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temp problems/please help brainstorm
https://www.slantsix.org/forum/viewtopic.php?t=31149		 Page 1 of 1
Author:  Russ [ Tue Sep 16, 2008 5:07 pm ]
Post subject:  temp problems/please help brainstorm
Hello folks, I just did a fresh rebuild, or rather, i had a reputable shop do the rebuild. slightly hotter cam and pistons, otherwise nothing fancy.
the engine is hooked to a modern four cour radiator, and running a 195 degree thermostat.
Ok heres whats going on: ran the engine the other day at aprox 2000k rpms, electric fan running ,engine sounding strong , at which time the
new autometer gauge
started to climb. 200, 210, 225, at which i shut the engine down. The radiator started to puke and steam .

Ok i am going to switch to a cooler thermostat, check the rotation of the fan, did not yet check timing, but can wrong timing cause over heating while doing a run such as i described?
WHAT ELSE?
something i am overlooking? please help. some around here aresuggesting
that the motor has to come apart
Author:  Russ [ Tue Sep 16, 2008 5:09 pm ]
Post subject: 
btw this was to do the initial run for break in
Author:  SlantSixDan [ Tue Sep 16, 2008 5:23 pm ]
Post subject: 
Did pan-test the thermostat to verify it works before you installed it? Did you check the hose running between the radiator and the water pump to see if it is collapsing when the engine's running at high idle?
Author:  Joshie225 [ Tue Sep 16, 2008 5:25 pm ]
Post subject: 
How quickly did the engine overheat? It's easy to have air trapped at the thermostat when filling the cooling system causing the thermostat to stay closed. Was the air coming through the radiator hot or cold?

Late timing will contribute to overheating. A lean mixture will also contribute to overheating. What carburetor are you using?
Author:  Russ [ Tue Sep 16, 2008 5:44 pm ]
Post subject: 
hi yes i pan tested the thermostat, and it works, the carb is the original holley 1920 i think, engine started right up so im thinking that timing must be close, there are new hoses going to the radiator, but i did not verify that they arent collapsing.
how can i purge any trapped air in the sys tem?
any thing else? thanks.
Author:  Russ [ Tue Sep 16, 2008 5:46 pm ]
Post subject: 
the engine took maybe 20 minutes run time until it ran up to 225 degrees, and it seemed sudden
Author:  emptypockett [ Tue Sep 16, 2008 8:54 pm ]
Post subject:  Hot Start Up
I learned a long time ago to drill 2 or 3 -1/8 holes around the perimeter of a new thermostateto relieve air pockets.They are not enough to change when it opens but aenough to bleed off the air,hope this helps.
Author:  emsvitil [ Tue Sep 16, 2008 9:00 pm ]
Post subject: 
I think it's a clogged up radiator....................
Author:  Doc [ Wed Sep 17, 2008 11:28 am ]
Post subject: 
I also suspect the radiator.
Newely rebuilt engines are known to send a lot of loose scale and rust into the radiator, right at start-up.
I spend a lot of time cleaning-out the water jackets of engines I rebuild and still see crap come-out of them when I do a block flush, prior to initial start-up.

Partially drain the radiator and look at the tops of the cores for blockage.
DD
Author:  Russ [ Fri Sep 19, 2008 6:52 pm ]
Post subject: 
Hey thanks for all the suggestions. This site is the best. Its like having a neighborhood full of gearhead buddies.
I am going to try the thermostat trick which sounds logical, and today i checked the fan which is pulling correctly.
I guess i will flush the radiator and block as best as i can and try it again.
Ill report later. RC
Author:  Aggressive Ted [ Fri Sep 19, 2008 9:17 pm ]
Post subject: 
My engine ran pretty hot on break-in, but with a 16 lb cap the radiator stayed at 220 and the block at 190 with a 195 stat. I installed a 180 degree stat and that helped keep it tolerable until the engine finally broke-in. I built mine pretty tight on the tolerances, so it ran hot for about the first 500 miles. After 2000 miles I could run the 195 degree stat again with no problems. You could always run the electric fan full time to get through break in.
Now that mine has over 40,00 miles on the rebuild (almost two years), the fan rarely ever turns on unless I am in traffic.
Author:  68barracuda [ Sun Sep 21, 2008 3:00 am ]
Post subject: 
Quote:
I also suspect the radiator.
Newely rebuilt engines are known to send a lot of loose scale and rust into the radiator, right at start-up.
I spend a lot of time cleaning-out the water jackets of engines I rebuild and still see crap come-out of them when I do a block flush, prior to initial start-up.

Partially drain the radiator and look at the tops of the cores for blockage.
DD
Hi Doc

Is it possible to do the Muriatic flush with engine in car sans water pump of course

Fanie
Author:  Russ [ Mon Sep 22, 2008 5:03 pm ]
Post subject: 
I flushed the radiator, switched to a cooler thermostat, switched to to a higher cfm fan, and the motor is now running like a charm.
thanks for all the help.
Author:  Doc [ Tue Sep 23, 2008 9:31 am ]
Post subject: 
Quote:
Is it possible to do the Muriatic flush with engine in car sans water pump of course.
Fanie
You have to be sure that all the aluminum parts are off the engine and not exposed to the acid.

I would not do a acid cleaning to an assembled engine if the engine has an embossed steel head gasket, the cleaning would open-up passages that the head gasket is suppost to keep closed.

For in car block cleaning, I usually remove the water pump, rear freeze plug and do a lot of scraping, probing and flushing to get all the scale and rust out of the block.
DD
Author:  KBB_of_TMC [ Tue Sep 23, 2008 9:51 am ]
Post subject: 
When I've seen overheating like that, 40% of the time it turned out to be a small leak causing loss of pressure. I now always pressure test the system after any work on it.
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