1.8T Turbo Waste Gate Question
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1st Gear
Joined: Dec 2010
Posts: 2
1.8T Turbo Waste Gate Question
First post as I just bought my first Audi, did some research and could not find my question answered so I'm hoping someone familiar with these turbos might know of the top of their head.
Background: '98 A4 AEB 1.8T Quattro 67K miles bought recently and has never had boost. Bought boost gauge and shows at most 1 lb boost under all circumstances.
Went through the usual checklist to see what it might be:
- Upgraded diverter valve (DV) to Bosch 710N (when timing belt changed right after purchase)
- Replaced vacuum hose from intake manifold to DV (this was collapsed but no effect on fixing problem)
- Did boost check with PVC fitting and it held pressure to 15 lbs with no leaks
- Checked resistance on N75-C valve and 29ohms and could not blow through the long pipe (I'm upgrading it to N75-J while I am at it)
So I decided to pull the turbo (a bit a a pain) and it appears to be fine (impellers spin freely).
When I checked out the waste gate, I applied pressure to the diaphragm with a bike pump and it will force the waste gate open.
However, without pressure on diaphragm, the waste gate actuator rod moves freely back and forth (wastegate opens and closes) and there is not any tension on rod to hold waste gate closed.
So my big question (and I think that this might be the problem): is there supposed to be some spring pressure on the waste gate(or should the rod be connected inside the diaphragm so it doesn't move freely) to keep the waste gate valve closed until boost pushes the diaphragm rod and this forces the waste gate open?
If so, this would explain the problem... If not, I would very much like to hear suggestions on what it could be. Also, now that I have pulled the turbo, is there anything I should do to check its health.
Best,
Mike
Background: '98 A4 AEB 1.8T Quattro 67K miles bought recently and has never had boost. Bought boost gauge and shows at most 1 lb boost under all circumstances.
Went through the usual checklist to see what it might be:
- Upgraded diverter valve (DV) to Bosch 710N (when timing belt changed right after purchase)
- Replaced vacuum hose from intake manifold to DV (this was collapsed but no effect on fixing problem)
- Did boost check with PVC fitting and it held pressure to 15 lbs with no leaks
- Checked resistance on N75-C valve and 29ohms and could not blow through the long pipe (I'm upgrading it to N75-J while I am at it)
So I decided to pull the turbo (a bit a a pain) and it appears to be fine (impellers spin freely).
When I checked out the waste gate, I applied pressure to the diaphragm with a bike pump and it will force the waste gate open.
However, without pressure on diaphragm, the waste gate actuator rod moves freely back and forth (wastegate opens and closes) and there is not any tension on rod to hold waste gate closed.
So my big question (and I think that this might be the problem): is there supposed to be some spring pressure on the waste gate(or should the rod be connected inside the diaphragm so it doesn't move freely) to keep the waste gate valve closed until boost pushes the diaphragm rod and this forces the waste gate open?
If so, this would explain the problem... If not, I would very much like to hear suggestions on what it could be. Also, now that I have pulled the turbo, is there anything I should do to check its health.
Best,
Mike
1st Gear
Joined: Oct 2011
Posts: 24
If you google a pic of your turbo it will show the rod that controlls the wastegate.. I just had to fix my turbo wastegate since i lost the outer nut! Yes there is suppose to be a nut on both sides of the waste gate lever to hold it to the rod!!! Mine is a 2001 and might be different! new to this as well but hope it helps!
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