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Old November 7th, 2000, 05:24   #1
valois
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Join Date: Jan 2000
Default WasteGate cleaning and maintenance

BetaTDI has been having problems with his car and asked for a link on how to do this proceedure, one does not exist, so I am outlining the proceedure for future reference.
First of all this proceedure applies to all the passats, and the 97 and 98 Jettas, it does not apply to any of the NB's or Jettas and Golfs after 99 as they do not have a wastegate, they use the VNT 15 turbo.

A small discription of the system follows.
I believe the system functions like this.
Most wastegated Turbos operate off of vacuum, this system operates on pressure. The wastegate is normally open and diverting exhaust gasses all the time. To develop maximum boost the wastegate actuator diaphram is pressurized which shuts the diversion of exhaust gasses allowing them to drive the turbo. This would make it a failsafe system, if a component in the system develops a leak or obstruction the result is less total boost, and not excessive uncontrollable boost. The wastegate would fail to operate, and therefore the majority of exhaust gasses are diverted to the exhaust system, boost would be limited to around 9psi in this case at maximum load whereas normally it will peak at 15psi and settle to 13 continous.
The system is controlled by the ECU through a wastegate solonoid valve. Again to be failsafe the solonoid is set so that when it is off the pressure signal sent to the wastegate actuator is derived from the pre-turbo intake system of the engine. Very little pressure is applied and therefore boost is limited. When everything is working as it should, pressure supplied directly from the turbo is applied to the wastegate solonoid valve (hereafter refered to as the WSV) via the red hose, it attaches to the compressor side of the Turbo with a banjo fitting. The ECU sends a ground signal to the WSV to actuate it, this in turn allows the pressure from the red hose to flow to the blue hose. The blue hose is attached directly to the wastegate Actuator diaphram. This activates the actuator, closing the wastegate and allowing more boost pressure. When the ECU senses too much boost by means of the MAP sensor (located in the ECU, the signal is taken by hose off of the upper intercooler return line to the intake manifold)it removes the ground signal from the WSV and it vents the actuator diaphram to the intake via the black hose.

The WSV is located in the left firewall near the airbox. The problem as I percieve it is that the black hose is located near the PCV inlet of the intake. This area becomes very dirty if the PCV is connected on the engine. Some of this crud finds it's way into the WSV and maybe even the actuator itself. The valve becomes partially blocked which will not allow full pressure to the actuator. The sysmptoms of this will be, a code being tripped in the ECU where the specified boost the ECU is expecting to see is not what is actually availible, the actual boost pressure is to low, the code is listed as Manifold Absolute Pressure difference detected or intermittant. This will generally thow a CEL(check engine light) and power will be reduced until the ignition switch is cycled off and then on. This condition will normally occur under high boost demand, ie..going up hills, 5th gear and above 3000 rpms.
Failure of the WSV will cause this problem, as will leaks in the red or blue hoses, or the actuator diaphram at the turbo is ruptured, or there is a kink or obstruction in any of the hoses or obstruction in the valve.
The first order of business will be to bypass the PCV. Remove it from the intake port, plug the port and attach a PCV filter to the outlet port on the valve cover with a length of 3/4" hose. The comprehensive proceedure for this has been outlined by others.
Next, clean the intake elbow thouroughly especially in the area around the small black hose which exits off the intake elbow. remove this hose from the intake and the WSV and spray contact cleaner into the hose until it comes out clear, be sure to use a product that is not harmfull to rubber or platic, test it first on some ABS plastic, and on a small section of hose to make absolutely sure it's not going to eat your hoses up. Once you have cleaned the black hose, remove the Blue one and red one and do the same. The WSV is in a small rubber mount that pulls straight up to disconnect it from the mount. Remove it and clean it completely. I would recommend spraying the ports while actuating the valve, this would require rigging up a connection to 12vdc on the connector and cycling it while spraying cleaner into the ports. I would also recommend some compressed air that can be purchased from most electronic supply houses to blow out the lies and valve before reassembly. Make sure the banjo fitting at the turbo is clean, securely connected, none of the lines have kinks or holes, it may even be a better idea to replace the lines. A hand pump can be used to verify the diaphram actuator is functioning properly, 13 to 15 psi should open it completely. If it will not open, the diaphram is shot, this can be replaced as an assembly, it's bolted to the turbo on a bracket. Keep in mind that the wastegate itself could have crud preventing it from closing completely. To clean this would require the exhaust Downpipe be removed and it would have to be cleaned through the exhaust outlet of the turbo. I hope this helps. I would appreciate any corrections or suggestions anyone has.

[This message has been edited by valois (edited November 07, 2000).]
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Old November 7th, 2000, 06:40   #2
Karl Roenick
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Default Re: WasteGate cleaning and maintenance

Cleaning it is worth a shot. No one wants to buy a turbo unnecessarily. Feto is trying this now, I think. Any success stories with this procedure? Those hoses can get cracked too, esp. at fittings. Might as well replace them, esp when they're some years old.
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Old November 7th, 2000, 07:01   #3
valois
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Default Re: WasteGate cleaning and maintenance

If it's due to obstruction the cleaning may help, what bothered me was that Beta replaced the WSV (N75) and it corrected the prblem for a while, then it returned, a clear indication there is probably crud in the system, he will give it a try and let us know. There are other things that can go wrong in the system, the Wastegate actuator diaphram can give, it's replacable, the WSV can die, it is also replacable. I would think this is even more reason to bypass the PCV on these older models, you should have seen the crud it put into the intake on the car I saw at 98,000 miles. I would believe that this would be hard on the turbo as well as clogging up the intercooler.
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Old November 7th, 2000, 07:40   #4
Karl Roenick
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Default Re: WasteGate cleaning and maintenance

It might also have been that the ecm took a little while after it had the faults cleared to come to the pressure control differential conclusion.

When the wastegate solenoid on the turbo gives out, vw says: replace turbo.

This crud is like the gunk at the bottom of the ic? A goopy type of thing? Not really restrictive, just over everything?
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Old November 7th, 2000, 07:44   #5
SkyPup
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Default Re: WasteGate cleaning and maintenance

no, it is not that at all, it is burnt caked on sludge and soot.
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Old November 7th, 2000, 08:00   #6
tomo366
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Default Re: WasteGate cleaning and maintenance

Rene,
You might want to hook up with Jon Bartlett on this issue. If I am not mistaken the samr thing happened to him and he ended up buying a new 1200.00 turbo unecessarily.
I believe it was the same problem.
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Old November 7th, 2000, 10:35   #7
valois
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Default Re: WasteGate cleaning and maintenance

The bentlys clearly shows the actuator on the GT15 as detachable. We were able to correct the problem on one 98 by switching my WSV with his, the code was still in the ECU as it had been thrown previously, but the car worked fine. When he went to get the WSV, VW indicated that it had nothing to do with Turbo control, infact he said he had to get angry with them to get the proper part ordered, The idiots wanted to argue with him. He tried cleaning the valve , but it had no affect. I would recommend cleaning the system before installing the new WSV as it appears it will just crap out again.
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Old November 7th, 2000, 10:47   #8
Karl Roenick
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Default Re: WasteGate cleaning and maintenance

That's good news on your model turbo wastegate actuator. I wonder if there is a part number. Can parts be ordered direct from Garrett? That might be a work around.

I'm just not convinced that was the case with BetaTDI since he put a brand new N75 in and then cleared the codes. I still think it's something like a leaking hose.

We've had several instances where vw is all too willing to plop in either a new turbo or injection pump. Two hugely-expensive items.
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Old November 7th, 2000, 11:00   #9
valois
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Default Re: WasteGate cleaning and maintenance

Karl, if he had a leaking hose the replacement of N75 would not have helped. Think about the turn of events, he had the problem, replaced the WSV and it returned within a month, if he replaced the WSV again it would probably fix the problem again, until the new one got obstructed, I am hoping they can simply be cleaned out, but I believe to do so it's going to have to be actuated while cleaning to free up the crud in there.
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Old November 7th, 2000, 13:03   #10
Karl Roenick
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Default Re: WasteGate cleaning and maintenance

I did not remember the time interval as a month. His is a very weird thing. It was working fine before it went into long term hiatus for installation of a sound system.

It would be fanstastic if this did the trick. I forget if he replaced the hoses.
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Old November 7th, 2000, 13:17   #11
valois
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Default Re: WasteGate cleaning and maintenance

Karl, Beta's two posts were" I have Vag-com now what" this is where he replaced the N75 and reported it worked. the follow up was "I am going to shoot my TDI" where he reported the same syptoms reoccuring shortly afterwords.
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Old November 7th, 2000, 14:30   #12
Karl Roenick
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Default Re: WasteGate cleaning and maintenance

Yes, valois, I reread the posts and it appears to have been a month. Only occurs at high boost. That could be key. I see that he visually checked the condition of the hoses but did not pressure test or replace any. Replacing the N75 sensor might have caused some movement of a hose that temporarily could have stopped leaking. That hose goes through some hot areas on the way down to the turbo I would think.

In any event, the cause for BetaTDI seems to be loss of n75/wastegate actuator for some reason. It doesn't seem to be the turbo or a split in the air duct piping because replacement of n75 made it go away for a while.
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Old November 7th, 2000, 15:55   #13
valois
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Default Re: WasteGate cleaning and maintenance

With the Vag-com the differences are apparent at idle between specified boost and actual. the differences are not severe enough to trigger the code and to lead top the loss of power until you get into the upper boost regions.
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Old November 7th, 2000, 16:05   #14
Karl Roenick
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Default Re: WasteGate cleaning and maintenance

I forget, was this for BetaTDI's that you noticed the boost request/actual deviation on vag/com or for the other fellow with 98,000 miles and the bad n75?
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Old November 7th, 2000, 16:17   #15
valois
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Default Re: WasteGate cleaning and maintenance

I have not had the pleasure of meeting BetaTDI or seeing his car yet. It was on the 98 Jetta, with 98,000 miles. What I am saying is if there is a problem with N75 it should be apparent using the vag-com and monitoring specified boost versus actual. Of course this could also indicate problems with the hoses or wastegate actuator itself.
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