Thump on cold starting

[rogermunns]

Car spec. is late 2007, 63000miles, DSG auto., non FAP.
Recently on cold starting (first start of day) there is a thump as it fires. This has come on in last three weeks. Nothing I can think of to suggest what this is, but concern centres around crankshaft pulley - is it 'dual' construction? Otherwise, runs beautifully, just a little hesitation and jerking at 1mph in heavy traffic.

[Guest 2]

Is it loud enough to hear in a video?


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[rogermunns]

No, it isn't. Its as if someone had kicked the car. You feel it as much as hear it. Like a single heavy shake.

[-M-]

Could be the pendulum support for the gear box - this would give a thump on starting plus uneven idle.

Could be a dual mass flywheel if you have a diesel etc.

[rogermunns]

It is a 2.0Tdi 140 with DSG box

[davmal735]

Mine has been doing this for the past 4 years. It's almost as though the first fuel delivery is too big. When starting warm it's as smooth as a whippet's ear.

[rogermunns]

Just went out to do a bit more investigation.

First, I have not used the handbrake for 3 weeks because I had a problem in heavy traffic. I stopped at lights put handbrake on, it only released after several attempts. Might the fact that I have not been putting the h/brake on be the reason I get a lump? Looking back, it does seem that the lumping started about the same time that I stopped using the h/brake.

I started the car a few minutes ago (handbrake as it has been for 3 weeks, i.e. off). Big bump. Stopped car after ~10 seconds. Another start, another bump. I do know from the last 3 weeks that once the car has been run (minutes or hours) then there will be no starting thump for the rest of the day.

It was after this little test that I put the handbrake on - and off!! - several times.

Tomorrow I will try a cold start with the handbrake on.

What sort of job (cost) is the DMF replacement if it has one? I don't do car work anymore, after 40 years of doing it myself.

[rogermunns]

Thanks, Davmal, your reassurance is nice.

[martin1810]

I doubt the epb is related to the thump. A vcds scan might show what the cam and crank sensors are saying on start up. They can cause some odd starts like you describe. A clutch/dmf replacement is expensive. Expect nearer £1000 than £500