I've been progressively doing all the little fiddly maintenance jobs on my BX 16V that most owners leave until necessity becomes the motivation and at times I can see the logic in the saying "if it ain't broke; don't fix it!!" this noise may be a coincidence or altenatively it may be a case of doing the above.[:o)]
When the engine is started on the car, cold, it gets an intermittant tap in it. Standing at the front of the car, it seems to come from the left hand front of the tappet cover. It has been suggested that it may be the cambelt touching the cover , but no matter how you push or pull on the cover, it seems to make little or no difference apart from a slight scraping noise when the cam gear touches the cover.
It isn't a deep or highly mettalic sound in fact it could best be described as a "light" but fast rattling noise. Also, if the engine is revved slightly to say 2000 rpm, it seems to come in on the overrun as the motor drops to around 1600rpm after which it just gives the occasional tap tap at idle. Once the engine has warmed up, it seems to disappear. I have strong suspicions that this motor may have broken a cambelt early in its life, prior to me getting the car & the pin at the top of the timing cover that is used as an anti rattle device for the metal strap with the "key holes" in it is missing. My suspicians are that this pin may have dropped out & been the cause of the breaking of the cambelt but that is just supposition.
I intend lifting the motor & retensioning the cambelt just as a precaution but wondered if anyone else has ever encountered a similar problem.
During a recent engine rebuild, we were told by an engine rebuilder to "burp" the hydraulic tappets; the small inner pistons inside the larger cylinders & I was also wondering if perhaps one of those possibly may just stick slightly when cold.
The car runs 5W - 40 Mobil 1 fully synthetic oil which is changed every 6 to 8,000 klms so I would expect that it shouldn't be sticking due to lubrication. If I didn't know better, I'd swear it was the belt flapping between the camshaft gears but if it were one tooth out, I could imagine some VERY hairy running to say the least.
I'm totally baffled, so I will appreciate any suggestions; just don't try to make it too scarey though. [:0][:p][;)][}:)]
Alan S [:D]
Ratat...tat noise
Moderator: RichardW
AlanS -
It reminds me of a long 16V discussion - on another forum - on the 16V's hydraulic valve tappets.
On Gabor's site you find a good description of the XM valve tappets giving popping sounds - also a hydraulic tappet issue.
The problem is air caught in the hydraulic tappets.
To my best - your description of the sound scheme - is very similar to a standard engine in need of valve clearance adjustment - or having worn camlobes. Such common problems usually are worst at cold engine - then flattens out with hot engine. This also points to the hydraulic tappets on a 16V.
The oilpump chain & sprockets may give a similar soundscheme - and this is in fact located LHS when standing in front of engine - but down in the block. This sound may more be like a rattle though - like old engine types with chain driven cams.
Play in oilpump axle ?
I think it's stetoscope time - to pinpoint exactly from where the sound emanates. May be worth lot's of time trying pinpoint the sound - before lifting up engine - saving you time later.
Don't miss the obvious : Generator & waterpump (HP pump RHS on 16V ?).
It reminds me of a long 16V discussion - on another forum - on the 16V's hydraulic valve tappets.
On Gabor's site you find a good description of the XM valve tappets giving popping sounds - also a hydraulic tappet issue.
The problem is air caught in the hydraulic tappets.
To my best - your description of the sound scheme - is very similar to a standard engine in need of valve clearance adjustment - or having worn camlobes. Such common problems usually are worst at cold engine - then flattens out with hot engine. This also points to the hydraulic tappets on a 16V.
The oilpump chain & sprockets may give a similar soundscheme - and this is in fact located LHS when standing in front of engine - but down in the block. This sound may more be like a rattle though - like old engine types with chain driven cams.
Play in oilpump axle ?
I think it's stetoscope time - to pinpoint exactly from where the sound emanates. May be worth lot's of time trying pinpoint the sound - before lifting up engine - saving you time later.
Don't miss the obvious : Generator & waterpump (HP pump RHS on 16V ?).
Thank you for that Anders, much appreciated.
Spent a bit of time out there today scratching the head & listening with the stethoscope & it sounds very much like a tappet on that LH cylinder yet when the stethoscope is placed on the rocker cover it can't be heard. The only time any sound is transmitted is when I place the stethoscope on the plastic cover directly in line with the end of the intake camshaft but again it's intermittent.
I did have one breakthrough though; I left the engine running & this noise kept coming & going so I removed the cover over the spark plugs. After a while the engine began running slightly roughly & did it in unison with a tapping sound which made me highly suspicious, so.....I blanked out as much surrounding light as possible, stretched across & waited & sure enough 'tap, tap, tap' and when I looked carefully down the plug hole, sure enough there was a spark arcing across; seems that I had a small hole in the insulated shroud over the plug lead which was allowing it to throw a spark onto the head. By pushing it further down the porcelain I managed to rid myself of that one but the other tapping whilst now not so constant is still there although this has quietened things down a lot. I checked all the other plug leads & the remaining tapping is not one of them but is still a mystery requiring further investigation. I may remove the top belt cover & give it a run & see if it is still there.
Alan S
Spent a bit of time out there today scratching the head & listening with the stethoscope & it sounds very much like a tappet on that LH cylinder yet when the stethoscope is placed on the rocker cover it can't be heard. The only time any sound is transmitted is when I place the stethoscope on the plastic cover directly in line with the end of the intake camshaft but again it's intermittent.
I did have one breakthrough though; I left the engine running & this noise kept coming & going so I removed the cover over the spark plugs. After a while the engine began running slightly roughly & did it in unison with a tapping sound which made me highly suspicious, so.....I blanked out as much surrounding light as possible, stretched across & waited & sure enough 'tap, tap, tap' and when I looked carefully down the plug hole, sure enough there was a spark arcing across; seems that I had a small hole in the insulated shroud over the plug lead which was allowing it to throw a spark onto the head. By pushing it further down the porcelain I managed to rid myself of that one but the other tapping whilst now not so constant is still there although this has quietened things down a lot. I checked all the other plug leads & the remaining tapping is not one of them but is still a mystery requiring further investigation. I may remove the top belt cover & give it a run & see if it is still there.
Alan S
Alan
Is it possible you've got a bit of dirt on the cam pulley, or a small lump on the belt etc. I know belts (especially the flat alternator drive type) belts can cause all manner of noises and remember my Renault 21 always made a noise as though the engine was going to seize up. I tried tightening it, replacing it, spraying it with WD40 (which worked for a short while) and eventually got so fed up with it that I coated it with vaseline which with regular top ups worked for about 3 or 4 years! - not to be recommended!
Jeremy
Is it possible you've got a bit of dirt on the cam pulley, or a small lump on the belt etc. I know belts (especially the flat alternator drive type) belts can cause all manner of noises and remember my Renault 21 always made a noise as though the engine was going to seize up. I tried tightening it, replacing it, spraying it with WD40 (which worked for a short while) and eventually got so fed up with it that I coated it with vaseline which with regular top ups worked for about 3 or 4 years! - not to be recommended!
Jeremy
Well, here's a progress report.
Today I had to use the car at short notice & knew it had the low fuel warning light on, so as an emergency measure, I filled up with normal low octane ULP (93 octane I think it is out here). When I started, being in a rush, I didn't take particular notice but felt as though I couldn't hear the normal tapping that I was worrying about. Having been on the mower/tractor for a few hours yesterday I partially put it down to a bit of temporary deafness due to excessive noise, but about 6 hours later (and it was b.....y cold today) I restarted it & bingo....no rattle!!
When I think back on it, the car didn't have the rattle when I bought it or for the first few thousand klms and then I started using PULP in it when this fuel became available in my area. In the past few days, I've made the comment on other forums where others have been having the same problems with their 16Vs that I suspected I may be the victim of some kind of detonation which is normally attributed to using too low an octane fuel, hence I had dismissed this as a possible cause. However, after today's experience, I don't know that the low octane was the problem but rather the high. The other option of course is that the car gets used on odd occasions & isn't a daily driver, so I wonder if stale fuel plays a part?
I've posted on another forum to see if the others with the problem get the same result; I'll post when I get some answers.
Alan S
Today I had to use the car at short notice & knew it had the low fuel warning light on, so as an emergency measure, I filled up with normal low octane ULP (93 octane I think it is out here). When I started, being in a rush, I didn't take particular notice but felt as though I couldn't hear the normal tapping that I was worrying about. Having been on the mower/tractor for a few hours yesterday I partially put it down to a bit of temporary deafness due to excessive noise, but about 6 hours later (and it was b.....y cold today) I restarted it & bingo....no rattle!!
When I think back on it, the car didn't have the rattle when I bought it or for the first few thousand klms and then I started using PULP in it when this fuel became available in my area. In the past few days, I've made the comment on other forums where others have been having the same problems with their 16Vs that I suspected I may be the victim of some kind of detonation which is normally attributed to using too low an octane fuel, hence I had dismissed this as a possible cause. However, after today's experience, I don't know that the low octane was the problem but rather the high. The other option of course is that the car gets used on odd occasions & isn't a daily driver, so I wonder if stale fuel plays a part?
I've posted on another forum to see if the others with the problem get the same result; I'll post when I get some answers.
Alan S