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-   -   Hard Start / No Start - Is your intercooler frozen? Check Here! (

GraniteRooster December 17th, 2010 06:26

Hard Start / No Start - Is your intercooler frozen? Check Here!
UPDATE 12/21/13

New TSB issued that includes all VWs with CBEA and CJAA engines (Audi A3 is unknown), including Beetle and Beetle Convertible. See attached PDF for complete TSB.

Intercooler kit changeover valve revised from 0C to 10C.

Current TSB in PDF format


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UPDATE 01/18/12

GraniteRooster's Frozen Charge Air Cooler (Intercooler) FAQ / Problem Summary

In an attempt to provide to most relevant details to the forum in summary format, I have compiled the following brief of the issues. This is multifaceted problem whose unresolved issues and discussion runs much deeper than this summary - I'd encourage folks to read the thread in detail for best understanding. At 1900+ posts and counting, you'll need a cup of coffee/tea and comfy chair ;)

When driving in winter conditions (below ~20-25F), external airflow over the air-air intercooler (IC) is cold enough to cause internal ice buildup in the IC and outlet charge hose assembly. Ice buildup may lead to a variety of operational difficulties including restricted intake, reduced power, LIMP mode, engine stumbling, melt water or ice ingestion, and catastrophic engine damage.

Affected Engines
All 2.0L CR TDI engines (CJAA/CBEA) installed in all 2009-2012 model year Jetta TDI, Jetta Sportwagen TDI, and Golf TDI vehicles. Vehicles in both US and Canada are affected.

Ice buildup occurs while driving in cold winter conditions, typically below ~20-25F. Melt water and ice ingestion may be experienced on subsequent engine start if the car is allowed to thaw while parked (such as in a warm garage, or warm parking lot above freezing temperatures).

This is a thermodynamic phenomenon caused by condensation and subsequent freezing or direct vapor deposition of water vapor as the turbo-compressed charge air is cooled through the IC and outlet charge hose assembly. Two main aspects of engine design contribute to the problem:
  1. Low-pressure EGR is used to control NOx formation for emissions compliance, however, this recirculates water vapor rich exhaust back to the turbo and IC.
  2. The IC design on these vehicles is very efficient, providing good heat transfer and economy (and good ice formation under proper conditions)
  • Restricted Intake & Reduced Power
  • LIMP Mode (flashing MIL’s, “Service Now” message)
  • Engine will not turn over (complete ice obstruction of intake)
  • Catastrophic engine damage (ice chip ingestion)
  • Engine will not turn over, "dead battery" starter action (due to hydraulic resistance in cylinder)
  • Starter/electrical fires (due to starter overheating during attempts to start locked engine)
  • Engine will turn over slow / not start (drowning)
  • Engine will misfire, stumble, and run roughly upon starting (water ingestion)
  • Engine will misfire, stumble and run roughly upon acceleration (water ingestion)
  • Catastrophic engine damage (water ingestion – hydrolock)
VW has issued Technical Service Bulletin (TSB) TSB # 21 11 06 / 2025464 Frozen Charge Air Cooler. The kit may be installed by dealers on documented vehicles under original 36k warranty. Customers outside 36k warranty have often been denied installation under 60k powertrain warranty.

A (basically ineffective placebo) temporary solution implemented by VW involves removal of the forward facing cold air intake "snorkle" so that the airbox draws air from the engine bay, which allegedly may be warmer. In practice, TDIClub member testing has shown this modification to make insignificant changes to intake air temperatures, and is therefore ineffective.

What to Do - Frozen IC happened to me! :eek: :( :mad:
If the car won't start after one attempt, or stumbles and dies after an initial attempt, ***STOP!*** You have some decision making to do...

Further attempts to start the engine may (or may not) cause damage from minor to catastrophic. Depending on the amount of water in the intake and engine, damage may occur to pistons, connecting rods, glow plugs, injectors, head gaskets, etc. due to hydraulic lock. There is also risk of starter and electrical system damage from repeated start attempts against a locked engine. You will need to choose:
  • Service the car (preferred) , or
  • Attempt to start the engine and get where you are going (risky)
The best solution is to clear the intake and engine of water and ice before starting. However, it seems the engines are often able to pass melt water with undetectable or no damage. The preferred actions are:
  • Option 1: If under 36k warranty period, have the car towed to a VW dealer by VWoA to have the water and ice drained out and problem documented for installation of Technical Service Bulletin (TSB) TSB # 21 11 06 / 2025464 Frozen Charge Air Cooler. Dealers typically will require this hands-on service and documentation to gain required approval from VWoA for installation of the IC TSB under warranty.
  • Option 2: Elevate the front of the car on jackstands, remove belly pan and lower IC outlet charge hose, remove water and ice from assembly. Reassemble and drive. This option will not be convenient for a typical owner in most typical situations, given need for jacks, stands, tools, light, etc. plus safe environment and time to complete the repair.
  • Option 3: Have vehicle towed to appropriate repair facility for removal of water and ice from the IC assembly
Owners should report problems to their VW dealer and VWoA (1-800-822-8987) (or VWoC, etc.) as they occur. VWoA has the ultimate say in warranty installation of IC Kits; they rely on dealers to be gatekeepers on diagnosis, therefore dissatisfied owners having difficulty with installation approval should increase negotiations directly with both dealer and VWoA. Owners with safety concerns due to this issue should contact NHTSA and report their concerns.

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UPDATE 01/17/12

Click hyperlink for .PDF copy of TSB # 21 11 06 / 2025464

(Credit 740GLE Post #1352)

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UPDATE 09/14/11

TSB # 21 11 01 / 2025464 dated May 24, 2011 has been super-ceded by TSB # 21 11 02 / 2025464 dated June 14, 2011 and most recently, TSB # 21 11 06 / 2025464 dated September 6, 2011. The latest TSB referenced updates to warranty table and labor information. It may be helpful to reference the latest TSB when requesting warranty work.

(Credit Aerox Post #1003)

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UPDATE 6/2011

There is now a TSB with a fix for this issue. TSB # 21 11 01 / 2025464 dated May 24, 2011, titled "Frozen Charge Air Cooler – Engine Will Not Start". It calls for installing a 1K0-198-803-B Cold Weather Intercooler Kit.

The kit includes:
  • New Intercooler (IC) with internal vacuum-actuated flap valve
  • Vacuum Sensor
  • Intake Elbow with Temperature Probe & Vacuum Actuator
  • required plumbing

Installation requires 3-4 hours labor and corresponding ECU software update. This kit was installed on my car by VW on 07/06/2011. Here are pictures of the kit installed on my '10 JSW, as seen from the front of the engine compartment. The post-IC intake charge temperature/vacuum actuator are circled in red. The rest of the kit is not easily viewed without removing the engine belly pan, etc.

EDIT 03/07/2012: Member UberVW_TDI posted nice pictures of the components of the kit in Post 792.

Integrated Temperature Sensor and Vacuum Switch / Blending Valve mounted on Elbow

Intercooler with vacuum actuated diverter valve

03G-906-051-K (VACUUM SENSOR)

EDIT 03/07/2012: Member PAJettaTDI posted good photos of his installation in his photo thread.

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ORIGINAL POST 12-17-2010

**I posted this at the end of the "Cold Start/Scare" thread in the MK5 forum - but thought I would post here in Mk6 JSW as well for the benefit of MK6 owners who do not frequent the MK5 forum... I hope that is OK.**

After a longtime lurking I have something to say and its not good - my car has been having significant icing problems as well.

I commute 100 miles each way from Northern NH to Southern NH 4 times a week. I leave at 5am and return at 5pm. Obviously NH is subject to freeze thaw cycles and we have been having some very rainy, humid conditions this November/Early December.

I have had rough starts with symptoms of water being drawn through the engine 4-5 times in the last 3 weeks. I have had the engine not turn over once.... paused 5-10 sec, checked myself, tried again, and cranked but caught rough and stumbled for 45-60sec...., and then again once pulling out of parking lot, engine RPM's (and airflow) rising, more stumble.

Then, Tuesday Dec 14th driving home, left South NH in 27 F degrees, rain, snow mix and temperature falling rapidly. 25 minutes into the drive, precip has transitioned to mostly snow, and temperature now 14 F degrees and still falling. 72mph in left lane, power cuts, Service NOW message, Glow Plug lights flashing. Finished 70 mile drive home with engine in LIMP mode and 10 degree external temperatures, wondering if my HPFP was expired. I was low on fuel, so left engine idling in LIMP and filled up with my favorite B5 before continuing home and shut it off. Read most of this thread... holy cow this is not good.

Next morning, 8deg, car fires up, no CEL's, drive 100 miles to dealer and drop it off. They let it sit till lunch outside in freezing temps. Bring it into shop, they drained almost a cup of water and ice out of the intercooler lines.

This is major spooky as I have already had one start that was "hydro-locked", but I didn;t know what was going on at this time so I forced it and it started horrible. I am real concerned about major long term engine damage from regular ingestion of big slugs of water caused by this icing/melt problem. This car is 10 months old with 33,000 miles, driven very regular route, broken in well and driven accordingly, 2 out of 3 fillups with B5 and the rest straight ULSD always from the same two stations, so the average bio-concentration in the tank is is usually B2-B4..... I intended to keep this car a long time, but having it ice up a couple times a week for several months of the year is just not going to work.

Dealer considers car fixed until it throws another code... and it doesn't throw a code when it hydrolocks or or rough starts. I question how many more times this can happen before I have bent or broken rods and worse.

Thanks to all for very cool and informative forum here - I have learned a lot and enjoyed my TDI very much until now. Thought I would let you all know of another iced up intercooler.

I am also starting a case with VWoA - the more the merrier.

timwagon December 17th, 2010 07:17

Sorry for my ignorance, but what are intercooler lines, and what fluid is normally found in these lines? Oil? Antifreeze?

bdisco December 17th, 2010 07:21

Do you ford any streams on your commute? Hydro-lock is never/ever good.

GraniteRooster December 17th, 2010 07:37

I would encourage all TDI owners in New England and other Snow Belts to come up to speed on this VERY QUICKLY - lest your fancy diesel wonder machine explodes its guts all over your parking spot from hydro-locking :mad:

Your intercooler is a "radiator" positioned in the intake between your turbo and the throttle body that functions to cool the intake air charge. The turbo compresses intake air which heats it up, and the intercooler cools the air before going in the engine for better efficiency.

Humid intake air can condense in the intercooler under the right conditions, and condensed water can lead to icing under the further correct conditions. This is what happened to my when my car went into limp as temps were dropping while raining/snowing - the intake choked down enough to throw a low Manifold Air pressure code.

When the car warms up later, the ice in teh intake will melt, leaving LIQUID WATER SITTING IN YOUR INTAKE. This can then get sucked into the engine when started - leading to rough starting, sputtering, and in extreme cases hydrolocking.

I have not spent enough time under the hood yet to discover exactly how this whole mess is arranged in our cars, and where the low spots that water collect are after the intercooler, but suffice to say there is a fellow in Wisconsin having his engine replaced by VW due to hydrolock caused by intake moisture and icing as we speak. And, there are TDI drivers all over the country in snowy climates reporting trouble with rough starting and engines that won;t crank over after being run in humid, near freezing conditions and then allowed to sit and warm. In my case, I drive to work when its 15-20 degrees out then if its 35 degrees when I go to lunch, I have a tough time getting her fired because its drowning in water.

I imagine if enough water collects in the right spot it could completely block the intake air path, which would pump a slug of water straight into the cylinders on startup under the right conditions.

Goodbye connecting rods.....

glennco December 17th, 2010 07:41

Here's a pretty good summation of your problem from another forum

GraniteRooster December 17th, 2010 07:44


Originally Posted by bdisco (Post 3220843)

Do you ford any streams on your commute? Hydro-lock is never/ever good.

Thanks, I already know what hydrolocking is - I used "hydro-locked" in quotes because it has not been PROVEN to be so - just my pretty well educated guess, and the symptoms match. Was it truly hydrolocked, or just mostly wet and cranky? Now thats a Fine line... hard to say until catastrophic damage occurs. Not sure I want to be the guinea pig on this.

I don't ford any streams, but the heavy wet weather in NH lately with slush, snow, heavy rain, and ice, all being swallowed at 75mph thats a lot of water going in the engine no matter how you look at it it, and no matter what car you are driving. Lots of drowned TDI's in NH and Maine lately from what I can see reading around here....

PaulGiz December 17th, 2010 07:45


Originally Posted by timwagon (Post 3220838)
Sorry for my ignorance, but what are intercooler lines, and what fluid is normally found in these lines? Oil? Antifreeze?

The intercooler is an air-to-air heat exchanger that cools down the charge between the turbo and intake port. Theoretically there should be nothing in the intercooler and associated plumbing but air.

In reality you will find at least some oil in there. A small amount of water may appear there due to condensation, but lots of water is a very bad thing.


tcp_ip_dude December 17th, 2010 07:45


Originally Posted by timwagon (Post 3220838)
Sorry for my ignorance, but what are intercooler lines, and what fluid is normally found in these lines? Oil? Antifreeze?

The intercooler cools the combustion air to increase density after it passes through the compressor side of the turbocharger (The act of compressing the air generates heat). The lines normally contain compressed air en route to the combustion chambers.

timwagon December 17th, 2010 08:00

Thanks to all for the explanations.

Now I have one more thing to worry about...exploding fuel pumps and frozen intercoolers.

Thaks a lot! :eek:

PaulGiz December 17th, 2010 08:06

Ugh. Two hard starts, both under the exact same conditions:

No precipitation. Very cold weather (7-12F), followed by warming (to ~40F). No troubles with cold starts at all. It's the ones after the air temp goes up 30F or so that give stumbles.

I smell a recall.

Be nice to put a drain petcock into the mix--I can't crawl under a car, in a driveway in the dead of winter.


VarmintSlayer December 17th, 2010 08:17

The thing is with a drain leg is it will tend to collect water, freeze then split open if not drained frequently.

PaulGiz December 17th, 2010 08:19

Flap valve? When IC is pressurized valve closes. When not pressurized, drippy, drippy, drippy.


bdisco December 17th, 2010 08:25

I'm coming from the Subaru camp back into the VW side again, but sure my Legacy & WRX had drains in the air-box. I don't recall seeing any water in the intake side of things. I'm sure under the right conditions sweating could occur. The Subies do tend to heat up a lot quicker compared to the VW diesel 1.5 vs 4 miles.

timwagon December 17th, 2010 08:34

The OP's trouble started 25 miles into a drive, so the engine was probably fully warmed up.

Not sure if a hot engine temperature would help with this issue once there's a "cup of water" in the lines!

tcp_ip_dude December 17th, 2010 08:36


Originally Posted by bdisco (Post 3220938)
I'm coming from the Subaru camp back into the VW side again, but sure my Legacy & WRX had drains in the air-box. I don't recall seeing any water in the intake side of things. I'm sure under the right conditions sweating could occur. The Subies do tend to heat up a lot quicker compared to the VW diesel 1.5 vs 4 miles.

Also, being a fuel throttled engine (diesel) as opposed to an air throttled engine (gasser), relatively speaking, the diesel moves a much larger volume of air through the intercooler (and engine), so I could see how a proportionately larger volume of condensate could accumulate on the 'cold' side of the intercooler. If this proves to be the case, then I can see how some sort of draining mechanism is in order. Very interested to see how this plays out and how VW responds.

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