Howling noise at Motorway speeds - Advice please!

[G-Lad 0]

Hi Folks,

 

My VR6 has had lots of cash lavished on it, but I still have a weird problem that seems to have been masked by others which are now resolved.

 

Here's a list of relevant work done to the car in the last 12months:

 

Chains, clutch, master and slave cylinder replaced

Full cooling system rebuild, most parts replaced. Cured oil temp too high issue.

New tyres 6mths ago, no steering wheel judder

New MAF sensor, Idle Valve & damper pot, and PCV valve

All new dampers, wishbones, bushes, engine mounts, top mounts, bump stops etc, retaining old springs OK

New genuine standard exhaust from the cat back

New front disks, pads and braided hoses

Full wheel alignment

 

It's got 125k miles on the clock and recently had an oil & filter change.

 

...but even though the obvious noise sources of blown exhaust, wallowy suspension, and warped disks have been sorted, it still makes a weird howling noise which builds up around maximum motorway speeds, and then goes away if I go faster (on private roads, of course). Clearly it is some resonant frequency issue. It seems to be more road speed related than rev related.

 

Significantly (I think), it doesn't always happen. It usually happens if I'm driving hard around corners (ie putting Gs onto the chassis), or if I hit bumps and pot holes. Sometimes I'll slow down for traffic and when I speed up it doesn't happen. This makes me think it's something changing shape due to torsion or heat.

 

My fuel consumption is diabolical considering all the other work. I struggle to beat 28mpg unless I crawl along at 60 in 5th gear.

 

I reckon it's probably a cracked manifold. What do you think? Any suggestions on how to check?

 

If it is, how big a job is that? I presume the lovely new exhaust is going to need removing. How much subframe needs to come off to get to the exhaust manifold, or is it purely done from the top down?

 

All advice gratefully received!

 

 

Chris

[davidwort 0]

wheel bearings?

[CorradoVR6-Turbo 0]

I would have thought wheel bearings as loading them on corning is the usual sign but they dont normally quiet at speeds..?

[Jim 1]

Agreed with wheel bearings... if it's speed and load dependant, it does seem like the next most likely candidate!

[mimjed 0]

as above, cv joints worth double checking. seals on doors also if it could possibly be wind related.

 

if it was cracked manifold you would know by now as you would require a hearing aid or two

[G-Lad 0]

thanks for the feedbak folks! i did have a cv joint rebuilt when the gearbox out... hmm i shall check which was rebuilt, which was replaced and what is still as was.

 

the bad fuel consumption has been worrying me, and i was hoping it'd improve more than it did when the exhaust back pressure was sorted. new centre and back box did help a bit...

 

wheel bearings under load and fast / wide cornering seems to make sense. its mostly on big left turns, thinking about it.

 

i did have to wear my gig ear plugs on a memorable drive to leeds, but thankfully it's mostly bearable now most of the exhaust is new. it's a proper WAAARP noise sometimes though, which i wouldn't have thought was wheel bearings.

 

..back to the garage i go!

[culshaw 1]

could the blower be jammed open (random guess)?

 

or you could lose the wolf in the boot..

[ben_wooduk 0]

Is 28mpg that bad in a VR? My valver can't better that figure by much :(

[G-Lad 0]

Is 28mpg that bad in a VR? My valver can't better that figure by much :(

 

maybe you're right! but i have to nibble around at sub 2.5k revs to beat it. My golf does 28mpg if i hoon it around at 5.5k revs, which of course is exactly what the valvers are built for ;)

[V-Dubstar 0]

Yeh 28 doesn't sound too bad if ur keeping over and around 2.5k!

[G-Lad 0]

could the blower be jammed open (random guess)?

 

or you could lose the wolf in the boot..

 

oh, isnt the wolf standard kit, along with the fa kit and triangle?! :nuts:

[G-Lad 0]

Yeh 28 doesn't sound too bad if ur keeping over and around 2.5k!

 

perhaps im labouring the fuel consumption worries in hope of convincing people that my manifold worries are right. i may be barking up the wrong tree. :lol:

[culshaw 1]

depends if you got a scared wolf... when it gets to them speeds...

 

swear i saw your car going down my road a couple of weeks ago... (Beeston) ?

[Jon_vr6 1]

I get 32-35mpg travelling from Manchester to Notts mixed driving and the hammer down on the A50 :D

[Novastrike 0]

I am the same as Jon_VR6. I get around 33-35 MPG on the motorway and thats doing between 70-75.

[Purple Tom 0]

Agreed, even factoring in my OBD2 conversion I get at least 33mpg at motorway speeds, and nudging 40mpg when just pottering about at 30-50 mph. When OBD1'd I still had to spank it a bit to get it to drop below 30mpg.

 

If the noise isn't rpm related then I would lean towards it being the wheel bearings, quite possibly the rear ones rather than front. Does the noise remain the same if you drop the gearbox into neutral and let the engine idle when doing 70mph? If it does then I would immediately rule out any exhaust related problems and concentrate instead on rotating parts.

 

I guess it could be the diff bearings too, which could show itself when cornering (as the diff will be experiencing differing loads on each side), but I doubt it tbh.

[G-Lad 0]

Are VR6 wheel bearings tightenable tapered ones, like a Mk2 Golf? ie can they be adjusted or would they need replacing, if that's the cause of my noise?

 

I'll do some high speed coasting on the way to Ultimate Dubs and see if my mystery noises do anything different when in neutral!

 

Cheers

[Reggit 0]

Have you tried just jacking each wheel off the ground and spinning it/feeling for excess play? You can often feel a bearing being a bit rough if it's on its way out.

[davidwort 0]

a rear wheel can be spun off the ground and bearing noise can be heard, or taken apart and you can see the pitting on races and rollers, not on the fronts though, only when the hub is off the car can you spin it and hear the roar!

[V-Dubstar 0]

Are VR6 wheel bearings tightenable tapered ones, like a Mk2 Golf? ie can they be adjusted or would they need replacing, if that's the cause of my noise?

 

I'll do some high speed coasting on the way to Ultimate Dubs and see if my mystery noises do anything different when in neutral!

 

Cheers

 

Can they be tightened?

[davidwort 0]

rears can be adjusted/tightened up a bit if too loose, not too much though, the washer needs to be free to move under slight pressure or the bearing will burn out if too tight, but if they are groaning they are shot.

[G-Lad 0]

thanks folks, i'll try jacking the back and wobbling with wheel attached. if the rears are wobbly i'll assume new bearings needed and can't just be be tightened. I know my Golf was just tightened up, but i haven't done many miles in it in the last year, so they could well be over tightened...

 

will be really annoying if it IS the fronts, as i've just had new brake disks and pads put on the front, so it's all been apart in the last 2 weeks and i'd like to think my mechanic might have noticed!

 

what sort of lifespan should wheel bearings have? I have a funny feeling after all the work ive been having to do, that this car has been seriously neglected from a maintenance point of view! not driven into the ground as such, but just obvious stuff left to the last dying days...

 

Last Q (for now!): Are VR6 C rear wheel bearings going to be the same as Mk2 Golf 16v? I bought some new rears for the golf but then just tightened them instead of fitting, so i still have them in their boxes from GSF.

[Wullie 1]

Make sure the handbrake is OFF when you try to wobble the rears as the wheel will be clamped by the caliper and any play will be disguised. And chock the other wheels for safety.

[Purple Tom 0]

The rear wheel bearings will be the same as a Mk2 Golf 16V, they're the same for many many VW's of the same era, even down to the mk2/3 Polo.

 

However, DON'T fit GSF bearings. They are of a really poor quality and you will find yourself replacing them in a very short amount of time. Go for genuine VAG (they aren't that expensive), fit them and forget about them. I went through 3 sets of GSF bearings in 4000 miles on my Polo GT before biting the bullet and getting VAG ones. I never had a problem after that.

 

If you're going to fit new wheel bearings, you might as well fit new rear discs too. I used Febi discs from AVS and they've been fine. As you have to drift the bearing races into discs it makes sense to start with new discs rather than old ones (unless your discs happen to be in very good condition). Would also be worth replacing the carrier bolts as they tend to round off, and have a look at the rear caliper sliders while you're at it.

 

HTH!

 

Tom

[G-Lad 0]

Thanks, top advice!

 

Surely then, when i had new front disks fitted 2 weeks ago, the front bearings would have been obviously lose to a skilled mechanic, and they would have replaced them? Obv I'll need to check them if its not the rears, or if after replacing the rears, the noise is still there.. Just trying to narrow it down logically :)