Awful knocking on startup

[JoeeS3]

Hi guys, ive had a really bad knocking on startup, it only does it when the car has been sat for a bit. if i turn it off and turn it back on straight away it is fine. i will get vids posted. but it knocks pretty bad and seems like it is misfiring like a ***** for a few seconds on startup then is fine? anyone had a similar problem or know anything about it?
Cheers in advance
Joe

 

[JoeeS3]

i also seem to be loosing coolant too, would putting the wrong coolant in cause anything like that? no mayo stuff in oil cap either

 

[S3 Paul]

I would check the plugs and coil packs...
Then look at the cylinder head gasket...
Mine did it a few years back on my old engine...

 

[JoeeS3]

I would check the plugs and coil packs...
Then look at the cylinder head gasket...
Mine did it a few years back on my old engine...

what happened to yours? was your head gasket gone? it seems fine when driving just a bit unusual on startup coil packs were recently change to along with spark plugs could it be a dodgey coilpack or would this be a constant thing if it was?

 

[S3 Paul]

Mine had a ******** head ,
Big crack,
The rattle i heard was the gearbox/ dual mass flywheel shaking as aresult of the rough iddle.
DO the revs sit smooth and steady?

 

[JoeeS3]

i think thats what it is!! the gearbox, as it seems to resonate with the engine vibrating everyting else and it idles rough for a few seconds. i think it may be just due to the cold that its idling rougher on startup then vibrating the gearbox, when its off choke and the revs come back down it is fine. i hope it is this anyway

 

[kwistof]

I had a knocking that I could mainly only hear on first start ups also.

Mine disappeared once I engaged the clutch and it turned out to be my DMF letting go and needing to be replaced.

 

[JoeeS3]

Hi kwistof it is my dmf, put the clutch down earlier on start up and nothing, brought it up and it started do it again, do you know why it only does it on.startup and how long til it gives in?

 

[dusty]

If you are losing coolant and you have no visible leaks your head gasket could have blown or you could have a cylinder head problem, coolant could be leaking into one of the cylinders, this would cause a misfire which could make the dmf sound noisy due to uneven idle until the coolant has found its way out of the cylinder into the exhaust, this sounds similar to the problems I had, I was losing coolant overnight but had no leaks I also had a slight misfire for about 5-10 seconds on cold start up, I kept using the car and topping the coolant up but coolant loss got worse and the misfire got worse, I pulled the cylinder head off and found a crack in the head so that explains the coolant loss, while I had the head off I dropped the sump to do the oil pick up pipe and under closer inspection realised I also have a bent con rod maybe this is because the piston has been trying to compress the coolant in the cylinder, I'm not sure but I'm needing a full engine rebuild now so I would get a leak down test or get the coolant checked for exhaust gases ASAP if you have no visible leaks

 

[kwistof]

Hi kwistof it is my dmf, put the clutch down earlier on start up and nothing, brought it up and it started do it again, do you know why it only does it on.startup and how long til it gives in?

Hi Joe,

It would be making that noise it all the time to be honest- but the most amount of vibration the DMF would have to suffer is on initial start up, hence why you are mainly hearing it at that point.

Too 100% make sure it is the DMF giving up....I did this - put the car on some ramps, then get someone to listen to the gearbox when you turn it on from start up and also give the car a few revs. If the DMF is knackered then you will be able to hear it knocking all the time and every time you apply a little throttle the knock should in turn get louder with the extra vibration applied. This vibration can then be removed by pressing the clutch down whilst still revving the car, and obviously when the clutch is engaged the noise should go away if it is the DMF coming loose.

Obviously when you are in the car you have all the other gubbins to listen through before you hear the DMF e.g SAI, Carbon canister and every other little tapping noise under our cars. I first heard my noise when I was starting my car up after leaving work as I work in a multi storey car park so the noise of the DMF was able to be heard knocking a lot easier with the sound bouncing off the walls.

After my discovery of the knocking I drove the car for about 1000 miles or so, then I upgraded to a SMF kit as I got annoyed the DMF gave up and I will never had that issue with a SMF

(I'm not to mechanically involved in my car when it comes to things like this so I didn't carry out any of the work to change it- but hope some of that information helps.)

Chris

 

[JoeeS3]

Hi Joe,

It would be making that noise it all the time to be honest- but the most amount of vibration the DMF would have to suffer is on initial start up, hence why you are mainly hearing it at that point.

Too 100% make sure it is the DMF giving up....I did this - put the car on some ramps, then get someone to listen to the gearbox when you turn it on from start up and also give the car a few revs. If the DMF is knackered then you will be able to hear it knocking all the time and every time you apply a little throttle the knock should in turn get louder with the extra vibration applied. This vibration can then be removed by pressing the clutch down whilst still revving the car, and obviously when the clutch is engaged the noise should go away if it is the DMF coming loose.

Obviously when you are in the car you have all the other gubbins to listen through before you hear the DMF e.g SAI, Carbon canister and every other little tapping noise under our cars. I first heard my noise when I was starting my car up after leaving work as I work in a multi storey car park so the noise of the DMF was able to be heard knocking a lot easier with the sound bouncing off the walls.

After my discovery of the knocking I drove the car for about 1000 miles or so, then I upgraded to a SMF kit as I got annoyed the DMF gave up and I will never had that issue with a SMF

(I'm not to mechanically involved in my car when it comes to things like this so I didn't carry out any of the work to change it- but hope some of that information helps.)

Chris

Thanks for the advice kwistof i believe it is the flywheel and im just going to start saving now for a new one then wen this one goes ill replace it for a smf, my coolant is still leaking though i know its not a cracked head or blown gasket as its been leaking for a good month now and ive use at least 2-3litres of coolant i would expect the car to be running very badly by now if that was the case, i will have to put somecardboard under my car for the night and see if i can source any leaks, thanks again for your help everyone

 

[dusty]

Leaks are pretty easy to spot because of the colour of the coolant there is a plastic housing bolted to the gearbox side of the head these are prone to getting hairline cracks in them look for traces of coolant on top of the gearbox

 

[JoeeS3]

found this very strange, i changed my coolant and thermo stat the other day, no coolant is leaking now and im not getting the knocking on startup??? but it was exactly the same as kwistof said his was whereby if i engaged the clutch the knocking would stop sooner. Surely me putting the correct coolant in and changing the thermostat wouldn't have stopped this? im so baffled by it.