04-01-2017 06:44 PM
I don't know many of the details normally required to offer an opinion about the cause of your problem. My first step would be to use a test strip to determine whether the pressure in the cooling system is caused by combustion gas entering. The test strip use instructions will be included with the strip.
If it is combustion gas damage to cylinder liner seats in your cylinder block may have already occurred. I don't know the history of the engine, there were updates to cylinder head coolant passages dating back to the 1990's, but it is possible that the engine cylinder head has never been off the engine or had the updated passages at the rear of the casing drilled. The 3406B engines were very rugged and very reliable. Their demise was fuel efficiency and emissions related.
01-22-2011 06:34 PM
I have a 3406B in my truck and for the pass few months it is spitting coolant out the over flow pipe which sometimes brings the low coolant light on but if i release the radiator cap it brings the coolant back up in the radiator if i have not done to many miles. It does not run hot only about 170 to 175 if pulling up inclimb. I have had the air compressor check and the radiator cleaned. No lose of power or missing in the engine.