Why is car running hotter when moving?

GTSnake

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Just came in from a drive around Woodward. During slow moving times the temp hovers around 230. When I start moving around it climbs to 240 almost to the red mark. This is hotter than when I had my Roe with the stock radiator. With that set up I never passed 220 degrees. This is running a little too hot for my taste.

I have the 180 thermostat, Alan's 3 core radiator and of course the turbos.

Is it possible that the radiator is moving coolant too fast through it? Why would it run cooler at lower speeds with less air movement and slower engine speeds? It only lowered down to 220 after a few minutes on the highway on the way home.

Anyone got any ideas?
 

GTS Bruce

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First guess. Air trapped in the cooling system. Coolant low or trapped air equals higher temps while running. Happened to me a couple of times and I am NA. The faster you go the warmer it got. GTS Bruce
 
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GTSnake

GTSnake

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I think I've burped it. I'll try it again. It ran fine during Spring. Only tonight did I notice it running hotter.
 

dave6666

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There is a relationship between:

-> Engine RPM.

-> Speed, or air flow.

-> Coolant temperature, as measured at the sending unit. Let alone other places too.

I don't know the balance between all of this, but will say this:

-> Higher engine RPM = higher heat load delivered to radiator.

-> At slower speed, the reduced heat load by the engine may be offset more than the reduced cooling capacity of the radiator due to less air flow. There is likely a point where that relationship flips. The better air flow takes over the increased heat load from the engine.

-> Water flow rate is likely not a linear relationship to the pulley speed due to pressure drop and other characteristics of pumped flow that change as velocities change.

My 2001 N/A GTS with Ron Davis radiator & 180 deg stat:

-> Will run toward those temps, but never past that last line before the red one, with the AC on and 100 degrees out.

-> It will briefly increase in temp as you take off from sitting.

-> It runs cooler sitting than 3000 RPM in traffic. 100 deg, AC on.

-> 180 stat means squat unless on the highway, at which point I will run at the lower middle 3 mark.

I think you either have a flow problem, or has been mentioned, air. Was this problem abrupt?
 

2MANYTOYS

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Just came in from a drive around Woodward. During slow moving times the temp hovers around 230. When I start moving around it climbs to 240 almost to the red mark. This is hotter than when I had my Roe with the stock radiator. With that set up I never passed 220 degrees. This is running a little too hot for my taste.

I have the 180 thermostat, Alan's 3 core radiator and of course the turbos.

Is it possible that the radiator is moving coolant too fast through it? Why would it run cooler at lower speeds with less air movement and slower engine speeds? It only lowered down to 220 after a few minutes on the highway on the way home.

Anyone got any ideas?


Have you verified that your gauge is accurate? They can be off 10-15 degrees.
 

Bobpantax

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"When I start moving around".

Please clarify what the above means. You have a 1304 RWHP twin turbo system. Bigger explosions, more heat. Has it done this since the turbos were put on? If so, your cooling system may be inadequate. After you get through checking the basic stuff outlined above, if the problem still exists, give Heffner a call in Sarasota and see if he will help you. There is no one who knows more about twin turbo systems and Vipers than Heffner.
 
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GTSnake

GTSnake

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I burped it again and it seems to have been running a little cooler.

But now I have bigger problems. My fuel pump quit.
 

big-n-italian

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i know it sounds odd, but if your car is getting too hot turn the air conditioner on. your car will cool down, and your temperature gage will drop fairly fast.
 

Bobpantax

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Heffner didn't build the guys car, CPE did. They would be my first call.

I saw that but if it is an inadequate cooling system, CPE would have been the people that allowed same. So, it would be standard procedure to call a more knowledgable, uninvolved source of data. Now, with his fuel pump failing, there may be other issues either related or unrelated. I wonder if he was running lean because of a fuel pump that was about to expire. If so, could this have caused the engine to run hotter? GR8 ASP?
 

Bobpantax

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Hi Big. When I had my GTS, in stop and go traffic in the summer, I used to put the heat on for short periods of time to bring down the temperature. Is this what you meant?
 
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GTSnake

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actually I was told it should run cooler with the AC on. The PCM will keep the radiator fan on continuously when the AC is running.
 

dave6666

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actually I was told it should run cooler with the AC on. The PCM will keep the radiator fan on continuously when the AC is running.

While the condenser pre-heats the air cooling the radiator and the compressor increases the load on the engine.

If I can remember tonight when I get home I'll shoot the IR at the condenser to see whassup there.
 

dave6666

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OK. Jumped out of the car from the drive home and shot the IR at the very bottom of the condenser below the oil cooler. Of course, with the car still running and the AC on.

Temps ranged from 150 to 175F depending on where I pointed it. Ambient temp was a little cool with some storms in the area, about 95F. Yup, that's cool for here.

Anyway, that explains why my car runs hotter with the AC on when not on the hiway, eh?
 

big-n-italian

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Hi Big. When I had my GTS, in stop and go traffic in the summer, I used to put the heat on for short periods of time to bring down the temperature. Is this what you meant?


turn the HEAT ON in the middle of summer bob? YUK!!

no. look what GTSsnake wrote: "actually I was told it should run cooler with the AC on. The PCM will keep the radiator fan on continuously when the AC is running."

i read this quite some time ago and have found this to be true. if my car is running hot, and i turn the AC on, i can watch my
temp gage start dropping fairly fast. works great everytime. atleast for me anyway. its a nice trick to know, especially with a supercharged car. ;)
 
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big-n-italian

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OK. Jumped out of the car from the drive home and shot the IR at the very bottom of the condenser below the oil cooler. Of course, with the car still running and the AC on.

Temps ranged from 150 to 175F depending on where I pointed it. Ambient temp was a little cool with some storms in the area, about 95F. Yup, that's cool for here.

Anyway, that explains why my car runs hotter with the AC on when not on the hiway, eh?


i dont know why your car runs hotter with the AC on dave. its should be doing the opposite. turning on the AC, is suppose to make the fan behind the radiator start running continuously, making your car run cooler not hotter. sounds like something may not be working right.
 
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dave6666

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i dont know why your car runs hotter with the AC on dave. its should be doing the opposite. turning on the AC, is suppose to make the fan behind the radiator start running continuously, making your car run cooler not hotter. sounds like something may not be working right.

Doesn't it explain itself there? The fact that before the 100 deg Texas air hits my radiator, the AC condenser preheats it 50 to 75 degrees more? The fan being on means squat to that.
 

Bobpantax

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turn the HEAT ON in the middle of summer bob? YUK!!

no. look what GTSsnake wrote: "actually I was told it should run cooler with the AC on. The PCM will keep the radiator fan on continuously when the AC is running."

i read this quite some time ago and have found this to be true. if my car is running hot, and i turn the AC on, i can watch my
temp gage start dropping fairly fast. works great everytime. atleast for me anyway. its a nice trick to know, especially with a supercharged car. ;)

I used the heater technique in stop and go traffic. See below for a member that has used it on the track.


10-21-2001, 09:09 AM #12

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Join Date: Dec 2000
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Re: What do you track rats do for not so \"cool\"ant temps??
If you need immediate lowering of engine temperature as opposed to all those future mods.Just turn the heater and blower all the way up.Hot inside car?Yep,make you think about hell.But it will make the motor run cooler. Bruce
 

mike & juli

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Bob and Bruce as always VERY good info, and for my own .02 here, YES, turning ON the heat (no matter HOW HOT it is outside) for a few minutes DOES REDUCE the temperatures noticeably. This I found out in stop-n-go traffic (not highway driving personally)...with LONG construction delays. I concur this was the BEST way to keep my car from overheating, tho a bit uncomfortable--it's tolerable. ~juli
 

TomH

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This may sound stupid but is there any way the polarity on the fan motor got switched? A backwards running fan could cause what you have.:D
 

big-n-italian

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Doesn't it explain itself there? The fact that before the 100 deg Texas air hits my radiator, the AC condenser preheats it 50 to 75 degrees more? The fan being on means squat to that.


i understand what you are saying dave. maybe its a texas air thing, i dont know. all i am saying is that we have hot days here too and this is what has always worked great for me. k?

this is the first time i have heard about the heater trick. how does that work? does the engine cool down because opening the heater core releases more antifreeze into the system?
 

dave6666

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i understand what you are saying dave. maybe its a texas air thing, i dont know. all i am saying is that we have hot days here too and this is what has always worked great for me. k?

this is the first time i have heard about the heater trick. how does that work? does the engine cool down because opening the heater core releases more antifreeze into the system?

The heater core is like another radiator. Works just like the one in the front, except this one frys eggs if you're equipped with such.
 

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