Boost pressure fault

[Clan]

Originally Posted by Bagnall

Front mount replaced.

Fixed

I'm surprised you left it so long and didn't just block them off for testing a long time ago , unless you had more than one fault ...

[Bagnall]

Originally Posted by Clan

I'm surprised you left it so long and didn't just block them off for testing a long time ago , unless you had more than one fault ...

I blocked them off before, fault still appeared on a quick drive. So I connected it back up. (Didn’t have vacuum test kit at this point)

Cleaned turbo, blocked off again after testing mount properly. Fault didn’t appear.

Didn’t make sense. But either way it’s fixed

Therefore, either the code was somehow stored in the ecu, or I had two faults? Sticky Turbo vanes and a duff mount.

Thanks for your input and everyone else’s

[Bagnall]

So yesterday and today the error code 6805 has reared it’s ugly head again. I’ve been fault free for about a month since changing the front mount and doing a turbo clean.

It’s not appearing as often as before, but showing the same code.... I’ve vacuum tested the mounts again both seem fine when stationary.

My current thoughts are:

1) vacuum pump - have tested previously with the needle moving rather than staying constant. Believe could be a sign of a bad pump. But it’s been fine for a month?
2) rear engine mount needs replacing - tests fine when stationary but could movement of the engine rocking back possible open up something and lose vacuum?
3) maybe I had two faults all along (front mount and turbo) and now after a revive clean it has lasted a month before sticky vanes returning....

Open to ideas or any input as to which to start with first or any further testing before throwing more money toward it

Thank you

[Clan]

Originally Posted by Bagnall

So yesterday and today the error code 6805 has reared it’s ugly head again. I’ve been fault free for about a month since changing the front mount and doing a turbo clean.

It’s not appearing as often as before, but showing the same code.... I’ve vacuum tested the mounts again both seem fine when stationary.

My current thoughts are:

1) vacuum pump - have tested previously with the needle moving rather than staying constant. Believe could be a sign of a bad pump. But it’s been fine for a month?
2) rear engine mount needs replacing - tests fine when stationary but could movement of the engine rocking back possible open up something and lose vacuum?
3) maybe I had two faults all along (front mount and turbo) and now after a revive clean it has lasted a month before sticky vanes returning....

Open to ideas or any input as to which to start with first or any further testing before throwing more money toward it

Thank you

For testing purposes just blank off the vacuum supply to the engine mounts before it's vacuum control valve ..

Take off the link to the turbo vane control arm and make sure it goes from one end to the other freely in the turbo ...

Yes the vacuum pump should pulse . you take the average value of the vibrating needle , it should get more stable the more vacuum it draws ... which should be around 26 to 28 In/Hg ..

[Bagnall]

Originally Posted by Clan

For testing purposes just blank off the vacuum supply to the engine mounts before it's vacuum control valve ..

Take off the link to the turbo vane control arm and make sure it goes from one end to the other freely in the turbo ...

Yes the vacuum pump should pulse . you take the average value of the vibrating needle , it should get more stable the more vacuum it draws ... which should be around 26 to 28 In/Hg ..

Roger. Will blank off the rear mount and see if it appears for a couple weeks. Will also test the turbo actuator.

[Clan]

Originally Posted by Bagnall

Roger. Will blank off the rear mount and see if it appears for a couple weeks. Will also test the turbo actuator.

just blank the complete system off as i described above , only start fault tracing if doing that fixes your fault .

[Bagnall]

So the vacuum tester is now broke, cheap Chinese C***....... However, the fault did appear when isolating the mounts. Therefore I’m pretty confident they’re ok. Also I did a vacuum test previously when discovering the front mount leak.

Today I swapped over the turbo boost solenoid valve (governor) 30637251 and the turbo engine mount valve 30611668 for ones from a breakers (I grabbed these before discovering the front mount leak)

The turbo actuator also seems to be moving freely.

I’ve done a bit more digging on the forum. And found the following links, they resemble my problem. Seems to happen on hills/demand and not so when the engine is warm.

https://www.volvoforums.org.uk/showthread.php?t=83830

https://www.volvoforums.org.uk/showp...9&postcount=18

From the above, I’ll be trying a mr muscle clean as detailed in the link if the problem persists. Will report back.

Thank you Clan for your input so far, is greatly appreciated. The thread is becoming tedious, but hope it may help someone in the future

If I was a betting man, I think the turbo sticking vanes is the favourite, and I always had two faults originally.......I’m just trying to avoid removing it unless certain - as from looking at it, it looks a nightmare to remove.

[Clan]

Originally Posted by Bagnall

So the vacuum tester is now broke, cheap Chinese C***....... However, the fault did appear when isolating the mounts. Therefore I’m pretty confident they’re ok. Also I did a vacuum test previously when discovering the front mount leak.

Today I swapped over the turbo boost solenoid valve (governor) 30637251 and the turbo engine mount valve 30611668 for ones from a breakers (I grabbed these before discovering the front mount leak)

The turbo actuator also seems to be moving freely.

I’ve done a bit more digging on the forum. And found the following links, they resemble my problem. Seems to happen on hills/demand and not so when the engine is warm.

https://www.volvoforums.org.uk/showthread.php?t=83830

https://www.volvoforums.org.uk/showp...9&postcount=18

From the above, I’ll be trying a mr muscle clean as detailed in the link if the problem persists. Will report back.

Thank you Clan for your input so far, is greatly appreciated. The thread is becoming tedious, but hope it may help someone in the future

If I was a betting man, I think the turbo sticking vanes is the favourite, and I always had two faults originally.......I’m just trying to avoid removing it unless certain - as from looking at it, it looks a nightmare to remove.

sometimes the vane ring cracks in rare cases and when it expands it sticks ... it is unlikely though if the vane lever moved freely with no resistance along it's full travel .

[Bagnall]

To conclude the thread, the problem did persist after swapping the above components.

Therefore opted for a mr muscle clean as detailed on the links above. It involves removing the exhaust from the turbo, I then made a Perspex template (surround with copper grease to perform a seal) with a small hole in it to attach a silicone tube to put the mr muscle in. Also a great idea for a second hole at the top of the template so you know when’s it full

Before the clean I had the code appearing daily. Since the clean it hasn’t returned.......

Also I operated the vacuum on the turbo actuator every 10 minutes whilst the mr muscle did it’s thing. Initially it took 20hg to fully operate, afterwards only 15hg with the vacuum tester. Could be used as a test for people in the future maybe?

Sticky vanes it must of always been, alongside a duff front engine mount.

Fingers crossed it lasts a while, if not I have the template saved for another clean and will attempt a turbo removal if necessary. If I remove the turbo, I may make a YouTube video - as there doesn’t seem to be one for an xc90. Please direct me to one if I’m wrong.

[gmonag]

Its great that you have had a good result but...
It will only be temporary. You will have to remove the turbo eventually and clean/replace.
I have been there.