Annoying resonating sound at 1900 rpm, what could this be?

Azur · 11th October 2021, 15:54

Hi,

I'm trying to figure out where to look for a resonating part at a speed between about 1700 and 1900 rpm. This is a 2.5 KV6 R 75. Something is resonating annoyingly at these revs, but I can't get the source clear yet. The sound is coming from about the height of the centre console in the engine compartment. Who has experience with which parts resonate? I'm trying to make a list, I'm looking at the heat shields of the exhaust, which are coming loose at the mounting points (already fixed), but what else could be vibrating and resonating?

Thanks in advance.
Emiel

roverbarmy · 12th October 2021, 12:31

That sounds like the point where the VIS starts to open the butterfly valve and they can cause resonance in the inlet tract (tromboning I believe they call it in the Land Rovers!).

Costa Fortuna · 12th October 2021, 12:36

That's exactly a problem I have yet to get to grips with - it's really annoying - so am going to enlist Mrs Costa to hold the revs whilst I go detective. Mine is quite harsh and comes in and out abruptly, harmonics I expect. I have a 2000 flavour 2.0 V6

Costa Fortuna · 12th October 2021, 12:40

Too metallic for the vis - it's like a heat shield or something. Mine also comes in at around 1200 rpm when on warmup phase goes away and returns at 1900. And could return higher up the rev range but general engine thrash makes it hard to determine.

xsport · 12th October 2021, 17:42

had a couple of these on my v6 over the years. one culprit was the small heatshield under the car next to the bottom lower rear mount. another culprit was a cracked (but hardly visible ) horseshoe exhaust to engine sump bracket. other causes could be the bolts for holding above the fusebox under the passenger glovebox . lastly on mine a vibrating heatshield between the power steering rack and engine block. i suppose the list is endless in reality ...

Azur · 13th October 2021, 08:47

Hi all and thanks for the reactions.

Indeed it does sound like a heat shield, more metallic than the VIS valves. And, the sound is more to the bottom of the engine. I know it is really hard to determine and it could be more things than one, but by creating the list it gives me and everyone else with thesame problems, a bit of insight where are the common problems with this resonating things. Thanks!

Costa Fortuna · 13th October 2021, 14:11

Good weather today so decided to find the rattly buzz. Found the main exhaust heatshield was adrift on one side, four fixings had failed as they do. Penny washers fixed that. So went around the engine bay and looked at all the heatshields of which there are a few - one or two were a little close to the power unit so eased them away. Whilst I was at it I replaced the alternator and discovered that the lower engine steady bush was toast.
Glad to say all buzzing/rattling gone. It's been there since I got the car so am pleased.
Hope this helps.

Azur · 15th October 2021, 10:13

Hi, thanks for the extra things to check and to put them on the list. Glad you where able to solve it! Well done.

11th October 2021, 15:54	#1
Azur Loves to post Rover 75 Saloon. 2,5 V6 Conn.SE auto, Moonstone green, White gold, Dorchester red Join Date: Mar 2018 Location: Hollandscheveld Posts: 479 Thanks: 684 Thanked 280 Times in 117 Posts	Annoying resonating sound at 1900 rpm, what could this be? Hi, I'm trying to figure out where to look for a resonating part at a speed between about 1700 and 1900 rpm. This is a 2.5 KV6 R 75. Something is resonating annoyingly at these revs, but I can't get the source clear yet. The sound is coming from about the height of the centre console in the engine compartment. Who has experience with which parts resonate? I'm trying to make a list, I'm looking at the heat shields of the exhaust, which are coming loose at the mounting points (already fixed), but what else could be vibrating and resonating? Thanks in advance. Emiel __________________

12th October 2021, 12:31	#2
roverbarmy This is my second home Roverless + 1.7D Sportage Join Date: Aug 2014 Location: East Norfolk Posts: 7,050 Thanks: 729 Thanked 2,021 Times in 1,449 Posts	That sounds like the point where the VIS starts to open the butterfly valve and they can cause resonance in the inlet tract (tromboning I believe they call it in the Land Rovers!). __________________ Oil in my veins!

13th October 2021, 08:47	#6
Azur Loves to post Rover 75 Saloon. 2,5 V6 Conn.SE auto, Moonstone green, White gold, Dorchester red Join Date: Mar 2018 Location: Hollandscheveld Posts: 479 Thanks: 684 Thanked 280 Times in 117 Posts	Hi all and thanks for the reactions. Indeed it does sound like a heat shield, more metallic than the VIS valves. And, the sound is more to the bottom of the engine. I know it is really hard to determine and it could be more things than one, but by creating the list it gives me and everyone else with thesame problems, a bit of insight where are the common problems with this resonating things. Thanks! __________________

15th October 2021, 10:13	#8
Azur Loves to post Rover 75 Saloon. 2,5 V6 Conn.SE auto, Moonstone green, White gold, Dorchester red Join Date: Mar 2018 Location: Hollandscheveld Posts: 479 Thanks: 684 Thanked 280 Times in 117 Posts	Hi, thanks for the extra things to check and to put them on the list. Glad you where able to solve it! Well done. __________________

12th October 2021, 12:36	#3
Costa Fortuna Avid contributor Rover 75 Saloon Join Date: Sep 2020 Location: POOLE Posts: 121 Thanks: 24 Thanked 44 Times in 27 Posts	That's exactly a problem I have yet to get to grips with - it's really annoying - so am going to enlist Mrs Costa to hold the revs whilst I go detective. Mine is quite harsh and comes in and out abruptly, harmonics I expect. I have a 2000 flavour 2.0 V6

12th October 2021, 12:40	#4
Costa Fortuna Avid contributor Rover 75 Saloon Join Date: Sep 2020 Location: POOLE Posts: 121 Thanks: 24 Thanked 44 Times in 27 Posts	Too metallic for the vis - it's like a heat shield or something. Mine also comes in at around 1200 rpm when on warmup phase goes away and returns at 1900. And could return higher up the rev range but general engine thrash makes it hard to determine.

12th October 2021, 17:42	#5
xsport Posted a thing or two rover 75 club se Join Date: Apr 2011 Location: Leicester Posts: 1,637 Thanks: 358 Thanked 419 Times in 310 Posts	had a couple of these on my v6 over the years. one culprit was the small heatshield under the car next to the bottom lower rear mount. another culprit was a cracked (but hardly visible ) horseshoe exhaust to engine sump bracket. other causes could be the bolts for holding above the fusebox under the passenger glovebox . lastly on mine a vibrating heatshield between the power steering rack and engine block. i suppose the list is endless in reality ...

13th October 2021, 14:11	#7
Costa Fortuna Avid contributor Rover 75 Saloon Join Date: Sep 2020 Location: POOLE Posts: 121 Thanks: 24 Thanked 44 Times in 27 Posts	Good weather today so decided to find the rattly buzz. Found the main exhaust heatshield was adrift on one side, four fixings had failed as they do. Penny washers fixed that. So went around the engine bay and looked at all the heatshields of which there are a few - one or two were a little close to the power unit so eased them away. Whilst I was at it I replaced the alternator and discovered that the lower engine steady bush was toast. Glad to say all buzzing/rattling gone. It's been there since I got the car so am pleased. Hope this helps.