C3 running at 140????

DorianL

solid fixture here in the forum
Staff member
Sid tells me his radiator water never gets too hot to touch.

In-dash gauge (still) reads 140 after replacing the temp sensor.

Cooking thermometer ;) reads the same under radiator cap: 140. Not sure how accurate that is. However, the water in the radiator never gets too hot to touch. Finger dip test. Outside temp: 40

Yanked the thermostat and it begins to open at 175 in water heating on stove.

Are we missing something?
 
how long is the engine running?
with the engine running and the radiator cap removed,
do you see coolant constantly flowing in the radiator?
do you see coolant flow with the t-stat removed?
and whats your oil temperature ?
whats your oil level?

any normal gas 4 stroke v8 engine that runs normally will generate enough heat to boil water after 10-15 minutes
if your radiator is not getting hot coolant , the first thing Id suspect is a mal -functional water pump.
an accurate infrared temp gun will help locate any restriction too coolant flow
BTW exhaust manifold generally run in the 350F-450F range on an idling engine after 12-15 minutes.
oil temps will generally reach 215F at about 15-18 minutes on an idling engine, but obviously the water pump must move coolant for the hot coolant to reach the radiator efficiently, and if your not flowing coolant , that heat transfer will not take place in a normal way, the use of an accurate infrared temp gun will help locate where the engine is building heat.
combustion in a 4 stroke engine generates heat, its building up and its going some place
most engines take about 10-15 minutes to reach and stabilize at their operational temps, obviously the engine rpms and loads , the water pump, thermostat and radiator and fans must all function correctly, and outside temperatures being induced on the coolant and outside air temps in effect during that time frame, effect that rate of heat build-up and stabilization window, but an engine does not have to reach full temp to run and drive, and the fuel/air ratio being a bit richer when cold helps (that's why the carbs have a choke feature) plumbing a extra coolant flow route under the plenum base may help marginally speed the process in cold temps, but its not going to do much, as the whole lower intake surface is constantly bathed in hot oil from the lifter gallery once the engines operational,temp is reached, oil thats hotter than the coolant by at least 15 degrees on average, if the engines coolant is not reaching over 140F the t-stat must be locked open, and the heat must be dissipated too outside airflow
irtemp.jpg



coolantflow.jpg


http://garage.grumpysperformance.com/index.php?threads/how-the-cooling-system-works-basics.853/

http://garage.grumpysperformance.co...ing-system-flow-rates-and-heat-transfer.9880/
 
Sounds like coolant is not circulating as Grumpy suggests with the water pump. The 71 water temp gets to 205 degrees running last week at idle for 18 minutes, oil temp was 212 after new sensor installed.
 
Thanks gents!!!!

Hmmmm, what I don't understand is why the temp sensor in head is reading so low?
 
Sounds like this engine should not run for long periods of time before this is resolved. Apparently he drove 100 km with no problems... no blowing a head gasket or steam coming from the rad cap. This was before he replaced the temp sensor which back then never got hot at all.
 
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Update: he tested his old thermostat... it open at 175 but does not close... even when left in cold water.
 
that t-stat not closing may explain the issue, because the radiator and water pump might be capable of,
dispersing the coolant heat at a rate fast enough, in 40F outside air temps, to prevent the coolant temps from going higher than 140F.

obviously swapping to a, high quality, fully functional t-stat in the 190F-195F temp range would more than likely correct the issue.
and yes I generally do drill a couple air /coolant holes in the flange before installing them, (LINK BELOW)

https://www.summitracing.com/parts/mrg-4365/overview/year/1972/make/chevrolet/model/corvette

http://garage.grumpysperformance.com/index.php?threads/correct-thermostat.5607/


tstatdual2.jpg

Thermostatdr1.JPG
 
Yes. I told him to drill holes in the flange.

We will see tomorrow if the new T-stat fixes the problem.

Btw, what is the purpose of that cup on the Stewart T-stat?
 
its just a protective shield for the spring and expansion modual
 
Btw, what is the purpose of that cup on the Stewart T-stat?
its just a protective shield for the spring and expansion modual

OK. Now you have me confused.
stewart open.png
On the Stewart type of thermostat, from what I have seen, that picture shows the thermostat in the OPEN position, like it would be if in boiling water. When it is closed, that "shield" is up against the flange. I added bypass holes by using a small rat-tail file and filing 3 equaly spaced "C" notches in the side of the cup (red in picture).
stewart bypass notches.png

Stewart type of thermostats work in reverse - when they fail, they do so in the OPEN position.
You then do not overheat, you just don't get any heat (if it is cold enough that you are using the heater).
http://stewartcomponents.com/index.php?route=information/information&information_id=11
 
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Stewart type of thermostats work in reverse - when they fail, they do so in the OPEN position.
You then do not overheat, you just don't get any heat (if it is cold enough that you are using the heater).

HA!!!! now that is interesting. Had I known, I would have ordered one of those...
 
Closing the loop here: the engine now runs at a steady 180-190. It was a defective t-stat
 
glad too hear the issues resolved and thanks for posting the out-come
 
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