New Crate Motor Overheating
Thread Starter
Navigator
Joined: Sep 2018
Posts: 9
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New Crate Motor Overheating
Hey everyone! I'm kinda at my wits end so i want to share my problem and see if anyone has any diagnosis.
I have a 1985 C4 with a new crate motor from Jeggs. There are approximately 800 miles on the new engine.
I'm unable to get the temperature to stay below 230 or higher.
When I press on the gas, the temperature goes up. When I let it coast, or idle, it goes down.
Here are the steps I've already taken.
1. Replaced the thermostat.
2. Removed the thermostat.
3. Verified the temperature on the gauge was similar to the engine using a laser temp sensor.
4. Replaced the water pump with a new one.
5. Replaced the coolant temp sensor and plug just above the water pump.
6. Verified the fan was turning on around 228.
None of those things have helped the temperature stay where it was before I replaced the engine. Previously it was about 190 at all times.
I haven't:
1. replaced my radiator
2. cleaned out my radiator
3. bought a new vette
Any help you might be able to offer would be incredible!
Thanks,
Jake
I have a 1985 C4 with a new crate motor from Jeggs. There are approximately 800 miles on the new engine.
I'm unable to get the temperature to stay below 230 or higher.
When I press on the gas, the temperature goes up. When I let it coast, or idle, it goes down.
Here are the steps I've already taken.
1. Replaced the thermostat.
2. Removed the thermostat.
3. Verified the temperature on the gauge was similar to the engine using a laser temp sensor.
4. Replaced the water pump with a new one.
5. Replaced the coolant temp sensor and plug just above the water pump.
6. Verified the fan was turning on around 228.
None of those things have helped the temperature stay where it was before I replaced the engine. Previously it was about 190 at all times.
I haven't:
1. replaced my radiator
2. cleaned out my radiator
3. bought a new vette
Any help you might be able to offer would be incredible!
Thanks,
Jake
Melting Slicks
Joined: Nov 2007
Posts: 2,830
Likes: 147
From: Gainesville FL
Hey everyone! I'm kinda at my wits end so i want to share my problem and see if anyone has any diagnosis.
I have a 1985 C4 with a new crate motor from Jeggs. There are approximately 800 miles on the new engine.
I'm unable to get the temperature to stay below 230 or higher.
When I press on the gas, the temperature goes up. When I let it coast, or idle, it goes down.
Here are the steps I've already taken.
1. Replaced the thermostat.
2. Removed the thermostat.
3. Verified the temperature on the gauge was similar to the engine using a laser temp sensor.
4. Replaced the water pump with a new one.
5. Replaced the coolant temp sensor and plug just above the water pump.
6. Verified the fan was turning on around 228.
None of those things have helped the temperature stay where it was before I replaced the engine. Previously it was about 190 at all times.
I haven't:
1. replaced my radiator
2. cleaned out my radiator
3. bought a new vette
Any help you might be able to offer would be incredible!
Thanks,
Jake
I have a 1985 C4 with a new crate motor from Jeggs. There are approximately 800 miles on the new engine.
I'm unable to get the temperature to stay below 230 or higher.
When I press on the gas, the temperature goes up. When I let it coast, or idle, it goes down.
Here are the steps I've already taken.
1. Replaced the thermostat.
2. Removed the thermostat.
3. Verified the temperature on the gauge was similar to the engine using a laser temp sensor.
4. Replaced the water pump with a new one.
5. Replaced the coolant temp sensor and plug just above the water pump.
6. Verified the fan was turning on around 228.
None of those things have helped the temperature stay where it was before I replaced the engine. Previously it was about 190 at all times.
I haven't:
1. replaced my radiator
2. cleaned out my radiator
3. bought a new vette
Any help you might be able to offer would be incredible!
Thanks,
Jake
Does it overheat when on the highway with a lot of airflow or does it only overheat when going slow?
Search the forums on this topic and you will find many posts that will tell you 230 is normal temperature for emissions. If it doesn't go higher then you may not have a problem. Do you have an '85 FSM?
I have a MemCal chip on my late '86 that programs the ECM to command the aux fan to come on at 160 and rarely does the temp reach even 190. I'm not sure of the '85 if it even has an aux fan. But checking the radiator is definitely a priority. It's good you replaced the water pump because it makes no sense to put a 33 year old water pump on new motor.
good luck
Melting Slicks
Joined: May 2014
Posts: 2,895
Likes: 592
From: New Port Richey FL
Long shot but worth asking, could the intake gaskets been installed backwards. I think if YOU remove the thermostat and look inside you should be able to see onto the head coolant port, if you see a blockoff plate I believe that is backward.
Last edited by s carter; Sep 23, 2018 at 04:29 PM.
Race Director
Joined: Oct 2008
Posts: 17,982
Likes: 1,074
From: Lansing MI
Someone else needs to chime in on weather or not you can see the block off from where the tstat sits. I dont know.
Last edited by PatternDayTrader; Sep 23, 2018 at 04:53 PM.
Melting Slicks
Joined: May 2014
Posts: 2,895
Likes: 592
From: New Port Richey FL
I always installed them plates rear and just confirmed it in the only book that I have that covers the 85 that is a Hays book and that is showing open by Thermostat and blockoff plates rear.
Last edited by s carter; Sep 23, 2018 at 05:09 PM.
Race Director
Joined: Oct 2008
Posts: 17,982
Likes: 1,074
From: Lansing MI
Agreed. I just dont know if you can see or feel in there through the intake, but you probably can.
Thread Starter
Navigator
Joined: Sep 2018
Posts: 9
Likes: 0
Hey Jake ... welcome to the forum.
Does it overheat when on the highway with a lot of airflow or does it only overheat when going slow?
Search the forums on this topic and you will find many posts that will tell you 230 is normal temperature for emissions. If it doesn't go higher then you may not have a problem. Do you have an '85 FSM?
I have a MemCal chip on my late '86 that programs the ECM to command the aux fan to come on at 160 and rarely does the temp reach even 190. I'm not sure of the '85 if it even has an aux fan. But checking the radiator is definitely a priority. It's good you replaced the water pump because it makes no sense to put a 33 year old water pump on new motor.
good luck
Does it overheat when on the highway with a lot of airflow or does it only overheat when going slow?
Search the forums on this topic and you will find many posts that will tell you 230 is normal temperature for emissions. If it doesn't go higher then you may not have a problem. Do you have an '85 FSM?
I have a MemCal chip on my late '86 that programs the ECM to command the aux fan to come on at 160 and rarely does the temp reach even 190. I'm not sure of the '85 if it even has an aux fan. But checking the radiator is definitely a priority. It's good you replaced the water pump because it makes no sense to put a 33 year old water pump on new motor.
good luck
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Thread Starter
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Oil Producer
Joined: Apr 2014
Posts: 9,375
Likes: 2,737
does your car have a plugged cat or multiple plugged cats? i recently had my 86 doing what you describe and the way i pinpointed it was i took a laser temp reader gun and got it before and after the cats and the temps were so far apart (much lower behind the cat than in front) i knew my issue was this.
my trans tunnel would get so hot and my oil temps would go sky high.
is it your oil going high? coolant? both?
my trans tunnel would get so hot and my oil temps would go sky high.
is it your oil going high? coolant? both?
Thread Starter
Navigator
Joined: Sep 2018
Posts: 9
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does your car have a plugged cat or multiple plugged cats? i recently had my 86 doing what you describe and the way i pinpointed it was i took a laser temp reader gun and got it before and after the cats and the temps were so far apart (much lower behind the cat than in front) i knew my issue was this.
my trans tunnel would get so hot and my oil temps would go sky high.
is it your oil going high? coolant? both?
my trans tunnel would get so hot and my oil temps would go sky high.
is it your oil going high? coolant? both?
Drifting
Joined: Feb 2016
Posts: 1,384
Likes: 339
From: Simi Valley CA
My friend's Tahoe just gave him this same problem. We replaced thermostat, waterpump, flushed radiator and more. Nothing helped. Finally pressure tested the system and found a rotted overflow hose wasn't allowing the system to pressurize. Without pressure the system doesn't cool enough. Autozone rents the radiator pressure test kit for free. You'll hear where it is leaking with the engine off using the kit.
Safety Car
Joined: Dec 2009
Posts: 4,363
Likes: 430
From: Birmingham Al
I would up grad to a 2-3 row Alum. radiator . If that's an Org. one it's shot . Most people have not realized that the outside temp has gotten hotter over the years and stays hotter longer so need to go with the flow and make sure their is NO air in the system . I just put a Champion in my 93 I know cheapeee but it works fine . The old radiators have small flus in them to start and over the years fill up with water deposits . I would say new radiator and if doing that up-grad to a alum. one .. Then if still over heating start looking at other things .. This is not rocket science hot water goes in the radiator cools goes back in motor ..
Thread Starter
Navigator
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Thread Starter
Navigator
Joined: Sep 2018
Posts: 9
Likes: 0
I would up grad to a 2-3 row Alum. radiator . If that's an Org. one it's shot . Most people have not realized that the outside temp has gotten hotter over the years and stays hotter longer so need to go with the flow and make sure their is NO air in the system . I just put a Champion in my 93 I know cheapeee but it works fine . The old radiators have small flus in them to start and over the years fill up with water deposits . I would say new radiator and if doing that up-grad to a alum. one .. Then if still over heating start looking at other things .. This is not rocket science hot water goes in the radiator cools goes back in motor ..
I think I have a plugged exhaust system or cat. It was over a year in the process of rebuilding the car and the exhaust sat open on both ends for quite a while. We had many problems with mice so I'm thinking a nest could have plugged it. I'm going to replace the catalytic converter and see if that solves the issue.
If not, the radiator is the next step
Thanks for taking the time to comment!