Intercooler / Turbo Pipes Maintenance

Into 3rd month of ownership with 106K miles on the OD. I haven't inspected the intercooler (IC) for oil pooling just yet. Will do at first oil change right after I pull a sample for analysis. Just starting to become acquainted with turbo and diesel technologies and checking my maintenance impulses so as not to overdo and screw up my turbo. My custom is to clean oil whenever I find it, fix any obvious leaks and watch for any further leakage and try to keep up on preventative maintenance. I know about cleaning the IC, but what about the plumbing?

These are my preliminary findings, considered remedies and reservations.

Under the car - Sooty oil droplets on the driveway below the intercooler as well as sooty oil residue in the valance and moist oil about the exterior of the lower IC hose and where it connects to the IC.
Under the hood - Sooty oil build up on the exterior of the upper IC hose and where it connects to the IC (located just below and behind the passenger side headlight) and nearby chassis, wiring and nearby components.

So it looks like leaks issuing from both intercooler ports which can't be optimal for boost pressure. I don't want to change my IC pipes at this time. I want to foster optimal IC/Turbo conditions within the existing stock parts.

Could this be a cheap fix?
ID Parts carries O-rings and an Intercooler O-ring seal kit.

Intercooler Pipes Seal Kit (A4 BEW)
Manufacturer: IDParts
OEM Number: 3C0145117/3C0145117F

It stands to reason that after 9 years and 100k+ miles the o-rings are likely hard and less effective at sealing. I ordered the kit thinking I'd first change the 2 big ones and have the others on hand, if/when I observe leaks elsewhere.

My Objectives:
1) Optimize stock boost pressure
2) Stop observed oil leaks
3) clean away all observed sooty oil residue from exterior surfaces of pipes, connections, wires, chassis and nearby components

The Fix:
(a) Remove the section(s) of the IC hoses (upper and lower) that connect to the IC and change the o-rings. The kit sold at ID parts contains 5; 2 large sized and 3 medium sized. I believe the 2 large ones install near the intercooler.

See the diagram of the Intercooler/Turbo plumbing that shows where the O-rings are located below:






As for cleaning I'd need something safe for rubber. I was thinking kerosene, maybe and/or dish soap or simple green .... any ideas?

What could go right: Improve boost pressure; stop leaks and better monitor for future leakage. It sounds good, in theory!

What could go wrong: I get tempted to clean the inside of the pipes, don't get it all out and some crap eventually comes loose and goes into the turbo. Or maybe I wind up having to replace more because sludge was keeping sealed what would leak otherwise. What else could I screw up?

What the hell, maybe I should just disassemble the whole thing, hot tank everything and replace all the o-rings at the same time!


Any words of advice from the wise would be appreciated.

if the connections are oily then they are leaking some boost time to replace the seals an look into a doggie collar for the top hose.

Good thread, I believe I have the exact same issue

mittzlepick said:

if the connections are oily then they are leaking some boost time to replace the seals an look into a doggie collar for the top hose.

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Ok, thanks, but isn't the doggie collar for the way up top hose; where it goes in by the EGR; the plenum, I think it's called? Up there I'm all good; no leaks. The observed leaks are right close to the intercooler, top and bottom ports, at connecting hoses, insofar as I can discern.

inspect the tabs when you change the seals on the rest it will eventually wear out and the collar is better money spent than replacing that hose when the tabs wear out. also inspect those tabs on the two pancake connectors, mine wore out on the top of the intercooler. but that's with 240,000 miles and high boost. and if your leaks are making it to the ground definitely inspect turbo that's seems like a lot of oil to me.

If the tabs are worn out, does that mean new hoses? I'm having the same issues. What is the best fix? I have the dog collar up top on the EGR, and that fixed the issue there.

jmasciulli said:

If the tabs are worn out, does that mean new hoses? I'm having the same issues. What is the best fix? I have the dog collar up top on the EGR, and that fixed the issue there.

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I'm still trying to figure that one out myself. Are there a doggie collars to address the other hose connections with worn tabs, such as at the intercooler, for example?

I have yet to undertake the maintenance as planned in this thread. I will soon, though, since it's spring cleaning time and I am experiencing some power loss issues on acceleration in low gears.

You aren't losing that much boost from weeping IC hoses.. Clean them, re-install, drive another 100k...

Well, an update to this thread.

I never got around to installing the O-ring kit because I kept putting it off because I thought it was going to be a messy job.I had cinched it up and had no further leaking so putting it off was easy to do. I just kept an eye on it in the meantime, which is easy, considering the Passenger side fender liner is all tore up which is handy for observing the intercooler and related boost plumbing.

So anyhow, a recent all around, up and down check of the car prior to a short road trip vacation and stop off to a GTG where the guru was kind enough to install 2 or 3 of those O-rings but the rest of then set didn’t make it back into my parts box. Oh well…

Any whoo … who would have thought that, according to the guru, there was an 1/8 inch separation in that boost hose plumbing, right where I always keep an eye on it, all this time, that I didn’t even see, which caused my N75 valve to crash from my long time chronic leak that was never apparent to me all this time!You see, as the theory goes, a boost leak like that, causes the N75 to under function, such that when the massive boost leak is fixed, the valve starts fully functioning (solenoid movement) as it had not for a long, long, time, which then suddenly breaks and leaves one in limp mode and in need of a new N75 valve.
Good thing the good folks at the GTG just so happened to have a replacement (albeit ALH) N75 valve on hand to sell me (and good thing I paid the $1450.00 for the other work .. other wise, I wouldn't have been back to get away, yuck, yuck and my vacation would have been shot and that that 500 mile drive back to San Diego would have been a slow trip!

Morale of story: Don't be a flake like me and completely ignore a 1/8 inch boost leak plumbing separation next to your intercooler (or anywhere on that diagram, for that matter), lest you reap the consequences!

I guess all that time my boost plumbing’s 1/8 inch separation had caused the oil to vaporize rather than to leak onto my driveway!Next I better get my ears checked, because I’ve been told I don’t listen too well. I suppose now I can put off the rest of the job since I don’t have the rest of the O-ring and am not sure where they’d go anyhow. I’d just try and look out for leaks and listen too, with my new hearing horn. ....... wha'd did ya say young man?

When the car is not running, the intake track is unpressurized. An unclipped boost hose like yours will only appear to be 1/8" or so unclipped. It would be easy to miss. When driving however the entire system pressurizes.
If the hose is 2.5" diameter, it is 4.91 square inches, and at 15psithat is a lot of force. You can be sure that the intercooler on its rubber mounts and the unclipped rubber hose flex away from each other. This causedthe leak you experienced, and was the source of the hissing noise under load that came from your passenger side wheel well. The amount of oil in your wheel well and fender liner could only come from a boost leak like i found. It was all over. Weeping o rings usually just get the pipe itself a little oily.

Also, dont bother cleaning your intercooler. Unless your turbo seals are leaking prodigiously, the entire intake track will always be covered in the oil introduced by the CCV system.

oldpoopie said:

When the car is not running, the intake track is unpressurized. An unclipped boost hose like yours will only appear to be 1/8" or so unclipped. It would be easy to miss. When driving however the entire system pressurizes.
If the hose is 2.5" diameter, it is 4.91 square inches, and at 15psithat is a lot of force. You can be sure that the intercooler on its rubber mounts and the unclipped rubber hose flex away from each other. This causedthe leak you experienced, and was the source of the hissing noise under load that came from your passenger side wheel well. The amount of oil in your wheel well and fender liner could only come from a boost leak like i found. It was all over. Weeping o rings usually just get the pipe itself a little oily.

Also, dont bother cleaning your intercooler. Unless your turbo seals are leaking prodigiously, the entire intake track will always be covered in the oil introduced by the CCV system.

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I can’t argue with such indefatigable logic. Here is a very skillful mechanic that anyone would be lucky to have on their side. Thanks for your contribution!

Lower intercooler tube to turbo hose ... the spring clip

My 2002 TDI had a new problem with losing boost air, immediately after I paid someone to do the TB and water pump at 255k miles. It is a Jetta Wagon (variant) with ALH engine type, was made in Germany for USA. When I needed boost as a result of the throttle position, gear selection, speed and grade, it would leak (lots of hissing), would hesitate, sometimes emit smoke in the exhaust, etc.

In this case the leak was escaping between the LOWER intercooler pipe and the hose that comes from the turbocharger. That's the connection that has the green o-ring gasket, the metal collar, and the two nubs. What I don't know is why my retaining clip (the outer steel spring wire-looking clip) was missing; I suspect that it had been taken off during an unrelated repair. The first attempt to remedy this was to tie some wire tightly around there, where the clip normally resides. The main problem with this is that after everything is hot (i.e. when I'd been driving for a half-hour or more), the leak upon acceleration was worse. This is probably due to all of those materials (resin and wire) being more flexible after being heated up.

So my point is that aside from the elastomeric (green) gasket inside that connection, and the nubs being engaged, you really need to make sure that the spring retaining clip is seated in its intended position. That clip will maintain the needed force, over the range of operating temperature and will maintain force as the pipe and hose assembly is flexing during normal operation. On my vehicle the part in question is 1J0-145-769. The green o-ring part number is more confusing. What I did find out, with certainty, is that when you buy the intercooler tube (1J0-145-840-G, in my case) it includes the retaining clip. And when you buy the connecting hose (1J0-145-828-T, in my case) it includes the green o-ring.
Aside from the usual parts diagrams that are available online (at retailers), I like to consult this one ... 7zap charge air cooler, Jetta variant.

Those two parts assemblies are not cheap ... 65 USD for the tube (w/ clip) and 85 USD for the hose (w/ o-ring). So it'd be cost-efficient to just buy a new clip (if needed), and a new o-ring. BTW, I've been buying my parts from Quirk Parts for the past year ... they are terrific; and offer very fair pricing.
My friendly mechanic likes to silicone-spray this kind of connection; so I had to insist that it be put together as a dry fit, with no added sealants or lubricants. My turbo boost is back to its greatest performance, flawless, since the boost air leak finally got resolved. Larry

Your mechanic removed that boost hose during the timing belt, and when he reinstalled it, likely didn't reinstall the clip, or didn't have it properly engaged. Who is your "friendly" mechanic?

Or more accurately, maybe find a less friendly, more competent mechanic.

Friendly mechanic

Yes, I had thought that myself; thanks OP for the advice.

The list of remaining things that I may try to fix on this MkIV (at 256k miles) is growing shorter; i.e. some things I feel like shelving in the "won't fix" category. Door lock modules (again), bypassed heater core, leaky roof (rack), I doubt that I will get to this year (and I don't want to keep mine into next year). Fuel leak (from IP, again) I may try to address; intermittent speed sensor dropout (probably ground-related), maybe will chase it.
My turbo and my intercooler should not need any further touching, while I have it. Larry

latching on to your thread

Having an issue with the lower boost hose myself. Had some whistling and it seems the nubs are a bit worn. Will order a new hose, but wondered if the dog collar inventor had made a collar for the lower hose as well? I have one on the upper hose and its been going strong for years.

wonneber said:

Oil comes from the turbo seal whet it goes bad.
Engine run away comes when the seal is bad enough.
Some oil in the IC is normal.
To much oil is time to replace the turbo

Rich W.

Click to expand...

Can oil collect from engine blowby? Or is it always the turbo seal?

03TDICommuter said:

Can oil collect from engine blowby? Or is it always the turbo seal?

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Some from the blow by but with the oil pressure from the oil pump it loads the IC until the boost pushes the oil into the engine & it hydro locks.
Usually not a pretty picture and from what I've read you have seconds to shut the key and stall the engine.

Rich W.

Well.......

My 2004 TDI Wagon had a boost leak. The lower hose on the turbo (to the intercooler) was the culprit. It was leaking at the turbo joint. Those ears that wear down? It was still relatively snug, but those EARS THAT WEAR DOWN? They still worked, but the metal wore through, and when that happens, IT LEAKS THROUGH THE EARS not the O-ring! It's because of what I would call a design flaw... anyhoo, I zapped the ears with a MIG to see if it would seal, and lo and behold, it held air. I'll take it for a test drive in the AM.