D5 (2005 on) random boost drop on motorway

[mlmcelligott]

hi

I have a vacuum issue on my 2007 v50 1.6d

Around town the car pulls like a train and never misses a beat. After about an hour on the motorway the car will loose boost. When that happens I can put the car in third and keep the foot flat to the floor and after thirty seconds or so it'll boost fine for ten seconds and then it'll loose boost again and the car will slow down. Again, after about thirty seconds it'll boost again and it'll repeat this cycle until I get off the motorway and then after a few minutes the boost will come back again and it'll drive fine until i get on the motorway again.

Ive made the assumption thats its got nothing to do with the turbo since it works fine on the back roads and in town. It only happens at high speed and only after about an hours driving so it has to be heat related. Im thinking its either a vacuum leak on a hose that only presents itself when it gets hot and expands, the vacuum control solenoid thats getting stuck or a leak on the turbo diaphragm...

Any ideas?

[Zebra]

Hi
I have had the same thing on my 2009 V50 1.6D. Dealer could not find an issue and the fault was intermittent. Eventually became a permanent problem and happened at low speed. Fault diagnosed as two things:
1)split hose (can't remember where but it was linked to 2)
2)stuck exhaust gas recirculation valve (?) which need replacing
Now works perfectly. Had I / they found the split hose first I wonder whether that would have fixed things.

To me it had felt like the Turbo as like you say it would not rev past 3000 but not in the end.

regards

Richard

[mlmcelligott]

Originally Posted by Zebra

Hi
I have had the same thing on my 2009 V50 1.6D. Dealer could not find an issue and the fault was intermittent. Eventually became a permanent problem and happened at low speed. Fault diagnosed as two things:
1)split hose (can't remember where but it was linked to 2)
2)stuck exhaust gas recirculation valve (?) which need replacing
Now works perfectly. Had I / they found the split hose first I wonder whether that would have fixed things.

To me it had felt like the Turbo as like you say it would not rev past 3000 but not in the end.

regards

Richard

Thanks Richard

I changed the EGR valve a few weeks ago and that solved another issue I was having so you just confirmed that maybe i have a split vacuum hose somewhere.

Are you familiar with how to check for a leak? I have new vacuum hose bought but when i had a look at the car earlier the vacuum hose disappears into the engine after it passes between the gear box and the fuel filter. I took the airbox out but still didnt have enough space to see where it was going. I found where it comes out the back of the engine and connects back into the connector where it meets the brake vacuum pipe before connecting into the vacuum pump. Im assuming theres a vacuum solenoid control valve along the route somewhere as well as a reservoir.

Whats the best way to access these or check them?

[rippedoffagain]

On another car forum I used to be on, the EGR issue came up so often that people devised their own "fix" to effectively disable the EGR permanently. It involved jamming a 10p coin (which they said was coincidentally an exact fit for the bore of the pipe) into the valve, so that it was effectively permanently shut.

The EGR valve opens to let a measured amount of exhaust gas back into the inlet side, so as to burn off more of the residue and improve emmissions. If it lets too much through, then the engine will choke on its own fumes, and because it is constantly exposed to the heat and filth of untreated exhaust gases (remember, its before the cat and the baffles and everything else, just raw, hot exhaust) it snots up quite quickly apparently.

I'm not suggesting that anyway should disable the EGR valve in this way, its on there for a reason, but lots of people seem to have success with cleaning them out.

[mlmcelligott]

Originally Posted by rippedoffagain

On another car forum I used to be on, the EGR issue came up so often that people devised their own "fix" to effectively disable the EGR permanently. It involved jamming a 10p coin (which they said was coincidentally an exact fit for the bore of the pipe) into the valve, so that it was effectively permanently shut.

The EGR valve opens to let a measured amount of exhaust gas back into the inlet side, so as to burn off more of the residue and improve emmissions. If it lets too much through, then the engine will choke on its own fumes, and because it is constantly exposed to the heat and filth of untreated exhaust gases (remember, its before the cat and the baffles and everything else, just raw, hot exhaust) it snots up quite quickly apparently.

I'm not suggesting that anyway should disable the EGR valve in this way, its on there for a reason, but lots of people seem to have success with cleaning them out.

The EGR on my car is electronic and not related to the vacuum system so i can rule that out of the list of possible issues, thank goodness! Im thinking the vacuum pipe, reservoir or the control valve are not holding the vacuum pressure when they get hot...

[SonyVaio]

My attention would be going to the boost control valve, recirc valve (not EGR) and actuator.

[mlmcelligott]

Originally Posted by SonyVaio

My attention would be going to the boost control valve, recirc valve (not EGR) and actuator.

Any idea how to get to the boost control valve?

[rippedoffagain]

Originally Posted by mlmcelligott

The EGR on my car is electronic and not related to the vacuum system so i can rule that out of the list of possible issues, thank goodness! Im thinking the vacuum pipe, reservoir or the control valve are not holding the vacuum pressure when they get hot...

I don't know the specifics on your car, but on the other forum I used to attend, it wasn't a vacuum pipe that bunged, it was the actual pipe that carries the exhaust gas. Inside there is a little valve which is controlled electrically by the ECU, but if the pipe that the valve sits in is mucky, it can't open and shut properly without sticking, so the ECU could be saying "right valve, close fully now", so the motor/actuator tries to do so, but the valve is physically stuck so stays open.