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Discussion Starter · #1 ·
Hi, my 8v turbo has starting acting up. The symptoms are as follows:

1. APC switch (on top of radiator) clicks on idle

2. Hissing noise under dash when turbo is boosting. This is especially noticeable on the motorway when over 75 mph, especially uphill.

3. Intermittent power when boosting. When hitting about 3500 rpm at full throttle, the car starts to partially lose power. When i take my foot of the throttle a bit, there is a power surge.

I have looked around a bit, and it seems it may be a fault in the overboost cut out switch or a possible vacuum leak. Does anybody have any suggestions?

Any help would be greatly appreciated. :)

 

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Discussion Starter · #2 ·
Help with an 8v turbo

hi I originally posted this in the workshop, but alas no reply. Hoping someone can help here ;)

Basically, my 8v turbo has starting acting up. The symptoms are as follows:

1. APC switch (on top of radiator) clicks on idle

2. Hissing noise under dash when turbo is boosting. This is especially noticeable on the motorway when over 75 mph, especially uphill.

3. Intermittent power when boosting. When hitting about 3500 rpm at full throttle, the car starts to partially lose power. When i take my foot of the throttle a bit, there is a power surge.

I have looked around a bit, and it seems it may be a fault in the overboost cut out switch or a possible vacuum leak. Does anybody have any suggestions?

Any help would be greatly appreciated. :)
 

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8vt woes

I'd guess the solenoid control valve is gone, pretty sure that they don't affect anything at idle so if it's clicking i'd guess it needs relacing.

If there's a hissing comming from under the dash it would prob be a loose/split hose, think your going to have to drop the underside of the dash and have a good look at the hoses, is the boost gauge still working?

Have a good look at your inlet and make sure all the vac hoses are OK and you've got no splits anywhere, it's a good place to start.
 

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If the pressure feed line to the APC pressure sensor bit under the dash had come off, could that cause the APC solenoid to act up?

from the hissing noise it definately sounds like a vacuum/pressure pipe has come off somewhere. I'd fix that first, and then see if the APC solenoid still clicks a lot. If it does then it'll most likely be faulty like Si says.

Either way, a leak somewhere is going to cause your turbo to play up and give you wierd boost.
 

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Discussion Starter · #5 ·
Hi guys, thanks for your replies! I had a rummage around the vacuum hoses under the bonnet on Saturday, and didn't find any leaks or split/cracked hoses. The car idels smoothly as well.

However, I haven't plucked up the courage to remove the underside of the dash. I guess that's the next step. SI: the boost gauge still works, but won't go all the way into the orange.

I think next weekend calls for some serious investigating. Will let you know how I get on.

Thanks again for your help! ;)
 

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The area under the dash can be quite easily got to by removing the one torx screw that holds the air flue in place. Pull the flue aside and you're in there. It is a lot easier to work in that area if you remove the speaker grille which gives more light into the area.

If you look in the engine bay on the LHS, there is one vacuum pipe that goes through the firewall. That vac line goes to a Y junction under the dash which one branch goes to the pressure transducer and the other branch to the fuel cut-off switch. The fuel cut-off switch has a further port which has a vacuum line that runs up to the dash boost gauge.

It's not uncommon for the fuel cut-off switch to leak. Often these are simply bypassed when they start to fail. When you're checking the vacuum lines down there, be careful to ensure that the vacuum pipe to the pressure transducer is connected. If you do not, you'll get runaway boost and possibly a broken engine.

This page at 900 Aero shows all the APC components, so you'll know what to look for when you're working under the dash. What I have called the 'pressure transducer' is the 'pressure sensor' on the 900 Aero page. Likewise, the 'fuel cut-off switch' is referred to as the 'pressure guard' on the 900 Aero page. Follow the instructions to check out the solenoid valve, too.

Good luck.
 

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Discussion Starter · #7 ·
Excellent Orca! Thanks very much! I now can't wait to get my hands on the car and sort it out. Will let you know how I get on. ;)
 
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