Question: I am working on a 1984 Ward/Ford school bus with an 8.2N DDA engine, air brakes, automatic transmission. The problem I am having is with the electrical system. I keep getting a fluctuation in the voltage. I have replaced/checked the alternator, regulator, batteries, wiring to these components, etc. but cannot locate the problem. The fluctuation is very evident when driving with the lights on for fog, darkness, etc. Fluctuation of 1.5-2 volts. Any suggestions? From Jack Hellbusch.

Bob Neitzel: I'm a lazy mechanic. I would check the simple thing - engine grounding. Based on the age of the vehicle, I would suspect a wiring connection or engine grounding fault. Make certain that there is an excellent ground between the engine and the batteries (.01 Ohm or less). A poor ground would cause the mentioned problem. A quick check would be feel for hot or warm wiring connections when the drop happens, again clear the indicator of loose or poor connections. Sometimes a poor engine ground can cause the electrical system to ground through the cooling system. Cooling system grounding can cause very rapid radiator failure.

Question: Have you had any problems with the T444E exhaust manifolds leaking at the turbo housing? The ones I have are 95 & newer and have quick warm-up devices. They only leak a little but it's enough to fail DOT. Most of the five are on the second warranty repair, with new tubes, gaskets, and housings. The dealer tells me this is very rare. Am I alone with this problem? If not, tell me what you did to correct this and make it go away.

Bob Neitzel: I checked all the Authorized Field Changes (AFC), Technical Service Information (T.S.I.) letter, and the Warranty Policy letters for any mention of the T444E exhaust leaks. Leaks at the exhaust manifolds to turbo housing are unusual. The gaskets are a metallic material and the system relies on heat expansion for a complete seal. The back pressure devise operates at low temperature and low RPM to increase back pressure and engine temperature. If the Exhaust Back Pressure Device (EBPD) is not functioning correctly, and remaining on, it could create too much pressure and cause the gaskets to fail. I would check that EBPD is not aggravating the problem.

As a note: a TSI letter states a new exhaust pipe and clamp went into production on 3600 and 3800 models to increase exhaust pipe life. The flange radius was increased at the turbocharger end of the pipe, and the clamp was redesigned to better match the clamping surface of the exhaust pipe and turbocharger. Don't confuse the old clamp with the new clamp as they look identical.