I was doing some work today on my air box to try and remove some troublesome codes. While hooking the secondary air pump breather hose back in to the airbox it snapped off. But this is a good thing, I noticed that where it snapped was brown and cracked and very well may have been the cause of some of these codes. (Here is a link to a post with a picture of the hose http://www.passatworld.com/forums/4...on/315301-disconnected-hoses-help-please.html ).
So, can I drive without this hose? My car has been getting this error for a long time and nobody has spotted it yet. I assume its been cracked for a while, but is it okay to drive with the hose completely removed? I took a trip around the block and nothing felt different, but getting on the highway to go to work tomorrow worries me.
Also, why is it brown? I am not sure what caused this problem in the first place, so hopefully someone can help me diagnose it.
You will be fine driving to work in the morning. You will get or already have a CEL for hose being disconnected. The pump only runs for a minute or so on cold start to help burn exhaust gases and heat up the O2 sensor. The reason for the brown color is most likely due to rust from condensation in the pump. The condensation can be from a faulty combi valve.
Here is a video on how the system works. What is refered to in the video as the secondary air valve VW calls the combi valve.
You should plug the hole on the airbox until you reconnect the air pump hose. It will stop unfilterred air from going through the MAF.
Soak the combi in brake cleaner overnight to help remove any carbon.
I remember seeing somewhere the combi referred to as the changeover valve. Or maybe it was the switchover valve ... (and there is a turnover valve too).
Would soaking it in brake cleaner "repair" the combi valve if its faulty? From the little bit I have read, it seems as though people rebuild these instead of replacing them. I am curious if I should look in to ordering a new part. I guess I won't know until I check it out.
Also, does anyone know of a good guide on how to remove the part? I think I know where it is but I am not positive I am looking at the right engine. This is about the best picture I found elsewhere, but I want to make sure I am on the right track
Unfortunately it is called that in many parts catalogs. It is used as an EGR valve in other cars, but here it is only used to put fresh filtered air into the exhaust stream.
MasterBroshi said:
Would soaking it in brake cleaner "repair" the combi valve if its faulty? From the little bit I have read, it seems as though people rebuild these instead of replacing them. I am curious if I should look in to ordering a new part. I guess I won't know until I check it out.
test it with a vacuum pump, or a syringe. if it lets air through when there is no vacuum, it's stuck open. if it does not let air through with vacuum, it's stuck closed. usually they are stuck open. have a go at cleaning it. it works very often and can go on working for years more. It has worked for me.
MasterBroshi said:
Also, does anyone know of a good guide on how to remove the part? I think I know where it is but I am not positive I am looking at the right engine. This is about the best picture I found elsewhere, but I want to make sure I am on the right track
well, first you will need to remove the two tubes running to the left of the valve cover to make space. one feeds the combi with air, the other is for venting of vapors. you may be able to remove the latter one, but if you don't have to, leave it alone. it's part of another system. there is a metal gasket between the tube and the combi port. you can salvage that maybe (I have), but it's cheap enough to get a new one. then it gets a little tricky because you won't have much space to remove the bolts that hold the combi to the back of the head, and you will be reaching far from where you stand (I am on the taller side, and it's still awkward). You'll need to work by feel. have a mirror handy to help you see.
Be organized with what you remove. have a system to keep bolts and parts removed together, label if you need to. if it's your first time, this will slow you down, but it will make for a successful repair.
Here's a more close-up picture with the Combi valve in it (not labeled). You see the large silver top of the Combi valve; the blue vacuum hose connected to it is what activates (opens) it. (Your hose will very likely be black, not blue.)
MasterBroshi, thanks for the photo credit. Very professional!
Combi is incorrectly called "EGR Valve" in many places. Especially salvage yard websites. I highly recommend picking up a Salvage Yard Combi (EGR) valve. You'll have to order it online b/c they are rare used, but you'll save $50-$100. iirc I paid $25 for my used combi valve off an '04 AWM with medium miles.
I also recommend picking up a MityVac or equivalent to test your Combi valves. A good one will hold vacuum.
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