Knocking noise, maybe dying ac compressor?

[Barney626]

So did an oil change on saturday, everything went well car drove and sounded fine since then but this afternoon started the car and a consistent knocking/banging noise is coming from the engine bay.

Not sure what it is and cant pin point where it's coming from. Engine hasn't lost power and the car still 'feels' fine, just this noise.

Noise speed totally depends on revs. Doesn't matter is clutch is in or what gear im in. Doesn't change when I turn on/off the aircon.

Any ideas on what it could be? Thought it may be either the AC compressor packing in or the alternator as it seems to be loudest when listening above the belt area...

Best video I could get of it below. Can hear the regular whining of the engine and the distinct knocking sound that sounds like someone hitting an empty paint can with something...

 

[Foxspeed]

disconnect a coil in turn & see if it changes/goes quiet...its a bad clip but sounds like it could be bottom end!

 

[Barney626]

Fairly sure it isnt anything to do with the cylinders as the car is still running fine and not being rough.

Will try it anyway and also try to get a better video from engine bay.

Just to confirm you can pull the plug out the top of the coil with the engine running to see if it changes?

 

[suj]

Just to confirm you can pull the plug out the top of the coil with the engine running to see if it changes?

Yep, take out each clip from each coil separately.

 

[Barney626]

So just disconnected each coil. All four made the engine go lumpy so it isn't a dead coil.

Tried getting another video moving my phone around the car a bit more. It's definitely loudest when you listen to the off side of the engine above the belt. Sounds like it's coming from the AC compressor area tbh.

I know that the AC system needs a regas so maybe could be related to that if the gas carries the lubricant?

If it does turn out to be a dodgy compressor, is it a DIY-able job to replace it if I only have jacks?

 

[Barney626]

Will be driving a few hundred miles on this over the weekend so could really do with knowing whether it could total my engine or not if I don't get it fixed before then?

 

[Foxspeed]

the pulling off a coil isnt to do with one being faulty it was more to see if the actual "knock" changed to help diagnose a knocking bearing

if the air con is low the compressor will be free-wheeling - you can tell be looking at the end of it and seeing if the end plate is turning if not the electric clutch is not engaged

to check drop the auxillar belt off & run it that way the alternator / compressor / idler are not rotating

 

[Barney626]

the pulling off a coil isnt to do with one being faulty it was more to see if the actual "knock" changed to help diagnose a knocking bearing

if the air con is low the compressor will be free-wheeling - you can tell be looking at the end of it and seeing if the end plate is turning if not the electric clutch is not engaged

to check drop the auxillar belt off & run it that way the alternator / compressor / idler are not rotating

Tbh the engine turned too noisy to tell if it changed after a coil disconnect. Will try again but doubt I'll be able to hear anything.

If it isn't turning could it just be the pulley? It looked like it was moving back and forth out axis by a millimeter. As far as I can see there is a small visual mark on the belt and every time that goes round once the noise 'knocks' once, so it's in time with that...

Is there a guide to taking the belt off? Never done it before so don't want to miss anything important. What's the best way to get access to it?

 

[Barney626]

So tried having a better look at the aircon pulley and think the aircon might be stuck on? Not sure if this is the end plate you mean.

Aircon is 'off' in both of these videos:

Can also see the pulley moving around quite a bit...

 

[Barney626]

So just tried disconnecting the coils one by one again and the noise never went away.

Also checked the obvious like oil level and whether the filler cap was tight on, no problems there.

Will have the car up on jacks tonight and get the wheel arch liner off to have a look at the pulley system.

The main question is, if it's just a noisy compressor or slightly loose pulley knocking can I drive on it for a few hundred miles without it ruining my engine? Obviously not ideal but won't be able to fix it before a trip this weekend...

 

[Barney626]

So had the wheel arch liner out and saw this on the belt:



Trying to source a new belt for tomorrow, reckon that's what is making the noise?

 

[Barney626]

Can I only use an 'F4R belt' or is there a generic size I can use? Even as a temporary one until I get a genuine belt...

 

[Foxspeed]

use the right belt if not it can be derailed/dragged in to the lower pulley and the timing jumps and bends your valves!

when you fit the new belt MAKE SURE IT IS SAT IN THE PULLEYS/PULLEY GROOVES CORRECTLY or it can cause again serious issues

 

[Barney626]

So got the new pulley in yesterday and sure enough the noise is gone.

 

[Foxspeed]

when was the cambelt done as the aux belt is usually done at same time???

 

[Gus]

So got the new pulley in yesterday and sure enough the noise is gone.

Bet thats a relief !! glad its sorted for you.

 

[Barney626]

when was the cambelt done as the aux belt is usually done at same time???

Says it was done about 15-20k miles ago in the service book but the aux belt is clearly older than that...

 

[Antti O]

You replaced pulley & belt and now it is sorted?
That aux belt was horror.

 

[Barney626]

You replaced pulley & belt and now it is sorted?
That aux belt was horror.

Just replaced the aux belt. Haven't touched the tensioner or pulleys.

Looked even worse when I got it out, I could see the blue structural chords that are encased in the 'base plate'

 

[Antti O]

So bad belt was problem. Glad to hear it is now sorted