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Old 06-26-2012, 11:21 PM
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502 SS Impala Overheating Issues

I have a 1996 Impala SS with a marine 502 motor that has always had an overheating issue but if I only drive it in the fall or winter it stays under control but it still tries to get hot. I decided to install a new be-cool rad the other day and it still wants to overheat.

I did a test yesterday by putting a 24 inch fan in front of the car with the hood closed and started the engine. I let the car idle for about 15 minutes and the temp went to about 215 degrees. I then held the RPM at 2000 and the temp continued increase 220-230 and then at 235 I increased the RPM to 3000 and the temp came down to 195. I let the car come down to an idle again and the temp went to about 220 and I then decided to shut it down. The motor is a 502 with Performer RPM heads with a Hogans Ramjet Style Fuel Injected Intake. The water pump is a reverse rotation Edelbrock #8853 that I just had rebuilt by Edelbrock because it started to leak.

I do not know much about the computer control system on these cars. I have been reading some things on line about overheating and more than once people have been talking about timing and fuel.

I need some help.

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Old 06-27-2012, 11:11 AM
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Possible air in the cooling system.
What mix of antifreeze are you using?
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Old 06-27-2012, 01:00 PM
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Did you try changing the thermostat? Maybe try a 180 in there? Maybe even try no thermostat and do the same test. Also what are you using as a fan? Electric or mechanical? I delt with the same issue recently on a SB 350. Ended up going with a flex fan and installing a new 180 thermo.
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Old 06-27-2012, 10:00 PM
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502 SS Impala Overheating Issues

I had the car at a local shop 2 or 3 months ago to have them see wht they could do with the overheating issue and they said they put a new thermostat in it but I do not know what temp stat they installed. They more or less gave up and told me to find a shop that knows race cars. I know that you can get a bad part even though it is bran new so I am going to install another new one myself this weekend. Does anyone know if there is a certain brand thermostat that is better than the rest.

The car has the original factory electric fans that pull the air through the radiator. The 2 fans are 13 inches in diameter and seem to move the air pretty good.

I am pretty sure that I got all of the air out of the system because I had the front of the car as high as I could get it and pulled a hose off of a fitting that is on the front of the intake until I got good fluid. I then pulled a pipe fitting out of the top corner of the radiator and kept putting in some fluid until I got a solid streem of fluid. I'm not sure about the mix but I would guess 60/40.
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Old 06-27-2012, 10:08 PM
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I had a similar problem and it was air pockets getting into the system had to drain it completely and do A pressure test to find where the air was getting in.
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Old 06-27-2012, 10:26 PM
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What is your timing set at. The fact that it coold down at 3K rpm may be due to the timing being more advanced from mechanical advance.
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Old 06-27-2012, 11:05 PM
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502 SS Impala Overheating Issues

I am also thinking the timing could be the cause but I purchased the car with this motor in it already and I was told that they tied everything into the original computer system. I'm not sure but I know that it's not like the older cars where you could play with the weights in the distributor and twist the distributor until you get it set where you need it. These new cars have everything set by the computer and from what I understand you can't just do things like the old days. I guess I also need some help on what I need to do to get the idle timing set so the computer doesn't change it back somehow. This is all new to me and I need help, I could also just be scared of the computer because I don't know enough about it since this is my first computer controlled fuel injected car.
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Old 06-28-2012, 09:06 PM
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I always use Stant T stats, but there are other good ones too. I doubt it's the stat, but it's a cheap thing to replace. I always drill an air bleed hole in my stats when I install them. Something around 1/8" in the outside perimeter will allow any trapped air to get out while you're filling your coolant mix.
Not sure about your Edelbrock water pump. Is it a high flow, or regular? If it's not a high flow I'd consider getting one. Sounds like when it's circulating faster it runs cooler.
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Old 06-30-2012, 12:40 AM
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1996 502 Impala SS Overheating Issues

I have tried to upload some pictures of the engine. If this does not work i will try again tomorrow. Maybe someone can see something wrong with the way it is set up.
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Old 06-30-2012, 09:28 AM
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Could it be that the radiator and twin electric fans are just not enough to handle the bigger engine? Bigger engine means more HP. More heat? Also on these computer controlled engines I would think you would need that controller to be reprogrammed for this motor? Sorry maybe you said the ECM came with this motor? I'd have to read back. But you have had shops look at it. I would think they would have suggested that if they thought it was needed. My gut tells me maybe the radiator is too small for the application. Wasn't the stock engine in that car a 5.7L? My brother in law had one back in the nineties. Can't really remember what power plant was in there though. Maybe call Griffin or a company like that and see what they recommend. Compare that to what is stock?
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Old 06-30-2012, 11:27 AM
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Buy or borrow an infrared heat gun and see what the temps are into and out of the radiator. Sitting still with the fans running you should get about 15 degree drop when everything is at operating temp.
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Old 06-30-2012, 11:31 AM
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My Camaro always ran pretty hot since I first got it in 1973. I always worried everytime I got into trafic, even in the winter. I finally decided I had to try and cure the problem, so I went to the largest radiator I could find. Even had to open up my core support and fabricate new lower mount to get it in the car.
End result was it ran 160 degrees most the time, and even in hot weather I never ran over 175. I upped the T stat to a 170, and it runs 170-180 in all kinds of driving.
You may need to get creative and see how much room you have for a big radiator. They also make double pass radiators that cool even better and fit the stock mounting. Not cheap at around $500, but they work better than std. single pass. Be Cool and Griffin both have direct fit, or slightly oversized width to handle high performance engines in your Impala.
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Old 07-01-2012, 12:18 AM
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First of all... Kudos for putting a 502 in your SS. Nice

Secondly I will second LocalBoy's words... You have effectively added 70% more of everything; displacement, power potential, fuel capacity.... but you've only modestly increased cooling capacity. This isn't just an "upgrade the pump and radiator" proposition. You need some serious cooling under that hood.

Ditch the electric fans. They are made to cool 260 hp. You have not only chosen to go with a non-reverse cooling motor, but you've also gone to a BBC which doesn't have much more coolant capacity than a SBC.

All the radiator in the world won't make up for airflow. Make the air MOVE. Given the original specs of the LT1 that was in there, you should have TONS of room for a mechanical fan. You might give up 5 hp at redline, but with a 502 marine engine, you should capitalize on the torque. Unless this is a race-only application, you won't notice 5 hp.
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Old 07-01-2012, 03:01 PM
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1996 502 Impala SS Overheating Issues

I understand the cooling fan issue and I thought that would be my next step but I called Be-Cool tech support and they don't seem to feel that it is a fan issue. I need to try and find out the CFM rating of the stock Impala fans because the guy at Be-Cool said that he would be glad to sell me a set of fans but he thought I should do more research before I spen the money on the fans.

I took the car for a ride last night which the outside temp was about 85 degrees. The route I took ranged from speeds of 30 to 45 mph and was about 4 miles around with hills flat areas and stop lights. The car seemed to be staying around 180 for the first 2 time around but on the third trip the temp would start to rise when I would come to a stop light and even when I took off and got up to 45 mph in high gear the temp kept on increasing.

The temp continued to rise to about 210 driving at a steady speed of 45 mph so I desided to drop down into second gear while maintaining the 45 mph. Once I was in second gear going 45 mph the rpm went to about 2750 and the temp came down to 180 almost instantly. I kept the car in second gear for about 1/2 mile still going between 40 and 45 and the temp held at 180. I came to a stop light and the temp started to rise and once the light changed I only let the car shift into second gear and drove home still at about 40 mph with a 180 temp.

I feel that the test I did last night tells me that it is not an air flow issue because I maintained a 40 to 45 mph (with electric fans) and when the rpms were low in high gear the car wanted to get hotter and when I down shifted into second gear raising the rpms the engine got cooler.

I now feel that it is a coolant flow issue like a thermostat not opening all the way or the Edelbrock water pump does not flow enough water to cool at lower rpms. I measured the crank pulley at a 7.750 diameter and the water pump pulley is about 5.625 diameter which matches the Z06 corvette a friend of mine has. I don;t know if this difference is diameters is correct for this motor but maybe I need a pump pulley diameter change.

I desided to change the thermostat today so I drained the fluid and un-bolted the housing and to my surprise there was no thermostat, someone has put a restrictor plate in place of the thermostat that has a 1 inch diameter hole in it so the motor has constant water flow. Why would someone do this and could this be my problem? I don't know the exact volume of water that can flow through that 1 inch hole compared to an actual thermostat but I would assume that the 1 inch hole in the plate would flow more water than the thermostat.

If it is not an air flow issue from the electric fans and it's not the thermostat the only thing that is left is that I need a higher flowing water pump or a pulley change. I don't want to make to much of a pulley change because I would think that I would start burning up bearings if I spin the pump to fast.
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Old 07-03-2012, 05:42 PM
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Quote:
Originally Posted by 502-SS View Post
I understand the cooling fan issue and I thought that would be my next step but I called Be-Cool tech support and they don't seem to feel that it is a fan issue. I need to try and find out the CFM rating of the stock Impala fans because the guy at Be-Cool said that he would be glad to sell me a set of fans but he thought I should do more research before I spen the money on the fans.

I took the car for a ride last night which the outside temp was about 85 degrees. The route I took ranged from speeds of 30 to 45 mph and was about 4 miles around with hills flat areas and stop lights. The car seemed to be staying around 180 for the first 2 time around but on the third trip the temp would start to rise when I would come to a stop light and even when I took off and got up to 45 mph in high gear the temp kept on increasing.

The temp continued to rise to about 210 driving at a steady speed of 45 mph so I desided to drop down into second gear while maintaining the 45 mph. Once I was in second gear going 45 mph the rpm went to about 2750 and the temp came down to 180 almost instantly. I kept the car in second gear for about 1/2 mile still going between 40 and 45 and the temp held at 180. I came to a stop light and the temp started to rise and once the light changed I only let the car shift into second gear and drove home still at about 40 mph with a 180 temp.

I feel that the test I did last night tells me that it is not an air flow issue because I maintained a 40 to 45 mph (with electric fans) and when the rpms were low in high gear the car wanted to get hotter and when I down shifted into second gear raising the rpms the engine got cooler.

I now feel that it is a coolant flow issue like a thermostat not opening all the way or the Edelbrock water pump does not flow enough water to cool at lower rpms. I measured the crank pulley at a 7.750 diameter and the water pump pulley is about 5.625 diameter which matches the Z06 corvette a friend of mine has. I don;t know if this difference is diameters is correct for this motor but maybe I need a pump pulley diameter change.

I desided to change the thermostat today so I drained the fluid and un-bolted the housing and to my surprise there was no thermostat, someone has put a restrictor plate in place of the thermostat that has a 1 inch diameter hole in it so the motor has constant water flow. Why would someone do this and could this be my problem? I don't know the exact volume of water that can flow through that 1 inch hole compared to an actual thermostat but I would assume that the 1 inch hole in the plate would flow more water than the thermostat.

If it is not an air flow issue from the electric fans and it's not the thermostat the only thing that is left is that I need a higher flowing water pump or a pulley change. I don't want to make to much of a pulley change because I would think that I would start burning up bearings if I spin the pump to fast.
So did the thermostat help? I would think it might. It would maybe keep the coolant in the radiator longer for it to cool. Hopefully it at least helped a little. Could be a combination of a couple of issues that need to be resolved. I'd probably look at the fans and radiator next. Let us know what you find.
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