Hello and welcome to the forum!
When does the noise happen? (under heavy acceleration/ when you lift off the throttle etc )
are there any other symptoms? (lack of power/ exessive smoke etc)
Have you had the codes read?
Its often difficult to diagnose faults at a distance but here goes some things that might help-
If you take the hose between the air filter and turbo off, you can get into the turbo (compressor wheel), with the engine switched off you can check if the turbo spins ok with your fingers and if there is exessive play in the bearing (by shaking it up & down) it should spin freely and there should only be about a mm of play, up & down, (and it should hardly make any noise)
With the airbox-to-turbo hose off, keeping your hands away from the turbo compressor/ impeller, and making sure there is nothing aroung it not fixed down (that could be sucked in) get someone to start the engine and rev it up (with/ without the hose on)- is the "screech" louder (it may make "wooshing" and "hissing" noises)
You have a 2002 Mondeo, so it won't be a euro4 with electronic actuator, it will be a euro3 with a pnumatic actuator, and it probably has a VNT and a front- mounted EGR, there are other ones, though, some had fixed-vane turbos, and some rear-mounted EGRs,
If you decide (in the future) to obtain a secondhand turbo, it will be important to get the right one, and the VNT has a tendency to get "coked up"/ sieze (this cannot happen on a fixed-vane turbo) so it would be helpful for you to take some pictures of the turbo/ manifold/ whole engine (with the plastic cover off) to see which type it is/ or it might help me spot a problem
If it has a VNT turbo (Variable Nozzle Turbo/ aka variable vane turbo) the vanes can get "sticky" and when the actuator moves them it may make a noise, - see if this is the noise you are hearing (by seeing if the noise coincides with the actuator rod moving) - you can also move it with your hands / use mole grips (carefully) if it is stiff - with the engine not running
All sorts of things can make noises - belts, power steering pumps, waterpumps etc etc etc, its important not to get to focussed on one thing or assume that it is one problem or another - a mechanic would have the fault codes read and a visual inspection/ listen to the noise/ try different things to pinpoint the fault, and noises/ sounds can be difficult to describe with words
On this age of car turbo boost hoses are bad for splitting, on a front- mounted egr (mk3 mondeo diesel) engine the 1st place to check is the hose between the egr and the intercooler - the split can be hard to see/ spot without taking the hose off
2002 diesels will be OBD1 and not OBD2 compatible, garages/ mechanics are often unaware of this and sometimes cant understand why their code readers (including £££££££, ones) don't work, if you are buying a code reader yorself, make sure its compatible, i can help you with this if you like (garage may charge £80 to get codes read, once, you can buy your own for £25 and do it as often as you like)
Lastly, with you having a 2002 car, its ok to blank the EGR (solid plate) with no problems (if its not already been done)
Here is a Mondeo mk3 TDCI euro3 with VNT & pnumatic actuator , front mounted EGR valve (illistrated) -
a different type - fixed vane turbo -
(see the actuator "can" is transverse, not longditudinal, realative to the car) the manifold comes in from the other side, and it has a rear mounted EGR , it is a TDDI, but you get TDCIs with the same layout -
How much up and down play is in your compressor wheel? (in mm)
its kaput. dont drive it til you get it sorted. You might be better getting yours refurb'd rather than buy a dodgy 2nd hand one.If you drive it & it fails completely,you're looking at a new engine
Its definitely a euro3 pneumatic EGR, it's just like the 1st illustration. The amount of play feels like more than 5 mm. It's woobbling all over the place.
Guess what - its the turbo - the cartrige bearing to be precise - bits of swarf can drop into the oil which can cause engine damage, so its a good idea not to drive the car
You could buy a new or refurbished cartrige (turbine/ compressor, and bearing housing) and fit it on (i would decoke the VNT mech and change the oil/ filter as well)
A cheaper option is to buy a secondhand turbo from a breakers, you can get one from about £100 for the whole thing, including exhaust manifold, and complete turbo
Frequent oil changes and allowing the turbo to spool down when its hot help it last longer , the reverse shortens its life
Also I realise it has to be a vnt with pnumatic actuator and front mounted EGR but is this set up found on later cars and can I use one from a later model? And does it have to be a 130bhp like mine or can it be from a 115?
Yes, It has to be a vnt with a pnumatic actuator, the fixed vane is tottaly different, even the exhaust manifold, it is theoretically possible to graft a fixed- vane one on, but you will need the entire assembly, including exhaust manifold and it would probably be a lot of hassle
Again, it is "possible" to fit one with an electronic actuator, but you would have to change a lot of parts, including the ECU, a lot of tuners did the opposite - (convert the euro4/ electronic actuator into euro3 pnumatic)
So for you it is best to stick with a VNT with a pnumatic actuator (that looks like the one fitted) it does not matter if it is 130PS or 115PS, they are the same (they may have scores of different part no.s, and the 2.2 has a couple more fins, allegedly)