Turbo Loss When Engine Cold

[dt1]

Scrote, I've not noticed the oil leak you mention. My Glaxy does also manifest the problem after leaving it parked for say 20 minutes after running at full operating temperature. The turbo does have space around it so I would expect it to cool quicker than the rest of the engine. This remains consistent with the temperature-related occurence, and clearly my reduced vane movement is something that needs attention. In trying to rev it more, I realise that my style and the very nice 5 speed auto usually keeps the revs well under 2,500. Unless my changed driving style and this magic goo does its stuff, I am psyc'ing myself (and a mate!) to take a closer look at the turbo.

 

Thanks for the Power Booster lead. Their web site has many encouraging reports although the ASA found little scientific evidence to justify their claims a year ago. At

[tim-spam]

I don't think that the ASA was saying that Power Boost did not work - they were questioning the claims made that, for example, it could return the engine to its 'as manufactured' condition. Having read their advertising blurb, it does make some pretty extravagent claims, but if it is effective in removing carbon build up from the inlet, combustion chamber and exhaust (including the turbocharger), then it may be just what's needed. The testimonials seem pretty convincing.

[dt1]

I received the Power Boost that I ordered from http://www.gbdriver.co.uk/. Good price and second day delivery included.

 

I have slightly greater actuator movement now when cold (~4mm vs the ~2mm previously). Movement when hot is no greater. I think I get slightly more revs before it goes limp when cold as one might expect. I have been revving the engine between changes so it's hard to say whether its from that or this gunge.

[scrote]

Interesting...

 

i note from the post above that the owner of the golf with a similar problem used two cans before the problem was resolved - Im wondering if your half way there dt1 ?

 

been super busy at work so have not had a go myself yet - but will do in due course

 

scrote

[dt1]

Although the actuator seems to be spring-loaded, with the motor off it is possible to move by hand the arm coming out of the turbo. Mine is very rough and notchy; no wonder its not happy. Sometimes when I hold a constant rpm with the throttle, it surges and fades which I interpret as the vanes sticking and then freeing up as the vacuum tries to move it. Since I'm expecting this dirt to be trapped between the ring used to change the vane angle and the housing, I don't see the goo making significant progress. I can see that it could help free vanes from sticking, but not the ring.

 

I will try to remove the actuator in situ next to confirm that it is not sticking. At the moment the two bolts holding the bracket are not budging.

 

The vanes part of the turbo is built into the exhaust manifold. So removing that is likely to be 'somewhat difficult'. I hope to take a closer look on Saturday, removing it if it is within me and a mate's capability. I'll try to record the process if we do it.

[tim-spam]

On my car, it looks possible to remove just the compressor section and rotor assembly, leaving the exhaust manifold and rotor housing on the engine and the exhaust attached - this should greatly reduce the amount of disassembly required. The only things to remove would be the induction hose connections to the turbo, the vacuum hose and the oil supply and return pipes - I guess that there will be some sealing rings for the oil pipes, which it would probably be better to replace.

 

Then you would remove the ring of 5 bolts holding the turbo to the ehaust manifold - 2 of these bolts hold the actuator assembly and do not have washers under them. Once the turbo is removed, the VNT mechanism will be left in the exhaust side rotor housing in the manifold. This is held in with 3 torx screws.

 

It appears that there are others who have done this - see the attachment.

 

TurboRemoval.pdf

It would seem from this that a lot of turbo problems could be fixed using this procedure, saving the considerable cost of replacement.

 

I hope this helps.

[buford_t_justice]

Would this Ecotek Powerboost stuff make it to the EGR Valve and help clean out the build up of soot ??

[dt1]

Tim, I don't have a firm view on this but would prefer to get the whole thing out for cleaning. I've been photographing it quite extensively and have a few pics on the link below. I think our approach will depend on our limited abilities, tools and rusted bolts! I've started soaking them with WD40.

http://galaxytdi.googlepages.com/turbo1

 

Hijacker, its my understanding that the EGR valve ('N18') is part of the vacuum system. If I'm right it won't be soot that's causing any problems you may have. The 'goo' passes through the compressor and cooler, gets burnt in the engine and exhausted through the vanes/exhaust. My, am I starting to understand this engine?

David.

[raymac]

On my car, it looks possible to remove just the compressor section and rotor assembly, leaving the exhaust manifold and rotor housing on the engine and the exhaust attached - this should greatly reduce the amount of disassembly required. The only things to remove would be the induction hose connections to the turbo, the vacuum hose and the oil supply and return pipes - I guess that there will be some sealing rings for the oil pipes, which it would probably be better to replace.

 

Then you would remove the ring of 5 bolts holding the turbo to the ehaust manifold - 2 of these bolts hold the actuator assembly and do not have washers under them. Once the turbo is removed, the VNT mechanism will be left in the exhaust side rotor housing in the manifold. This is held in with 3 torx screws.

 

It appears that there are others who have done this - see the attachment.

 

TurboRemoval.pdf

It would seem from this that a lot of turbo problems could be fixed using this procedure, saving the considerable cost of replacement.

 

I hope this helps.

 

Can't help thinking that the red line every day part to clean it sounds a bit dodgy and could end up expensive :rolleyes:

[tim-spam]

Yes, I would agree that red line every day sounds a bit excessive - a bit American perhaps! I just make sure that I give it a bit of stick from time to time once the engine is warm.

 

Mine has now covered just over 80,000 miles and tripping into limp mode is just starting to happen once in a while when the weather is cold and damp, so it looks like I shall be looking at cleaning the VNT mechanism before long. I would think that the clearances will be at their minimum soon after a cold start, as the internal turbo components, such as the rotor and VNT parts will warm up very quickly, with the outer casing taking a little longer, especially when the ambient conditions are cold and damp. If these clearance gaps are reduced by a layer of carbon, this will evidently cause the mechanism to stick during the warm-up phase.

 

The procedure leaving the exhaust manifold in place looks to be a bit more fiddly, but much quicker - there is a considerable amount of dismantling required to remove the inlet and exhaust manifolds. The main potential problem looks to be access to drill out any of the ring of 5 bolts should they shear - if this happened, I guess that the manifold would then have to come off anyway.

 

Earlier in this thread, I stated that a sticking VNT mechanism was probably the most expensive thing to put right - the main dealer response to this problem is a new turbo. However, if everything comes apart with not too much difficulty, this could end up being a near zero cost fix (apart from the few hours of labour, that is).

 

If this procedure is required only once every 80,000 miles, I won't be complaining too much.

 

P.S. Thanks for the pictures - these could prove very useful when preparing to do the job.

[NikpV]

I wonder if autos are going to be more prone to this - gulp - why are turbos so expensive? - materials? tolerances ? ????

[tim-spam]

I wouldn't think auto / manual would make much difference. Turbos are manufactured to very tight tolerances, and have to work at very high temperatures and speeds (over 200,000rpm). That makes them a comparatively expensive item to manufacture, but the main reason they are so expensive to buy is the usual dealer ripoff. As these cars get older, and the demand for aftermarket replacement grows, there will be an increasing number of suppliers selling at far below dealer prices - it is already possible to by re-conditioned turbos for under

[NikpV]

I wouldn't think auto / manual would make much difference. Turbos are manufactured to very tight tolerances, and have to work at very high temperatures and speeds (over 200,000rpm).

 

 

sh*t 200,000rpm = 3400revs per second - forces involved will be huge coupled with the high temp !!!! what material are the blades made of??

[tim-spam]

But remember, the rotor is only around 45mm in diameter, and if the rotors are accurately balanced (which is very important), the forces on the bearings are not enormous. On the exhaust side, I think the material is a type of nimonic alloy similar to that used on aero engines. In terms of the centrifugal stresses (which are proportional to the product of radius and rotational velocity squared) within the rotors themselves, they will have been designed to withstand these with a fair factor of safety. Whilst the exhaust rotor gets a rougher deal due to the temperatures involved, the inlet rotor is the most critical structurally, as structural failure would have much more serious consequences for the engine.

[NikpV]

umm will get my A level kids(physics) to do the calcuations - general observation the alloy is going to needto be pretty stiff if the stress is not to result in too large a strain (high E-tens of TPa) especially if the clearance between blade and body is small - and thats not even considering creep and fatigue

[dt1]

Well, the job has started. I have the turbo off and will try to crack it open tomorrow. However, it turned out to be a much bigger job than I expected. It took two of us most of the day. Nevertheless, provided you have a good jumble of tools between you it is not all that hard; just very tricky getting access to the bolts.

 

I was unable to loosen any of the 'easily' accessible bolts that hold the exhaust part of the turbo together (despite having applied WD40 almost even night since Wednesday). So the only other option is to remove the exhaust manifold with turbo which we did. I had hoped to be able to drop the manifold out through the bottom but this looks impossible (without removing the drive shaft).

 

So we then removed the inlet manifold and exhaust recirculation bits. We did not realise until the end that the big cover across the top of the engine compartment gives considerably more space when working from the top. So although it remains necessary to remove all the inlet parts, we may have dismantled more than necessary. We will see if we can get stuff back in a more assembled state later.

 

The big 17mm nut holding the oil feed pipe would not unstick from the pipe (as described in the above PDF). So I have the extra hasle of replacing this. However, another writeup I've seen recommends replacing this anyway. The exhaust bolts have thick washers; one of those are still missing. Many gaskets to replace and probably many of the nuts.

[tim-spam]

I hope it all goes well - just think of the money you're saving. The dealers would have just said, "New Turbo." and charged you well over

[dt1]

I've got the turbo open now. One bolt needed heat and another was very difficult. I ended up cutting its washer with a dremel cutting disk and this relieved some tension and gave another surface to exert leverage against with a punch.

 

Having removed the vacuum actuator, the arm coming out of the turbo still only moves 2mm. The actuator itself moves freely against its internal spring. The dirty side opened easily with some light hammer action. After removing the actuating ring some vanes are fee, some are notchy and some barely move.

 

The Torx head bolts are not unscrewing yet. I presume an overnight soak with WD 40 might help. The circlip holding the actuator arm on went zooming off into an unknown corner of the garage so if I don't find that I will need another from somewhere. Ideas?

 

A post somewhere said a new turbo cost

[NikpV]

Keep going - it will be worth it :rolleyes:

[tim-spam]

A post somewhere said a new turbo cost

[dt1]

Well the torx screws freed quite easily after an overnight soak in WD40 and a bash with a hammer/nail. Even the circlip crawled out of a corner so things are looking up. So now time to get the turbo clean and my hands black with soot...

[tim-spam]

Just out of interest, I wonder if anyone has ever fixed the charge pressure positive deviation problem by replacing the boost control solenoid, the T-MAP sensor or the various hoses. It seems that most people who have had this problem have done (or had done for them) one or more of the above, and it never seems to work - I've read quite a few forums, and the story is almost always the same. In the end, the only thing that seems to work is cleaning the VNT mechanism (either by stripping it down or using one of the aerosol de-cokers) or replacing the turbo.

 

I've also just found the following post on another forum, which may be of interest:

 

"As already stated, you most likely got the boost pressure - positive deviation code. It means the ECM saw more boost than it wanted and to keep you from blowing the engine up, it cuts the fuel. This is what we call limp mode. Once you cycle off the key, it resets itself till the next time you get too much boost.

There could be any number of things that can cause overboost. A faulty N-75 valve (but that usualy causes a negative deviation code), sticky vanes inside the turbo, or the vacuum actuator itself gets stuck in the full boost (retracted) position.

The cheapest & easisest thing to do is to try to free up the moving parts of the turbo. As already stated, this can be done with a vag-com. In measuring blocks group 011, click on basic settings & the car will cycle the vanes through the full range of motion every 10 or 20 seconds or so. If you don't have a Vag-com, you can remove the vacuum line that goes down to the turbo and apply vaccum to it with a hand held vacuum pump. Pump it so that the actuator it at its full retracted position and then release the vacuum. Repeat several times. If you don't have a vacuum pump, then it can be done by hand. The spring in the actuator is very stiff, so it takes tough fingers to move it up & down. You can get assistance by using an open ended wrench on the end of the lever and use it as leverage. Whichever method you use, spray some penetrating fluid around the lever while you move it through its range."

 

I didn't know before that you could use VAGCOM to do this - could be useful. I'm very sceptical about the use of penetrating fluid around the lever - I can't see this doing much good.

[dt1]

The tolerances in the vane chamber are extremely tight. Having started reassembling mine, simply swopping the three spacers around made a difference in how freely the vanes moved. The spacers are only 1/100th of a mm different in length. The design relies on the vanes being exercised to keep a clear arc. The vagcom feature sounds excellent for those of us who don't use the whole rev range frequently.

 

I agree with Tim that penetrating oil on the actuating arm will do no good. Even if you get any into the chamber it will simply drain to the bottom and evaporate away or get blown out.

 

The vanes move between two discs. Both are extremely hard although the main one through which the vanes are mounted is thick and solid. The other one is fairly thin. It appears to have the same hardened surface on the one side but the other side reveals two finishes. This probably means it is coated or has some fancy case hardening. I think the thin one is not as as hard because mine is scored where I suspect the vanes spent most of their life and the vacuum probably keept trying to make them move.

 

I thought you might be interested in how much movement there is. My actuator arm moves about 11mm now that it is clean. These are the approximate vanes positions in the closed and open positions.

[tim-spam]

Wow - that looks pretty clean (unlike your hands, I guess!). What did you use to clean the carbon off?

[dt1]

Latex gloves, scouring pads and lots of elbow grease and sore fingers. The soot comes off very easy. However there is a 'varnish' buildup in many places which is very difficult. Vagcom/revving engine will help with the soot but the varnish is less likely. The thin disc still shows some of it. On initial reassembly, some vanes were still catching a little. So I took fine wet&dry to it to remove the remaining varnish and to deburr the scratches. Now it is fine. The metal on both discs and the vanes is so hard I think it would be fine to use fine emery cloth on all the hard bits. I decided not to touch the impellor as it is quite delicate.