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MG MGF Technical - What's that noise???

Hi Guys,

Had a great day yesterday blatting around an air field. :o) Good to see JT in his new TF135 too.

Got back to London, and noticed a couple of new sounds.

One was a clicking - a quick delve into the engine bay through the inspection grille gave the answer to that one: the remote oil filler neck and dipstick assembly had completely come away from its mounting on the plenum: the metal tapped insert had pulled out from the plastic! Blast. I need to put it back in: anyone got any suggestions for a suitable adhesive?

Second noise is associated with the exhaust note: there is another quite discreet, slightly higher pitched tone to the normal Daytona 'tune'

I say its exhaust because it seems associated with engine speed, and alters pitch and magnitude in parallel to the exhaust note.

Got me wondering whether there may be a small hole in the flexipipe in the exhaust down pipe (it's still the original, 7 year old, 70k mile item). But I've never come across a description of a failing flexipipe sounding quite like this...

Any suggestions chaps???

Thanks!
Rob Bell

Rob,

Item one. When Dave Andrews plugged the waterways in my new head he used heat resistant epoxy, I would say that a dab of that should be the trick. I also think that halfords may have a proprietary adhesive to do the same job..

The way you discribe noise No 2 it seems similar to the noise I had before replacing the flexi the other week.

I'm off to see Mr A on Thursday, I'm going to release just a little tension off the cam belt. It's started to 'sing' a little.

Tim
tim woolcott

BTW.... What airfield?
tim woolcott

Thanks for the suggestion Tim - will pop over to Halfords this evening to see if they have anything suitable. Mind you, I doubt that the plastic plenum ever gets *that* hot, so perhaps any adhesive would do? Having said that, I think you're right, heat resistant epoxy would be ideal given the fluctuation temperature conditions of the engine bay over prolonged periods of time...

How would you describe the noise you heard when your flexipipe seemed to be failing, Tim?

The airfield in question was Colerne - for the Wessex sprint :o) David Smith was there as well, in a surprisingly good looking (for a freebie) MG Montego! :o) Motoring doesn't get much cheaper than that! LOL
Rob Bell

Tim,

>>When Dave Andrews plugged the waterways in my new head he used heat resistant epoxy ..

What was this all about?

Dave
Dave

Hi Rob,

Have you checked the bottom of the filler tube for damage. Mine cracked three years ago because the top came adrift.

By the way, did you receive the parcel I sent to you or has it gone adrift in the post?

Bruce
Bruce Caldwell

Dave,

On K16 heads there is an (unnecessary) water drilling down thru the head in the centre of the inlet port, if the head is ported properly then this water drilling is breached. I normally block it with 5mm dural bar fixed in place with heat resistant epoxy such as Devcon. The bar is an interference fit so the epoxy is just a backup. VVC and VHPD heads dont have this drilling.

Dave
Dave Andrews

Bruce - no I didn't check this - thanks very much for the heads up on this.

Tricky to check - as you know, it's down a deep dark hole, otherwise known as an engine bay! LOL ! ;o)

Was the cracking very obvious? I did notice some fumes in this area of the engine bay - and it did seem worse when I moved the assembly back into its original position - so a crack is certainly possible. How obvious was it with yours Bruce? I think that I'll have to drop Victoria a line if the housing is knackered...

Yup - the parcel - I think - has arrived. Had a parcel 'attempted to be delivered but it was too big to fit through the letter box' card come through at the end of last week - but I haven't had time to collect it. Hopefully Yimmy will be able to pop into the post office today :o)

Dave, thanks for the epoxy's name. Would it be suitable for relocating the metal insert back into the plastic plenum - and is this something that Halfords would stock?

Cheers
Rob Bell

Rob,

Try http://www.gluelines.co.uk/devcon.htm for the epoxy.

I could passing your way on Thursday night so I could drop in to see if your noise is the same as mine..
tim woolcott

That'd be handy Tim - pop in, I'll have the kettle on! :o)
Rob Bell

Rob

Interestingly after fitting the 820 airbox my car developed a high pitched noise that changed tone as the revs increase. It sounded almost like a supercharger. I never did find where the noise was coming from but since the new exhaust and cat by-pass where fitted I haven't heard it.

Sorry that doesn't appear to help much.

Neil
Neil Stothert

Hi Dave,

Thanks for the explanation.

> >VVC and VHPD heads dont have this drilling

I never ceased to be amazed at all these little differences.

By the way, I just checked with Phil Raby - the HGF/Porting and rolling road articles are going to be used sometime this year. Keep looking out for them.

Now looking forward to the upcoming day at Emerald. Are you still unable to make it? I know you couldn't make the original date, but we're now up there on Saturday 10th May.

Dave
Dave

Interesting thought Neil, thanks. I'll check that, although it doesn't sounds as though it is coming from the direction of the airfilter. Actually, other than 'from the rear of the car' the noise's origin is very difficult to pin point, but seems to be more from behind my right ear than the left...

Dave, as DL says, if you can make it up to DW's on Saturday, it'd be great to see you again! :o)
Rob Bell

Hi Rob,

Yes the broken filler tube was obvious 'cos I had a slight oil leak onto the ground.

Bruce
Bruce Caldwell

Any epoxy resin (2 pack) would be OK I reckon.

Sets rock hard in 10-15mins
Tech

Had a thorough look around when I got back from work. No evidence of a leak from the remote oil filler - thanks for that Bruce. Pretty sure that the noise is not cam-belt related either - compared the engine sounds to my brother's 2000 MPi.

Which leaves the flexipipe as one possibility - but to be perfectly honest, there isn't much visual evidence for a leak from this area (although there does appear to be more fumes in the engine bay???)

Thanks for the epoxy tip Tech - in the end I bought some stuff from Halfords that's good for environments up to 150C - temperatures well in excess of what the plenum will experience. Need to clean all the surfaces up, so will be trying the stuff out tomorrow evening.

So... still not really any closer to figuring out this noise. In all honesty, it is a fairly intermitten noise that is best heard from low speed where the engine is under load and accelerating...

Actually, it does sound a little like a 'belt noise'... argh! Now I am going to start hearing things!!!
Rob Bell

Epoxy'd the oil filler last night - seems to be holding, but what I hadn't appreciated was that the mounting hole in the plenum had become ovalised. Result: the oil filler can be moved... argh! So I suspect that I'll have to be adding more epoxy when the thing falls off again :o(

The noise, I am becoming more convinced is due to the flexi-pipe leaking. I *think* that the exhaust noise has increased - but that could be psychological. I'd definitely appreciate everyone's thoughts tomorrow.


In the mean time, I guess I'd better give Janspeed a call to see if they can get be a nice new extractor 4-2-1 manifold... ;o)
Rob Bell

Rob,

I'll bring my jack and ramps tomorrow, if we get time i'll have a look / listen for you.

SF
Scarlet Fever

Nice one, thanks Andy - I've just not had any time to do this recently...
Rob Bell

Had a look at this on Saturday (thanks again Andy! :o))

The noise that I was initially most concerned about is, I am pretty sure now, from the flexi-pipe.

Despite a slightly ill MG, I put my car on Emerald's rollers anyway, and discovered that the car was a full 10 bhp and 10 lb.ft torque down on the previous figure recorded on Dave's RR.

Can this really be due to the flexipipe - or is there another problem that I am missing???

I ask because just once - on the way to Norfolk - the car suffered from a misfire - never to occur again.

There is also now a rattle that is best heard from the driver's side wheel arch - which may - or may not - be related to the flexipipe.

Any thoughts guys?
Rob Bell

As you know Rob, i am on my fourth flexi-pipe.

Symptoms include:

Rattles / buzzing and / or (rather ironically) a REDUCTION in exhaust noise! (I assume because some of the gasses leak out before they get to the silencer).

A reduction in power, this can vary from a minor drop (the car may feel just a little less sprightly) to a major drop - when my last flexi went ½ way round last year's Treffen the car went from being able to keep up with the Trophy and TF 160s to having difficulty keeping up with the MPi Fs. At the time i estimated a drop of between 10 to 15 bhp, so your experience is in keeping with the symptoms. I also had an oil consumption problem as well though (no air through filter due to bodged installation, therefore increased suction within the plenum and a leaching of oil past the scrubbers in the head into the plenum via the breather hoses). How much of this drop was due to the oil problem is unclear, but the lack of power was very noticable (and worrying when you are 300+ miles from home!)

A replacement flexi cured the power drop, at pretty much the same time i also had the filter re-installed correctly. You will be pleased to know that Scarlet was running perfectly for about 2 months up until Feb 8th...

Having seen the 7 year old original nuts on the flexi side of the catalyst on your F Rob, you'll forgive me if i withdraw my offer of help! :-)

SF
Scarlet Fever

>>A replacement flexi cured the power drop, at pretty much the same time i also had the filter re-installed correctly. You will be pleased to know that Scarlet was running perfectly for about 2 months up until Feb 8th...<<

Hmm - does that mean that the power drop was cured by sorting out the airfilter or the flexipipe then Andy? But if you've found that the flexi results in reduced power pretty much every time it fails (Scarlet's on her 5th isn't she?), then I guess I can breathe slightly easier.
Rob Bell

I suppose it depends on the size of the breach Rob, if there is a large amount of turbulence being built up inside the flexi due to the escaping gasses then i'm sure this could cause a noticable drop in performance. The extent of this power failure would also be difficult to predict IMO and would explain the varying degrees of power loss i have experienced in the past.

I have 'worn out' 3 flexi pipes and am currently on my fourth one and each one had differing effects on the sound levels and power drop off.

If it is any consolation, i am 90% certain that this is what your problem is, get it changed and see if it cures the problem (it's due for changing anyway isn't it? 7 years old and 60ish K). :-)

SF
Scarlet Fever

The difficulty right now is that I would like to replace the manifold with a 4-2-1 type. Unfortunately, at the moment, I have no way of knowing exactly when I can get hold of one.

I certainly do not want to waste money on a replacement standard flexi if I am going to be investing in a new manifold...

Arrrghhhh!!!

I'll see if I can grim and bear it for a little while - unless the CO levels in the engine bay being swept back into the cabin become an issue!
Rob Bell

I was going to lend you Scarlet's one, but it will be tricky to jack her up at the moment (the car needs to be quite high to get access to the manifold studs), so i don't think i'm going to be able to.

How about Victoria at the MGF Centre? She managed to sort Tim out with a cheap 2nd hand one.

SF
Scarlet Fever

That's certainly true Andy. But I think that it is going to remain resolutely as 'option B' for the moment. The new manifold on its own will be expensive enough at the moment! LOL
Rob Bell

This thread was discussed between 06/05/2003 and 12/05/2003

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