Annoying Hiss!

[mattford]

Hi all,hope someone can help! I purchased an S-plate Galaxy 110 tdi at the beginning of this year. All has been good until the last fortnite when the car developed a hiss almost overnight. The hiss can only be heard when the engine is under load and corresponds exactly with the turbo spool up. The noise appears to be coming from inside the "cab", somewhere in front of the driver. I thought I'd found the problem when I found a vacuum line running from the engine inlet ducting to the ecu (located in the dash under the instrument dials). Having replaced the entire length of hose, the problem still persists. Could the ecu itself be leaking? Is there another vac hose in the same kind of area that Ive missed? Is there any easy way of simulating boost pressure in the manifold with the car at a standstill without destroying the clutch.

Hope you can help,

Matt.

[Neils TDi again]

Is there any easy way of simulating boost pressure in the manifold with the car at a standstill without destroying the clutch.

 

Yes another vacuum line runs from the T to the brake servo also the actuator may be leaking on the side of the turbo or indeed the vacuum valve on the bulkhead which works on a duty cycle waveform to regulate the vacuum to the turbo geometry.

 

Listen under the bonnet as some one applies a rising rev range from the pedal.

Edited July 8, 2007 by neil_wiles

[mattford]

Tried the brake servo and actuator, still no joy. Any idea where the vacuum valve can be found? As i said originally, the noise definately sounds like its in the cab. thanks,matt

[Neils TDi again]

IIRC the front lower block just in front of the gearbox bolts.

 

I am at work so no TIS but if no-one comes along before hand I will look when I get home.

[mattford]

Found the source of the leak!! Its coming from a plastic plug on the ecu. Does anyone know if I can get one off the shelf from Ford, or am I gonna have to trawl the scrapyards? Also, does anybody know if it is literally just a plug, or does it serve a purpose? It looks as though it may be some sort of relief or bleed device. Thanks for the help, Matt.

[seatkid]

Woah! Before you bung this up, IIRC (depending on model) there should be a pipe connected to the ECU. IIRC it comes from the boost piping that runs down the battery side of the engine.

[mattford]

Dont panic,the vac hose is there and attached! the "plug" in question is on the opposite side of the ecu to the electrical plug and vac hose (its a black plastic,

push fit item with an o-ring seal).

[mattford]

FYI, just found out that the black plug is nothing more than a breather for the atmospheric side of the T-MAP sensor. My hiss probably means a damaged hose internally or worse still the diaphram of the sensor itself, allowing boost pressure straight through. Anyone know where a new sensor might be found?

[seatkid]

damaged diaphram, the sensor is a "differential" type, one side measures the boost pressure wrt to the other side - atmosphere.

 

If you can read the numbers on the sensor you might find a supplier (car or electronics).

[mattford]

All fixed and didnt cost a penny. Problem was a split hose inside the ecu (it runs from the bulkhead fitting to the t-map sensor). Thanks for all your info. PS Dont trust haynes when it comes to removing the ecu! Theres no bolt "accessed from under the console", at least not on mine. On my Gal the wiring plug had to be removed, allowing access to two T20? tamperproof torx bolts. Once these were out the ecu could be slid towards the center console and out.