Technical Multijet boost leak?

[Cinq999]

Apologies if this has been covered before.

1.3 Multijet

With the warmer weather I've had my windows open for the first time in a while, and I've noticed my turbo noise is noticeably louder than before.

When under boost, there's a loud "whooshing" noise......not a whistle, but a "whooshing", like air is either being blown or sucked through a gap.

I obviously thought boost leak, but have checked the hoses as best I can, and can't see anything. No noise when stationary and engine revved, only when driving with boost. Checked figures on Torque app, and boost and intake manifold pressures seem to be about right.

No loss of power, no excessive smoke.

Is there a relatively easy way to check for boost leaks?

I'm tempted to remove the whole lot of pipework from turbo to intake manifold and replace all the clips and clean all the hoses thoroughly.

 

[DaveMcT]

A boost pressure gauge will tell what is going on, but otherwise it needs a careful check of every pipe and joint in the air side of the turbocharger.

There is another possibility -
I noticed a (really quite nice) turbo whistle. Eventually I decided to investigate and found the compressor vanes were damaged. I was never able to prove it but believe something was dropped into the pipe when the car was serviced. In your case, this might be "scare mongering" but if it's easy to take a look.

 

[Cinq999]

As the weather looks good this weekend, I'm going to take the intercooler and all the pipework off from turbo through to inlet manifold.

I can then check it all over and replace all the clips.

I service it myself, and haven't touched any of the intake side since last year, so hopefully shouldn't be anything that's got to the turbo.... assuming the air filter is doing its job.

I'm hoping it's just where a clamp is letting a tiny bit of air out/perished hose. It's not leaking enough to throw up fault code, but just enough to make a noise.

 

[llamallama]

Also a quick check of the air box wouldn't hurt either,

I went a bit nuts and stuck a pod filter with my 1.3 multijet gp, now I can hear the intake nice n clear,

And yep I also checked all the hoses and clamps, next thing for me to do is buy a nice narrow front mount intercooler cause the one that's on it now is not the original and is a complete ****e

 

[Cinq999]

Problem appears to be solved.

I got under the car today and checked all the hoses and pipe work, nothing seemed to be damaged, and all the hoses looked in pretty good condition.

I fitted new high torque clamps to all the hose connections from the air box right the way through to the inlet manifold. I left the original clamps in place, but just added a second on each joint, and it seems to have done the trick.

I'm guessing there was just a tiny leak where one of the rubber hoses joins a metal pipe. Not enough to affect the boost pressure (checked with gauge), but enough to make a noise, probably amplified in the engine bay.

I also double clamped all the radiator hoses while I was there.

Got a 5000 mile round trip from the UK to Morocco in August, so over the last few months been trying to get everything spot on.

 

[DaveMcT]

Slightly off topic but considering your journey plans - Does the multijet have a coolant pipe across the front like the petrol models do? If so check it carefully for corrosion as they are a common source of coolant loss.

 

[Cinq999]

Don't worry, in the past 6 months I've fitted new radiator, water pump, thermostat, and checked all the hoses and pipes.

Now the hottest it gets is 93 degrees....and that's at full load on a several mile uphill stretch @ 32 degree air temp. Sat in traffic it'll sit at 87-88, never any hotter.

 

[DaveMcT]

Fabulous.

Excuse my lack of knowledge about Multijet coolant pipes. The issue on petrol models is external rust on a low cost steel pipe that runs from the water pump between engine block and exhaust manifold. It's hidden away so the first people know it's failed is when the coolant boils.

 

[Trimdoner]

There is actually a similar steel pipe on the multijet as well, from water pump to radiator and across to heater hose. Ours is quite heavily rusted but I check often for signs of leakage and spray it with waxoyl occasionally.

It's a real pain to get at if it leaks, as of course it's tucked away behind the manifold and turbo.

 

[goggs]

Now the main boost leak that has been noted, known by garages and like to check, is a split hose at intercooler. Another leak reported by someone on here was, manifold to head joint where the studs had sheared.
As to boost make sure the Turbo is not clogged with carbon, especially around waste gate aperture. Plus of course make sure Turbo actuator works.

 

[DaveMcT]

I had a VW 1.9 TDI 90 that was as flat as the proverbial. I eventually went to have it chipped (long before remapping was possible). The engineer connected up a boost pressure gauge and took it for a drive with me riding shotgun. The boost pressure was all over the place. Basically it went straight to overboost, the ECU cut the fuel supply until the pressure dropped. With higher revs the boost crawled back up but any sudden pedal pressure caused the same problem.

The engineer adjusted the turbo waste gate and installed the new chip. Wow - it felt fast. But then it would because I probably never had the full 90 due to the excessive boost pressure.

Your problem sounds like not enough air. This will quickly clog the DPF filter with soot so you need to get it sorted. We had a thread about low power on a Multijet. It turned out the inlet manifold and anti run-on choke valve was clogged with soot.. You need to check for leaks but also need to check the inlet is not full of soot. The limited airflow leads to ever more soot recirculated via the EGR.

 

[CarlosT]

There is actually a similar steel pipe on the multijet as well, from water pump to radiator and across to heater hose. Ours is quite heavily rusted but I check often for signs of leakage and spray it with waxoyl occasionally.

It's a real pain to get at if it leaks, as of course it's tucked away behind the manifold and turbo.View attachment 201308

Yes it is, I found the easiest way was to remove the manifold.

 

[Bamboocross]

It’s good practice to clean the map sensor on the back of the inlet manifold and check the wastegate moved freely when ever you have weird boost problems