2002 VW Passat-Crunching brakes

I know that VW’s are known for funky problems so I am hoping someone else out there has had and resolved this issue.
Sometimes when it has recently rained heavily (I live in Portland, OR, so it’s not uncommon), the brakes will make a crunching sound when I press the pedal down, and there is also increased pressure, as if there is water stuck somewhere. It will drive fine for a few minutes and then will start shuddering, spewing exhaust, and nearly stalling. The engine light will often flash, and for this reason I brought it into my mechanic who is a VW specialist. It was first diagnosed as a faulty engine coil, and that was replaced. The problem came back repeatedly and he said I would have to wait until it “got worse” for him to figure it out. I’ve been riding it out since then, and once I get to my destination and the car sits for a little bit (usually 4+ hours), it runs fine again.
The rainy season has started so I’m a little worried about this happening on a regular basis. This has never happened in dry weather. I would really appreciate any insight!

The crunchy brakes are perfectly normal. Rust builds up really quickly on brake rotors and drums. When you first start driving the surface rust gets ground off in the first few brake applications. That’s just the way it is.

The other stuff is almost certainly unrelated. Describe “spewing exhaust” - sights? sounds? smells? Describe the exact conditions under which this happens. Does it, for example, have anything to do with applying the brakes? Acceleration? Idling? etc.

The flashing engine light is normally a very bad misfire. It would be perfectly reasonable if a new ignition coil took care of it - however, wet weather related running issues are very often just bad spark plug wires. Did you get new wires with the new coil? If not how old are the wires? How about the spark plugs?

If the problem was diagnosed correctly as an ignition coil fault then the mechanic should have changed the spark plugs at that time.
Aged and/or misfiring or incorrectly gapped spark plugs can kill a coil over time.

I bring up the crunching brake noise because it always precedes the rest. When the noise (which is more specifically like stepping on crunchy, squeaky snow, both as far as sound and feeling) happens, I anticipate that the car is going to go crazy. This has been happening for awhile though, so I can’t say that there is 100% correlation.

The exhaust comes out in big clouds, not evenly. There is no smell that I can recall and the engine sounds rough and choppy. Applying the brakes and idling makes the shuddering worse. Also, I’ve only noticed the engine light flash when idling. Once I’m in 3rd or 4th gear it runs well.

I had the spark plugs replaced when my timing belt was done, and it hasn’t made a difference. I’m honestly not sure about the wires. An oxygen sensor replacement was recommended, but I was suspicious as it seemed that a faulty O2 sensor would cause consistent problems, not just weather related?

Thanks for your response.

This is still murky to me both as to the complaint and any reasoning by the mechanic for doing what he did.

O2 sensor problems are frequently misdiagnosed so I wouldn’t get into that area just yet.

At this point I would advise having a chain type auto parts store (AutoZone, Advance, etc) scan the car for codes to see if anything is present. With the CEL flashing there should be something there.
These parts store will do this for you free of charge although I believe that in Hawaii and California they are not allowed to.
Post any results back for discussion.

Based on the brake application, shuddering, CEL flashing, etc, etc it almost sounds like there is a brake booster fault. (Essentially a vacuum leak which can then cause all kinds of problems including codes for O2 sensors, etc.)

If this car has the 2.8 V6, then it has a coil. The 1.8 has coil on plug. This simply sounds to me like the plug wires are getting wet and arcing, especially since this happens “when it has recently rained heavily”.

Try spraying the wires (you can use a mister like you would for your house plants) while the car is running OK. If it starts up with it’s sputtering and what-not, then you’ve identified it. If you’re not sure which are the spark plug wires…you’ll see three on each bank of the motor, and they all go into that nice, new $200 coil your mechanic just put on. You may have to get them fairly wet, but if they’re OK, you can almost use a hose…but stick with the mister.

I notice you haven’t mentioned codes ? If your mechanic hasn’t run the codes he’s worse than useless . The most common problem in your vintage VW is a failing coil pack - easy fix and if you don’t fix it you will mess up the cat converter .
Try a competent mech .

There was a dealer in Portland, recently changed owners, but they had some outstanding mechanics on staff. If all else fails, you could go there (I’m sorry, I can’t remember what the name is, but they used to sell Suburu’s and VW’s). However, I think any competent mechanic should be able to figure this out.

Thanks for all the advice!

ok4450–Unfortunately, the light only comes on when the shuddering etc is going on, so I have to wait for it to happen to have it scanned for codes. The light doesn’t always stay on–will a misfire be picked up after the fact?

Genex–Yes, the mechanic ran two tests, first the valve cover gasket was replaced and then the coil pack. The spark plugs were replaced with the valve cover gasket, not the coil pack, which now sounds backwards.

I wish I had been paying better attention but I was really busy at the time (full time school and work) and just wanted the problem fixed. I’m beginning to think the problem is the mechanic and not the car.

Chaissos-- I have a 1.8. The misting sounds like a fun experiment! Also, I think you’re talking about Ray Reece? They were recently taken over by Dick Hannah. I’ve been there to buy parts but never for service, so I’ll check it out. There’s also a VW shop basically across the street from me now that may be helpful.

I should clarify based upon my original post–#3 coil was replaced first (almost 3 years ago), and the coil pack replaced last December. The more recent time it was still misfiring occasionally at the shop & this is when I was told I would have to wait for it to get worse for a diagnosis.

Yes, Ray Reece…my BIL used to work there. They were very helpful to me, and I’m in Texas…go figure. I’m not sure what happened with the new management.

The 1.8 had a recall out for bad coils, too (amongst other things). Stop by and see if it applies to your motor. Ours was left stranded on the road by those things.

The dealer will do all the recalls, regardless of whether or not they do any other work.

Luckily, the bad coil recall was the only one of many that applied to my car. I got reimbursed after the fact for the one I had replaced in '09 but if I’d known I would eventually be replacing all of them I would have waited! The coils have gone down in price quite a bit because of all the issues and are about $20.

I’m going to try misting the wires…it seems very likely to me that the spark plugs/wires are the issue. If that has no effect I’ll wait until the problem arises again and bring it to Ray Reece and see if a) the coils are the problem and b) the recall is still applicable.

Thanks again for your help!

There were 2 (two) recalls for the coils…make a phone call, at least. Ours were replaced back in '08, then again in late '09.