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Topic Engine Rattle / Buzz |
Engine Rattle / Buzz bnsc100 - Thursday, 3 February, 2011, at 11:36:23 pm |
Re: Engine Rattle / Buzz IFlyLow - Friday, 4 February, 2011, at 5:35:28 am |
Re: Engine Rattle / Buzz bnsc100 - Friday, 4 February, 2011, at 10:06:05 am |
Do you have the original motor mount? *NM* Boxsterra - Friday, 4 February, 2011, at 8:55:43 am |
Absent any other symptoms other than the noise/buzzing I'd guess a loose heat shield... MarcW - Friday, 4 February, 2011, at 1:55:55 pm |
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bnsc100
I’m posting "my list" today. This is item #2...
Car:
1999 standard Boxster
5 speed manual trans
Miles = 32,000
Pleasure car driven couple times a month. Oil is changed annually, usually approx every 3,000 miles. I use Mobile 1 0/40
Issue:
When I'm driving and under "neutral throttle" I get this buzzing around 2,800 RMP. If I hover around this speed at neutral throttle (neither accelerating nor engine braking) I can make this buzz constant. I originally assumed for a while it was just a frequency thing at that RMP that was making some shield or something rattle…
On engine braking I get a small buzz as the needle is falling through the 3,200 RMP range. Between say 3,200 and 3,000.
When the engine is under load (hard acceleration) I can sail through the 2,800 RMP zone with no buzzing at all.
When I’m driving very slow and shifting slow and easy I get the sound off and on as I lift the throttle slowly and again apply throttle after a shift… When doing this slowly, I get the sound as I gently pass through the “neutral throttle” zone.. Usually when babying during warm up.
Issue is same on cold driving and fully warm engine.
NOTE: When I am parked and in neutral gear and I just slowly apply gas, I get the rattle, but only for a short bit as the needle rises near 2,800. I can hold it at 2,800 in this situation and it will not buzz constantly like when I’m driving.
I had a very reliable indi look at the car and they said it was probably the vario cam system. Said that it is probably “engaging / doing something” at that point in the rev range and somehow is allowing temporary slack in the chain. “Under load (acceleration), there is added tension taking up the slack…” Was told to avoid hovering in that zone / accelerate through and address it at next major service as it would not be a cheap investigation (cam cover removal…).
I hope to drive the car five more years (approx 10K miles) and then do a ton of work at the 15 year / 45Kish miles mark. However, I hate to ignore this as I know with certain BMW models, the chains can cause major issues when they start losing tension… Plastic rails inside break and its downhill from there. NOTE: This has been doing this for probably at least 8K miles / several years. I did do an oil analysis one year ago that came back good. Was told Silicon was high but probably not abrasive as wear metals were low… Was told to check air filtration system (looks ok to me)…
Thoughts? Tensioners? Vario Cam issue? I do have a cam hold down tool and have pulled/resealed a cover before (broken plug tube pieces inside), but dont really want to go through the hassle just yet. FYI, I did a very slow and careful job on that so dont think I messed anything up and I think it was doing this before anyway, I just did not pay good attention at that time... FYI, never rand the car until I pulled the cam cover and got the broken tube pieces out....
Im pretty sure IMS would be rattling at all rev ranges and would have “gone” long ago… : )
Re: Chain Tensioner / Guide Plastic bnsc100 - Friday, 4 February, 2011, at 2:24:29 pm |
The swirl may be nothing. There can be a bit of 'color' in the oil what looks as best I can... MarcW - Friday, 4 February, 2011, at 3:27:14 pm |
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bnsc100
I did my first DIY oil change on the car approx 2 years ago / 7,500 miles ago. Again, annual changes at approx 3,000 miles. I did see the "caramel swirl" in the oil. Noticed it more when I was dumping my large drain pan into milk jugs for disposal.
At the time I had no idea what it was and it was the first DIY I had done since watching Dad as a kid... I only recall it after recently reading about the chain guide "break-in" and that it can produce some brown residue. At that point my car probably had 25K miles give or take a few thousand.
Not sure if platic shows up in oil analysis. Never found bits in the filter. Have never dropped the pan and probably wont, as I think that would be overkill given the evidence. Yes?