The AC/heater (HVAC) system may unexpectedly switch to the defrost mode when accelerating. This system is operated by engine vacuum and should be inspected for any vacuum leaks if this problem develops. There is also a revised vacuum check valve available to address this concern.
Car problem reports
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Most reported 1998 Dodge Ram Van 3500 problems
On 3.9L V6 and 5.9L V8 engines, the intake manifold gasket may leak and cause increased oil consumption and a spark knock during acceleration; the gasket should be replaced.
Leak detection pump failure can be caused by the internal diaphragm switch sticking, or in some cases, contamination from debris or carbon particles from vapor canister. If black carbon particles are present in the LDP, replace vapor canister in addition to LDP. The purge solenoid should also be checked for debris or carbon contamination and replaced as necessary. All evap system hoses are subject to cracking and splitting causing leaks, Inspect hoses carefully. In cases of contamination from carbon particles or debris, all hoses and tubes must be blown out with compressed air to remove contaminates.
Some vehicles may exhibit a "buzz", whining", or "moaning" like noise from the transmission when reverse gear is selected. The condition is caused by a resonance of the transmission regulator valve. Our technicians tell us that the repair involves replacing the transmission regulator (aluminum) valve with a steel one.