Rattle rattle - if it is not the heatshields, what then ?

[williamsF1]

I have a annoying rattle.... and tomorrow I am going to the mechanic with another problem (servo) and I would like to have this rattle checked out.

Here are the facts:

98 Boxster w. TipTronic. Stock Muffler w. chrome exhaust tip.

It is mostly there when the car is cold (below 80C) when it gets warm it tends to disappear.

It is not always there, if the car has been warmed up and then left for some hours sometimes I do not get it... but mostly it's there.

I think I can feel it in the car (speeder pedal), but maybe thats just imagination.

It is not constant, I only get it for 0.5 to 2 seconds, and it's mostly when the car is shifting between low gears (4-5 gear change I cannot hear it, perhaps just due to engine noise) I have it for about 1 second. Sometimes I can make the rattle last a bit longer if I accelerate VERY slowly and reach that point just before the gearshift where it rattles.

It sounds like a rattle and not a grinding / rotating noise.

It's been there for 1-2 months and in my opinion it hasn't gotten either worse or better.


A. Where should I ask the mechanic to look ?

B. Could it be a bad motor mount ?

C. Could it be a bad pump (maybe related to my servo problems) ?

D. Could it be the catalysators ?


Any ideas are very very welcome

[mylamb]

williamsf1,

It could be one of your catalytic converters. I had a frequent rattle that was hard to diagnose and we finally realized that one of the cats had disintegrated and was causing the rattle. In the US, Porsche cats are backed by an 8 year, 80K warranty. I don't know what it's like overseas but I don't think you would be covered anyway on a 98. Since you're going in anyway, ask them to check the cats. It won't be cheap if you have to replace one...


Good luck

[williamsF1]

Hi'

Thank you for taking the time to help me out on such short notice!

Any tips for diagnosing the cat ? (I read about banging it with a rubber mallet.)

Would a cat rattle go away when it got warm ?

Price-estimate for a cat-replacement ?


Thank you

[P-DUB]

i thinks it probably the valve train waiting for oil. Once it gets oil (a second or so, it;s fine?). If you turn it on and let it run until the rattle goes away (1 - 2 seconds) turn it off, and then turn it back on again, is it still there or gone. If it's gone, it's the valve train or trane?

[mylamb]

Best bet is to get it checked out. Describe the noise and make sure you're present when they test it. It's very easy for a mechanic to go "I didn't hear it." I have had to sit with techs at even the most well reputed shops to point out the noise because they couldn't find it on their own - regarding suspension & exhaust work. I have heard of our cars rattling while cold but never experienced it myself (once the cat was fixed.) Not sure on 98's, because there are 2 & they may have different internals for later cars which have 4, but you should figure on $1200-$1500 if one has to be replaced.

[Wret]

I had an exhaust rattle that only occured when the engine was warm. It would go away in minutes so finding it with a rubber mallet proved fruitless. I gave and replaced the most likey suspect, the muffler, with a used one. The problem went away.

I have since dissected the muffler. There was nothing obvious flapping around in there. Maybe a baffle rubbed a certain way when the metal expanded.

[williamsF1]

I went to the mechanics today...

They said the Cats didn't make any noticeable sound when they checked it out so they replaced both my heat-shields instead and hopefully this will cure Rattle 1. If the heatshields is not 'it' Im still glad I got them replaced as I have had them welded twice within 3 months.

However rattle 2 was a steering-wheel rattle. It began just rattling once in a while and if I drove the car for more than 2-3 hours the steering wheel felt like it was full of sand - I was advised this might be degenerated fluid, but the mechanics insisted it was the servo-pump dying ... I have a pretty long drive tomorrow, I sure hope it will last the day!

Anyways now the steering wheel rattle it is there all the time sometimes constant, other times only a certain RPMS and the noise level is different aswell... First I thought it was the power steering fluid, but I have had it checked out twice now and it is not it... so I was diagnosed a new servo-motor and they gave it a price-tag of 1.650$ incl. fluid and a new tensioner belt.

I think thats pricey but I cannot live with the constant rattle from my steering wheel so unless I find a better offer tomorrow it's off to the mechanic again

Could a defect servo-pump make a rattle - I mean the actual pump ?

Thank you for all the advice and suggestions !


Kind regards
Morten