Collection of noises on cold start

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heavydee, Nov 5, 7:29pm
I have an 06 Honda Accord V6. Used to idle and run as smooth as anything. Recently it's developed a raspy, tappet noise when started from cold. Goes away once warm. Difficult to describe, not something I've come across in other cars.

Took it to a shop who held onto it for a day a day and couldn't hear anything. It's since gotten worse and does it every time when cold, but goes back to sounding normal once warm.

Any ideas what it could be? Could a worn oxygen sensor cause that?

intrade, Nov 5, 7:38pm
well if its a chain drive motor. Then the question is have you changed the oil once a year or 10.000km what ever is sooner with correct factory spec oil and filters.
Because that noise sounds like your cam chain if it has it is about to go fubar.

heavydee, Nov 5, 7:42pm
It's got a full service history from new. Cam belt motor with proof it has been changed.

The shop I took it to ruled out issues with the valve train as they said it would constantly make the noise, not just when cold.

intrade, Nov 5, 7:51pm
tappets make noise when cold when there is insufficient oil pressure due to for example a faulty oil filter oil drainback valve. To name one reason. any mechanic with a brain should be able to tell you this.

cattleshed, Nov 5, 7:51pm
Get a stethoscope and determine where the noise is coming from. Check your oil level. Perhaps it is low? Oil quality and grade? Replace oil filter. Drain and fill with manufacturer specified grade engine oil. Not sure if hydraulic tappets and if adjustable. May need adjusting. IF it is tappet noise and IF they are non adjustable and IF the noise is still there having replaced oil and filter MBL8 may be worth adding.

franc123, Nov 5, 7:56pm
Needs to be pinpointed exactly where it's coming from. It may require you leaving it at the garage for a few days so they can do several cold starts and find out where it's coming from. It could be even something silly like loose exhaust shielding which is only reacting to the vibrations only generated when running cold. Those V6 Accords were also hard on engine mounts which again if one of those fails it could be generating poor harmonics and upsetting something else. If by chance it is due for service I would do that at the same time. I seem to recall those engines still require a manual valve clearance adjustment, if there is no record if this being done in the last 100000km it will need doing.

tamarillo, Nov 5, 7:56pm
Did it by chance start after oil filter change? Some filters have a by pass valve giving valve train instant oil on start up, and if a cheap filter is used without this a noise occurs. Just a long shot but happened to me once on a bmw.

intrade, Nov 5, 7:58pm
well thinking if they are shimmed then it would make noises cold and then stop hot when play from expansion is enough to stop the noise. Not all new cars have hydraulic valves quite a lot manufacturer went the cheap rout and shimmed them Some are incorrect shimmed from brand new.

heavydee, Nov 5, 8:11pm
Yes, my understanding is the valve clearances are meant to be adjusted at 100 km, and there's no specific mention of it in the service history. I suggested this to the shop and the guy brushed it off.

heavydee, Nov 5, 8:15pm
Thanks for the advice everyone. I'm not certain it's got anything to do with the valves, I just don't know how else to describe the noise.

Looks like I'm taking it back to the shop for an oil change and proper diagnosis.

heavydee, Nov 5, 8:22pm
Ok, cheers. Sounds like an oil change is a reasonable first step then while it's in the shop for another listen.

intrade, Nov 5, 8:22pm
noises are difficult to discribe and recording them also dont works well most times.

heavydee, Nov 5, 8:27pm
Yes, I've checked the oil level and it had been changed on time. I'll book it in for a service and mention the suggestions on here to the mechanic.

utwo, Nov 5, 8:41pm
I'd definitely check the valve clearances. Like you said, they're supposed to be checked at 100,000km. https://youtu.be/iLdgivYwUiQ?t=150

franc123, Nov 5, 10:46pm
I've seen that happen more than once, I dont use non genuine oil filters on my own stuff any longer because of it either. One car had hideous hydraulic lifter noise for a minute and another one had a timing chain rattle for several seconds after starting, both engines were cold and were running specified oil. Putting decent filters on solved both issues, sure its really just an annoyance but it shouldnt be happening!

gpg58, Nov 5, 11:59pm
Seems unlikely to be valves imo, as the oil thins / warms up, it surely would get louder, not quieter.
If fault continues after oil and specified filter change, i would start looking at oil pickup strainer for blockage, or oil pump and relief valve next.
Personally if i had to pay, and it runs fine when warn, i would worry about adjusting valves later, and perhaps drop sump and check oil pump etc now.

marte, Nov 6, 12:04am
Mine started a camchain rattle on startup suddenly line morning, after a night or just driving around.
After the first startup of the day it's ok, it's only when it's near dead cold.
I put some engine oil cleaner in it and it's helped a bit over time & I will change the filter & oil in 100 kms or so when the filter wrench cap thing arrives.
It's done 3200 kms since the last oil/filter change.

Alternatively it's a slightly blocked oil pickup, or worse it needs a new oil pump as well as the balancers removed, or something to do with a sticking one way valve on the oil pump.

But the engine cleaners helped & weirdly at the same time it happened, I'm getting a slight vacuum pull on the oil cap ( like it should be? ) & It misses with the cap off.
It needs a new valve cover gasket too. Slight oil leak & I can check for wear on the camchain adjusters guides.

kazbanz, Nov 6, 9:01am
Just a guess. The car sits outside at night engine bay gets cold and even possibly a bit damp. At the garage it was kept inside the workshop. The issue is with one of or both of the accessory belts. That kinda fits with how op describes whats happened.

strobo, Nov 6, 9:25am
OP said "It used to idle and run as smooth as anything." so it's not just noises ,it's not running very well either !so there is more going on than noises.It sounds more like opening a can of worms. In the past iv'e used proma MBL8 as a diagnostic tool on the mechanical s ,lifters etc ,if the noises remain after fitting that stuff ,there is a definite worn out mechanical part or parts somewhere that needs attention .A full service + tune up. should be done prior to pointing fingers at any items,often things during this process show up. At first glance a stethoscope of sorts should be used in the area of where the noises are coming from .ie pulley bearings , valve covers, at least isolate which area ,front , rear or top side.hot and cold .at least make some deductions .If owner can't draw anything from that op could get a garage to do a mechanical assessment and report on the engines condition .paid for and done without guessing

franc123, Nov 6, 9:33am
In the past I've had alternator clutches that have been on the way out make nasty noises when cold as naturally in the few minutes following a cold start the alternator is working very hard to recharge the battery. It's all very much guesswork until the area of concern can be ID'ed.

strobo, Nov 6, 9:37am
Come on intrade #12 !Your eyes and ears don't tell lies do they ? lol ;-)

dublo, Nov 6, 2:55pm
Similar problem with our NZ-new, full service history, 1999 Accord V6. Bought at 64000km in 2009 and had cam belt, water pump and drive belts changed. About 2014 and at about 90000km noticed slight rattle in valve gear, several seconds after first cold start of the day and only in cold winter weather. It continued for approx. 10 seconds. Honda shop listened to it after leaving car there overnight, said don't worry, valve gear bullet-proof. Also said no need to check valve rocker clearances unless rattle is continuous. In 2018, at 119000km, I took the car to our WoF garage, he confirmed noise coming from valve gear, suggested lighter oil. I was using 10W/30, changed to 5W/30 semi-synthetic and continued using Ryco filters. Result was better - rattle not as prolonged, and this winter, at 127000km, we noticed the noise had almost disappeared, just an occasional rattle. The engine uses negligible oil between its annual oil and filter changes and is "Rolls-Royce" quiet.But I still listen carefully when I do the first start of the day.

strobo, Nov 6, 4:50pm
#22 .The trouble with multigrade lighter oils . thinner oil flows faster to the moving parts when cold , but there is no oil retention to the top end parts over night and drains away quicker than cooking oil from a fry pan.That's why I use mbl8 or lucas/Moreys treatment between oil changes ,Iv'e seen the results!.You know then on cold mornings there is a good coating of oil around inside the engine and hot runs there is always protection.Nothing but the best!Less noise/full protection or in most cases noises totally eliminated!

ralphdog1, Nov 6, 7:56pm
How long is the noise apparent after starting?

nice_lady, Nov 6, 8:18pm
Use a long screwdriver with the handle end on your ear and the pointy end at different places on the engine.