70chev Posted September 26, 2011 Share Posted September 26, 2011 My monte has been overheating off and on ever since I have put the new motor & transmission in this past June. (350 original motor & 350 transmission with 1800-2000 stall converter. I have a 160 Degree thermostat in it and it runs at that to start out at. Then it will start inching up on the temp gauge. I seem to notice that when I climb a hill it will start going up. It seems it over heats most of the time on the freeway. It will do it in town sometimes, and other times it is ok. Tonight I was coming home on the freeway and it was running between 210 & 220 degrees, and it is 40 degrees outside so you would not think to would be running that hot. The radiator is about five years old. I have changed the thermostat twice. If I leave the thermostat out it will not overheat it runs at about 170. When the car gets up to 220 I pull over and stop, turn it off, let it sit for five minutes, start it up and it will go back normal. Thoughts or questions? Quote Link to comment Share on other sites More sharing options...
Mo's70MCs Posted September 26, 2011 Share Posted September 26, 2011 I'd start with making sure the gauge isn't the factor. What are you basing all your findings on?... are you using a fan clutch? Quote Link to comment Share on other sites More sharing options...
70chev Posted September 26, 2011 Author Share Posted September 26, 2011 I got a new temp gauge from JEGS ( JEGS Brand) No fan clutch Quote Link to comment Share on other sites More sharing options...
cny first gen 71 Posted September 26, 2011 Share Posted September 26, 2011 I would test the thermastat make sure its opening at the correct temp also you may want to try one of Rad the caps with the thermastat built into it just to see. Quote Link to comment Share on other sites More sharing options...
Mo's70MCs Posted September 26, 2011 Share Posted September 26, 2011 Novice question I suppose? How about condition of lower radiator hose..spring in it? Stock water pump? Are you worried about it reaching 220°.. does it ever get hotter? Will it idle fine with radiator cap off, and not overheat? Quote Link to comment Share on other sites More sharing options...
TrunkMatt Posted September 26, 2011 Share Posted September 26, 2011 If it isn't ovrheating with the thermostat off, it sounds to me like either a thermostat issue, or a flow issue where the water-pump isn't circulating fast enough... maybe there is some debris in it? I know you said you replaced the thermostat, but many people have had multiple issues, even with new ones... seems to be a poorly made part these days. Quote Link to comment Share on other sites More sharing options...
CrazyDavey Posted September 26, 2011 Share Posted September 26, 2011 if it's "creeping" up that doesn't sound like a thermostat, they're pretty much open or closed. Same with a water pump, they work or they don't. If the system is not keeping up with the motor I would be checking the flow through the radiator...I trust the shroud and tunnel are in place....JMO Quote Link to comment Share on other sites More sharing options...
Mike 57 Posted September 26, 2011 Share Posted September 26, 2011 You stated that is does not overheat without the thermostat, is that at highway speeds also? If that is true I would try a high flow thermostat. High Flow I would also check the ignition timing and vacuum advance. Quote Link to comment Share on other sites More sharing options...
DavidTX Posted September 26, 2011 Share Posted September 26, 2011 I think a fan clutch would help. Sounds like you aren't getting enough airflow through your radiator. Sounds like you are getting more heat from the torue converter slipping (going up hills). Adding a transmission cooler in front of the radiator should help. If transmission fluid temp is high then it will seriously affect the longetivity of the transmission. Quote Link to comment Share on other sites More sharing options...
bigtankjones Posted September 26, 2011 Share Posted September 26, 2011 Also, check that your belts are tight. Could slip at high RPMs Quote Link to comment Share on other sites More sharing options...
Mo's70MCs Posted September 26, 2011 Share Posted September 26, 2011 Too many factors to give a definite diagnosis.. you gotta delete all the variables. My daily driver is not sporting a fan clutch and it runs cool all day long. .030 over stock 350, shroud+ rigid fan. Let it sit in bumper to bumper traffic and it warms-up a bit. It'll get between 180° & 210° and not trusting the accuracy of the inexpensive temperature gauge (Sun) trio, I'd say it's plus or minus 5° and at times I feel comfortable with that. Now on a warm day.. it gets much higher yet it'll always come back down, I'd say my situation is normal. Specially knowing the type of abuse this block is been under.. as far as overheating is concerned. What sort of condition is the radiator & Cap? I know you mention the rad is 5 years old. (3) core? Are you using a coolant recovery system.. with the right recovery cap? Quote Link to comment Share on other sites More sharing options...
Vaughn Posted September 26, 2011 Share Posted September 26, 2011 I had a High flow thermostat in my 502 motor and car would never overheat. One day at about 500 miles on motor the thermostat crapped out. I put in a regular Thermostat (same temp) and the car ran 20 degrees hotter and even more on the hiway and going up hills. Bought a new high flow and problem solved. As the name says, it just adds a little more flow. Quote Link to comment Share on other sites More sharing options...
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