Hey guys,
I hope this isnt anything too serious but lately on my 450SE ive noticed a 'knocking' noise. It's louder when the engine's cold and gets quiter as the engine warms up, to the point where u can hardly notice it. Im pretty sure its coming from the engine.
My car was recently converted to LPG , would this have anything to do with it?
Im not THAT mechanically minded, but i hope this isnt anything too serious! The car runs fine, as it always has. Ive heard of big end bearings going, causing knocking etc but surely if the car's running fine it couldnt be that?
Ryan
Is it a regular, deeper knocking sound like someone striking the engine block with a wooden mallet, or just something that happens occasional and less intense?
If it was a big end bearing it would be worse under load and you would still hear it when the car warms up.
My dad had a VS Commodore where a big end bearing bearing failed after 1500km, that was the characteristic of the sound. As you would expect, it was his last Holden. ;)
If it only happens when cold, it could be piston slap. I don't think I've ever heard piston slap occurring in an MB motor, though. It is almost normal in Volvo red block four cylinders.
Is the engine running smoothly when this happens?
Tim
hey TJ,
its not really that intense, but its regular. The car runs perfectly... no problem there at all. Im not even sure if its anything to worry bout, but i thought id better check . I guess really i need someone to have a look at it. Might drop it into my mechanic. I Wonder if its anythin to do with the LPG?
Get it checked by someone knowledgable - soon.
It doesn't sound right.
Bill
Is the noise there on every cold start?
How long before the noise disappears, seconds or minutes?
koan
yeah i should get someone to have a look at it. It may well be just me being paranoid but id rather be sure.
Funnily enough this morning i didnt really notice it... but last night on the way home from work it was quite loud. Tends to get quieter as the engine warms up
would the engine running lean cause it?
LPG is supposed to have a much higher octane rating than petrol so knocking would only be an issue if it was running too lean.
M-B engines can knock when cold - both my previous W211 - E320 and my present 164 - ML 500 had/have a little piston slap which is only audible when I stop to open the gate when leaving on a cold morning. They both have V6 and V8 versions of the same motor
Not audible from within the car - only when standing outside with a stone cold idling motor and disappears within minutes as the engine warms up.
I have never heard either my 450 or my 6.9 make the same noise though - totally knock free on a cold startup.
Bill
hmm okay , who knows perhaps it is lean?
can anyone reccomend a good mechanic north of the river (perth) to take a look at it, or does any one wanna have a look? :P
or would i be better taking it to the people who installed the LPG?
Youtube is your friend. Sounds like a time to video the engine idling both cold and hot and post for us to have a listen.
Some things to note though...
If the knock is more like a tap, or clank, it could be as simple as a hydraulic lifter not pressurising properly.
If the engine is missing on 1 cylinder (fouled plug) then the missed stroke can sometimes sound like an engine knock. I know whitey, my 450SE race car, sounds like its knocking when 1 cylinder (#2) fouls and then when another fouls (usually #6) the engine sounds like it running with no bearings...
Go around your 8 cylinders with a timing light and make sure all 8 are firing...
Is your Oel pressure good, and hits 3bar as soon as you press on the accelerator?.... Oel pressure (or lack of it) has a close relationship with the condition of the bearings.
Whitey also had a terrible knocking when i bought it but would subside as the engine warmed up. After much mucking around I discovered a number of issues which have been fixed and made the engine quieter when cold....
1. the oil pickup in the sump was blocked so the oil system was slow to pressurise
2. the chain tensioner was worn and not holding enough pressure enough of the time so the timing chain would vary from tight to loose to tight accompanied by strange noises.
Some people also suggest adding a cup or so of ATF to your engine oil, the purpose of which sounds reasonable (can't think exactly what it is know) but if things become quieter after that then it means something.... i think its supposed to help unstick stuck lifters etc. Can't hurt to try it.
Hope this helps,
I.
Yep - just cleared a varnished (BAD) 4.0 liter inline 6 that sounded like a bad rod at low rpm, especially cold
I used 1 qt transmission FLUSH and ran it five minutes, and let it sit for a week
Then used 5 quarts ATF and 2 quarts motor oil and ran it around the block a couple times,
THEN used 6 quarts heavy 15-40 oil (just like our cars - are you using high viscosity? 5-30 can be atrocious in these) and 1 quart trans fluid
Smooth and silent.
FYI
hmm well it does tend to miss a bit and run rough when its cold. Maybe thats what the knocking sound is.
Oel pressure's good...
Im using Mobil 1 fully synthetic, i think its 5w-50.
Is that okay?
Might try adding some ATF then, see if it helps at all
ATF is to act as a detergent and is usually only used as a flush and not left in for any length of time.
Mobil 1 should be a high detergent oil anyway.
I would be more in favour of getting the noise checked and see what it really is, get the gas mixture checked and if you think you have an oil problem try Castrol GTX 20-50, or Castrol synthetic 10-60 or one of the LPG specific oils.
Give us the noise as a sound or video file and see what comes up.
Bill
YOUR OIL IS TOO THIN
Mobil 1 5W-50 is in fact the recommended oil for these engines in their product data. I have used the 5W-50 in the past with no problems other than slightly elevated consumption initially. I have now reverted to the Synth S 10W40 with a cup of ATF on the changeover as the lifters were slightly noisy. I now have no problems with noisy lifters and the consumption has dropped to about 250mL/1000km with some redline activity. There is certainly no abnormal engine noise and the engine is original with 343,000 km on the clock.
One of the best places to go NoR is the "Star Shop" in Osborne Pk. Herbert should be able to help you out, just don't bring any parts from AutohausAZ with you. ;D
Tim
Ach! I stand corrected.
I run 15-40 high-detergent (basically a truck oil) in mine - as lighter weights seem to eat cams in 126s
I'm amazed at the thin oils used in such old, high mileage engines.
Comeon buggers, think of when you're old and your cartilidge wears out between yr bones - the aches and pains - makes you wish you had "THICKER" cartiledge.
We all know that older engines no longer have the same tight clearances as new engines - that's why some guys experience oil consumption with thin synthetics - clearly the oil does not provide adequate protection and lubrication at cold start-up.
Don't get me wrong, I'm all for synthetics, but only from 20W - 50W to 20W-60W.
I use Castrol 20-50 (non-synthetic as we don't get synthetics that thick) and my engines run super-smooth - without taps and knocks, leaks - and zero oil consumption - and the oil remains superclean.
What more could one want?
An older engine in good condition that is using oil is running on too thin an oil for cold start-ups.
An older, higher mileage engine, in my opinion, is not suited for such thin synthetics.
"clearly the oil does not provide adequate protection and lubrication at cold start-up."
And cold start-up is critical as most engine wear occurs when the engine is cold - why then run it on such thin oil (in places like RSA and OZ) which will just accelerate engine wear ??
I use Castrol GTX (original formula) 20-50 in my 450 and my 6.9 has Redline synthetic 20-50.
I have no problems with either except the cost of redline is now $135 per 3.6 litres and at 12 litres for a 6.9 it's a bit of a knee trembler but there is zero consumption and zero problems.
I have used Castrol synthetic 10-60 in the past with no problems.
Bill
Quote from: Ryan1980 on 12 August 2008, 02:06 AM
hmm well it does tend to miss a bit and run rough when its cold. Maybe thats what the knocking sound is.
Check the leads are connected to the right plugs. I'm probably wrong but I've had this before. When hoplessly mistimed and misfiring after putting the distributor back in and some injectors not working I've noticed a "donk" as the engine wallowed on a few cylinders then failed. It was some time ago but never thought much about the source. It sounded like that wooden mallet sound TJ spoke of, not just a single knock but it would just happen before the engine stalled. I timed the engine at idle and the stalling stopped but I couldn't get rid of the misfire and an occasional knock but not pinging. Two ignition leads were on the wrong plugs :P Who knows what damage I've done trying to rev that misfire out. But it was 3+years ago, it's still a better beast now than it was when I got it.
The thing is, I haven't noticed it again, even though now my plugs seem to foul easily over this winter and there's at least two cylinders misfiring during a cold start. Still no knocks during a misfire and when running warm, all is well. Anyway, if the leads are fine, I'd visit the LPG place if it only started occuring after the LPG install. Get their thoughts on what's going on.
Re: the oil, (pompy will be shaking his head in disappointment) but not for long ;). Early last year I started on full synths, Mobil 5w-50 and this year to Castrol 10w-60. I'm really not sure what to think. I am blowing smoke on a cold engine during acceleration that clears when it's warmed. I have relatively new valve seals and no smoke on the overrun, so this stuff is going past the rings. I would go thicker synth but it's hard to get hold of in my town. I agree with the notion of thicker oil regardless what you use. Higher tolerances, worn surfaces and bigger gaps need thicker oil. All depends on how worn the engine is I suppose. My 350's done over 400,000km and was abused by the previous owner so far as oil wasn't changed very often, just topped up. The thinner synths - I've changed the synth oil three times in the last 15 months with only 5000km approx travelled and have noticed the oil not only comes out black, but stinking of fuel as though you could set it alight. It's done a lot of cleaning I'd imagine and although I've heard that black is nothing to be worried about, to my mind it means impurities and the oil loosing its characteristics. The blow by gasses and other crud is turning this thin oil into water. Well, sort of. Next change, if I can't find a thicker synth, I'm going back to thick mineral.
When my 6.9 is on the road, I'm sticking with GTX 20W-50 with 5,000km changes.
Tim
Hah! (tosses his cape of crepulence over his well-engineered shoulder)
I stand affirmed.
Begone with your unhappy knocks and watery oil-like substances.
Petroleum - the thicker the better!
Hey guys finally got around to taking a video of my engine and the noise it seems to make. It doesnt seem to make it when its completely cold,and the car idles fine when cold. After it warms up a little and the idle drops, and the car is sitting around the 80 degree mark, thats when it seems to get really loud. The car also struggles to idle when in drive at this time.
After the car is completely warmed up (around 85-90 degrees) the car runs great and the noise seems to get quieter.
Anyways check this out -
http://hk.youtube.com/watch?v=nnU6lZjqxIM
That's very noisy, there's something wrong there. :o
If the oil pressure is acceptable, I would think it might be detonation of sorts. You should check the ignition timing, mixture and spark plugs ASAP. I would not be driving the car until it is fixed... engines do not enjoy making sounds like that. ;)
Tim
It would also be a good idea to pull the oil filler cap off and have a really good look at the camshaft/oiler pipe and ensure it isn't loose. The top end also sounds noisy, although perhaps the tappets just need adjusting.
Tim
.
Sounds like a diesel.
Good pick up Pat on the frequency. I was reluctant to say it's just tappets because whilst some of it sounds valve related, it still sounds like something else is going on.
First step Ryan, have to take both rocker covers off and inspect the cams, oil pipes, valves, rockers and cam bearings. Check that all rocker retaining springs are intact and look for dry components.
Whitey did the same thing on Saturday, 360bpm loud-as-all-getout knock until it'd warmed up and I'd given it a few revs.
Curious because it has sat since the sandown race day where it has been revved regularly to over 5000. The knock sounds like from the front of the engine, at the top, like the tensioner isn't pressurising... Also as I've stated many times before, whitey has the lowest oel pressure of any M117 but still hangs in there...
What I would do Ryan is go to a you-pull-it type wrecker which has a D-jet 350SE or 450SE and remove and buy the chain tensioner, for testing purposes, and see if the tone of the knocking changes/goes away. If so, renew your cam oiler junctions on both cams and install a new chain tensioner.
I'm going to check the cam oilers on whitey this weekend.
Ian.
Thanks for all your help guys. It seems to have only been doing it since its been converted to LPG. Do you think it could be running too lean ? Or perhaps the installer didnt adjust the ignition timing correctly?
Oil pressure is at the top of the guage (3 bar) so that seems ok, although i guess i could try a thicker oil.
I hope its not the chain tensioner because that sounds like a big job.
I was under the impression that if it was bottom end it wouldnt get quieter as the engine reaches operating temp?
Chain tensioner is real easy its just two bolts and the unit sticks out the side of the engine behind the alternator.
Remove the battery and battery tray and you'll have plenty of access to the tensioner.
Ian.
Quote from: Ryan1980 on 26 August 2008, 07:51 PM
Oil pressure is at the top of the guage (3 bar) so that seems ok, although i guess i could try a thicker oil.
Just on this point, the indicated pressure is measured from the left hand bank, the hose is connected to the block or head (can't remember exactly) facing the firewall. Just because it shows 3bar doesn't mean the rest of the oil circuit is getting enough oil, there could be a blockage above the cams or elsewhere like the tensioner that 13B mentions.
It seems too coincidental that the knock occured after the LPG install. No idea what they could've done to cause it though.
okay cool
how do i check the cam oiler?
If they did any work on the gasoline fuel system that required opening the lines, there is a chance that something got in and is holding an injector open. Did they add any injectors for cold start or WOT enrichment?
I also wonder about timing if the distributor was moved and I still think the plug wires could be out of whack.
Michael
hmmmm not that i know of but i guess i could ask them.
If the plug wires were wrong would the engine be running rough ? It seems to be running fine once operating temp is reached, no complaints from me there.
I remember the LPG guy saying something about a stepper motor, which , from memory allows more gas into the system on startup and when the engines warms up it reduces it. Perhaps its reducing the amount of LPG too early,
would the engine running lean make this noise?
If the engine is running too lean, it can make that sort of noise for sure.
It sounds like it could be leaning out prematurely and perhaps too much.
To check the cam oilers, you need to pull both rocker covers, which is very straight forward.
You can get a bit of an idea by shining a torch through the oil filler cap as well. If the oilers are loose, you must replace the fittings which are inexpensive.
Tim
Quotehow do i check the cam oiler?
Take off your cam covers.
Haha, you beat me to it 13B. ;)
thanks guys
sounds like its leaning out to me.
I'll take it to the LPG place.
As you can see i have a lot to learn, but ill get there some day :P
I messed around with the mixture screw a bit and the noise appears to have gone away... touch wood!
I hope it's your lucky day.