Question about 3406B in my Freightliner

[Jim Sixty]

I left home this afternoon and went about 5 miles and stopped for fuel. The temp guage had worked it's way up to over 200 degrees. The cooling fan had not kicked on. It cooled at an idle and I shut it off. It is full of antifreeze and wasn't building much pressure in the radiator. I then drove it a little further and left it Idle while loading. it stayed down 150- 175 range. When I got it on the road under a load, it warmed back up again. I took it home and let it cool again. It doesn't seem to be circulating, the heater blows just luke warm air at best. The top radiator connection is hot, but the lower hose isn't. The heater hoses are not hot, nor ar the hoses going to and from the water filter. This seems to be an all at once kind of deal, Iv'e been hauling grain with it after work for 3 weeks now and it hasn't had an issue. I would like to think thermostats, but would think it would still circulate throught the heater. Any chance a water pump would act this way. It only has about 40,000 on an inframe over haul, the head and spacer plate were replaced at that time. The radiator was new last year? not too many miles on it either.

Thanks, for your help,
Jim

[tctractors]

The 3406 motor fitted into trucks in the U.K. were fitted with a plastic style impellor in the water pump, this item was pressed on the shaft and was a cause of many problems to blacken the CAT name, the pump itself was modified many times there was even a V.H.S. tape sent out detailing the changes that would send an Elephant to sleep, so the first place to check is the pump followed by the coolers (heat exchangers) the cooling system is very simple to test with the aid of a heat (temp) gun pointed at the top side of the spin on oil filter.

[Jason 10/D4]

Think id try a thermostat first as that is the esiest and cheapest. Jason

[catsilver]

Experience would tell me to go for the water pump as TC says, its unlikely to be caused by the thermostat if the top hose is as hot as the thermostat housing, but this is where the infra-red thermometer comes in, it will save a fortune in troubleshooting time and cost.

[tctractors]

Jason, the overheating of these motors can realy muck up a thick wallet (Pocket book), to realy sort the cooling side the thermostats might well need checking, the heat gun is 1 of many ways of checking them out, but the thermostats are fairly costly perhaps to costly to just change out, the water pump rebuild kit is moderately cheap and realy needs that eyeball check, in saying that I do like to do the boiling water test on thermostats, so once you start getting inside the lump, I would also strip out the coolers, the gasket kit is just a few coins, once checked you know its sound, I realy make every effort to sort running faults in a complete style and rarely find that I have pulled something to bits in a time wasted moment, there is always some good or betterment to be made from taking the time to look.

[Jim Sixty]

Thanks everyone, I took it apart this afternoon and sure enough the impeller is loose on the shaft. I guess now the question will be new or rebuilt.