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td 18a heads

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#1 Randy Van Horn

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Posted 19 June 2012 - 06:19 PM

i've heard that the heads on these motors are known for cracking. can anybody tell me why and what i can do to prevent it from happening on my dozer? thanks ,Randy

#2 crawlernut


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Posted 19 June 2012 - 07:24 PM

Randy, this topic has been covered alot on this forum. The cracking problem is caused by many factors. First, is the complex head design in the gas start diesels. The metalurgy wasnt great and thin castings and weak points were inherent in the design. The other factor was coolant level. When working the machine in hills with low water level, the front and back heads would become uncovered with coolant and hot spots developed, then when machine changed aspect the water would recover and rapid cooling would occur. this heating cooling cycles would put stress on already weak points and cracking developed. Also not letting the engine cool down before shutdown added to the problems.
Later models were fitted with the auxiliary water tank on top of the hood to raise the water level in steep terrain. Not sure on the 18A, but the 14 also was fitted with a "jet head" which had better coolant flow to correct the heating issues.
Some others on this board will have some additional comments and will chime in shortly. Jim.
The functioning rustaholic.

#3 M Diesel

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Posted 19 June 2012 - 10:51 PM

The 18A did not have jet heads as such, but were revised to cross flow heads at #15000 and later, which includes all A models.

18A also has a pressurized system with a special pressure relief in the vent line. The relief valve is mounted on the carb side near the top of the radiator. It is important to seal the radiator cap and make sure vent pressure relief is working properly. It can fail in the open position if crud mucks it up.

18A does not have the overflow tank which is important for the reasons Jim said. Air in the radiator top tank was not a good idea but there is no choice in the matter without an overflow tank.
One of the main problems is the tall engine and short radiator. They are almost the same height which is not helpful. You can easily tilt the tractor downward and have the rear head above the radiator top tank.

Gary M

1949 Cub
1951 M - 1951 MD - 1957 450 - 1953 Super C

1953 TD9 "Ichabod JR" aka "Icky"
1949 TD18 "Brutus" -- 1956 TD18-182 "Yard Dog"

1964 Loadstar 1600 -- 1975 Loadstar 1700 dump truck
1949 Massey 44