Knocking/tapping sound coming from top of engine when revving

RachelHG · 2024-01-02 14:51:05

Hi everyone,

wondering if anyone on here has had a similar problem. I have a fiat scudo 2001 reg 1.9 deisel engine non turbo. I was driving at about 30 miles per hour and suddenly heard a loud knocking/tapping sound coming from the engine. I pulled over and opened bonnet. I smelled something too, like smthing had gotten too hot but not burning and there ws no smoke or steam. Oil and water levels were fine. Didn't seem wise to drive with the sound so called breakdown. It does not make the noise when idle, just when revving or accelerating. It does not seem as loud now when I switch it on and rev the engine.. maybe because it has cooled down as this was the next day.

There is also a problem with the relay. Indicators and hazards stop working randomly then start again. Not sure if this could be connected.

Will be super grateful for any insights.

Thanks,

Rachel

AlvyLad · 2024-01-02 16:51:15

Herm, I'll leave this to the better mechanically minded experts here, to me sounds a bit like belt snapping (partial shredding), that perhaps even water pump start clanking and then stopping...
Better still would be if you'd perhaps make a video w sound?

RachelHG · 2024-01-02 17:01:00

Hi AlvyLad,

Thanks for your reply. I recently had the timing belt changed and it looks in good order to me. Good idea bout making a video.. will try do it asap although the sound seems to have gone quieter now maybe because engine hs cooled.

OAT · 2024-01-02 18:19:01

While having the belt changed recently is reassuring, it does also suggest an opportunity for something not to have been quite right with the fitment or adjustment. I hope not but that is what instantly jumps to mind without anything else to go on.

A vid would be useful. Hopefully a more minor bearing or component failure.

I shouldn't worry too much about the indicators till you get the engine sorted. smile

Last edited by OAT (2024-01-02 18:19:33)

JohnDragonMan · 2024-01-03 00:39:06

it can be anything from an injector not firing right to the timing being slightly off. a tapping sound can indicate oil starvation to the valve train as these engines use the oil to hydraulically cushion the cam pressing the valve open helping keep things quiet. hows the servicing on the van been? it can be wise on a service to use an oil thinner/flush to help break down anything blocking an oil gallery.

yes a video/audio recording would be good. smile

kenbw2 · 2024-01-03 01:41:38

JohnDragonMan wrote:

helping keep things quiet

I assume that's in relative terms tongue

RachelHG · 2024-01-04 18:58:58

Hi thanks all for your replies.
Due to my lack of knowledge I got confused between the timing belt and the serpentine belt.. I was talking about having the serpentine belt changed recently. Not the timing belt.

The van had a service back in the summer, my mechanic did it so I don't know if he used an oil thinner.

Will try and record the sound asap. Thanks again for responses.

Casper · 2024-01-08 02:31:56

JohnDragonMan wrote:

it can be anything from an injector not firing right to the timing being slightly off. a tapping sound can indicate oil starvation to the valve train as these engines use the oil to hydraulically cushion the cam pressing the valve open helping keep things quiet. hows the servicing on the van been? it can be wise on a service to use an oil thinner/flush to help break down anything blocking an oil gallery.
yes a video/audio recording would be good.

Was thinking hydraulic tappets myself. Does the DW8 have them? (Never needed to look into it before) I had a Fiat Stilo with them and when a service was wellllllll overdue it sounded like a bag of tapping crap. This was due to the dirty oil and hydraulic tappets. An oil change would cure the problem.
Would a non electronic injector make much noise unless it has a partial block and even then would you hear it as a tapping when in the cab?

JohnDragonMan · 2024-01-08 23:02:57

yes it does very much so. the cam lobes directly contact the "shims" (spacers) above the valves. the valve train setup is practically identical to the Fiat FIRE engine found in the old Panda, Cinquecento (sporting), Uno and Punto.. pretty much any 90s Fiat with an over head cam 8 valve engine size between 750cc to 1400cc

i have never known an injector its self to sound noisy while injecting. however an incorrect spray pattern or low pressure could cause a knock.. just like when a diesel is cold starting. however a bad burn would be very easy to tell by the smoke from the exhaust. low pressure is unlikely on a HDI as it has a common rail at a constant pressure

you could unplug the electrical connector from each injector individually and see if the knock goes away if it does on one cylinder that that would indicate an injector/burn issue.

another thing you could do is go down a long hill and turn off the ignition (but instantly turn it back to the aux radio powering position or the steering lock will come on!) then listen to see if you can hear the tapping sound still. that would indicate a mechanical taping and not a injection/bad burn knock as the injectors would be electrically off.

what i want to know is how fast the tapping sound it to the sound of the engine. just from that i will be able to tell what part it is.

OAT · 2024-01-12 02:38:03

Without hearing it, it's all speculation.

Casper · 2024-01-12 12:26:16

OAT wrote:

Without hearing it, it's all speculation.

Remember in the 70's when cars had small stainless steel hub caps? I wonder what shit in his youth used to take them off and put old nuts and bolts in them and pop back on again. big_smile

The Dispatch | Expert | Scudo Hub

Get help & share your Citroen Dispatch (Jumpy) | Peugeot Expert | Fiat Scudo tips

#1 2024-01-02 14:51:05

Knocking/tapping sound coming from top of engine when revving

#2 2024-01-02 16:51:15

Re: Knocking/tapping sound coming from top of engine when revving

#3 2024-01-02 17:01:00

Re: Knocking/tapping sound coming from top of engine when revving

#4 2024-01-02 18:19:01

Re: Knocking/tapping sound coming from top of engine when revving

#5 2024-01-03 00:39:06

Re: Knocking/tapping sound coming from top of engine when revving

#6 2024-01-03 01:41:38

Re: Knocking/tapping sound coming from top of engine when revving

#7 2024-01-04 18:58:58

Re: Knocking/tapping sound coming from top of engine when revving

#8 2024-01-08 02:31:56

Re: Knocking/tapping sound coming from top of engine when revving

#9 2024-01-08 23:02:57

Re: Knocking/tapping sound coming from top of engine when revving

#10 2024-01-12 02:38:03

Re: Knocking/tapping sound coming from top of engine when revving

#11 2024-01-12 12:26:16

Re: Knocking/tapping sound coming from top of engine when revving

Board footer