Tapping noise ?

[Rav4logrox]

Hi RAV4 owners, 

I’ve noticed a subtle tapping noise from under the Bonnet when I have parked up and the engine is just ticking over. I have put a video on the bottom to see if any fellow RAV4 owners know what the potential problem maybe before I spend thousands of pounds. 
Its a 2.0 Diesel, D4D with 750000 miles, 53 plate.

[Grumpy stumpy]

Cam belt maybe ? Does it get faster with engine revs increased ? Or any other drive belt ? Sounds like something catching so may be a strand from a belt .

[Rav4logrox]

1 hour ago, Grumpy stumpy said:

Cam belt maybe ? Does it get faster with engine revs increased ? Or any other drive belt ? Sounds like something catching so may be a strand from a belt .

When it’s reved the noise goes, the noise does also occurs when pushing the clutch pedal down when stationary. 

[furtula]

Any idea which side of the engine it's coming from? Should at least help eliminate some things.

[Rav4logrox]

Hi there 

it’s difficult to pinpoint, but would say it’s the middle as opposed to the left or the right side

Many thanks 

[Rav4logrox]

Ok, popped to the garage and they checked the noise, they don’t think it’s the clutch or the flywheel, there’s talk of it being a belt as mentioned previously. 

The tapping appears to be more prominent on the drivers side after additional inspection. 

If anyone has ever experienced this kind of problem or noise ? 
 

Thanks again 

[furtula]

Could be the belt, but to me the knocking does not appear to be in very regular intervals.

Try to inspect the belt by eye, with a nice strong light if you have any.

Did you try disabling the AC, could be the compressor?

Does it behave the same when car is cold, and warmed up, on idle? Does it maybe knock less when warm, or in longer intervals?

My guess would be the intake manifold, or intake manifold flaps, since i had something similar. You can see bunch of examples on youtube.

Put your hand on it, try to feel for any obvious vibrations, or try to use a long screwdriver to amplify the sounds from the car (screwdriver test), if you dont know what i mean, check online for examples.

[Rav4logrox]

On 12/12/2019 at 2:59 PM, furtula said:

Could be the belt, but to me the knocking does not appear to be in very regular intervals.

Try to inspect the belt by eye, with a nice strong light if you have any.

Did you try disabling the AC, could be the compressor?

Does it behave the same when car is cold, and warmed up, on idle? Does it maybe knock less when warm, or in longer intervals?

My guess would be the intake manifold, or intake manifold flaps, since i had something similar. You can see bunch of examples on youtube.

Put your hand on it, try to feel for any obvious vibrations, or try to use a long screwdriver to amplify the sounds from the car (screwdriver test), if you dont know what i mean, check online for examples.

Hi there 

Yes the knocking is quite sporadic and not really in any sequence, it does also happen intermittently so it’s quite frustrating to say the least. 

I haven’t tried to disable to A/C so will definitely give that a try, the tapping occurs when idle, and when both warm and cold, it did however reduce in noise when I reved the car..

I’ll have a look on YouTube now for examples, many thanks for your assistance 

[Mikeyjd]

You say the noise also occurs when you press the clutch. Is the cable fouling on something maybe? When you press the clutch, the cable changes shape slightly, maybe it is lying very close to a moving part and occasionally touches it. If it is that, it would be pretty easy to move the cable slightly.

[Thermal]

To me, it sounds like a radiator fanblade hits something. That could explain the sound disappearing when revving, because the fanblades also rev and deform slightly .

Also, most clutches are hydrolic these days, without cables.

[Rav4logrox]

Thanks for your help, the noise has now stopped, which was super strange as nothing occurred for it to stop. The only thing I did do was turn my air con on and off again, which I wouldn’t have thought that would have been the problem. 
 

The fan blade is a possibility too, definitely sounds like something catching, we figured out that the noise wasn’t just from when lifting the clutch, it does however have a slight ‘squeal’ when the pedal is lifting, but I think that’s something else. 
 

l do love these cars so it’s frustrating when something like this happens

 

[furtula]

Cold weather causes bunch of new sounds to appear, enjoy the car, don't stress about it.

Squeal when operating the clutch is fine, it's usually the tiny rod  going out of the clutch slave, that operates the lever, and the squeal is caused by the contact between the rod and the lever.

You can put some lube there if it annoys you.

 

 

[Thermal]

Something else that could cause the tapping noise: There is a mechanical clutch in belt driven airco systems, that engages when the airco is switched on and disengages when switched off.

The tapping noise can occur when the airco is switched off, but the claws of the clutch do not fully disengage because of wear.

Years ago, there was a topic on this forum somewhere (I think in the Avensis section) on refurbishing and re-adjusting the airco clutch, but I could not find it quickly.

Have a look!

And on the subject of squeal when the clutch pedal is depressed,  the spring that retracts the clutch pedal is a notorious squealer. A bit of grease on its hooks takes care of that.

[IanML]

I'm not a diesel person, but I seem to remember some diesels have a vacuum pump for the brake servo, because there is no manifold vacuum.  Allegedly, (probably this site) the pump can make a ticking noise.

[Thermal]

Not only diesels, my 1.8 petrol Avensis had one.

That has to do with the variable valve timing system, where there is no reliable inlet vacuum for the brake servo anymore. However, the vacuum pumps produce a "different" tapping sound, unlike what is heard in the first post.