change the belt, or did he change the belt along with tensioners and rollers? If he just did the belt, get it done again properly immediately (with tensioners).

I will check with them tomorrow...I'm sure they said they used a 'kit' but what was in the kit I don't know.

I have drieven about 130 miles since it was done and all seems well.

Cheers, Lee

[JasonH]

It's the tensioners that fail not the belt, so it's essential to check that the tensioners were replaced.

If the cambelt was not fitted with the correct locking kit and cam timing gauge the 4 cams will not be correctly timed to each other and the crankshaft. The engine will not run as well as it could. If done really badly then bye bye engine.

If the cambelt wasn't correctly timed and tensioned it doesn't need replacing it just needs to be set up correctly.

[Bernard]

Check pipes from Auxiliary air pump as these do split and give the same noise.

[loonatic]

Check pipes from Auxiliary air pump as these do split and give the same noise.

Thanks mate...where might I locate the auxilary air pump ?

Cheers, Lee

[Bernard]

The Auxiliary  pump is mounted down low Nearside front in the engine bay i believe but the hoses that split are at the top near Radiator  towards centre of car. You can usally hear then blowing even on tickover but gets worse with revs . Sounds similar to a blowing manifold.

[TheBoy]

The Auxiliary  pump is mounted down low Nearside front in the engine bay i believe but the hoses that split are at the top near Radiator  towards centre of car. You can usally hear then blowing even on tickover but gets worse with revs . Sounds similar to a blowing manifold.

If the one way valve is shot, it often blows a hole in the pipe from Secondary air injection solenoid near top of rad, to one way valve.  If this is the case, it sounds like a hairdryer for first minute after starting (assuming nobody has unplugged the pump)