High pitch whistle noise from inlet side of engine

Post Sat Jun 01, 2013 3:03 pm

Afternoon all,

I've just removed and refitted the following on my 325 cab:

1. BBTB replacing original TB
2. M50B25 injectors (fully cleaned) replacing original M20B25
3. Custom chip from Speedtouch for my injectors

The car started first time ok and ran a bit rough for a while, which I understand is normal when you change the chip. I left it idling for a good 10 minutes and when it had calmed down, took it for a short drive. However, after no more than 500 yards, going up a steep hill, it suddenly started making a loud high pitch whistle noise. This is a constant pitch when at idle and dips down to a lower pitch when you blip the throttle. It appears to be coming from the inlet side of the engine, though I cant pinpoint where. I've tried wiggling everything that can move and it made no difference.

Any ideas please?

Post Sat Jun 01, 2013 3:08 pm

Did you fit a nice new gasket with the BBTB?

Post Sat Jun 01, 2013 3:11 pm

I did, yes! Bought from the dealer, but it was only a flimsy bit of card. Should this be oiled or spread with some gasket sealant?

Ah - what I didn't check was to cut the gasket to take account of the larger bore! Damn. Could this have caused the problem? Not a massive job to take it off again.

Post Sat Jun 01, 2013 3:16 pm

Make sure the mating surfaces are spotless,I needed to enlarge the gasket centre hole when I fitted my BBTB,and used a smear of polyurothene sealant on the brake servo pipes to ensure a leak-free seal.
Being 'anal' here and getting the thing properly airtight will help.

Post Sat Jun 01, 2013 3:58 pm

I did clean up both surfaces where the TB meets the manifold, but my guess is it's something to do with that join leaking air as you've suggested. Job for tomorrow, got all cleaned up now!

Cheers

Post Sun Jun 02, 2013 2:23 am

worth checking the alternator... they whistle when the diode pack is on its way out

Post Sun Jun 02, 2013 10:09 am

If the whistle is throttle position dependant, then it's an inlet side air leak. Usually a manifold to head gasket, but very likely the TB to manifold if you've been playing with it.
There's also the ICV hose, servo connection and the usually blanked off fuel tank vent to check.

Post Sun Jun 02, 2013 4:24 pm

Sorted! Took the BBTB off and used some instant gasket stuff to re-seat every single connection on the air intake side, but when i started the car, it was still whistling really loudly. Had a good push and pull around everything I could find to no avail. The I realised I'd only put one of the three bolts in that hold the small triangular shaped cover on the intake manifold above the rocker cover that has a vacuum hose going to the fuel pressure regulator. Ah-ha I thought. Took it off, put some gasket sealant round that and put the other two bolts in and hey-presto - no whistling (apart from me whistling a happy tune!).
Phew!