Hot Spot, etc.

[Unregistered]

My recent purchase whose A4 serial number indicates manufacture around 77 or 78 has a very hot spot in the front area of the manifold, the only area where there is no paint, indicating this has been the condition for some time. The pump was rebuilt this week with new seals and impeller. The old impeller was still intact. I removed the old very dirty thermostat and did an acid flush, once with the hose clamped off after the “T”, and once with the clamp removed, I then installed a new thermostat. Water draw from the 5-gallon bucket appeared normal, maybe a little faster after the first flush. The engine feels normal to the touch except for the front area of the manifold. Compression is normal except for the aft cylinder, which is down to 70. It has been suggested I try flushing with Salt Away. Is it possible to overdo flushing with either the Muriatic acid or the Salt Away? What would be the suggested procedure to resolve the issue of this hot spot? I did order your service and overhaul manual yesterday and very much appreciate the assistance you provide.

Sincerely
Bob Levy

[Don Moyer]

Manifolds tend to clog before any of the other water jackets because of the heat to which they're subjected, and to really get them cleaned out usually requires removing them and taking them to a local machine shop for hot tanking, glass beading, etc.

Don