I found my boost leak

[S2central.net]

This has drove me bananas for a long time, but I found it almost by accident last weekend when I was checking the car over just before a trek to Dublin airport.

Symptoms I had were a distinct reluctance to hit full boost and often when it tried I would get the dreaded cutout from having sucked in excessive air during vacuum.

If you follow the narrow guage tubing from rear of IM you'll see a line that connects to a 1-way valve which controls flow of air into the vacuum reservoir... For some reason I noticed that one of the tubes looked like it wasn't sitting properly on the fitting. I pulled off the tube and heard air escaping from the vacuum reservoir so this must connect to the vacuum side - explaining the excessive air draw then overboost protection at full duck.

I have no idea what drew my eye to this and I have examined all the other tubes in the past and declared them happy. This one hides behind the valve that I had never seen before... I'll try to photo the booger.

Its a bit of PITA to photo cos of where it is but it looks and feels like there are three connections on this 1-way valve - only two of which are easy to see.

The engine is now happily boosting to 1.3-1.4 bar as it should on full beans and I got the grin factor back again - running with BP Ultimate and the remnants of some octane booster that was in the tank from a previous tank of watered down 95RON.

It wouldn't be appropriate to talk about the velocity encountered over the Slane bridge but it was very early morning and damn nice to let that engine sing loud and proud when despatching a rather stoaty looking guy in a black beemer with Latvia plates who thought it was fun to ride on my rear bumper for a while... Didn't see him again - LOL.

[mcandmar]

The M1 toll bridge heading northbound is great fun, known as Irelands only drag strip

Oh and watch the slip roads, the boys in blue like to sit on the off ramps and catch people flying bye, especially those pesky northerners with lead feet

[S2central.net]

I promised an update on this... Got some photos at the weekend. I need to update my previous drawings of the 'vacuum tree' based on these findings.

Follow the photos in order and it makes most sense. I always knew the recirc valve (A/C equipped cars only) was actuated by vacuum but I had always assumed the connection came from the vacuum reservoir, but it doesn't - its an integral joint on that confounded 1-way valve near the bulkhead. This is the joint which was loose on my car. Note that none of these joins where the solid hose mates with braided hose have any form of clip/crimp on them so it is asking for trouble.

Anyway the path of knowledge starts at rear of the inlet manifold. On the ABY there are two take of points. The upper one connects to FPR and the ECU via a metal T-piece. The ECU connection is a solid green coloured tube.

The lower one (replaced with a section of 4mm blue Samco by me some years ago) connects to the auxiliary vacuum tree for the aircon and difflock systems. The difflock uses a solid pink tube.

This auxiliary vacuum tree is the one of interest for now... Any of the joints in this tree can cause excessive air to be ingested under vacuum. If its a bad leak in the cabin you will hear it at idle. In my case, it was in the engine bay.

[S2central.net]

Pic 2

[S2central.net]

Pic 3

[S2central.net]

Pic 4

[S2central.net]

Pic 5

[S2central.net]

ALSO - With my trusty MityVac I was able to prove there are actually two vacuum reservoirs on aircon equipped cars. I always I assumed there was just one until last weekend...

Under the rear seat you can see where the solid pink hose comes from the engine. It goes into a 1-way valve (as like the aircon-recirc function, uses vacuum for actuation of the difflock mechanism) and then a T-piece to a solid white hose which connects to a vacuum reservoir tucked in behind the rear left trim.

So - there is a front vacuum reservoir on the aircon equipped S2 and a rear vacuum reservoir on ALL S2's. Exciting or what ;-)

[S2central.net]

Nuther annotated picture for clarity and posterity... Too much excitement for one night - I'll try to update other drawings and info I have on this at S2central.net.

[Dan_s2_coupe]

if the in pipe on pic no 4 isnt connected will this cause a boost leak

I fitted pauls load ecu today and when i pulled the ECU out i heard so air escaping had a look and found the rubber hose from the solenide had nothing connected on to it and i couldnt find the hose it connected to is this the pipe on the pic that comes through with the aircon pipe cus i will have 2 have another look 2morrow

[newsh]

http://s2central.net/images/Vacuum_and_PCV/

[4WheelDrifter]

I find the vacuum tree sticker on the underside of the bonnet pretty useful.

[Greg_S]

im still trying to find my boost leak at moment. Was trying to do it at home the other day on my own but couldnt get enough pressure with a double barrel foot pump so borrowing a compressor and can hopefully track it down.

Got to about 10psi and would hear a squeak but lost pressure too quick to trace where it is coming from. Very fustrating since I wont have time to take another look until prob feb now. :-(