Knocking noise on 2006 Boxster S 987.1

[Ross67]

Good morning all, newbie here. I have a technical question I'm hoping someone may be able to help with. I recently bought a lovely Boxster S 3.2 ltr 987.1. The car is in stunning condition, low mileage (55k) drives as a 987S should (I've had a couple in the past and keep coming back to them!) and burns no oil. However, over the last few weeks I've noticed a very slight knocking noise coming from the engine area. I've had the car 'scoped and there's no sign of bore scoring, and it's a 2006 registered car so past the IMS problem era (I believe). The knocking noise is most noticeable at around 3k revs in second and third gear when the engine is slightly labouring. It doesn't appear to be getting worse but I'm concerned it may progress over time.

Is it possible the noise might not be engine related at all and something less painfully expensive? Someone did mention potential big end knock, which would result in a full rebuild at some point. How likely could this be on the 3.2 engine?

[Dan888]

Engine mount?

[Ross67]

It could be a mount or I'm wondering if part of the exhaust might be causing something similar to engine knock. When in higher revs there no sound of it at all and the car pulls as it should. I'm possibly clutching at straws hoping there's not a engine rebuild needed in the future.

[iborguk]

Hi and welcome.

Where are you based ? You may be better off getting it in front of someone and folks on here may be able to suggest who , dependent on the answer.

Edited August 10, 2022 by iborguk

[Menoporsche]

Does it knock in neutral? I know you said labouring. Just wondering about eliminating wheel bearing etc. 

[Ross67]

8 hours ago, Menoporsche said:

Does it knock in neutral? I know you said labouring. Just wondering about eliminating wheel bearing etc. 

It's hard to hear it in neutral. I've tried to have a good listen but couldn't hear anything. It's an annoying tap as it's only there around a certain rev band. Once the engine is singing over 4k it's not noticeable, and it's not noticeable with the roof down as the wind noise is enough to drown it out (although that doesn't mean to say it's disappeared). I've taken it to one indy who used a stethoscope to try to locate the source, but with no luck. As I mentioned in my first post, they also had a look at the bores and found nothing untowards. In the end it was suggested it could be possible big end knock, which was somewhat alarming. I spoke to Hartech who said they'd have a listen but as I'm in the south east it's a long way to go just for someone to listen to a slight tapping.

Now I know these flat sixes can be somewhat idiosyncratic and throw up all sorts of weird and wonderful noises but this one sounds a little more than the usual rattles and knocks that a six produces.

I guess I simply carry on driving it and see if something goes bang or investigate further if it becomes louder with time. It still drives like a 987 should and the weather's lovely!

[Menoporsche]

If someone put a stethoscope on the engine casing while it should be knocking and they don't hear anything, I'd say that rules out/ minimises the likelihood of any expensive problem in the engine.

[Ninesomething]

Be highly surprised if it's an internal engine problem. These engines are not quiet. There are many external things such as waterpump, pulleys, mounts that could make a noise. That or it's one of those things. Does the car have FSH?

I have suspension noise that no-one else can hear. 

Edited August 11, 2022 by JonSta

[½cwt]

If it is a tapping/ticking it could be a lazy hydraulic tappet which does no harm; really not worth the cost of taking the engine out to sort out according to my indie  £1200 in labour for a £20 part (and then the gaskets, remaining 23 tappets while your are in there, plus you'd might as well do the chain guides and upsetting the exhaust system with will probably throw up another £300 just to spite you and suddenly you are in for £2500.  My internet diagnosis would be front engine mount.  Much easier and cheaper to fix and they do seem to go after around 15-18 years and 75k+ miles.

[Ross67]

Thanks everybody for the replies. I really appreciate it. I'm going to see how it goes over the coming months. I feel reassured that there are many other things it could be apart from more serious internals. I've always sung the praises of the 987/997 generation cars. I've never had problems with all the ones I've owned and spent ages pushing back against those who complain about the supposed chocolate engines on these cars. I've always found them to be reliable - and I know some people are unlucky - but this noise did set off a rather panicked train of thought around £12k engine rebuilds etc.

The car is due a service later in the year so I'll get someone to have a really good poke around to see if there are any signs of poor engine mounts or other potential causes.