Overheating at hwy speeds

Ashmann70 · Jul 10, 2018

Hey gang. I 've been having troubles with my cooling system. No leaks, but water temp rises fast when on hwy. Never gets to overheating point but comes very close to it. Especially when I run my ac. New thermostat(autozone) fresh complete engine rebuild around 5k on engine. Seems like there is a lot of pressure on upper radiator hose... any ideas where to start? I was thinking maybe I need to relocate overflow and put twin fans on.... heads cam intake have been upgraded, if that means anything. Oh and it's a 94 gt

Mustang5L5 · Jul 10, 2018

Deflector installed under the car on radiator support?

96pushrod · Jul 10, 2018

On my 96 (has a 5.0) my engine used to run a little warmer than I liked at hwy speeds, good ole Georgia heat, with 4.10 gears. I put in a aluminum 3 core, new 180 degrees tstat and got all the air out and it runs nice and cool now.

Did you install the thermostat backwards? I’ve also had them stick shut and run hot. You should feel coolant moving through the upper hose. Does your radiator feel hot? If not you’re not getting any coolant flow.

Ashmann70 · Jul 10, 2018

96pushrod said:
On my 96 (has a 5.0) my engine used to run a little warmer than I liked at hwy speeds with 4.10 gears. I put in a aluminum 3 core, new 180 degrees tstat and got all the air out and it runs nice and cool now.

Did you install the thermostat backwards? You should feel coolant moving through the upper hose.

Yes it is in correct. I see movement in radiator when cap is off. If it sits at idle with cap off it circulates as should. But when thermostat closes it will spill over radiator.

Ashmann70 · Jul 10, 2018

Mustang5L5 said:
Deflector installed under the car on radiator support?

I will double check. But I think it is

96pushrod · Jul 10, 2018

Did you put the head gasket On the correct way? I know it’s kind of hard to tell at this point lol

What temp thermostat do you have?

General karthief · Jul 10, 2018

What are your actual temp readings? If you are watching the stock gauge then you need to put a manual gauge in it, even mounting it temporarily where you can watch the temp reading while driving, the stock gauges can be suspect. Also try jacking up the front of the car as far as you can to get all the air out, squeeze the bottom hose several times to pump trapped air out. The engine temp will rise a little when traveling at 60 and 70 mph anyway and also when using the ac, 210-215° would not be unusual, what temperature thermostat did you put in?

Ashmann70 · Jul 10, 2018

Ashmann70 said:
I will double check. But I think it is

Ashmann70 · Jul 10, 2018

96pushrod said:
Did you put the head gasket On the correct way? I know it’s kind of hard to tell at this point lol

What temp thermostat do you have?

I was thinking about that. I'm sure they are. As I recall there is a port without a opening on the gasket. Went to the back side of the head. 190°the tune is set for the fans to come on earlier the factory setting..

Ashmann70 · Jul 10, 2018

General karthief said:
What are your actual temp readings? If you are watching the stock gauge then you need to put a manual gauge in it, even mounting it temporarily where you can watch the temp reading while driving, the stock gauges can be suspect. Also try jacking up the front of the car as far as you can to get all the air out, squeeze the bottom hose several times to pump trapped air out. The engine temp will rise a little when traveling at 60 and 70 mph anyway and also when using the ac, 210-215° would not be unusual, what temperature thermostat did you put in?

190°

Ashmann70 · Jul 10, 2018

Ashmann70 said:
190°

When you say to pump the bottom hose, engine on, cap off?

96pushrod · Jul 10, 2018

Ashmann70 said:
I was thinking about that. I'm sure they are. As I recall there is a port without a opening on the gasket. Went to the back side of the head. 190°the tune is set for the fans to come on earlier the factory setting..

The gasket is supposed to block off the front holes so it forces coolant to the back of the block for cooling.

Ashmann70 · Jul 10, 2018

Mustang5L5 said:
Deflector installed under the car on radiator support?

No... its missing.. Could that make it run hot?

Ashmann70 · Jul 10, 2018

96pushrod said:
The gasket is supposed to block off the front holes so it forces coolant to the back of the block for cooling.

Well... I remember seeing the difference on the gaskets. I think they also had the word FRONT on one side... that would suck if i got that wrong! And it would affect the temp wouldn't it

96pushrod · Jul 10, 2018

Yeah they say “front” but they’re been messed up before lol. One of the gaskets almost looks upside down but that’s how it is. The coolant goes in and right out the block without cooling the rear cylinder banks. Even if you have one side wrong it would run hot.

Run it and see if you notice a temp difference in the back.

JD1964 · Jul 10, 2018

If it sits there and idles for extended periods without overheating, but only overheats with constant load, such as highway driving, my guess would be the radiator is plugged up with gunk inside.

91TwighlightGT · Jul 10, 2018

Ashmann70 said:
No... its missing.. Could that make it run hot?

Yes. That is supposed to create a low pressure behind the radiator to help force air through it. It also explains why you are overheating at speed.

mikestang63 · Jul 10, 2018

get an aluminum air deflector. the stock plastic ones over time tend to get weak and not as rigid. Overheating at highway speed is an airflow problem or a clogged radiator or collapsed hose.

General karthief · Jul 10, 2018

Ashmann70 said:
When you say to pump the bottom hose, engine on, cap off?

Right, I jack mine up as high as I can when I refill the radiator, I squeeze the lower hose several times to help pump out the air, start it up (still jacked up) and as it warms up keep pumping the lower hose a few more times.

Ashmann70 said:
No... its missing.. Could that make it run hot?

Yes, at speed it creates a low pressure area much like a rear spoiler on a nascar, this low pressure area allows the air flowing into the engine compartment through the radiator to escape under the car, with out it pressure builds in the engine compartment and you will have reduced or no flow through the radiator.

Mustang5L5 · Jul 10, 2018

Here's the stock style one.

https://www.americanmuscle.com/radiator-air-deflector-8793.html

Unsure who sells the aluminum one

Overheating at hwy speeds

New Member

That is…until I whipped out my Bissell

I think they're a little easier to get off

New Member

New Member

I think they're a little easier to get off

wonder how much it would cost to ship you a pair

New Member

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New Member

New Member

New Member

I think they're a little easier to get off

New Member

New Member

I think they're a little easier to get off

there is enough sticking out to grab on to

wonder how much it would cost to ship you a pair

That is…until I whipped out my Bissell

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