View Full Version : need boost/turbo advice... fast!

05-26-2010, 11:27 PM
Hi all,

got a timing belt and waterpump fitted today at tweak it performance in mona vale. Good guys who got it all sorted for me. BUT, the cars made a wierd fluttering noise when the throttles released as long as i've owned it... and i've always thought it should've performed better (2000 GP 1.8t). So I asked Tweak it to boost tested it today and it's only holding 3-4 psi (it is in std tune by the way so I think it should be at 8-9.. correct me if i'm wrong).
Anyway they think it's then actuator on the turbo (has excess play and isn't closing properly - ill get more detail tomorrow). So to find out they needto take the turbo off - labour costs rapidly increasing!! But I just want it sorted - last few mechanics have missed this.

Do you think i'll be cheaper buying a new RP KO4 kit in oppose to replaceing the actuator and gaskets... seeing as tho i need to pull the fing turbo off!

Can anyone PLEASE help me.. the cars at the mechanics now and I want the best most cost effective solution asap as I really need the car for work!



05-26-2010, 11:43 PM
On the short, crank the actuator rod nuts down and boost it til it blows. Most cost effective, but the least reliable.

You can probably find a used actuator for <$40. Call around. Post local. Then do the work yourself. A mechanic set of sockets and wrenchs, two small vise grips or locking pillars to pinch off the coolant lines, a new manifold-to-turbo gasket, and a new turbo to downpipe gasket. The compressor side is just hose clamps (7mm drive). A curved 14mm wrench IIRC sure helps with getting the downpipe off. Total cost <$100 even if you need to buy a few tools.

05-30-2010, 02:02 AM
cheers crispy.
Is it possible my problems could be the MAF or N75?
I ask because the mech reckons he tried to bend the actuator rod (don't know if I like the idea of that) - which took the noise away, but did nothing for changing boost....

05-30-2010, 10:33 AM
It sounds like your problems (fluttering on throttle lift, and low boost) are symptoms of a torn Diverter Valve. Both of these are classic symptoms of a DV with a torn diaphragm. This is a very common failure. In fact it is so common, I would say if the unit is original it is almost certainly bad. I would replace the DV first. It is pretty easy and cheap to do.

This is what you want:

The "710n" version is the slightly upgraded version that is less susceptible to failure compared to the factory issue part.

05-30-2010, 03:46 PM
I replaced that first up. That was done before the boost test... didn't change things unfortuantly..

05-30-2010, 04:05 PM
In that case, next step is to disconnect the hose from the N75 to the wastegate actuator and take it for a [careful] spin. If you can hit more boost , it is a bad N75 or limp mode. If you can't, something is wrong with the wastegate.

05-30-2010, 04:27 PM
sweet thats what i'm thinking. Was thinking of swapping it with a manual boost controller and seeing if that helps.
However now I'm kinda pissed that my actuator rod is BENT.. if the n75 is the culprit.
Will give it a go and get back to you

05-30-2010, 04:29 PM
Sounds like his car is stock. No tune. If that is correct you may just have a boost leak.

05-30-2010, 04:48 PM
yeh it is completely stock.
But the boost isn't getting into the lines (or no more than 3-4 psi anyway).. so it's going out the exhaust due to a buggered actuator (this is what i've been told.. im gonna go inspect the actuator again now and maybe try diconnect the vacuum line to the wastegate and drive it) OR it's control related and could be the n75 or something else.. hopefully much simpler and inexpensive! (than removing the turbo).
A little off topic, but how do most mechanics quality diagnostic machines compare to the VAG-COM? Is it really criticazl our cars be checked with VAG?

05-30-2010, 04:52 PM
So they did a boost leak test and it wont hold more then 3-4 psi. If so then your problem is definitely a boost leak.

05-30-2010, 05:00 PM
But, they reckon it's because the spring is buggered in the wastegate so the actuator isn';t closing the flap in the turbo so boost is escaping that way.
After they bent the actuator rod, the buzzing noise dissappeared... but boost stayed the same (the car possibly feels slower). At the same time they also put a new 710n that I supplied but tell me the buzzing that has now dissapeared wasn't due to replacing the 710n, but to the mod they did to the actuator

05-30-2010, 05:35 PM
I just took it for a spin with the vacuum line from the wastegate to n75 disconnected... made no difference unfortuantly. In saying that, I'm just going by the fact the car goes the same with the line connected... so very subjective, but I'd reckon I could differentiate between 3-4 psi and 9-10.
By the way, should the actuator rod move when under throttle in neutral or is it only under load? I couldn't quite get a screwdriver in deep enough to feel for resistance to the spring (have to run to work no time to remove the airbox). But I guess that's the next step?