Rune

My escort 1.8 Gti has become strangely noisy, it has what sounds much like an induction roar in some rev ranges, most noticeable if I put my foot down when the car isn't revving very highly

Say for example I'm trundling along in slow traffic with the revs at around 1500 then put my foot down, perhaps an approaching hill or traffic clears I get a sound like an induction roar even though it has a standard (new) air filter

Even wierder, if I fit an induction kit and take it for a drive there's hardly any noticeable difference to the sound of the car

Things that have changed since the car last sounded 'normal':

It wasn't driven for around 2 months towards the end of last year because of the brakes being locked on that took some diagnosing, turned out to be the flexi hoses on the front brakes, I had new front and rear flexi hoses fitted

A new clutch was fitted

It did get worse when the middle box on the exhaust split and my local garage found that the baffles had also colapsed. I had the exhaust from the cat back replaced with a new one

It does have a stainless back box on the exhaust, but this was on the car well before it started sounding like this, the new exhaust parts have eased it somewhat but nowhere near completely

The sound it used to have was higher pitched in general than it is now even without this 'roar' kicking in


Anyone have any ideas what can or could cause this?

fiend

iTrader: (1)

Has the airbox been drilled?

phil_focus

has the snorkel to the air box fallen off? i know the focus makes a lovely induction roar if you remove the snorkel 8)

Rune

The snorkel is in place and it hasn't been drilled, I did think of the possibility of air getting in (or out) somewhere it shouldn't be myself

Did just think of something though, one of the plastic lugs for fixing the filter box to the bracke is missing, obviously this means there's a hole in it which has been taped over

Could well be that when that was originally done whatever tape they used was good enough to stop it sucking in air, but over time starting to let air in

I'm thinking I should try getting another airbox or doing a more permanent repair to the existing airbox before looking anywhere else

16vzetec

it wont be air after the air flow meter as then it would run bad, its before the air flow meter somehow.
my mk1 focus roars really loud with std airbox, its actually quite annoying sometimes coz its just a transport car not a boy racer car lol

phil_focus

it springs to mind if you have fitted a new air filter is the air box sealing properly on the filter???

if so, was the old one really filthy cos it might be that its normal due to more air being able to flow into the air box. in which case live with it and love it cos i hate modern silent cars, fucking danger in my opinion...too many people just dont look before stepping out into the road!

Rune

I put a new filter in it just after I got the car back at the beginning of last summer and yeah the old one was pretty dirty, but the sound of the car didn't alter at all after that

Not long after that I put the stainless exhaust box and an induction kit on it, sound DEFINITELY changed after that lol

Sounded great

Then towards the end of last year the brakes started sticking, kept getting worse until it couldn't be driven so it basically sat there for about two months while I was replacing brake parts in an attempt to sort it

Mot got due so I whipped the original filter box back on and put it into the local garage, they solved the brake issue, did the mot and I got it back

About two weeks later this noise started to appear, wasn't that noticeable at first but gradually increased

When I found the baffles in the exhaust middle box had collapsed I thought we'd found the cause and expected it go back to normal after renewing that

Got quieter but didn't go away, as it is now there isn't much difference in the sound regardless of it being the standard airbox or the induction kit, just a slightly nicer loud with the kit, but still not sounding the same as when I originally had the kit on

I think I need to either take the airbox back off and make sure it's got a good seal all round or try another 'known good' airbox on there to see if it makes any difference

If it doesn't I guess that'd point to it something other than air being the cause

Did I mention the noise completely disappears once you hit around 110mph?

Eases off around 60-80, kicks back in there until you get up well over a ton at which point it goes away

And it's soddin annoyin me!

fiend

iTrader: (1)

Exhaust leaking/blowing from a joint or manifold?

phil_focus

i agree, thats the next thing to check.

Rune

From the cat back it was all replaced with new (except the back box which is about 8 months old) just last week

I've had a look underneath and as far as I can tell it's not blowing anywhere


I tookthe airbox off and did a more susbtantial fix to the hole in the bottom where the lug's been snapped off than the tape someone had put over it

Cut a piece out of a plastic carton, glued it over the hole, put some silicon round the edge of the patch and covered it with gaffer tape ... I'm pretty sure it ain't gonna suck any air in through there for a while

Checked the seal around the airbox and that the snorkel was properly in place, all looks to be fine and the filter itself is still pretty spotless, doesn't look like it's been in there more than five minutes it's so clean

Then I took it for a drive and on the motorway cruising along at a little over 4000rpm was positively deafening


I'd thought it was either an exhaust problem or sucking in air somewhere but it doesn't seem to be either


Guys at the local garage when I asked if they had any ideas said 'mind you do have that stainless backbox on it'

To which I said 'yeah but it weren't doing this until about 6 months after that went on'

The reply to that was 'Oh ... dunno then'


Don't know if this gives anyone much of a clue or not, but it does the same thing, possibly even worse if I'm driving along in a rev range where the noise isn't there, then take my foot off the accelerator, might even be a bit louder than when it happens under acceleration

I'm almost positive that it started happening around the same time as I had the problem with brakes sticking on and was getting brake parts changed, but I'm sure that's coincidence cos I can't see how a brakes issue that's been fixed would be causing this

Could it be something that a diagnostics check would detect?

MarkN

Doubt a diagnostic would shed any light on it.

I had exactly the same problem with an RS1800 Fiesta last year, - sounded like induction roar but the filter hadn't been touched on mine. To cut a long story short it turned out to be a big crack in the exhaust pipe near the back box where it went over the rear beam. It looked like the rear box rubber mount had got weak and put strain on the pipe and cracked it. It was cracked two thirds around the circumference of the pipe at the top - and it wasn't that obvious from below as the bottom part of the pipe was still holding it together.

I sorted that and it was fine. I would be tempted to use your hand to check for leaks with the engine started from cold - it would be immediately obvious. Be careful you don't burn yourself tho.

Rune

As I've said mate, half the exhaust was renewed last week, and the rest of it checked out at the same time so I don't think it's an exhaust problem

Garage checked it when they put the new back section on for me and I've been under it myself for a look since

phil_focus

this is a very weird issue then and without seeing the car i think its gonna have most of us stumped.

MarkN

Could it be resonance rather than induction roar? I.e. at a specific RPM you get a really loud roaring noise that will get quieter if you accelerate through it or slow down?

Presumably it stops instantly if you dip the clutch and let the revs drop?

Either way - my money is still on an exhaust problem. If you're cruising at a steady speed on the motorway then then throttle is not going to be open enough to create a deafening induction roar. It can only be the exhaust.

What makes you so sure its not the back box? If it blew the baffles from the middle box out of the exhaust they could potentially damage the back box on the way out.

Rune

Could it be resonance rather than induction roar? I.e. at a specific RPM you get a really loud roaring noise that will get quieter if you accelerate through it or slow down?

That's very much the behaviour I've been talking about mate, I didn't really say that it was defintely an induction roar, I said this:

My escort 1.8 Gti has become strangely noisy, it has what sounds much like an induction roar in some rev ranges, most noticeable if I put my foot down when the car isn't revving very highly


What's meant by resonance and what might be the causes?

The baffles never blew out of the box btw, they collapsed at I presume the same time as the middle box split (possibly caused by a stone or some such, I drive over a mountain or two fairly regular)

Thing is, this noise started well before there that happened with the exhaust and I've not been able to find it 'blowing' anywhere so I'm tending to think the exhaust is fine

It also doesn't sound like it's coming from the back end of the car

Rune

Here's a page with what looks to be some useful stuff about annoying noises coming from your car

http://www.aa1car.com/library/vibrations.htm

Incidentally I'm changing the wishbones on it this week (well, helping a mate change them for me lol)

Came up as an advisory on the mot about the bushes being worn, and when I checked they were also on the previous two mot's as advisories but the previous owner obviously didn't feel the advice worth paying any attention to

phil_focus

it doesnt have to come from the back end of the car to be the exhaust. it could be a cracked exhaust manifold and thats at the front!

Rune

well I kinda guessed the exhuast just doesn't stop when it gets to the front of the car ;P

I have looked over the exhaust manifold included and it seems ok

About to take it round to my garage and gonna fit the wishbones, check out brackets, mounting bolts etc etc and also gonna try taking it through the rev ranges without it moving to see what happens

I'm thinking that whether or not it does the same at a standstill should help narrow down possible causes

Let ya know later how I get on

phil_focus

good luck mate.

if it still does it at stand still it will be easier to find the cause so fingers crossed for ya

Rune

[INSERT LOTS OF SWEARING HERE]

Doesn't do it a standstill

We went over inch of the exhaust again, definitely no leaks, all the brackets are sound, doesn't look like it can be knocking against anything except for one spot

There's like a rubber cover on the bottom of the chassis that looks like it's always been there. It's right at the back of the car above the backbox, looks like it's purpose is to prevent the backbox knocking against the underside of the chassis and while it's dirty as you'd expect it isn't showing any sign of wear, as it would if the exhaust was banging against it

With me under the car and my mate revving it to hell'n back doesn't come anywhere near banging against it

We checked just about every nut'n bolt we could get our hands on and nothing was loose

If you put your head under the bonnet and rev the engine about the loudest thing you can hear when hovering your ear over just about every part of the engine is the timing belt going round

That was a new timing kit went in around last august btw


What seems odd to me is that even though it only makes this noise when the car's in motion it's only in certain rev ranges, around 1700-2000 and somewhere around 3800-4000

If it happens in the lower range and I drop a gear to make it rev a bit higher the sound disappears, even though you're moving at the same speed


Short of strapping myself underneath the car while someone else drives it I'm clean out of ideas lol

About the last two things I can think of to try is change the airbox, though I don't think it's that or you would expect some kind of change when I put the induction kit on it but there isn't one

The other being to pick up a standard backbox for the exhaust, but again I don't think that'll solve it as the noise seems to be coming from the front of the car

I'm gonna try em anyway purely cos I don't know of anything else I CAN try

MarkN

I reckon it could be resonance in the exhaust. The fact it only happens in narrow RPM ranges and you can accelerate past it makes it even more likely.

Be interesting to see what happens when you change the back box.

Rune

Be interesting indeed if it does turn out to be the back box

It was fine when it went on new around 8 months ago and this resonance or whatever it is only started about 2 months ago, it'd raise the question of why this started happening after it'd been on the car 6 months

My mate that does stuff to the car for me spotted an escort estate in a scrappy near where he lives so I'm gonna try getting down there sometime this week to get some bits off it

We'll check out what state the back box on it's in and have that if it's sound, I'll get the airbox off it, he says the wheels look to be in better nick than mine and they're the same ones so I might have one or two of those

Mine's also missing the plastic cover over the towing hitch at the front and the one that covers the bolts holding the spoiler on at the back so I've fingers crossed it's got those on it cos the spoiler ones in particular I know you can't even buy from Ford any more

Could be a productive little trip

I'll let ya know if I get the backbox and try it, most likely get one new if the one on the escort at the scrappy's shite anyway

phil_focus

makes me wonder a bit more now if its your back box.

depending on how many miles you do it could we take 6 months for the back box to bed in making it louder and giving you resonance at those frequencies...revs.

only way to know that for sure though is to swap with a good one

Rune

could we take 6 months for the back box to bed in making it louder and giving you resonance at those frequencies...revs


That's a fair point mate

I've done a bit of reading on resonance and where you hear it coming from isn't necessarily an indicator of where the cause of it is situated

Don't do a massive ammount of mileage as I work mostly from home, an average week say around a hundred miles, if I'm out 'on site' more than usual up to about 150 with the occasional round trip of a few hundred miles

In this car since I got it only 2 longish trips adding up up to about 450 miles

I'd say I've done about 3500 miles since the backbox went on, give or take a few, and maybe around somewhere between 500 to 1000 since I first started hearing the noise

Puts it at the car having done 2500-3000 since putting the box on, which I only really did cos the one it came with had a great big hole in it ... well I did only pay Ł280 for the car lol

What kind of mileage does it take for an exhaust to bed in?

phil_focus

depends on the car mate but i would have thought a little sooner than that.

still could be that though

Rune

Just back from the scrappy ... and some toerag had beat me to the escort they had there

Another place told me to come back Friday and they should have one, so I'll wait tosee if that works out, if not I'll just pick up a new one day next week

jammerrs

id swaer its resonance, the heat sheild on my dads scoob catches at certain rpms and certain amounts of load. maybe something to look at if theres smething that could be touching the exhaust

or even if the bushes holding the exhaust or something are worn

Rune

I had all sundry bits, brackets, gaskets, bushes etc replaced when I had the new middle section fitted mate, two of us have been under it trying to find if anything on the exhaust might be coming into contact with something else and neither of us could see anything

If things go to plan and time permitting, I'll have a standard backbox on it by the beginning of next week, hoping to do it over the weekend so we'll see if that changes anything

Also discovered today that the wheels on the car ain't the same size as the original, it has 195/50/R15s on it and they should be 175/65/R14, so I'm gonna a set of the correct size, mate at the local scrappy's looking out for a set for me

Our local scrappy's the main place for auto recoveries etc in south wales, they hold the contracts with pretty much all the main insurers so it's a great place for parts, tyres etc

Don't like the idea of wrong sized wheels on it though cos as I understand it that throws all kinds of things in the engine management system out don't it?

MarkN

I thought a GTi had 15" wheels as standard. The Ghia had 14" wheels, but that had 185 60 14s on it IIRC. No GTi would have had 175 tyres on it.

Where did you get the idea that is should have those tyres on it?

botters

iTrader: (2)

sounds like it could be a partially blocked cat to me mate

MarkN

Re the wheel size is it one of those really early GTi's on like an M or N plate? I had been assuming it was one of the later ones with the half leathers on an R or S plate.

phil_focus

dont worry about your wheel and tyre size. escorts run 14 inch wheels with iirc 185/60's or somthing like that and also 15inch with 195/50. my escort had the 14s standard and i fitted 15s to be able to fit the bigger rs2k brakes and had no problems. theres nothing different on the cars between the wheels and it doesnt mess with your engine management!

lots of people runs 16s and 17s but the only problems i've heard of is reduced wheel bearing life running big wide wheels.

Rune

Re: Wheel size

I need a new spare for it cos of damage after hitting a rock on a mountain road, looking round on the net for one I came across some site (can't remember which one) that gave the originally fitted wheel'n tyre sizes of your car after entering the reg number

It came back with the 14 inch wheels but I wasn't gonna just accept that as being correct, so I rang a guy in the parts department at the Ford plant down the road from me that I've dealt with before and asked him to check what their system said was the original wheel size

He came back with the same 14 inch wheels, I hadn't mentioned any reason for asking or sizes so it's not a case of just saying 'yeah they're the ones' due to not really knowing

The car btw is a 98 model on an S plate, but it's an estate and apparently gti estates are pretty uncommon, no idea if that explains the different wheel size or not

My mate at the scrappy said he'll keep his eye out for a decent set of the 14s and he's only gonna charge me fifty quid for them, and that's with decent tyres, so at that price I'm figuring it can't hurt to try them


Back to the exhaust, I've not had chance to get a backbox yet, evils of work taking precedence'n all that, but I have managed to take another look underneath and noticed two things that I hadn't when I first looked

Firstly there's a heat shield above part of the exhaust middle section and while it doesn't look close enough to the exhaust for them to bang against each other (the exhaust itself and the shield), the shield is quite loose. Could it be that resonating in certain rev ranges?

Suppose the only way to check would be to remove it ... but I guess it's there for a reason, seems to be protecting brake pipes from the heat of the exhaust

Secondly, there is a short piece of angle iron bolted to the underside of the car right above the back box and this is covered by a piece of rubber. There's only an inch or two of space between this rubber and the top of the backbox, another possible cause?

Also, it almost looks as if the back end of the box is a fair bit closer to the back bumper (damned close) since the new mid-section of the exhaust has gone on than it was before.

Unsure whether that's contributing as the resonance was there before the mid-section was renewed

I'm half tempted to take the backbox off and take it for a short drive just to see what happens lol


Someone mentioned the possibility of a partially blocked cat, how would I go about checking for that and fixing it if it did turn out to be the cause?

MarkN

Your car should have 15" wheels and not 14"s. I've even checked the original '98 catalogue and that confirms it. Your dealer is wrong.

You can check the cat by taking it off and shaking it to see if it rattles. However, - if the cat breaks up it normally blocks the exhaust which gives a severe drop in performance.

We've been saying exhaust to you for the last week or more. Thats the next thing to try.

Rune

There isn't any noticeable loss in performance, it goes really well so going by what ya said maybe there isn't an issue with the cat

Tbh if there was a problem with the cat I would've thought that it'd have gotten picked up when it was mot'd a few weeks ago

Regards the wheels I am inclined to agree with you guys and I never for a minute thought that wrong sized wheels would suddenly cause this resonance I'm getting, I was more looking for opinions there


I've also pretty much agreed that it's almost surely exhaust related which is why I've been under the car looking at it and said I'm gonna try a standard backbox on it, just ain't had chance to go get one yet

As soon as I've got one and put it on, I'll post here on whether that solved it and you guys can have the pleasure of saying 'we told ya so'

I hope ...

phil_focus

fingers crossed you get it sorted soon mate and just to confirm the escort gti's came with 15" 5 spoke like the mondeo si wheels and also like the escort cosworth wheels.

the tyre size for the escort on 15" wheels is also 195/50.

if there was anything wrong with the wheels it would be speed related not revs related so they seem fine to me and people regularly run 16" mondeo si alloys on gtis and the cossie alloys and 17" without any problems other than going 17" and bigger can shorten the life of your wheel bearings.