2.4 140ps turbo problems

[Jonboxall]

Hey,

Iv had a few problems with the turbo on my mk7 2.4 140 rwd 350 van.

It started thowing codes for underboost and overboost etc

So after allot of research, i pulled it out and did a good variable vane clean as i found the control ring was getting stuck on the edges of the turbo, so i also ground out all the carbon/rust that was causing it to get stuck and its perfectly smooth now wothout any sticking points.

I also noticed some play in the hella actuator so i stipped that down and replaced the worm gear, shims and motor.

I had a really good feel of the bearing and there is next to no play and is really smooth.


So after putting it all back togeather and testing, i cant get it to throw the codes anymore but i have noticed a siren noise coming from the turbo side of the engine bay. (Im not sure if this was present before or not).

I instantly thought of a boost leak where iv put it back togeather, so iv been back in and replaced all the gaskets and seals, but no change to the siren sound.
So iv done some reading on this and people suggest a bearing failire? However the bearing does feel really good and iv checked in the intercooler and theres deffinetly no exess of oil in there. (Theres a light film of oil in the tubes, but iv put down to the crankcasebreather fumes)

Any ideas what else this siren noise could be or is it deffinetly the bearing?

And if so does it have to be a new turbo or can i just get a turbo cartridge?

Thanks guys!

[scas]

im not sure if its the same as a tddi mk6 turbo, but in that theres the tiniest dowel in the turbo that lines up with a thing in the maniford-if its not lined up the blades can just touch the maniford making a squealing noise.
as i say yours may not have it

[Frag]

Siren noise was quite common on 140ps rwd,
Sounds like police siren and alters as boost changes.
I think you'll find it's blowing slightly from the shaft that goes into the turbo to move variable vanes,
It's not detrimental as such,as long as you can live with the noise.
(If you Rev it till it makes noise,then wiggle that shaft you'll hear the noise change or go)

[knobby1]

Hey,

Iv had a few problems with the turbo on my mk7 2.4 140 rwd 350 van.

It started thowing codes for underboost and overboost etc

So after allot of research, i pulled it out and did a good variable vane clean as i found the control ring was getting stuck on the edges of the turbo, so i also ground out all the carbon/rust that was causing it to get stuck and its perfectly smooth now wothout any sticking points.

I also noticed some play in the hella actuator so i stipped that down and replaced the worm gear, shims and motor.

I had a really good feel of the bearing and there is next to no play and is really smooth.


So after putting it all back togeather and testing, i cant get it to throw the codes anymore but i have noticed a siren noise coming from the turbo side of the engine bay. (Im not sure if this was present before or not).

I instantly thought of a boost leak where iv put it back togeather, so iv been back in and replaced all the gaskets and seals, but no change to the siren sound.
So iv done some reading on this and people suggest a bearing failire? However the bearing does feel really good and iv checked in the intercooler and theres deffinetly no exess of oil in there. (Theres a light film of oil in the tubes, but iv put down to the crankcasebreather fumes)

Any ideas what else this siren noise could be or is it deffinetly the bearing?

And if so does it have to be a new turbo or can i just get a turbo cartridge?

Thanks guys!

Turbo under/overboost codes are often caused by a poorly EGR, or if you have the EGR blanked off....the sensors themselves rarely fail. Check all the boost hoses and intercooler for splits....mine had it at the hose elbow near the inlet manifold, was at the rear and hard to find. The 140 turbo is electronically operated and they can stick sometimes. The turbo doesn't have bearings, they use bronze bushes in oil.

Lord Knobrot

[Jonboxall]

Thanks guys!

I definetley think i go the locator pin lined up, aswell as the pivot arm for the variable vanes, and i tried to match up the rotation of the body on the unit using the marks left by the bolt washers. (I was stupid and didnt make a mark across the joint when taking it apart).

Im doing an oil change this weekend so will test the variable vane control arm air leak theory as im warming it up, although i usualy cant get it to make the siren noise whilst stationairy.

And i havent checked the egr, so il take it out and give it a good clean to see if that helps atall.

[Jonboxall]

Not sure if i should make a new thread, but as i think its still turbo related il add it here, iv not managed to fix the whistle but its not causing any problems atm.

But the van has now developed a squealing noise, (sounds like a belt slipping) only happens when the engine is cold, the sound doesent change with revs but more as a put my foot down, if i drive very light footed when its cold i can avoid it squealing. It also happens when the engines warm if im pushing it up hill, but again dosent seem to fluctuate at the same speed as the revs?

My instant thought is the turbo bushing being starved of oil?

Or fouling of the turbo blades on the casing, but i felt the bushings a couple of weeks ago and they had almost no play.

[knobby1]

Still reckon you've got a split hose or intercooler.

Lord Knobrot

[Jonboxall]

Hey, just as un update, i rigged up a makeshift boost leak tool and found a leak where the hard 90deg pipe joins the front of the turbo from the airfilter box, and where the final boost pipe joins the map sensor unit. But after fixing both of these i havent noticed any differnce to the noises.

So i went ahead a baught a new turbo core and oil feed pipe etc. (More for piece of mind then anything) After fitting that the siren noise is completly gone.

But i am still getting the “aux belt style screetch” when driving on a cold engine. Noise goes away after warming up.

I am also getting a “cough” or a quick release of air everytime the revs pass the 2k mark. This occurs in almost all gears but is most prominent in 2nd?

[Jonboxall]

With regards to cough or missfire at near 2k revs, i ran the van with the maf (or the sensor next to the air filter box which i belive to be the maf) disconnected today and didnt noticed any misfires, soon as i reconnected it it started to do it again.

Might be a stupid question, but does this mean the maf is deffinetly faulty and i should order a new one or is it more complicated then that?

[knobby1]

With regards to cough or missfire at near 2k revs, i ran the van with the maf (or the sensor next to the air filter box which i belive to be the maf) disconnected today and didnt noticed any misfires, soon as i reconnected it it started to do it again.

Might be a stupid question, but does this mean the maf is deffinetly faulty and i should order a new one or is it more complicated then that?

MAF and MAP sensors rarely fail....but it's not unheard of. A code read would tell you.

Lord Knobrot

[Jonboxall]

Im getting no codes with the maf plugged in, (other then the one about pwm).

2 codes with the maf unpluged, 1 about maf and 1 about temp sensor.

[knobby1]

Im getting no codes with the maf plugged in, (other then the one about pwm).

2 codes with the maf unpluged, 1 about maf and 1 about temp sensor.

The MAF also does AIT I think..!!?? Hence the two codes when you unplug it.

Lord Knobrot

[Jonboxall]

Just a Final update incase it helps anyone else with problems, after much investigation and trial and error i have solved most of the problems.
It turned out that i had 4 individual problems.

1. The first problem that was causing the overboost and underboost fault codes along with codes relating to turbo position sensor problems was caused by the variable vane mechanism sticking.
I originally tried the oven cleaner method for cleaning out the system which did help and cleared out allot of crud, but the same problems soon came back.
The real solution was to strip it all down and take a grinding tool on the dremmel to the outer surface of where the control ring rotates as this had built up rust and carbon deposits that rubbed on the control ring.

408DB877-2163-4474-B81D-068148F28A05.jpeg

2. The police siren noise coming from the turbo at slow speeds. As someone suggested im sure this was coming from where the variable vane control lever enters the turbo.
I fixed this by replacing the CHRA or Turbo cartridge with a good quality melee aftermarket one.

3. The screeching sound coming from the turbo, only present under heavy load on a cold engine, or when going up steep hills fast.
This turned out to be caused by an exhaust manifold stud that had just fallen out? So i replaced this and checked all the others(one other was ready to fall out) and solved that problem.


4. Is the engine cough or miss-fire, but as this is unrelated to my original problems i will start a new post with more details

Thanks everyone!