Gurgling noise while pressure testing, lost 6-7 psi

[MikeWasHere05]

So after my MAF blew out I somehow developed some kind of a boost leak (PC-16 setup spiking 14, should be around 21), I built a pressure tester and used it today:



We put it in the TIP and stopped off the PCV line (theres only one on the TIP, right?). We then pressurized it to 15psi and 20psi, both times there was a weird gurgling noise coming from the turbo area. We fixed all the small air leaks that we found, but the car is still not making as much boost as it should be. There aren't any visible oil/coolant leaks, could this be something like a turbo seal? Is there supposed to be a gurgling noise?

Thanks

[Ewok_Fetus]

Told you that you had a boost leak...

[Jibberific]

Dude mine did pretty much the same thing when i pressure tested it, but i put my testing thingy on the compressor inlet. i pressurized it with like 10-12 psi and it didn't make any hissing sounds, but i heard a gurgling/bubbling coming from somewhere. like 'bloop-bloop-bloop" as if the air was bubbling up through some thick liquid.

But my noise wasn't coming from the turbo, it was deeper in the engine compartment. I'm thinking it's oil in the intercooler but i haven't dismantled it to find out yet.

[MikeWasHere05]

Told you that you had a boost leak...

I had a few small leaks, but they were all there when the car spiked 22 pounds. Now the leaks are fixed and I'm spiking 14...

[MikeWasHere05]

Dude mine did pretty much the same thing when i pressure tested it, but i put my testing thingy on the compressor inlet. i pressurized it with like 10-12 psi and it didn't make any hissing sounds, but i heard a gurgling/bubbling coming from somewhere. like 'bloop-bloop-bloop" as if the air was bubbling up through some thick liquid.

But my noise wasn't coming from the turbo, it was deeper in the engine compartment. I'm thinking it's oil in the intercooler but i haven't dismantled it to find out yet.

After searching for a little bit (like I should've done in the first place) I found that this gurgling noise may be normal, for both our sakes lets hope so.

But I'm still hitting 14psi... gonna go check the N75 now.

[Jibberific]

Would a bad n75 cause surging? It's weird, my boost issues are kind of intermittent. It has the GIAC 91 basic file, and it's never boosted above 15 psi since i've had it.

Sometimes it will hold steady at 15, which is about 5 pounds less than expect it to be. And other times it will surge pretty badly, with my needle waving back and forth between 10 and 15 pounds. I was thinking a new n75 would help? for only 80 bucks it would be a cheap solution to our problems, but i don't know the difference between the J and H and C versions so i don't know what to do.

[MikeWasHere05]

I pulled my N75 off the wastegate and the car didn't boost above 14psi again...

Could it possibly be a bad wastegate?

[mike-2ptzero]

That noise is normal, its just air getting past the rings and into the crank case. That pressure will travel up the oil drain line to the turbo.


Mike you most likely have a loose or broken wg.

[MikeWasHere05]

That noise is normal, its just air getting past the rings and into the crank case. That pressure will travel up the oil drain line to the turbo.


Mike you most likely have a loose or broken wg.

Oh boy, figures. What's the test? Is it something where I have to pull the turbo to find out, or can I possibly avoid all that work?

This car: surprise after surprise...

[mike-2ptzero]

Can you reach the wg actuator arm?

[MikeWasHere05]

Can you reach the wg actuator arm?

Thought about that, gonna check it out later. I don't think the wastegate is bad, as the turbo has less than 10k on it. It's more likely that when I disassembled the turbo two months ago I messed something up.

Is there a certain number of threads that I can count out to adjust the arm back to normal myself, if thats all I need to do? Or is it something that I need to send to a shop?

[mike-2ptzero]

Its best if you take it back out. Put the turbo on a bench while giving the actuator some air from a air compressor. You want to tighten it down closed and have it open at the set psi that the actuator is set for.

[MikeWasHere05]

Took the turbo out, the wastegate actuator arm has both nuts on it and the wastegate is closed tightly. It takes a good amount of force for me to manually open the wastegate by pulling the actuator arm.

It doesn't appear that the wastegate is broken, however maybe theres something that's affected only at 15psi+?

Could you clarify your post mike/somebody who understands? I want my turbo back (if it is in fact broken) to OEM K04-15 settings.

If in fact my turbo is not the problem, then I am completely and totally stumped. One of the exhaust mani->turbo bolts was kinda loose, but a very minor exhaust leak shouldn't cause this much of a problem I would think.

[MikeWasHere05]

So now that I fully understand how the N75 and such work, I've figured out that I can test the wastegate by pressurizing the line going to the wastegate at whatever the stock wastegate spring is supposed to be set at. If the wastegate opens at anything under that stock specified pressure than the spring is faulty.

Is this a correct assumption? Does anyone know the stock K04-15 wastegate spring pressure?

[MikeWasHere05]

Through my searches I found this link: http://www.clubgti.com/forum/showthread.php?t=127285

They don't seem to really give a straight answer, but I've gotten this piece of information:

On other forums they advise me to regulate the opening of the WG for the stock presure(0.9bar) for the K04 to open.

.9bar is 13psi, the maximum that my car is currently boosting. It would seem from this that my N75 is busted, if it didn't regulate the pressure correctly and just let it pass right through it would hit 13psi and the wastegate spring would open the wastegate. However I disconnected the N75 and the problem still persisted. I also performed an ohm test on the N75 and got a reading of 31ohm, which is within specifications according to Bentley.

Confusion continues.

[Ewok_Fetus]

Through my searches I found this link: http://www.clubgti.com/forum/showthread.php?t=127285

They don't seem to really give a straight answer, but I've gotten this piece of information:


.9bar is 13psi, the maximum that my car is currently boosting. It would seem from this that my N75 is busted, if it didn't regulate the pressure correctly and just let it pass right through it would hit 13psi and the wastegate spring would open the wastegate. However I disconnected the N75 and the problem still persisted. I also performed an ohm test on the N75 and got a reading of 31ohm, which is within specifications according to Bentley.

Confusion continues.

So change out the N75 if you thing it is bad... When I disconnected my N75, I got no boost at all... Also, if an N75 is busted mechanically, that doesn't mean that the coil will read anything different... The solenoid coil will still register within range, but if the plunger on the inside is busted, you could have problems...

[MikeWasHere05]

So change out the N75 if you thing it is bad... When I disconnected my N75, I got no boost at all... Also, if an N75 is busted mechanically, that doesn't mean that the coil will read anything different... The solenoid coil will still register within range, but if the plunger on the inside is busted, you could have problems...

Disconnecting the N75 will prevent the wastegate from ever opening should = lots of boost. I'm not sure why you had no boost at all...

Anyways, I gave up and decided to try and put it back together when I discovered at some point the TIP developed a massive shred where it connects to the turbo. Apparently its recent, as it wasn't there when I pressure tested last week. Just ordered a $175 APR TIP from ecstuning. I really really fucking hate this car.

[ILoveT]

One of your N75 wires may need to be soldered back on.

[MikeWasHere05]

One of your N75 wires may need to be soldered back on.

? Why do you say that?

[ILoveT]

Because it happened to me. I was only boosting 3-4 PSI. I found out it was a common problem so I checked it.

Just peel back the weather cover and see if one of the wires is just hanging out. There are only 2 so it should be an easy process.

[MikeWasHere05]

Checked the N75 wires... they're fine. Put the car back together (now with an APR TIP) and the problem is still there. If it matters, after 3 miles on a battery reset my block 032 is +1.6% at idle and -3.9% at part throttle.

At full throttle in third my car will hit 12-13psi and flutter about ~2psi in that area. Sometimes the car will jump, like the wastegate just slammed shut but then blows open again. I guess I should replace the N75, but I don't have the money to be throwing at this problem with $200 hoses and $100 valves. Is there a way for sure to check the N75 valve?

I'm going to try and get a buddy to give me his for 20 minutes, but I don't know when I'll be able to meet up with him.

EDIT: Can I buy a MBC and just straight up replace the N75? I know I would need a bleed style, rather than a ball and spring. What brands do you guys recommend?

[ct1.8t4me]

Do you have a cat? (not feline)

Have you tried running with the vacuum line completely off the wastegate actuator to see if the turbo spools higher? I would try that regardless of whether or not you have a cat I guess. If the turbo spools higher then you know something else is limiting you. If it does not then I would think everything points to the turbo somehow. Just don't blow your engine up. Also, if you DO have a cat, and the turbo does not spool any higher - look at the cat for failure.

When my cat failed the catalyst itself broke free inside the housing and rotated basically becoming a brick in the exhaust stream.

[Nebone]

If you need to try a N75, come to south RI and Jake (317ssayzarc) can probably swap his in since his car is in pieces. Send him a PM. I have an N75H valve lying around and you can try that when I'm there next weekend.

[MikeWasHere05]

I have a few PMs out to people about purchasing their N75s, so we'll see how that works out.

I do not have a cat, testpipe setup. I'll disconnect the vacuum line tomorrow and see what the deal is after everythings been checked.