Strange popping / dripping sound when idling

[webbiegareth]

Hi all,

Our Ford AU has a very strange "popping" sound when idle, it's NOT in time with the engine - it seems totally random, kind of like water dripping onto a metal surface. It sounds stronger from the driver's side of the engine, and you can hear it louder sticking your head under the car.

I suspected an exhaust manifold leak as I knew the muffler had a few holes and the mechanic thought there was a hole in the engine pipe as well (between cat and manifold).

Here was the original video:

http://youtu.be/thrqtC3I5wY

You can hear it loudest when I walk in front of the car and lean on it a bit, right before I start revving the engine - you can't hear the sound anymore of the sound of it revving, only when it's idling.

Oh and I realise how bad it sounds when it's revving... it's an old engine, I just want it to last as long as possible then we'll put in a newer engine. So all the repairs we're doing to the car is everything apart from the engine

We've now had pacemakers, new metal cat and a redback 2.5" catback exhaust fitted. The damn sound is still there!

http://youtu.be/9742LdDf7v0

(totally out of focus, but that's with the new exhaust system fitted).

Does anyone know what the hell this sound is?

[poppa smurf]

may be miles off here but I get a similar sound from my belt,.....doesn't always do it but it sounds similar

[mongrelEF]

These videos are always difficult...
Suggest crank end float? Try running without the belt and check play on the tensioner pulleys, water pump, and aircon compressor?

[Evgeni]

I have the same sound. I thought it was a bearing or end float, but it disappears once the engine revs. I had the sump off recently everything looked ok.
I'll try running without the belt - but so far, complete mystery as to what it is.

[webbiegareth]

Thanks guys... have you had it for a while? It's not going to kill the engine quickly if it's crank end float is it? I figured it wasn't a real problem with the main components of the engine though as like Evgeni said, it disappears once the engine revs.

I figured it was an exhaust manifold leak as it sort of sounded a little bit like one I found on youtube, however after replacing the entire exhaust system is mustn't be that (else I have extremely bad luck and the new system wasn't installed correctly - I doubt that though!).

I'll swing by the mechanics on the way to work this morning and give him a listen.

[Evgeni]

Originally Posted by webbiegareth

Thanks guys... have you had it for a while? It's not going to kill the engine quickly if it's crank end float is it? I figured it wasn't a real problem with the main components of the engine though as like Evgeni said, it disappears once the engine revs.

I figured it was an exhaust manifold leak as it sort of sounded a little bit like one I found on youtube, however after replacing the entire exhaust system is mustn't be that (else I have extremely bad luck and the new system wasn't installed correctly - I doubt that though!).

I'll swing by the mechanics on the way to work this morning and give him a listen.

A little over 2 years ago I took the box out to do the rear main and converter seal. This is when I first noticed the noise, so who knows how long it has been going on. I can only hear mine when I am under the car. I have done over 80000k's since - over 201000 now.
It doesn't seem to affect performance. I'm getting around 16l/100kms on lpg. City driving with the air con on. Figures get better in winter with the air con off.

[mongrelEF]

End float won't kill it too quickly. I've seen a few engines with 3-5mm end float that still ran like kittens. The best one was a 3.9 Falcon engine with 7mm! But you wouldn't have known - we only rebuilt it because it was smoky

Basically - it's a Falcon, thrash it into the ground and then replace the engine, just like everyone else haha

[webbiegareth]

Is that what it is though? The engine is very smooth.... idles smoothly, accelerates smoothly, cruises smoothly etc etc... doesn't use any oil between services...

[mongrelEF]

Without seeing it.... couldn't tell you, sorry. You can check things out; remove the bellhousing dust cover and starter to look for damage, drop the belt and check your ancilliaries/check end float (very roughly), drop the exhaust and shake it out, and check the chain over. After all that, is the engine really worth any further digging if you're waiting for it to die anyway? Sometimes it's best not to look too hard; it can get expensive fast!

[webbiegareth]

I swung it by the mechanic this morning but it was a waste of time - it was raining heavily, and they have a metal roof so we couldn't hear the noise, and couldn't hear it outside in the rain too. Naturally once I got to work and parked it, it had stopped raining and I could hear it. Aaaargh! I'll try again when it's not raining.

The exhaust is all new, unless they've got a leak in it. You're right, I don't want to spend much working it out as I can get a lower km's engine fitted for $850.

The car itself was my girlfriend's mum's car with 250,000km's on it - most of them country k's (they live out in a little country town out in whoop-whoop), and she drives like a grandma so it's never been thrashed.

[AUFanboy]

I know this thread is a few months old but I'm bumping it cause mine has the same sound! I figured it might just be oil dripping back into the sump from the head, or transmission oil splashing back into the transmission sump from the cooler return line. Hopefully.

[Evgeni]

Originally Posted by AUFanboy

I know this thread is a few months old but I'm bumping it cause mine has the same sound! I figured it might just be oil dripping back into the sump from the head, or transmission oil splashing back into the transmission sump from the cooler return line. Hopefully.

All these little ticks all disappeared with Penrite 15w60 in my case. Probably increased oil pressure enough to stop any metal to metal contact, who knows.

[AJ09]

Very interesting read!!

Our AU1 has the same noise too.

I started a thread re bottom end noise and quite a few helpful AFF members put my mind at ease.

I did all the usual checks with belts, pulleys etc etc.

One thing I did find is that the guts of my cat converter is loose, however there is still some noise from the engine. Thicker oil helped to quieten it a lot.

It's still there but doesn't really bother me now ( especially now I know so many others have the same thing) it only happens around 1200-1500rpm with no load and it's not very often the engine operates like that anyway.

Cheers

[Jim Goose]

Originally Posted by AUFanboy

I know this thread is a few months old but I'm bumping it cause mine has the same sound! I figured it might just be oil dripping back into the sump from the head, or transmission oil splashing back into the transmission sump from the cooler return line. Hopefully.

I have an AUII as well and to me it always sounded like oil slap... was more noticable when the car is parked on a slope.
My previous EL also had the same noise.
Comes and goes.

[AUFanboy]

Stuck my head under the car again this morning and had a listen. To me it doesn't sound like metal on metal, more like a splash/drip sound. I think the big oil drain passages are in the back of the head so it might just be oil sloshing down there into the sump, maybe the crank hitting some oil on the way down.

Makes sense that thicker oil would reduce the splashing. But I think I'll stick with my favourite Mobil semi-synth 5w-30, it doesn't burn/use any and I get low 7 litres/100km on the highway

[Bill M]

My AU2 XR6 ute does it as well.
I have had the ute since new from Dec. 2001
It has made that noise for as long as I can remember.
I can recall discussion on this forum relating this noise to the charcoal canister solenoid.
Bill.