UKSaabs

Check all the vac hoses, and replace with silicone for good measure.

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'75 96 V4 Anniversary Restoration Project
'09 9-3 Turbo-X Wagon No. 38
B204 Haynes Roadster Project

From what we have been told it is probably a bigger leak than that. Could be a split intercooler.

My thought is that it's the dump valve not being held closed by the boost pressure due to split vac hose.

It gives the same symptoms as a burst hose, but without necessarily causing a check engine light as the air isn't leaving the system.

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'75 96 V4 Anniversary Restoration Project
'09 9-3 Turbo-X Wagon No. 38
B204 Haynes Roadster Project

Possibly or a split diaphragm in the valve, rare on the 9-5 common on the 9000, relatively.

Thanks gents - interesting thoughts. The dump valve was a Map Tun item which I've changed back to a new OE one - still no change.

I've had a good look over the hoses - large and small - and although everything looks ok and I can't hear any leaks some of the hard plastic vac hoses - the black ones that provide vac to the servo and the one into the top of the inlet - are not a tight fit into their respective orifices. They're not rattling around but you can pull them out by a few mil.

The suggestion of a leaking intercooler (and presumably it's connecting hoses ?) is interesting. How is this established/confirmed ? Pressurising the system and listening for leaks or what ?

One point that continues to bug me is how the fault developed initially. To re-iterate - the car sneezed, continued to run, sneezed, continued to run, and then died. Having pulled over it turned over but refused to start. Having sulked for 5 minutes (me and the car !) it started and ran fine apart from the lack of boost.

That sounds like something else - vapour lock maybe ? - but how does a split intercooler for example kill the engine completely and then allow it to start 5 minutes later ? It doesn't compute.

In a perverse way I'm almost enjoying the quest and learning new stuff. But it will be nice to get my turbo back.

thinking about it, that's not dissimilar to what happened on my old 9-3 'vert a few years ago ... coughed, idle became really poor and/or stalled ... and it was the hose popped off between delivery pipe and intercooler. Refitted and all good again. A blown intercooler/pipe means the mixture will be wrong as the engine thinks it's getting pressurised air from the reading it gets from the MAF sensor, but because of the leak only gets air at atmospheric pressure ... when this happens on a diesel without a DPF it smokes like a destroyer because too much fuel is injected (it uses the MAF sensor reading for this). When my 'vert died, I'm pretty sure it turned the engine management light on. That could be enough to get the ECU to go to a fall-back map which uses the throttle position only - certainly if you disconnect the MAF sensor the car will use this, because otherwise the engine tends to stall at idle with the MAF sensor connected when there is a big pressure leak.

I'd go with checking the intercooler and hoses. Ideally use a proper kit - take the delivery pipe off the throttle body and use the blank plug there, then remove the hose from the output of the turbo and fit the other plug (with the airline connection) there - or vice-versa.

You can then pressurise the lot and check for leaks, I know others have suggested workarounds involving bicycle inner tubes ...

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'98 9000 2.3T CSE, stage 3
'04 9-5 Aero manual, stage 3
'08 Jaguar XFR
'10 9-5 2.3T Turbo Edition

Many years ago I was looking for an air leak on a brand new 737-200. A colleague suggested I turn the power off and listen, he didn’t realise that the leak was big enough that I couldn’t get enough pressure to make a sound. If there is a big enough leak you won’t pressurise the system enough to hear or feel the escaping air you will need to use your eyes and hands to find it.

In the case of the 737, a steel nose wheel steering cable had been rubbing on an aluminium static pipe, from build, and by the time I got involved had sawn halfway through the pipe. I never did see it but I felt it.

I agree plus the fact that you won't build any boost pressure while stationary to hear a leak anyway - engine has to be under load.
There are a few versions of this but it works pretty well and is a very useful tool to have anyway:
https://www.seatcupra.net/forums/thread ... de.269836/

this is the tester I bought and used, £79 from Amazon - seems to be the cheapest I could find from a quick search.

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'98 9000 2.3T CSE, stage 3
'04 9-5 Aero manual, stage 3
'08 Jaguar XFR
'10 9-5 2.3T Turbo Edition

However you do it, you need to disconnect the delivery pipe at the throttle valve and probably the outlet pipe from the air filter. Thus the inlet manifold and throttle valve won't be tested. If the pipework and intercooler are sound, no leaks, the try the inlet manifold and throttle valve separately. Why? Simply because you can't guarantee that all the valves will be closed so it is possible that both inlet and exhaust valves will be slightly open on one cylinder (depending on the engine design) some engines have a point in the cycle where the two are open together. If that is the case you won't pressurise the manifold. The most likely position for an engine to stop is with one piston just short of TDC on the compression stroke.

Thought i had posted earlier but have we ruled out blocked/collapsed exhaust preventing boost. Had this on my GM900 a few years back. Even Saab dealer stumped with that one.

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9-5 Aero Estate 2005 in grey
9000 Aero 1995 in black
1994 GM 900
1987 9000 16V S Turbo

Hi Bewildebeest.

Was going to ask, did you fit the replacement DIC. That should sort ignition niggles. I would change the plugs at the same time.

As for boost issues, I did a post on a complete overhaul I did recently. Its not too bad a job. Main issue is getting to the plastic oil trap at the back of the block if you need to replace any cracked PCV hoses.
viewtopic.php?f=2&t=202555
I had several vacuum leaked and that can cause all sorts of lumpy idle and spluttering, as well as leak boost.

I’ve also got a spare MAF if it helps. I can’t guarantee it’s condition though.

I would start with vacuum hoses and check for air leaks by hand. The valves and T near the throttle body is known to crack. The hoses are all reasonable value

Since it started after a 5min wait, it could also be Crankshaft position sensor. These are known to fail and will start to give up when warm. Car won’t start until cools down a little.

It’s a preemptive job I’ve been meaning to do.

There's certainly no shortage of steam coming out the back on these cold mornings. Are you thinking of the cat collapsing ?

Yes Steve - fitted the one I bought from you and went to new '7' plugs gapped at 0.9.
I only bought it as a spare because I'd seen it recommended on here to carry one ! Now I'll carry the 'old' non OE one as a spare.

I was all set to use it for work this morning but after reading your other comments re the crankshaft position sensor I decided against it. A lot of my route is dual carriageway and 'smart' motorway so didn't fancy another impromptu stop on a non-existent hard shoulder.

I've had a nose down behind the rad and can just make out some very very rusty (and therefore presumably original) hose clamps correctly in place on the ends of the intercooler.

She's going to a specialist on Wednesday so I'll report back after that.

Ah yes. I've got those rusty hose clamps. I can recommend JCS-HiTorque for shiny new Stainless steel clamps if you can get to the old ones to remove them. UK manufacturer https://www.jcshi-torque.co.uk/ available on auction sites

Cheers Steve - I'll bear those clamps in mind but given the total lack of access I won't be 'going in' until I have to.

I've been thinking a bit more about the suggestion of a collapsed cat - since day one it has 'smoked' a lot on start up (presumably more steam than smoke) and can stink out my 800 sq ft unit in a matter of minutes (faster than my 140,000 mile 2.0 diesel Peugeot). Is that a symptom of a faulty cat ?
My other question concerns the APC valve - what happens if they fail ? If I pull off the hose to the wastegate actuator will that prove anything ?

From memory, you can access the intercooler hose clamps much easier from below ...

Regarding the potentially blocked cat, I seem to remember reading (not sure if on here or elsewhere) you can confirm that with a infra-red thermometer and/or IR camera, if blocked the cat will be hotter than the pipe leading into it.

If you take the hose off the wastegate actuator, you should hit fuel cut if you floor it - certainly in 3rd gear or above - this happened on my 9-5 when the connection to the wastegate actuator snapped off at the APC solenoid (must have been whacked and weakened when the garage re-installed the engine after its' rebuild).

In addition to the above ... I had similar issues on my 9000 recently, it coughed like it had hit boost cut - but hadn't - a couple of times. Parked it on drive, went to start it again later and nothing ... turns out the coughs were the fuel pump in its' death throes ... so don't rule that out as a possibility either. Fortunately the 9-5 has a schraeder valve on the fuel rail you can test the pressure at (the 9000 doesn't).

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'98 9000 2.3T CSE, stage 3
'04 9-5 Aero manual, stage 3
'08 Jaguar XFR
'10 9-5 2.3T Turbo Edition

Agreed, you need to take off the front undertray and attack from below. It would also be good to do this and check that the hoses are securely pushed onto the IC if not already done. Had that on on a members 9-5 a some years ago and a few of us went to help. It all looked OK and seemed OK from above but did not run well or idle unless the MAF was disconnected (have you tried that?). Once under and tugging it could be seen that a hose connection to the IC was not actually attached, just looked like it was from all angles. They are quite stiff and take quite a pull to see if they are clamped on.

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Alan

'03 9-5 2.3t Vector Estate Auto Noob Stg 1
'01 9-3 2.0t SE Vert Auto
'81 Triumph TR7 DHC