Blacktop 20v, rattly noise at 1500rpm please help diagnose.

[RobertC]

Audio clip of noise

1500rpm is the only point where the noise is present. Above and below it goes away.

With the bonnet up it "sounds like" its coming form the cam belt end of the engine.

Apart from the noise the motor appears to run fine. Has done 130,000km.


Is this what a stuffed vvt pulley sounds like?

[RS13]

When a VVT pulley goes it sounds more like a diesel at idle. Simple way to check, put 12V to the VVT solenoid on the engine while idling, if the noise goes away then it could be that.

Almost sounds more like something rubbing on the covers.

[touge_ae101]

if the engine has been sitting for a while sometimes the oil dries out/falls out of the shims/buckets. there is normally a thin layer in there which dampens the sound a bit.

but i would be checking under cam covers as well I had a bolt/stone get jammed under cam covers in the aw11 and chewed the cambelt/crank sprocket down until it broke. would not want to be doing that on an interference engine..

[Rick]

Mine old 20v made a funny noise around 4000 rpm from memory, when I looked into what was causing the noise what had happened was the hydraulic tension for the cam belt had failed and there was no tension and the cam belt was flapping and hitting the plastic cam cover. So that's an easy check, just take off the top cam belt cover and press/pull on the cam belt to feel if there is any tension.

[Bling]

Checked all parts of the exhaust for rattles etc?

[jacobrjett]

make sure everything thats bolted to the engine is tight...

seriously ive had about 5 or 6 rattles on my old bzr, because things kept coming loose.

the front and rear engine mount slowly came loose, the powersteering/alternator brackets came loose a couple of times,

and one time just a little loose bolt that holds the plastic spark lead cover down actually made a rattle.

pretty much every single part was something I had touched though lol. I just got some loctite and gradually as everything that had come loose i loctited them and tightened them the $&#$% up.

id get in there and make sure everything from the engine mounts, powersteering/air conditioning/alternator brackets and all the little bolts around the engine are tight before looking into replacing stuff.

[jacobrjett]

hmm that seems like a more metallic sound then the sounds mine used to make though.

[RobertC]

will do a bit more investigating tomorrow. Took off the top two bolts of the belt cover and its definitely louder if you pull the cover away from the belt.

[stolic]

+1 for alt vibration.

when running in a 7age I built, it developed a sound like a camshaft was about to have a messy divorce with the head. wasn't until I was leaning over the engine listening to certain engine death, that I randomly put my hand on the alt.... turns out the nut had come off the lower bolt. new nut and BAM the sound is gone...

Hope your issue is as easy to solve

[85AW20v]

And put a bit of hose in your ear with the other around the engine to track the noise down - bit like a stethoscope. You'll definitely know when you get close to the source of the sound.

[jacobrjett]

yeah just loose bolts make obscene rattles,

you said you took the timing cover off and it got louder, you have put a replacement engine in right? if you did im guessing you did the cam belt and the waterpump while it was easy, im pretty sure the bolts for the water pump bolt it to the block behind the cam belt, try those bolts maybe...

[jacobrjett]

or even the timing belt tensioner/tensioner pulley...

i dont know if this is of any help, but when i was trying to diagnose a rattle in my car when i first got it (i was hopelessly trying to convince myself it wasnt a main/big end bearing at the time ) i found a lot more vvt pulley sound videos of the sr20 engines, im not sure if they work the same as the 4age but they sounded like this

https://www.youtube.com/watch?v=40V8fqhmon0

[RobertC]

All fixed thanks. Car is one I have just purchased, previous owner didn't know if cam belt had been done. (didn't want to tell me it hadn't been done...)

Car has done 130,000 kms.

So ordered parts for the timing belt, pulled off number one timing belt cover and revved the car to 1500rpm turns out the noise was the belt slapping on the cover.

So did the full timing belt replacement. (small hickup meant I had to to the whole process twice as the new water pump leaked !!!!

Old tensioner was like this (supposed to require 100kg to compress the piston, now my thumb is strong but not that strong)




Car runs beautifully now though.