Technical Odd noised from the engine

[The Panda Nut]

I am having ongoing issues with a noise that sems to emanate from the engine. When cold, at odd times, a bit like air con cutting in and out it makes a rude noise that sounds like a dry starter motor or a just-about-to fail alternator bearing. It also sounds a bit like the starter being activated while the engines running. The noise is abrupt and short lived sometimes quite a lot and others jsut once or twice. It seems to go away when the engine is warm. I have spent hours listening to each area of the engine and can hear nothing much thats odd with one exception. There is a loud metallic knocking thats really noticable listening against the throttle body, it sounds like a stuck hydraulic tappet or a small end or bad piston slap. It seems that this may be the most likely source of the noise I hear described above. You cannot hear this tapping noise listening anywhere else on the block or cylinder head and the fuel rail is also pretty silent.

Today I stripped out our 2014 car and had a listen to that and its totally silent on the throttle body no tapping or knocking a all. Has anyone any ideas what I mat be hearing.

This is all irritating as the car is quick and economical and its smooth-running and fast. It feels way quicker than the newer car. Both are 69hp VVT 1.2 engines. As its my daughters car used to ferry her to work at night I need to trust it and currently its under question. Any ideas however left field would be appreciated particularly any possible links between the bearingy arttle and the tapping. Im wondering if a cam belt tensioner could be involved.

 

[koalar]

I am having ongoing issues with a noise that sems to emanate from the engine. When cold, at odd times, a bit like air con cutting in and out it makes a rude noise that sounds like a dry starter motor or a just-about-to fail alternator bearing. It also sounds a bit like the starter being activated while the engines running. The noise is abrupt and short lived sometimes quite a lot and others jsut once or twice. It seems to go away when the engine is warm. I have spent hours listening to each area of the engine and can hear nothing much thats odd with one exception. There is a loud metallic knocking thats really noticable listening against the throttle body, it sounds like a stuck hydraulic tappet or a small end or bad piston slap. It seems that this may be the most likely source of the noise I hear described above. You cannot hear this tapping noise listening anywhere else on the block or cylinder head and the fuel rail is also pretty silent.

Today I stripped out our 2014 car and had a listen to that and its totally silent on the throttle body no tapping or knocking a all. Has anyone any ideas what I mat be hearing.

This is all irritating as the car is quick and economical and its smooth-running and fast. It feels way quicker than the newer car. Both are 69hp VVT 1.2 engines. As its my daughters car used to ferry her to work at night I need to trust it and currently its under question. Any ideas however left field would be appreciated particularly any possible links between the bearingy arttle and the tapping. Im wondering if a cam belt tensioner could be involved.

Flip the aux belt off and listen again

does it have aircon ?

 

[DaveMcT]

A sticking starter will make a short screech as the engine starts. Alternator tightening up is more continuous but worse when very cold. My alternator was charging fine but getting noisy on engine start. I've had this on other vehicles so got under the car and found the cast casing was cracked. New alternator (£100) no more noise and of course it charges just the same.

I posted an alternator "How To" on another thread. You'll have to search for it. It's not too difficult if you disconnect the "dog bone" engine mount and wedge the edge forwards away from the fire-wall. That extra 1 inch of space makes all the difference when working on the top mounting bolt.

 

[Goudrons]

Is the metallic knocking coming from the air box mounts?
There a couple of rubber bushes with metal inserts with the bolts through them that hold the air box down on the 69hp.

I have had the rubber parts perish away and on our old 2012 and that caused the airbox to rattle like a biscuit tin full of marbles.
I only noticed when I saw rubber dust around the mounts.

The other noise at start up could be a dry or failing bearing, these can tend to be noisy when cold and quieten down when they get warm and expand a bit.
Alternator, water pump, cam tensioner could all be suspect.

 

[DaveMcT]

My Multijet had worn out airbox mounts and cracked mounts within the airbox. The engine is not running so I cant comment about any noises. Replacement rubber bushes were really hard to find (two for the engine posts and one for the peg at the back). I got some from Poland but they take weeks to arrive.

The broken plastic was repaired with aluminium tube and 2mm sheet "welded" using Lumiweld aluminium brazing rods. All stuck together with acrylic body mastic. It was a faff but a lot less cost than a new airbox that's likely to have the same problems.

 

[The Panda Nut]

Simple ideas always the best. Thanks why didnt I think of that.

 

[The Panda Nut]

My Multijet had worn out airbox mounts and cracked mounts within the airbox. The engine is not running so I cant comment about any noises. Replacement rubber bushes were really hard to find (two for the engine posts and one for the peg at the back). I got some from Poland but they take weeks to arrive.

The broken plastic was repaired with aluminium tube and 2mm sheet "welded" using Lumiweld aluminium brazing rods. All stuck together with acrylic body mastic. It was a faff but a lot less cost than a new airbox that's likely to have the same problems.

Bloody brilliant suggestions thank you all. My airbox mounts are grots but are firm when done up. Oddly my wellies just let go. I had been wondering why I always seems to have things in them when walking the dog. Clearly disintegrating for a while and shedding runbber internally.

 

[The Panda Nut]

I think
Early cam belt change with water pump and all the tensioners. Its not far off due.
New air box mounts - home made
Run without belt for a day or two
New alternator
New Air con pump
In that order.

 

[DaveMcT]

My repaired airbox.

The metal tube is cut and filed to the same angle as the original. It’s also made about 10mm short to make space for the rubber cushion.

I drilled it out but TBH would have looked better left without the hole. With hindsight, this would have been the easier way because the plate could have been cut oversize and trimmed after welding to suit the job.

Lumiweld is a solder/braze for aluminium. The strongest joints are made by “tinning” both surfaces with the material to provide a key. Then align the parts, heat again and add a fillet all around.

I had some tube just right to go inside the original mounting "tube". If I was buying material for the job, I would use a wider diameter tube cut to the full length and solder a washer to the end to carry the grommet.

Top plate 2mm aluminium.

Lumiwelded to angle cut aluminium tube.

Screwed to the box top.

View from underneath with acrylic sealer as a glue. Same glue and pop-rivets keep the plastic tube from pulling off.

 

[DaveMcT]

Plus one for posh petrol. Tesco Momentum with 5% booze is OK but Shell Optimax is batter still. But they only benefit engines with a knock sensor. Older cars are no better either way.

The 100HP feels like its had the hand brake left on when filled with vanilla 95 octane. The 1.2 is even worse. All cost about the same per mile (though Shell might be a few p more) so really there's no point in using the cheapo gunk.

 

[koalar]

I think
Early cam belt change with water pump and all the tensioners. Its not far off due.
New air box mounts - home made
Run without belt for a day or two
New alternator
New Air con pump
In that order.

If the noise was constant you could spray a little water on the aux tensioner they normally quieten down for a few seconds if there on the way out

 

[RalphM]

If the air box mounts are getting a bit tired you can get a cheap box of
rubber O rings from Aldi pick the right size and push it down with a socket
and it will fill the gap round the mount so stopping a bit of the movement.

 

[DaveMcT]

If the air box mounts are getting a bit tired you can get a cheap box of
rubber O rings from Aldi pick the right size and push it down with a socket
and it will fill the gap round the mount so stopping a bit of the movement.

That's what I thought, but the airbox mounts are big lumps of rubber

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The job uses two of the smaller rubbers and one larger rubber. However two kits will do the job for not silly money and you get spare bigger rubber.
This is the only set I could find apart from going to one of the main manufacturers that use this engine.

 

[The Panda Nut]

Flip the aux belt off and listen again

Why didnt I think of that. Simple things always the best. Its quioet for now but if it misbehaves again I will surprise it!! yes air con that seems to work OK. After new condenser and dryer it ought to!