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318isCoop 
Newbie
Joined: 07-January-2005
Status: Offline
Points: 7
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 Topic: E36 318iS Coupe engine knock
Posted: 07-January-2005 at 11:41 |
Not sure if anyone can help me here but I've got a 1996 318iS E36 Coupe (M44 engine 1.9 140bhp) with a regular engine knock.
It's only noticeable when it's warm and you're sat stationary with no Radio on. You can hear it above the heater fan (set at 1) but more clearly when the fan is off. When you're sat in the drivers seat (right side) it sounds as though it comes from around the transmission tunnel area although towards the front bulkhead.
It's doesn't appear related to the clutch as it's still there when the clutch is up or down and doesn't change in any way by pressing/releasing the clutch.
It's a regular knock similar to what you might expect from a big end bearing but not as loud or harsh.
The frequency of knocks is not fast enough for tappets and there's a few things I find strange about it:
- It seems to be a consistent frequency knock regardless of engine speed. I've sat there stationary and slowly increased the revs up to 2000 and can still make out the knock but it doesn't seem to speed up which makes me think it's maybe an auxilliary pump of some kind that might be electronic? I've no idea what electronic pumps are on it other than the integral fuel tank pump.
- Once the car's warm, you can hear it when you pull up to standstill most of the time, occasionally it's not there but that's only in a very few cases.
- If you pull up and the knocks not there, you can usually trigger it off by dipping the clutch, selecting a gear and then start to pull off (both forward and reverse).
- Now here's the other strange thing, I've just found out that you can occasionally get rid of it when stationary by blipping the throttle so the revs go 2000+ and then let it drop down to idle normally. This seems to get rid of the knock which can only then be triggered again by selecting a gear as above.
I bought it in 99 and it's got a full BMW service. BMW have never raised it as a problem but if it's an oil pump or something similar I'd rather know now so I can do something about it before it fails.
Any help would be appreciated.
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neileg
Really Senior Member II
Joined: 20-July-2004
Location: Northumberland
Status: Offline
Points: 638
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Posted: 07-January-2005 at 11:56 |
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Don't know about the M44 but the M42 cracks its exhaust manifold and this sound like a tappetty knock. More obvious under load, though, than at idle.
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Cheers, Neil
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b318isp
Moderator Group
Joined: 10-October-2002
Location: Ireland
Status: Offline
Points: 2057
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Posted: 10-January-2005 at 08:16 |
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Wuold it be an exhaust bracket or baffle?
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318isCoop
Newbie
Joined: 07-January-2005
Status: Offline
Points: 7
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Posted: 17-January-2005 at 12:56 |
 neileg wrote:
Don't know about the M44 but the M42 cracks its exhaust manifold and this sound like a tappetty knock. More obvious under load, though, than at idle. |
Hmmm...not sure it's going to be this although it does come in when you're starting to pull away, but then stays even at standstill. The frequency and level of knock is the same at idle or under load.
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318isCoop
Newbie
Joined: 07-January-2005
Status: Offline
Points: 7
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Posted: 17-January-2005 at 13:05 |
b318isp wrote:
Wuold it be an exhaust bracket or baffle? |
I don't think so.....mainly because I was underneath it for 8 hours a few months back changing the rear brake pipes (jeez I'm glad I don't have to do that again soon!) and had a lot of the exhaust off and didn't notice any problems.
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318ih
Newbie
Joined: 10-January-2005
Status: Offline
Points: 24
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Posted: 18-January-2005 at 06:39 |
hi mate, i have a quiet tapping on my s reg 318is coupe not all the time found out it's the breather on the fuel line i think it's for returned fuel/air. you can feel it tapping if you press your finger on it. i'm not sure what it's called i'm just going to replace it, it's on the right of the engine bay on the inner wing
hope this helps 318ih
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318isCoop
Newbie
Joined: 07-January-2005
Status: Offline
Points: 7
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Posted: 19-January-2005 at 17:06 |
318ih wrote:
hi mate, i have a quiet tapping on my s reg 318is coupe not all the time found out it's the breather on the fuel line i think it's for returned fuel/air. you can feel it tapping if you press your finger on it. i'm not sure what it's called i'm just going to replace it, it's on the right of the engine bay on the inner wing
hope this helps 318ih
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This looks very promising. I had a quick look tonight and could hear the knock clearly from the point you mention. When I touched one of the pipes that I believe connects the Activated Carbon Canister (bolted to the inner wing) to the Breather Valve, I could feel the knock very clearly. Not sure if it's the Canister or the Breather that's knocking but it's definately from that area. I'll have a better look at it at the weekend when I've got more light. Thanks for the pointer.
Have you replaced yours yet and did it fix the problem?
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318ih
Newbie
Joined: 10-January-2005
Status: Offline
Points: 24
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Posted: 20-January-2005 at 05:25 |
hello again, at least you know what the things called. i have not replaced it yet or got a price that will have to wait till weekend, if you get yours fixed in the next week or so let me know if that was the noise. glad to help
318ih
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318isCoop
Newbie
Joined: 07-January-2005
Status: Offline
Points: 7
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Posted: 02-February-2005 at 03:46 |
Hi 318ih,
Quick note to let you know that I got a new Breather Valve from BMW (�34 +VAT. Not held in stock. 2 days to get in) and replaced it last weekend.
Good news...it's fixed the problem, the knock has completely disappeared.
If you haven't already swapped yours, it's fairly easy to change, you just need to be careful when you remove the wiring loom connector, as if you try and remove the spring clip from the connector you can easily break the small plastic tabs that hold the clip in the body of the connector.
I would never have looked at this valve as being the problem so appreciate your help with this.
Thanks also to neileg and b318isp for your suggestions.
Cheers, 318isCoop
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318ih
Newbie
Joined: 10-January-2005
Status: Offline
Points: 24
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Posted: 03-February-2005 at 09:12 |
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ManicAJK
Newbie
Joined: 18-January-2005
Location: Milton Keynes
Status: Offline
Points: 23
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Posted: 03-February-2005 at 14:30 |
did you change the whole valve or just the bracket?
I bought the new style bracket from bmw last week which moves the valve from the suspension turrett to bolted to the side of the engine. This is where the valves are on both of my mates 328 coupe and 323 cab, both of which are 2 years newer than mine. I have a makeshift bracket in place on mine at the moment and it has definitely cured the problem on my 328 coupe. All I need is some decent weather to swap in the new bracket now.
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E36 318iS Coupe engine knock