Breather Hoses and Throttle Body Cleaning



One of the things that tend to need to be done on the 5 cylinder cars especially after 100,000 miles is a really good clean of all the breather pipes for the crankcase ventilation system. After a while the pipes become clogged with old hard oil deposits and condensation, forming a delightful mixture of oil and water known as "mayonaise". This strangles the engine of it's abiltity to scavenge the gasses out of the crankcase affecting running and in extreme cases emisssions, the cure for this is to clean them all out with a good quality aerosol spray carb cleaner, I prefer to use Wynns as it has a good powerful spray.

To start with you need to remove the trunking above the airflow meter completely and clean the inside of that first (a good bundle of lint free rags is essential for this job), next unclip the airflow meter as if you were replacing the airfilter and spray the top of cone and wioe clean , do the underside of the plate also. The next pipe to do is the pipe that runs from the back of the airbox to the top of the valve cover, this is held in place by a hose clip at this end, take the cleaner and spray it into the pipe and wathc the muck come out the other end. this pipe is one pipe that takes a lot of heat from the exhaust and manifold so it is likely that it will be very soft and need replacing the part no for my Coupe is 035 103 221 R, if you don't fancy paying the money that Audi want for this part, it is possible to use 3/4 inch heater hose and make one yourself along with a couple of new hose clips to secure, the difference is about 17.00 gbp, enough said really.

The next pipes are the ones surrounding the Idle Stabilisation Valve (ISV), you will need first of all to disconnect and remove the ISV then undo the hose clips attaching the various pipes and clean thoroughly with the carb cleaner. There is also a pipe that attaches itself to the cylinder head between the injectors this is also another good one to look at. There is also a metal tube that runs from the valve cover (connects up near the ISV) downn the right hand side of the block that needs to be taken off and cleaned, this is another classic one to get badly gunged up, you may need to soak this one for a while or run some stiff wire through to help dislodge any muck in there.

Depnding on how far you want to take it the dome that the the metal pipe runs to can be renove by prising it off with a flat bladed screwdriver, inside you will find a recess with lots of old oil and in it, at the bottom there should be a drain hole into the sump, chances are this will be blocked and need unblocking with some wire or drill.

Next up comes the throttle body, this is removed by unscrewing the four allen headed bolts, removing the throttle cable and the multi plug on the side of the TB, note that you may need a new TB to inlet manifold gasket, although I have reused mine with no problems. Once it is off then you will carfully need to open the buterflies on the TB and clean with a soft rag and cleaner, DO NOT take the TB apart, the only thing to remove is the idle screw, try and remember how many turns it takes to get it out, this will help when you come to reset the idle speed. It may help to put the TB in a vice ( light pressure only) as it seems you need two pairs of hands for this job.

Once you have finished all this and reassembled it you may find that the car runs a bit lean so maybe best to get the mixture checked and adjusted if necessary. I would ceratinly clean these hoses once every couple of years as some of the air passages are quite small and clog easily

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Copyright 1999 Iain and Ralf
Dec. 1999