Knocking on start up

This is the Forum for all your Citroen Technical Questions, Problems or Advice.
Blue007
Posts: 17
Joined: 14 Oct 2024, 06:22

Knocking on start up

Unread post by Blue007 »

Hi everyone,
Cut a long story short,had to go do some work in oxford,Anyway van was running fine before, (dispatch 2L 2008 lwb)
The roads are a 3rd world country,potholes everywhere,some are so wide I would say dangerous,
Anyway started to get a knock sound especially on start up,will try add the sound)
Looked on various forums,some say coolant temperature sensor but can't find it,
Others air intake temperature,don't seem to have it on my engine,( after seeing a video) but there's one below it but nothing attached inside the hose,
Also since being here ns tyre needs pumping up every 2 days( not sure if that coincidence or not, been to tyre fitters couldn't find a problem with the tyre,,
Was OK before,seem I can't add video off the noise,
Thanks in advance Ste
Attachments
20260214_083320.jpg
RichardW
Forum Treasurer
Posts: 12532
Joined: 07 Aug 2002, 17:12
x 1475

Re: Knocking on start up

Unread post by RichardW »

You need to upload the video to YouTube then share it here.
Richard W
Blue007
Posts: 17
Joined: 14 Oct 2024, 06:22

Re: Knocking on start up

Unread post by Blue007 »

Not sure how you do that Richard W
Blue007
Posts: 17
Joined: 14 Oct 2024, 06:22

Re: Knocking on start up

Unread post by Blue007 »

User avatar
Sloppysod
Moderating Team
Posts: 1481
Joined: 23 May 2015, 23:35
x 382

Re: Knocking on start up

Unread post by Sloppysod »

Blue007 wrote: 15 Feb 2026, 08:39 Not sure how you do that Richard W
Do you have a Google account?
If so..
https://support.google.com/youtube/answ ... %3DDesktop

Blue007 wrote: 15 Feb 2026, 09:00 Hopefully this works
Possibly, but people need an account to view. So they don't
.
Stu 🏴󠁧󠁢󠁷󠁬󠁳󠁿

"Some cause happiness wherever they go, others whenever they go"Oscar Wilde (1854-1900)
User avatar
Paul-R
Moderating Team
Posts: 9184
Joined: 07 May 2009, 16:24
x 1909

Re: Knocking on start up

Unread post by Paul-R »

Sloppysod wrote: 15 Feb 2026, 10:51
Blue007 wrote: 15 Feb 2026, 09:00 Hopefully this works
Possibly, but people need an account to view. So they don't.
If the photobucket link contains a photo or other image then upload it directly to the forum using the process here viewtopic.php?f=9&t=56795

If it contains a video of some kind then upload it to YouTube and then post the YouTube link here.

If it contains an audio file then I'm afraid I don't know how to host it somewhere. Maybe YouTube will do it? Not sure at all.
As I get older I think a lot about the hereafter - I go into a room and then wonder what I'm here after.

Inside every old person is a young person wondering what the hell happened.

"Trying is the first step towards failure" ~ Homer J Simpson
Blue007
Posts: 17
Joined: 14 Oct 2024, 06:22

Re: Knocking on start up

Unread post by Blue007 »

Well what a ball ache that was,not into this kind off stuff,
But thanks to thoughs who suggested youtube
First one ever.😀
https://youtube.com/@std-s7w?si=3f35CC67o4w-va51
User avatar
Sloppysod
Moderating Team
Posts: 1481
Joined: 23 May 2015, 23:35
x 382

Re: Knocking on start up

Unread post by Sloppysod »

Blue007 wrote: 15 Feb 2026, 16:52 Well what a ball ache that was,not into this kind off stuff,
Everyday is a school day, well done👏👏

It soundis like a normal Diesel until around the 7 seconds mark, then it sounds like it's blowing a raspberry!
Alas, no idea, other than something flapping around in the intake system or......
Stu 🏴󠁧󠁢󠁷󠁬󠁳󠁿

"Some cause happiness wherever they go, others whenever they go"Oscar Wilde (1854-1900)
PaulC5
Donor 2024
Posts: 2512
Joined: 06 Jun 2023, 15:26
x 654

Re: Knocking on start up

Unread post by PaulC5 »

Maybe there is an air leak in one of the vacuum pipes or ducting. Can you hear it under the bonnet ?

For the tyre going down, you might have to remove the wheel and wet the tyre, valve and wheel with soapy water and look for bubbles showing a leak. If the tyre is not leaking then it could be a damaged wheel.
Blue007
Posts: 17
Joined: 14 Oct 2024, 06:22

Re: Knocking on start up

Unread post by Blue007 »

😀 it sure is,was doing it on my phone,sloppysod,
That noise is the lowest I've heard,a couple of times knocking like hell,
Did look under the bonnet when it is really bad, couldn't really find anything as such, as in loose.
Blue007
Posts: 17
Joined: 14 Oct 2024, 06:22

Re: Knocking on start up

Unread post by Blue007 »

PaulC5 wrote: 16 Feb 2026, 12:09 Maybe there is an air leak in one of the vacuum pipes or ducting. Can you hear it under the bonnet ?

For the tyre going down, you might have to remove the wheel and wet the tyre, valve and wheel with soapy water and look for bubbles showing a leak. If the tyre is not leaking then it could be a damaged wheel.
Hi Paul C5
When in the cab it feels like it under the floor panel,but under the bonnet it seem to knocking all the engine,
Googling some say coolant temperature sensor can have a effect,on mixture,bought one I believe now its behind air filter housing,
Ait sensor on some models but It seems that on some models it's incorporated into the mas sensor,( I assume)
On the video I seen scudo engine looked the same as mine but he had two sensors, still can't find what that sensor is.in the pic.
As for the tyre took to a fitter, checked it no leaks/air bubbles,changed the valve, day later lost 5psi,went back checked it again resealed it, after doing leak test
PaulC5
Donor 2024
Posts: 2512
Joined: 06 Jun 2023, 15:26
x 654

Re: Knocking on start up

Unread post by PaulC5 »

Probably not the exhaust but you could check if any of the brackets have rusted off, I've had it on a couple of Citroen cars and noticed by a metallic knocking noise but took some time to find where from. Just pushing the tail pipe might make the noise before looking underneath. On the C3 and the Cactus I was able to buy repair brackets from Autodoc that just clamped on to replace the welded ones that had rusted off.
User avatar
Sloppysod
Moderating Team
Posts: 1481
Joined: 23 May 2015, 23:35
x 382

Re: Knocking on start up

Unread post by Sloppysod »

I take you have eliminated broken engine mounts? Even if the 'looks good, may be worth investigating with a crowbar.
Stu 🏴󠁧󠁢󠁷󠁬󠁳󠁿

"Some cause happiness wherever they go, others whenever they go"Oscar Wilde (1854-1900)
Blue007
Posts: 17
Joined: 14 Oct 2024, 06:22

Re: Knocking on start up

Unread post by Blue007 »

Sloppysod wrote: 17 Feb 2026, 13:46 I take you have eliminated broken engine mounts? Even if the 'looks good, may be worth investigating with a crowbar.
Changed the main one that goes through the shaft about 6month ago,that one was split very bad
The arm that connects to it was OK,the others seem OK,
Blue007
Posts: 17
Joined: 14 Oct 2024, 06:22

Re: Knocking on start up

Unread post by Blue007 »

Paulc5/Sloppysod
Apologies for not get back sooner had to go into hospital,
Just updating checked mounts, the o/s need to be replaced not as bad as the one that goes through the shaft(actually order them) but missed the delivery as in hospital, so resending this week.