Dear Hotfeet,
This is a fairly common, if elusive, problem with XPAG engines.
It is true that the water passages need to be CLEAN. Not only can old crud
block the passage of water through the block, but a layer of scale can
prevent a proper escape of heat from the engine. (Sort of like preventing
heat loss from a water heater by wrapping a blanket around it.) However, on
some XPAG blocks, not all water passages are completely obvious.
Behind the frost plugs on the side of the block, there are often drilled
passages to aid in the distribution of water. After removing these plugs,
you should be able to see then, or at least probe around and find them. Pass
a drill through these holes and make sure they are open.
Also, be sure you are using the correct head gasket. The earlier XPAG engine
had round water passage holes. If the earlier gasket is used with the later
head, there will be a partial blockage. An early head with a later gasket is
OK. By 1953, you should probably have the later head.
The thermostat is very critical to proper operation. Much to my surprise, my
TD used to overheat due to the TOTAL LACK of a thermostat. It wasn't until I
put in an 85 degree (C) thermostat that overheating went away.
Carb condition will NOT substantially alter the operating temperature.
Certainly not 30 degrees. It's important to have the carbs in good
condition, but that is not the cause of your overheating.
Timing can play a part. If the timing is too far advanced, the engine can
overheat somewhat, but again I doubt that this is sufficient to cause a 30
degree difference. It certainly should be checked, however.
What is the condition of the radiator? If this has never been cleaned out
professionally, do it. Often scale or dirt builds up on the inside of the
radiator and prevents the proper transfer of heat. Any radiator shop should
be able to clean this out. Even if this is not the direct cause, you'll be
happy you had it done.
Also, check the condition of the water pump. Make sure that the impeller is
is reasonable shape - not all rusted away.
Are you sure your temp guage is telling the truth? I've seen these things
lie "like a rug" and get their owners needlessly concerned.
If, after you check these things, the situation has not improved. Get back
in touch and we'll take you to the next step. The things I've mentioned can
all be checked without taking the engine out of the car. So start there
first.
Good luck and keeps us informed.
Regards,
Lew Palmer
lew.palmer@uci.com
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original message follows
I have a 53 TD that will not stay below 220 f I can go about 3 miles before
it cranks all the way up there. I have heard that I should have the core
rebuilt, I'm not sure but i thought when my father rebuilt it last time he
had this done. I haven't had the oppurtunity to rebuild and set the twin
SUs. Could this be a factor? The thermostat is the original and I do not
know what its threshold is. I tested it on the stove and it functions.
Also
the brakes are to the floorboard and I have rebuilt the whole system, what
else can I do?
Chris "Hotfeet" Bowman
53 MG TD
72 MGB-GT
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