Volkswagen Passat Forum banner

1 - 19 of 19 Posts

·
Registered
Joined
·
25 Posts
Discussion Starter #1
Has anyone actually tried to drill out secondary air passageways in a 2.8 l ? ( in heads, for carbon build up)Garage says you need to pull engine to get at them.
 

·
Registered
Joined
·
4,586 Posts
I'm curious to know why your asking about drilling out the heads?
Carbon build-up is mostly caused by the type of fuel used and the driving habits and or conditions of the driver.
Todays engines are less susceptible to carbon build-up as say a 60's or 70's engine.
Today's engines rev higher than the older ones. Higher rev's make it more difficult for the carbon to build up. Todays engines have tighter tolerances which seal the combustion chamber better. Less oil blow-by means less carbon. Fuel injection also contributes to a naturally cleaner engine. The fuel injectors spray such a fine pattern of fuel it is much more atomized than that of the old carbureted engines. Carbureted engines can actually allow raw fuel into the engine.
A car that's continuously used for short trips or hauling heavy loads at low speeds will carbon up horribly in a relatively short time.

All of my cars get driven on the freeway as much as possible. I rev my engines between shifts (manual trans) to at least 4k RPM.
My wife uses her car for short 5 minute trips all week long to work (2 miles to her work) and back. She never gets her above 3k RPM.
On the weekends I take her car out and I'll hit the freeway and just lay on the gas to get the engine to shift at a much higher RPM.
Some people think I'm a bit nuts for this type of behavior, but I can tell you that every one of my vehicles is incredibly clean and deposit free inside the engine.
That includes pistons, valves, intake runners and the EVAP system. I'm also doing a lot less EVAP repair / maintenance than others.

And yes, removal of the heads is necessary to get at the ports.
 

·
Registered
Joined
·
26,649 Posts
He meant plugging the exhaust port for the combi valve. You might have a buildup in that area as it does not flow exhaust (unless the combi is stuck open). It could plug up if you have high enough oil consumption and you can remove the combi and clean about 4" or more with a flexible handle brush. Re-drilling would require pulling the heads. You could have the combi valves coded out by a tuner.
 

·
Registered
Joined
·
25 Posts
Discussion Starter #4
Actually the ports after the combi valve, the ones in the heads, are plugged. Combi valve and ports have been cleaned..thx
 

·
Registered
Joined
·
26,649 Posts
If you can't get to them with a bendable metal handle brush, I would go with the tuning option. It's far cheaper and easier than pulling the heads. How many miles? I've only heard of 1-2 V6 with carbon plugged ports.
 

·
Registered
Joined
·
26,649 Posts
There are places that "chip" or "tune" the ECU to ignore the SAIP system. They often do it along with tune for higher performance (marginal in the V6), but they can also to them for single items.
Check these results and see if any would help:
 

·
Registered
Joined
·
25 Posts
Discussion Starter #9
Chip folks said they could not help.
However, I put some seafoam into the secondary air channel, down stream from the air pump. Started engine and white smoje was pouring out of both exhausts. So, air is going through, but apparently not enough volume to keep "low flow" CELs from coming on??
 

·
Registered
Joined
·
26,649 Posts
I'd try some wire brush pipe cleaner or even a coat hanger. Anything that can be bent and pushed inside to scrape the passage clear.
 

·
Registered
Joined
·
25 Posts
Discussion Starter #11
Ok, thx. But I have cleaned the passages downstream of the combi valves. Problem is the additional passageways that are perpendicular to the main tube, which is only about a half an inch in diameter. Plus you can't tell exactly where you are with your brush. Then to make a right angle turn? I'll keep trying chemicals,like sea foam, hopefully to dissolve the ,most likely, carbon.
 

·
Registered
Joined
·
26,649 Posts
I guess I can look at the set of heads I have and see where the ports come out on the exhaust side (if I can see them).
 

·
Registered
Joined
·
346 Posts
Ok, thx. But I have cleaned the passages downstream of the combi valves. Problem is the additional passageways that are perpendicular to the main tube, which is only about a half an inch in diameter. Plus you can't tell exactly where you are with your brush. Then to make a right angle turn? I'll keep trying chemicals,like sea foam, hopefully to dissolve the ,most likely, carbon.
best thing I have found is flexible rifle cleaning brush/kit:
98204


or a piece of 16AWG or higher wire.
 

·
Registered
Joined
·
26,649 Posts
Finally remembered to check out the heads. It looks like the port is behind one of the exhaust valves. Pictures did not show them, but I could barely see them with a flashlight. I don't know that you would be able to do anything with them with the heads in the car, even out of the car you would need an angled pic or bent coat hanger. I suspect the proper way to clean it is either hot tank or with the one exhaust valve removed.
 

·
Registered
Joined
·
26,649 Posts
Thought of some other things to try (if you are still willing) while sitting up with insomnia.
1: The carbon you broke loose from the main tube may just be plugging the smaller inlets to the exhaust. You can try blowing the carbon out the opposite direction with an air hose plugged into the O2 sensor hole. Remove the combi valve and make sure the exhaust valves are closed on the side you work on.
2: You can probably clean everything out by using blasting media through the combi port. This would require unbolting the cats and pulling them away slightly (no need to fully remove from car). Again, make sure the exhaust valves are closed (remove valve covers and check).
 

·
Registered
Joined
·
25 Posts
Discussion Starter #18
Thank you very much for this. I will try these. Of course I can t help but wonder why did they need to go through the combustion chamber in the first place. If air is needed for the cats, why not just plumb that air directly into the exhaust pipe right before the cats, and avoid the engine all together?
 

·
Registered
Joined
·
26,649 Posts
Older domestic car's air injection systems used an air pump into the exhaust manifolds. They had small metal tubes into the manifold at each exhaust opening. This was before O2 sensors were used. Probably lighter, easier and more space efficient to put them inside the head. This
 
1 - 19 of 19 Posts
Top