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 Thursday Notes

Subject : ISB Sticking Valves/Bent Push Tubes
Product Name: MR - ISB/QSB SPT Group : 002 Cylinder Head
Date: 01/06/2000 Equipment Application : ALL
Distribution : Internal and Distributor Service Information Originator : Daniel Fedewa
Warranty Impact:

    As the ambient air temperatures have started to drop in out Northern Regions we are reminding the field, by this Thursday Note, on the ISB sticking valve / bent push tube issue.  The 4 valve cylinder head on the ISB runs at a cooler temperature, which in some cases is allowing tar to condense on the exhaust valves.   This may result in sticky valves and bent push tubes.  The 2 valve head runs at a hotter temperature, thus preventing the tar build up.   To reduce the risk, the following recommendations should be followed.   This may be found in the PITs document "JJGN-44BKRU"


Short Term:

Reactive short term:    Repair and clean cylinder head as required.

Proactive short term:   To prevent or decrease the risk of this occurring to an engine which frequently idles for long periods of time in arctic temperatures, Cummins recommends the following:

  1. Use of a winter front on these trucks
  2. Use of a block heater when the engine is idling.
  3. If the truck is already equipped with an exhaust brake, it should be turned on during idle
  4. Prior to shutting off the engine after extended idling (6 hrs) it is important to bring the engine to operating temperature (minimum of 140 degrees) to remove any carbon build up on the valves. This can be accomplished by driving the vehicle for 20-30 minutes or;

Thanks to Jerry J. Weigel for supplying this TSB information

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This page was edited on: May 3, 2004