75 Corvette is running hot
Thread Starter
Intermediate
Joined: Nov 2006
Posts: 44
Likes: 0
From: Fort Myers Florida
75 Corvette is running hot
Motor was just rebuilt and heater core was bypassed, He put a plug in the small outlet of the new water pump( should a hose be run back to the intake from the water pumps small outlet to help cool motor?) and used no thermostat. I have no need for heat right now I live in Florida. Also fan was replaced with a electric fan. which is on the backside of radiator and pulls air, is that ok?
at idle temp goes to 235 in about 10 to 15 minutes and keeps rising. I added a second temp gauge just to make sure factory one is reading right.
Also I tried a cooling additive which I hoped would reduce the temp but have not noticed any change. Any ideas? I don't want to fry my new motor. What is a safe normal temp? At idle and while driving?
at idle temp goes to 235 in about 10 to 15 minutes and keeps rising. I added a second temp gauge just to make sure factory one is reading right.
Also I tried a cooling additive which I hoped would reduce the temp but have not noticed any change. Any ideas? I don't want to fry my new motor. What is a safe normal temp? At idle and while driving?
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
Alot of things can cause this, but mine has never been hotter than 200*
1)Clogged radiator/too small
2)Poor air flow
3)Too much anti-freeze/do not excede 50/50. Anti-freeze does not conduct heat as well as water
4)Collapsing bottom hose
5)Too much advance
6)Too lean mixture
7)Engine too tight
I am sure the guys will add more.
1)Clogged radiator/too small
2)Poor air flow
3)Too much anti-freeze/do not excede 50/50. Anti-freeze does not conduct heat as well as water
4)Collapsing bottom hose
5)Too much advance
6)Too lean mixture
7)Engine too tight
I am sure the guys will add more.
Thread Starter
Intermediate
Joined: Nov 2006
Posts: 44
Likes: 0
From: Fort Myers Florida
Radiator is a stock replacement.
16 inch pull fan
no antifreeze just one gallon of coolant additive and the rest distilled water as listed on bottle.
hoses are good not collapsing
timing is set a 8*
Stock 350 engine
Is it ok to plug small outlet on water pump if not using heater core?
or should it run straight to intake?
16 inch pull fan
no antifreeze just one gallon of coolant additive and the rest distilled water as listed on bottle.
hoses are good not collapsing
timing is set a 8*
Stock 350 engine
Is it ok to plug small outlet on water pump if not using heater core?
or should it run straight to intake?
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Are you sure the system is full? Since the thermostat is out you should see coolant flowing into the cool side of tha radiator with the cap off. If there is air in the system it will be on the heads and that is where the heat is generated
Instructor
Joined: Oct 2005
Posts: 143
Likes: 0
From: Independence MO
You should use a thermostat regardless. If you are in a warm area use a 160. The thermostat slows down the water and gives the fan time to cool the water. Check that your fan is running the right direction and make sure it is running full speed. I had an electric fan on a car and it was slowing down from age and I did not relise it. Put on a new fan and no more problems. Also be sure your alternator is putting out because if it is not charging a full charge the battery will be low and the fan will run slow too.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
Radiator is a stock replacement.
16 inch pull fan
no antifreeze just one gallon of coolant additive and the rest distilled water as listed on bottle.
hoses are good not collapsing
timing is set a 8*
Stock 350 engine
Is it ok to plug small outlet on water pump if not using heater core?
or should it run straight to intake?
16 inch pull fan
no antifreeze just one gallon of coolant additive and the rest distilled water as listed on bottle.
hoses are good not collapsing
timing is set a 8*
Stock 350 engine
Is it ok to plug small outlet on water pump if not using heater core?
or should it run straight to intake?
As Sixfooter said, Have you burped all the air out?
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
Do all the easy stuff as mentioned above first.
Check the flow thru the rad coils when looking into the radiator. Rev it a little to check for increased flow. You should have very good flow out of the tubes. Without the thermostat at over 200°, you shouldn't have any air pockets.
Mist a fine garden hose spray over the rad and see if it cools down. You didn't say if your replacement rad was new or not.
Lastly check the water pump itself. There are some cheesy replacements out there.
Check the flow thru the rad coils when looking into the radiator. Rev it a little to check for increased flow. You should have very good flow out of the tubes. Without the thermostat at over 200°, you shouldn't have any air pockets.
Mist a fine garden hose spray over the rad and see if it cools down. You didn't say if your replacement rad was new or not.
Lastly check the water pump itself. There are some cheesy replacements out there.
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Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
Cruising
Joined: Jan 2007
Posts: 12
Likes: 0
From: Arcadia Florida
I instaled alluminum radiator with dual fans and 195 thermostst in radiator with a160 thermostat in motor im in florida to and u cant make mine run hot except when i tride to use only one fan I think u should try thermostat in your engine just my thought good luck
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
What kind of pump do you have.? Does the fan have a shroud?
Thread Starter
Intermediate
Joined: Nov 2006
Posts: 44
Likes: 0
From: Fort Myers Florida
Thanks alot I will try all of these things tomorrow. The radiator is new but from China. I may upgrade to aluminum down the road. the water pump is also new from advance auto parts,everything is new but I know that does not mean it could be a bad part It has happened to me before.Thanks everyone for your advise. I am going to replace my thermostat with a 160* stat as advised. I had A 195 but took it out to see if it would run cooler but I see it has an important role in cooling. I also am going to have my alternator tested because after my fan runs when I turn off the car sometimes my battery is weak when staring. I shelled out 188.00 bucks
for the yellow optima I don't think It should be weak just from the fan running for a few minutes after the car is turned off. Thanks,Mike
for the yellow optima I don't think It should be weak just from the fan running for a few minutes after the car is turned off. Thanks,Mike
Melting Slicks
Joined: May 2006
Posts: 3,438
Likes: 41
From: Raleigh NC
St. Jude Donor '13-'14
I had this exact same problem. I just cranked it up, let it get up to temp and when it started going past the thermostat levels I just popped the radiator cap. I had to do it a few times, but got all the air out and all the coolant in.
This may not be the best way, and someone will probably criticize this, but: problem solved for me.
This may not be the best way, and someone will probably criticize this, but: problem solved for me.
Advanced
Joined: Apr 2006
Posts: 87
Likes: 0
From: Finly IN
Running hot
1. Check seals around radiator.
2. Check airdam on front. It's required to direct air into the radiator.
3. Check compression on each cyclinder to ensure there isn't a leak of exhaust gases into coolant from a leaking head gasket.
4. Check the timing.
2. Check airdam on front. It's required to direct air into the radiator.
3. Check compression on each cyclinder to ensure there isn't a leak of exhaust gases into coolant from a leaking head gasket.
4. Check the timing.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
Thanks alot I will try all of these things tomorrow. The radiator is new but from China. I may upgrade to aluminum down the road. the water pump is also new from advance auto parts,everything is new but I know that does not mean it could be a bad part It has happened to me before.Thanks everyone for your advise. I am going to replace my thermostat with a 160* stat as advised. I had A 195 but took it out to see if it would run cooler but I see it has an important role in cooling. I also am going to have my alternator tested because after my fan runs when I turn off the car sometimes my battery is weak when staring. I shelled out 188.00 bucks
for the yellow optima I don't think It should be weak just from the fan running for a few minutes after the car is turned off. Thanks,Mike
for the yellow optima I don't think It should be weak just from the fan running for a few minutes after the car is turned off. Thanks,Mike
Thread Starter
Intermediate
Joined: Nov 2006
Posts: 44
Likes: 0
From: Fort Myers Florida
I dont have the shroud on because it was chewed up from the past owner had a broken motor mount. Do you think I should replace the shroud?
I have not had the car on the road yet I am just now getting ready for new paint but have drove it aroung the block a few hundred times and have replaced almost every moving part on the car about twelve thousand dollars so far and still have only a primed car bus very solid.
I have not had the car on the road yet I am just now getting ready for new paint but have drove it aroung the block a few hundred times and have replaced almost every moving part on the car about twelve thousand dollars so far and still have only a primed car bus very solid.
Thread Starter
Intermediate
Joined: Nov 2006
Posts: 44
Likes: 0
From: Fort Myers Florida
I am also hearing a slight grinding noise while putting the car in drive and reverse can this be U-joints? I changed the rear diff oil and added gm additive but it made no change?
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
In your OP you said this was happening at idle, so the seals and air dam don't apply.
You do need a shroud for slow sleed/idle conditions. Even an electric fan sucks only just what is in front of the blades without a shroud.
You said that your battery is losing charge. That may indicate the your alternater isn't putting out enough to run the fan and charge the battery, but the hose mist test will tell you if the rad can cool.
160° is too cold. Here is a pic of the best tstat around available at Advance.
You don't need a tstat for your idle testing.
Also consider getting an original shroud and going back with the clutch fan. You get good airflow thru all of the rad at idle when you need it most.
You do need a shroud for slow sleed/idle conditions. Even an electric fan sucks only just what is in front of the blades without a shroud.
You said that your battery is losing charge. That may indicate the your alternater isn't putting out enough to run the fan and charge the battery, but the hose mist test will tell you if the rad can cool.
160° is too cold. Here is a pic of the best tstat around available at Advance.
You don't need a tstat for your idle testing.
Also consider getting an original shroud and going back with the clutch fan. You get good airflow thru all of the rad at idle when you need it most.
Pro
Joined: Aug 2004
Posts: 732
Likes: 1
From: Green Lake Wisconsin
I vote for burping the air out of the system, getting a shroud around your fan, and reading your plugs to check for a lean idle condition.
Put a voltmeter on your alternator when the car is running, should tell real quick if it's shot.
Check all the simple (and cheap) stuff first. Move on to the PITA (and expensive) stuff after that.
Put a voltmeter on your alternator when the car is running, should tell real quick if it's shot.
Check all the simple (and cheap) stuff first. Move on to the PITA (and expensive) stuff after that.
Intermediate
Joined: Nov 2006
Posts: 48
Likes: 0
From: Elmer NJ
i think u should put a shroud on as soon as possible. the fan sucks the air, but w/o the shroud, it doesn't pull all air thru radiator. make sure to put 50/50 mix of antifreeze in, lowers the boiling point of the water
Last edited by ford4play; Jan 7, 2007 at 01:41 AM.