Diagnosing a noise by forum!!!

[the wombat]

I appreciate diagnosing a car noise via a forum is nigh on impossible, but any thoughts appreciated.

Without any build up, my Q4 starting making a whistling noise in the engine bay today. I can' think of anything that would cause it to start, and it was not doing it yesterday.

So, to describe the noise:
- Its a whistle, could be like an old fashioned steam kettle boiling. Not quite a screech, but close
- It starts when the engine is running and stops when the engine stops
- Putting it in gear, depressing clutch make no difference
- Its quite loud at tickover, but reduces a little when the engine is revved
- Its coming from the back of the engine somewhere, but I am having real trouble locating it. Initially thought it might be a belt or the power steering pump, but ruled those out. Its not related to cambelt or balancer belt or alternator (all too far forward), but seems loudest at each end of the engine
- Can't see anything rubbing rotating things anywhere

I wondered if there might be an intake leak causing it, but really not sure. It seems too consistant a noise to be a bearing, and a sudden onset, but don't really want to drive the car (was retro rides tomorrow, so number 1 son has chosen the V6) until I know what it is.

Anyone experienced anything like this before? Any thoughts appreciated.

[wrinx]

Camshaft rubbing...had something similar once, caps were a bit tight but perhaps yours aren't being lubricated???

Water pump???

wrinx

[Steve Webb]

Strange one, especially if you say it seems to be at the back of the engine but noisiest at both ends.
Does the car have aircon? And if it does, does the noise change as you switch it on and off? There are aircon pipes running across the back of the engine to the pump, up by the power steering reservoir.

Any chance of a video of the noise?

[the wombat]

Chrs for the responses.

The car does have AC pipework although the condensor has been butchered out. Will check that.

Cams is a good point as well. I havevthought the top end excessively noisy since I got the car, and will probably do the belts and re-check th valve gear and clearances in the next year.

Will try and post a vid of the noise in the next day or so.

In the meantime, v6 power for Retro-rides

[the wombat]

Just taken it out for a quick run to see if I can get a better idea.

Noise is not there when cold, but comes in when the engine is up to temp.

Interestingly, I hsve no power steering when the car is idling, and it comes back increasing in strength when the revs are raised.

This seems to suggest the noise is power steering related. location suggests rack or pipework, but not entirely sure.

Not sure what valves etc are on the rack end of things, but will flush the old oil and replace to see if that helps, and have the pump off at the same time to see if it has an issue.

Any experience out there of PS issues?

[wrinx]

Nope...apart from a very loose belt when it was worn, but you'd have spotted that.

wrinx

[Steve Webb]

Any experience out there of PS issues?

Only that I fixed a small leak with leak-stop fluid, the cap of the reservoir doesn't seem to fit correctly and interferes with the strut brace.

Oh and the pump connects to the rack on the drivers side if I remember correctly. I loosened one by accident thinking it was an aircon pipe!!

[AlfaJack]

I have had a PS pump wear out - this was a good few years after it ran dry (split pipe, burnt through on the exhaust manifold). It only rattled though when cold and quite loudly - lasted ages like this and then just stopped pumping.

Biggish job to remove it as I had to take out the inlet ,manifold too.

[the wombat]

Sounds about right.

Tax is out on it at the end of the month, so other than drain and replenish, will probably leave it until its spring shakedown (about to become a student again so can't see having the time).

Took the V6 to retro-rides instead. Another successful long journey so just about shaken down now but a few things to do:
- Need to fit the 2.5 or a 156 GTA half shaft bearing carrier so I can fit the oil cooler lines and add an oil cooler. Engine is consistent at temp of between 90 and 100 in this weather but I would like to run it a bit cooler
- Fit a 2.5 TD rad - its a little bigger
- Get the A/C working as I have just got home and am melting - black car, no sunroof, humid weather!!!

Will post what I find with the Q4 steering as I discover it!!

[the wombat]

Drained and flushed the PS system today with cheap Halfords PS fluid and some Wynns additive which has a detergent in it. After prolonged testing, drained and refilled with a decent PS/ATF fluid.

Seems to have got rid of the noise so far.

In studying the workshop manual, the pressure relief valve is in the pinion housing in the rack itself. Assuming this was sticking partially open due to crud collecting, it would explain why the noise was at the back of the engine and so difficult to track down whilst looking in the engine bay from the top.

The likely reason this occurred is old fluid (I had not changed it when I bought the car and was not sure if the previous owner had the system out and drained when they did the engine work), and it had been in for tracking and would have been lock to lock quite a lot during the tracking process which probably shifted the crud around.

Would hate to have to drop the rack out. Its a different game to doing it on a regular 155 due to the drive to the rear end being right in the way. I hope this has sorted it!!!

[wrinx]

At least was something simple and easy to fix...unlike most jobs on a Q4! :lol:

I'm still putting off changing the coil packs :(

wrinx

[the wombat]

Ouch, coil packs!!

Steering noise not 100% solved it seems. Came back yesterday but quieter. Gone this morning when the car was cold, then came back again quite quick but quiet, and gone when I got back home and engine was nice and warm.

Probably still some crud moving around, so maybe another flushing over the weekend.

[AlfaJack]

Here's a couple of pics of my old one.