T6.1 TDI450 strange thumping at idle

[KeithRMelb]

My van's back from having the flywheel replaced under warranty and from having the intake manifold replaced under warranty, but now I have a new odd sound. Once the van is fully up to temperature I get a strange intermittent knocking/thumping at idle that sounds to me a bit like water boiling near the intake manifold, like the system hadn't been bled properly when the manifold went back on. It's a slow non-metallic thump completely unrelated to engine speed, that can be heard from inside the van and from outside the van. Moving around the engine bay it appears to be from somewhere close to the intake manifold, ie, back upper engine. Oil level is good, coolant level is good.. I have video

You can actually hear the noise stop during the recording..

 

[manfrotto]

Hi and welcome to the forum,
As your van is still under warranty, I would just take it back to the dealer who did the other work.

 

[mmi]

EGR self test.

Post in thread 'Where’s This Bit From? . . . . Tonight’s Quiz'

6 Jun 2021

Well, not exactly a bit, rather T6 diesel behaviour - every now and then.

T6. Engine hot. Starts when vehicle has reached standstill. Engine on tick-over - 830 RPM. Stop/start doesn't shut off the engine.

Sound clip attached - a "hiccup" regularly every 1.5 seconds. Can last up to two minutes. Recording made outside. Best heard on right side of vehicle (standing by right front wheel). Can be heard in cabin, too.
View attachment T6_CXEB_Hiccup_20181213.mp3

• mmi

• 

 

[KeithRMelb]

EGR self test.

Post in thread 'Where’s This Bit From? . . . . Tonight’s Quiz'

6 Jun 2021

Well, not exactly a bit, rather T6 diesel behaviour - every now and then.

T6. Engine hot. Starts when vehicle has reached standstill. Engine on tick-over - 830 RPM. Stop/start doesn't shut off the engine.

Sound clip attached - a "hiccup" regularly every 1.5 seconds. Can last up to two minutes. Recording made outside. Best heard on right side of vehicle (standing by right front wheel). Can be heard in cabin, too.
View attachment T6_CXEB_Hiccup_20181213.mp3

• mmi

• 

Thanks for that. Van's on 108000, non-adblue, and I'd never heard it before that last round of works, and it wasn't even straight away after the manifold replacement. But since the dealership also managed to destroy the brake pad sensor plug and gave it back to me "the brakes need checking" but with the sensor plugs neatly zip-tied out of the way.. don't really want to risk the van going back there - dodgy pricks were obviously thinking I'd just say "well hang onto it and do the brakes too" but I knew they were about 90% and they would have just charged me for a brake replacement that didn't need doing while they fix the harness plug that they smashed.