Name that squeak (belts, timing belt, bearings, mouse?)
Posted: Sat Feb 01, 2025 11:36 am
by ChrisZ
It's a squeak. Started when the weather got cold, would go away when warmer, now not going away. Can't isolate it, doesn't change much with throttle. Any idea what it is?
Positive side I do not smell the timing belt burning.
Re: Name that squeak (belts, timing belt, bearings, mouse?)
Posted: Sat Feb 01, 2025 2:16 pm
by worf
When did the noise start?
What did you do to the 928 just before the noise started?
Do you still have an air pump?
Do you still have the diverter value assembly that shunts air either to the air box or the catalytic converter?
Do you still have the OE catalytic converter?
Re: Name that squeak (belts, timing belt, bearings, mouse?)
Posted: Sat Feb 01, 2025 3:26 pm
by ChrisZ
Started in early December.
It got COLD. As in 5-10f cold. Brrr cold.
Yes, I have the air pump. And am annoyed as the lid to the air pump filter is frozen shut with rust/corrosion/whatnot.
Where is the diverter, I don't remember seeing that on an 86 pipe organ intake.
Yes I do have the OE cat.
Re: Name that squeak (belts, timing belt, bearings, mouse?)
Posted: Sun Feb 02, 2025 12:54 pm
by linderpat
Bearing in the torque tube? It seems loudest at that site, towards the front of the tube?
Re: Name that squeak (belts, timing belt, bearings, mouse?)
Posted: Sun Feb 02, 2025 2:02 pm
by worf
Re: Name that squeak (belts, timing belt, bearings, mouse?)
Posted: Sun Feb 02, 2025 2:07 pm
by worf
Since the frequency of the noise is NOT (right?) RPM dependent there are few culprits I can think of.
“Chirping” noise from the right side, aft of the front wheel, is often some part of the air pump system that has been disconnected or has otherwise become disconnected. It’s usually due to the output having no connection to aftermarket cat.
A quick test is to cut the air pump belt. But, that’s a problem pre-S4. At least when it’s not super cold outside.
Re: Name that squeak (belts, timing belt, bearings, mouse?)
Posted: Mon Feb 03, 2025 1:56 pm
by ChrisZ
It's pretty super cold right now :-). But on an 86.5 how does one adjust the tension, is it just a loosen the air pump?
And if so how much of a bitch is it to pull and rebuild? When the engine goes really low RPM it changes, but that's about it.
I had an air pump on my 68 911L seize once, took out the crankshaft end. Really annoying. Is it really necessary?
Re: Name that squeak (belts, timing belt, bearings, mouse?)
Posted: Mon Feb 03, 2025 2:21 pm
by worf
ChrisZ wrote: ↑Mon Feb 03, 2025 1:56 pm
It's pretty super cold right now :-). But on an 86.5 how does one adjust the tension, is it just a loosen the air pump?
Order the ‘short belt’ from Roger that just drives the fan. It’s the first belt, so, not too hard to do.
Re: Name that squeak (belts, timing belt, bearings, mouse?)
Posted: Thu Feb 06, 2025 10:40 pm
by ChrisZ
Will do. Holy smokes that is a complicated pile of piping. Looks like I can loosen the belt as well and try it without the main fan. If it doesn't make the noise on startup I've found the problem....
