924 turbo clunk

[doctor13702]

Eventually i decided to forget the 944 (too mant problems) and i have bought a very good 924 turbo(177 BHP model).
When the car is on idle i have noticed that if i open the throttle really quick there is a clunk noise, the engien mounts are brand new and there is no evedence of any metal moving, is there an actuator that prevents the turbo from opening too fast? Could this be some some of relief valve?
The car has dome 80,000 miles and there is a FSH, it has been well looked after and really this is the only thing that is bugging me.

Thanks for your help guys

Doc
It may be old...but hell it's quick )

[Lawrence Coppari]

If it is anything like a 944 turbo, you won't get any boost when you crack the throttle at idle. Boost does not build until after 2K rpm at least. Turbocharger does not know anything is happening yet. It's snoozing at that point.

Why don't you open the hood, stand in front of it, and have someone else crack the throttle so you can see what is going on
Something could be loose on the engine. Get someone you trust so they don't screw up and run you over.

[doctor13702]

I have tried looking under the bonnet when someone snaps the throttle open, there is no sign of anything making contact, i have even been under the car when someone has done this and still nothing......

By the clutch housing there is an iten that looks like an actuator, the noise is coning from that sort of area but i cannot get that close on the underside to be sure.


Doc
It may be old...but hell it's fast

[Obin Robinson]

hmm,

there are several things that an cause that "clunk" and i think i know what might be doing it.

please tell me if the car "clunks"

while moving?
while sitting still and idling?
when decelerating?

i'm not sure if you mean "open the throttle quick" by meaning that when the car is stiing still, you snap the throttle hard, or if it means that while under acceleration you hit the throttle hard to accelerate further.

does the clunk come from:
under the car?
under the bonnet / hood?
the back of the car / cargo area?

from the left side? or from the right?

believe me, i've solved a hundred or so different "clunks" in our 924 and they can be a pain to fix, i'd be more than willing to help you on this one.

obin
obin

[doctor13702]

Hi Obin,

The clunk occurs when the car is stationary, and the noise seems to be coming from the right underside of the car.

When i said about opening the throttle i meant that when i floor it for a second, at that point i am getting a metallic clunk.

Any ideas would be gratefully recieved

Doc.
It may be old....but hell it's fast

[Obin Robinson]

wow,

okay, that's a new one! here's my theories and experiences:

once my exhaust system brackets busted and every time i opened the throttle, i got a "clunk". it was from the long, s-shaped tube hitting the exhaust system. check to make sure that your exhaust system and all the hangars and brackets are TIGHT and not rattling.

this may help you too:

start your car and put the handbrake up so that it doesn't roll away. then pop the hood and prop it up. you can open up the throttle by simply twisting the little lever on the throttle body. hopefully then you'll be able to isolate the "clunk" in the engine compartment. i am not sure why a turbo would make that sound, but we can't totally rule out something wrong with the turbo.

also, when you oepn up the throttle while under the hood, of course be careful with spinning belts and such. make sure the engine is not wobbling like crazy, because the problem could also be your motor mounts. this can definitely cause a "clunk" in the engine compartment.

good luck! tell me how it goes!

obin

[drew1]

Jack up the car and check the right top strut mount. the bearing in it could be gone.

drew1

[doctor13702]

Well i have been under the car and had a look at the exhaust, all the brackets are done up tightly and there is no sign of freeplay, i have checked the mounts again and there is no excessive movement in them, but i have noticed that the clunk seems to be coming from the bottom crank pully, i remember that on certain Audi engines instead of having a woodruff key on the crank they had a tiny hole in the end of the crank, and a small semi-circular 'bump'on it and the 'bump' went into the hole on the end of the crank, the idea was that the front pully was done up so tight that this was done more as a form of location rather than fixing. These did pose problem as when the 'bump' wore down it would stop the bottom pully from spinning and cause lots of damage
I am going to take it to a specialist and get them to look at it, if i get an answer i will let you all know.
Thanks for your help guys

Doc
It may be old....but hell it's fast