Exhaust Manifold Aft Water Exit

[jtownsend003@aol.com]

While working (onboard) on the cooling system of my late model A4 the exhaust manifold, aft water exit fitting (a very corroded brass nipple) broke off while trying to remove it, leaving old corroded thread material stuck in the threads of the manifold water outlet. Can anyone give me the size of this water outlet? Is it 3/8" NPT? 1/2" NPT? Can anyone recommend a good tool/size/brand to clean out this mess? I would imagine an appropriate thread chaser.

Thanks.

Jim

[Don Moyer]

Jim,

Both the front and rear outlets on your manifold are 1/2" tapered pipe-threaded holes. The drill size you'll need to clean out what's left of the corroded fitting is 45/64". You might find it easier to get an 11/16" drill and it will work just as well (it's only 1/64" smaller). Both of these drills should be available with 1/2" shanks to fit in that size electric drill.

Most any hardware store should stock 1/2" pipe taps for $10 to $15.

Technique-wise, after you run the drill into the hole, you can take an ice pick and try to work some of the remnants of the threads out of the hole to make it easier to clean out the rest of the threads with the tap. In worst case scenarios, some pipe taps are a little longer than others, so you may have to take your tap to a bench grinder and remove a 1/4" or so from its tip so you can chase the threads deeper into the manifold. If this becomes necessary, have a container of water handy to dip the tap to keep it cool so as not to lose its temper.

Good luck,

Don