Faster MPH = Higher temperature
Senior User
Joined: Feb 2004
Posts: 295
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From: conway arkansas
hey man i had the same problem on two of my company trucks one is a 1 ton 93 ford with a windsor, the other is the one i drive its a 91 3/4 ton with a windsor, they both had the same exact problem is what you are talkin about, i can tell you what it is, you got yourself a bad fan clutch, it sounds cheesy and unbelievable but thats what it ended up being on both mine,
Post Fiend
Joined: Mar 2002
Posts: 19,402
Likes: 38
From: Bonita Springs FL
If you're driving down the highway at 60 to 75 mph like it says in your first post, I can guarantee you that it's not your fan clutch. Here's why:
The fan's job is to pull air through the radiator at low speeds when there is insufficient air flow. You're already doing 60 to 75 - all that air is flowing through the radiator at that speed before it ever hits the fan. The fan does NOTHING at those speeds, whether there's a working fan clutch or not.
You have other problems. I promise.
The fan's job is to pull air through the radiator at low speeds when there is insufficient air flow. You're already doing 60 to 75 - all that air is flowing through the radiator at that speed before it ever hits the fan. The fan does NOTHING at those speeds, whether there's a working fan clutch or not.
You have other problems. I promise.
Postmaster
Joined: Aug 2004
Posts: 2,908
Likes: 2
From: West Mansfield, Ohio
It'd be just like stickin your head out the window at 70 MPH and then holdin a box fan in front of u (if it was possible)...... that box fan isnt going to do any good. Just an example. I agree you have other problems but i'm pretty sure its something simpler than the head gasket....
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
The fan clutch does nothing at highway speeds. The fan is used to provide airflow thru the radiator at speeds below ~35MPH (depending on aerodynamics). Above that speed the vehicle's motion thru the air forces air thru the radiator.
Another thing that can cause problems with engines heating up at highway speeds are missing airflow directors under the hood. Remember those little flaps of plastic or cardboard that people rip off and throw away because they don't know what they are or they are in the way??? Those flaps keep the airflow from bypassing the radiator.
Another thing that can cause problems with engines heating up at highway speeds are missing airflow directors under the hood. Remember those little flaps of plastic or cardboard that people rip off and throw away because they don't know what they are or they are in the way??? Those flaps keep the airflow from bypassing the radiator.
Elder User
Joined: Feb 2004
Posts: 553
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From: North Bend Washington
How about a collapsed lower radiator hose. I've heard of this happenig at highway speeds with an old lower hose. But how can you tell at highway speeds? I've watched one collaps as a hot engine was stopped and started cooling down. You will have to wait for the pressure to drop. Is your fan shroud on?
Last edited by mike93; Aug 27, 2005 at 06:52 PM.
Thread Starter
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Freshman User
Joined: Aug 2000
Posts: 38
Likes: 1
I have had to leave the New Orleans area. I will update this post in a few weeks after life settles down a bit. Thanks for your help to date.
Kevin
Kevin
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Elder User
Joined: Feb 2000
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From: Temperance,MI
When mine did this in the winter, driving at 55 at about 25 out, would climb to R drop off to 45 dropped ot high N.
Checked my oil clean, wasnt loosing any coolant, did a leak down test held fine, so put me down to a water pump, fan, half stuck thermostat, and a good reason to put my new rad in. Ran the old stuff out filled it with flush and water you would be suprised how much build up you can have put the new high flow pump on(had it there at the shop for the 331 build) and put my new rad in with a 180 stat now I run at 180. Flush it first my old rad in the side tanks there was so much build up it wasnt funny.
Curtis
Checked my oil clean, wasnt loosing any coolant, did a leak down test held fine, so put me down to a water pump, fan, half stuck thermostat, and a good reason to put my new rad in. Ran the old stuff out filled it with flush and water you would be suprised how much build up you can have put the new high flow pump on(had it there at the shop for the 331 build) and put my new rad in with a 180 stat now I run at 180. Flush it first my old rad in the side tanks there was so much build up it wasnt funny.
Curtis
Junior User
Joined: Jun 2004
Posts: 74
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Lower Radiator Hose
Long shot....Could it be a lower radiator hose coooapsing at high rpm wthen your driving 60-70 mph. I had a problem with this once. I just put in a fresh 383 stroker in a 1975 chevy truck and i was stumped. New Radiator, water pump. everything to include hoses. the problem was the lower radiator hose did not have the coil inside causing the hose to collapse under high rpm when drivng at constant 70 mph speeds. just a thought. let me know Ryan......
Moderator
Joined: Jun 2003
Posts: 3,547
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From: Calhoun GA
Originally Posted by kjk
...When checking the water level I noticed a lot of air bubbles in the radiator while running. After cooling with a water hose it would not get hotter while I was looking around trying to figure it out. During a 10 mile stretch at 50 MPH the temperature was just above normal, and went right back up upon return to 70 MPH...
Hotshot
Joined: Oct 2003
Posts: 17,795
Likes: 99
From: Ashland City, TN
Flush it with the prestone home kit,
and then run the cleaner through it and flush it again.
There easy to use, and you will only spend about 20 dollars to flush, pluss new antifreeze after the proccess is done.
barsleak should do you no good. so avoid that.
But radiators can go bad at anytime.
The newer GMC's and Chevies dont even use the old school green antifreeze, tehy use the RV red stuff, I dont think it has as much gumming up properties, i guess you could say.
but that cleaning solution you mix in with water cleans out all the gum, but its best to flush first, and then flush after, and replace with 50/50 antifreeze.
Going slower only means your generateing less heat, a headgasket would have nothing to do with it.
Air in the radiator could be from an odd hole, or just air in the system that needs to come out, which should go out through the resivour, which if it can't breath, then the air cannot escape.
Compression test, and a clean and refill will be best choices!
You will spend 30-40 dollars max.
while a headgasket replace will cost more time then anything.
and then run the cleaner through it and flush it again.
There easy to use, and you will only spend about 20 dollars to flush, pluss new antifreeze after the proccess is done.
barsleak should do you no good. so avoid that.
But radiators can go bad at anytime.
The newer GMC's and Chevies dont even use the old school green antifreeze, tehy use the RV red stuff, I dont think it has as much gumming up properties, i guess you could say.
but that cleaning solution you mix in with water cleans out all the gum, but its best to flush first, and then flush after, and replace with 50/50 antifreeze.
Going slower only means your generateing less heat, a headgasket would have nothing to do with it.
Air in the radiator could be from an odd hole, or just air in the system that needs to come out, which should go out through the resivour, which if it can't breath, then the air cannot escape.
Compression test, and a clean and refill will be best choices!
You will spend 30-40 dollars max.
while a headgasket replace will cost more time then anything.
Freshman User
Joined: Dec 2004
Posts: 32
Likes: 0
That's not true, the fan clutch comes on at any time the temp rises, no matter what speed you are running at. Fords in that year have a very bad air movement problem under the hood. If the fan isn't kicking in when the truck reaches around 180 degrees, there's a problem and the truck will just overheat, even if you are doing 100 mph.
If there was a head gasket problem, he would be losing anti freeze and would be continually filling it. Also, the whole cooling system would become pressurized to the point it would blow by the cap as soon as he started it not to mention anti-freeze blowing out the exhaust.
I would check and CLEAN the radiator even if it appears fine. You could have a collection of crud in the bottom that is restricting fluid flow. Then make sure the fan cluth is engaging. You'll know when it does because it'll sound like it's trying to suck the grill right off the truck..
If there was a head gasket problem, he would be losing anti freeze and would be continually filling it. Also, the whole cooling system would become pressurized to the point it would blow by the cap as soon as he started it not to mention anti-freeze blowing out the exhaust.
I would check and CLEAN the radiator even if it appears fine. You could have a collection of crud in the bottom that is restricting fluid flow. Then make sure the fan cluth is engaging. You'll know when it does because it'll sound like it's trying to suck the grill right off the truck..
