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300-6 overheating mystery ...please help 
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Post 300-6 overheating mystery ...please help
I have an 83 f250 with an 82-85 carbed 300 that overheats.
I put in a new stock radiator, both hoses, an electric fan on the outside that pushes air through the radiator, and most recently a new water pump. It's currently running with no thermostat and it still boils. usually runs 185* or so going down the road but in town, in traffic or sitting at idle the temp just keeps climbing. I try not to let it get over 210 before shutting it down but im sure it would just keep going if i let it run..
With the whole cooling system replaced what is left?
I've seen vehicles that never get over 140* without a thermostat.
Is there something I'm missing?
This motor runs perfect otherwise and has great power.
any help is appreciated

Jeff

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97' ranger 4x2 4 cyl 5sp 110k fuel sipping daily driver
83' F250 4x4 300-6 4sp ???k 4" up w/ 36x12.5x16.5s ---my toy and winter beater
gone but not forgotten....
90' F150 4x2 300-6 5sp 120k rotted out and scrapped, kept the motor
93' F150 4x2 300-6 5sp 223k 5 years of service, sold for what i paid... blown up by stupidity...


Sat Sep 01, 2012 2:42 pm
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Post Re: 300-6 overheating mystery ...please help
:) Hi Jeff.First,install a 160* stat.Sometimes the coolant goes through the rad too fast without one to cool properly.My 84 F150 has a 160*stat and standard cooling with a clutch fan,and as far as I know the fan has never engaged.Had this setup for about 3 years now,and no problems.Check for pinched hoses or hoses that squeeze shut under suction.
When I installed the new rad and stat,I let the truck idle for about 3 hours and the coolant in the rad never got over 145* according to a cooking thermometer in the rad filler neck.
Good luck.Have fun.Be safe.
Leo

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Sat Sep 01, 2012 4:51 pm
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Post Re: 300-6 overheating mystery ...please help
2 other things to think about that can make an engine run hot:

timing - could be retarded a bit
jetting - running too lean

The previous suggestion to check for a hose collapsing on the suction side as engine warms up is spot on too.

Good luck !
Rusty.


Sun Sep 02, 2012 11:30 am
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Post Re: 300-6 overheating mystery ...please help
A few things come to mind...

If it overheats at idle, but cools down at speed, you can rule out radiator capacity. Sounds like a lack of airflow through the radiator. Do you still run the stock fan as well as the electric? Is the fan clutch bad? Is the polarity of the electric fan correct (don't laugh, this has bit me big time before)? Is the water pump spinning the correct way?

It could also be a leaking head gasket allowing exhaust into the cooling system. The gas can accumulate around the water pump impeller and stall coolant flow at idle. Very difficult to diagnose, until the thing lets go completely.

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Sun Sep 02, 2012 12:06 pm
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Post Re: 300-6 overheating mystery ...please help
Agreed - verify timing. Retarded timing makes an enormous difference (runs hot, less power).


Sun Sep 02, 2012 3:56 pm
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Post Re: 300-6 overheating mystery ...please help
MechRick wrote:
A few things come to mind...

If it overheats at idle, but cools down at speed, you can rule out radiator capacity. Sounds like a lack of airflow through the radiator. Do you still run the stock fan as well as the electric? Is the fan clutch bad? I........ Is the water pump spinning the correct way?
.......


Agree 100%

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Mon Sep 03, 2012 10:43 pm
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Post Re: 300-6 overheating mystery ...please help
MechRick wrote:
Is the water pump spinning the correct way?

This only sounds like a silly thing to mention.

The EFI water pumps spin the opposite direction of the Carbed due to the EFI having the Serpentine belt setup.
If you put on an EFI pump, if you have a late model serpentine belt, any sort of combination of that, you need to set it up similar to whatever year you got it out of or replace the pump with what your setup needs.


If you don't want to put in a thermostat, you can take an old t-stat and just cut out the middle so that it doesn't allow full flow through it, but I'd recommend a t-stat

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Mon Sep 03, 2012 11:32 pm
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Post Re: 300-6 overheating mystery ...please help
This only sounds like a silly thing to mention.

The EFI water pumps spin the opposite direction of the Carbed due to the EFI having the Serpentine belt setup.
If you put on an EFI pump, if you have a late model serpentine belt, any sort of combination of that, you need to set it up similar to whatever year you got it out of or replace the pump with what your setup needs.


I only mention this because without a thermostat in the system, a water pump impeller that is spinning backwards will move a bit of coolant through the engine. I don't know if a serpentine pump will swap in place of a V belt pump, but I've seen enough parts counter screw-ups, miss-boxed parts, and badly built (impeller on backward or wrong impeller) parts that I thought it deserved mentioning. After all, if it was an easy fix, he probably wouldn't have posted to the forum.

Sometimes it pays to think 'outside of the box'.

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1994 F150, 4.9L/ZF 5 speed, C-Vic police driveshaft
EFI head w/mild port work, 3 angle valve job
1996 long block with stock hyper pistons, ARP rod bolts
Stock speed density PCM
Stock cam installed straight up (aluminum cam gear)
Hedman header, full mandrel bent duals, crossover, super turbos


Tue Sep 04, 2012 2:16 pm
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Post Re: 300-6 overheating mystery ...please help
yup, those pumps bolt in exactly the same place

not sure if the pump length is the same

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Tue Sep 04, 2012 2:21 pm
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Post Re: 300-6 overheating mystery ...please help
thanks for all the input guys.

I put on a new reman carb about 1 1/2 years ago so I doubt that jetting is an issue.
The timing was 2 teeth off till about a week ago when a friend mentioned the same thing.
The hoses are both new but I'm gonna check the bottom next time i have it running to see if it's collapsing, i hadn't thought of that...

I have a friend who's been wrenching on engines for many many years who says the same thing about running no stat, BUT what i don't understand is that the top hose gets so hot that i can't touch it WITHOUT a thermostat. so putting one in would restrict flow and make it worse. right?
I think I'm still gonna go out this weekend and try the 160* stat just to cover all the bases, it would be nice if a $6 part fixed all my problems.

I run a very powerful fan spinning the right way but no stock fan. I bought a water pump that looks the exact same as stock. I don't know how it would be spinning back wards, my truck is an 83 so i always buy parts for 83 straight 6 with v belts. I don't think they were EFI until 86 or 87 Right?

Thanks again for all of the input, I'm gonna check for collapsed hoses and then maybe think about pulling the head to check the gasket. I hate to say it but i'm almost to the point of cutting my losses and finding a small V8 to put in it, i won't be as happy but i could atleast trust it to get to work.
.

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97' ranger 4x2 4 cyl 5sp 110k fuel sipping daily driver
83' F250 4x4 300-6 4sp ???k 4" up w/ 36x12.5x16.5s ---my toy and winter beater
gone but not forgotten....
90' F150 4x2 300-6 5sp 120k rotted out and scrapped, kept the motor
93' F150 4x2 300-6 5sp 223k 5 years of service, sold for what i paid... blown up by stupidity...


Wed Sep 05, 2012 7:50 am
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Post Re: 300-6 overheating mystery ...please help
If the top hose gets that hot and if the lower hose is cool, you're not getting flow or at least not enough flow.
We need a little clearer timeline on the problem. Has this problem always been there or did it appear recently? If it's recent, what did you do or change just before it appeared? What have you done or changed since it appeared?
Since the radiator is new and presumably OK, have you backflushed the block?
Check the lower hose for liner collapse.
Check the water pump to see if the impeller is loose on the shaft (happens way more often than you would believe) :bang:

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Wed Sep 05, 2012 9:54 am
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Post Re: 300-6 overheating mystery ...please help
An easy way to check coolant flow (since you have no thermostat in the system) is to pop the upper hose off the radiator and start it up. Coolant should run out of the upper hose fairly quickly (5-10 gpm).

I think it is an airflow issue, though. If you are running, say a single 14" fan, and the ambient temps are above 85 degrees or so, it's probably just not enough. Remember that a pusher fan isn't ducted to the entire radiator. It's only cooling the diameter of the fan (154 cubic inches of radiator surface).

A better setup would be to run two 12" fans, staggered high and right, low and left (226 square inches of radiator surface).

Better yet, would be a ducted stock fan off a late model (1996?). But then you lose the horsepower benefits of running the electrics (you do have it wired so they are not running at cruise, right?).

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1994 F150, 4.9L/ZF 5 speed, C-Vic police driveshaft
EFI head w/mild port work, 3 angle valve job
1996 long block with stock hyper pistons, ARP rod bolts
Stock speed density PCM
Stock cam installed straight up (aluminum cam gear)
Hedman header, full mandrel bent duals, crossover, super turbos


Wed Sep 05, 2012 12:59 pm
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Post Re: 300-6 overheating mystery ...please help
This truck originally came with a big block according to the vin. A friend of mine pulled it out and put in the 300 to be used to push snow. he ran it a few times in the winter and then i bought it. The truck has had this cooling problem since I've owned it. nothing i've done has changed anything. I have done all of the obvious dumb guy stuff.

I thought for sure it was the timing, found it was 2 teeth off. it runs beautiful now like it's brand new but still overheats. Same with the radiator, water pump, fan, with thermostat(180*) and without one.
I understand what your saying about the fan but the new one that's on there pushes ALOT of air. it's wired to a switch in the dash and then to a key-hot in the fuse box and runs the whole time the engine is running. I don't remember what size it is but you can feel hot air being blown all over the engine. I can't run a stock fan because of the way motor is mounted, seems like it's further forward than stock but thats just the way it bolted to the transmission. no room for a stock fan. The new water pump was in perfect condition when put in a week ago.

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97' ranger 4x2 4 cyl 5sp 110k fuel sipping daily driver
83' F250 4x4 300-6 4sp ???k 4" up w/ 36x12.5x16.5s ---my toy and winter beater
gone but not forgotten....
90' F150 4x2 300-6 5sp 120k rotted out and scrapped, kept the motor
93' F150 4x2 300-6 5sp 223k 5 years of service, sold for what i paid... blown up by stupidity...


Wed Sep 05, 2012 6:22 pm
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Post Re: 300-6 overheating mystery ...please help
I've seen and heard about issues with fans that are always on. I don't think that's the problem here, but it might crop up in the future when you fix the system, I still think it's the thermostat.

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Wed Sep 05, 2012 8:23 pm
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Post Re: 300-6 overheating mystery ...please help
:) Hi Kashjeff.What the problem with the water pump rotation is is this.With a V belt system the pump rotates in the direction of the engine rotation.If a pump for a late model egiine got put in an early model box,the belts will cause the pump to rotate the wrong way for the water to properly circulate.The temp of the top hose just pretty much proves my point.Double check the pump to be sure that you have the right one installed.Have seen this mixup happen several times.The serpentine belt system,because of the way that the belt is installed will turn the pump for that system the correct way.Watch the rotation of a serp system vs a v belt system when they spin over when cranking.
Good luck.Have fun.Be safe.
Leo

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Thu Sep 06, 2012 12:53 pm
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Post Re: 300-6 overheating mystery ...please help
Heating up at idle only, indicates a airflow problem at idle.
You can also lower your idle running temps a bit by making sure your vacuum advance is on full manifold vacuum. Double check your timing with and without the can connected.
You should have in the neighborhood of 20° min difference between the top inlet radiator hose and the bottom outlet. Check with an IR temp gun.
Always run a tstat. It creates higher pressure between the pump and the tstat to minimize steam creation at the valve bridge.
It's very unusual to install an serp water pump with a v belt pulley without a lot of modification. They won't fit. That's why they are made that way.
No pusher fans are going to give as much airflow as the proper oem clutch fan and shroud. Again airflow at idle.
Tstats are poor quality these days, check it before installing.
Good luck with it.


Fri Sep 07, 2012 4:01 am
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Post Re: 300-6 overheating mystery ...please help
i have a very stupid question....
My electric fan is mounted on the outside of the radiator pushing air in. I read on summit racing's site the the fan is more productive on the inside, between the motor and the radiator.
If i was to remount the fan inside should it blow towards the motor or towards the radiator?

Also want to say thanks to all who take the time to post, much appreciated.

Jeff

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97' ranger 4x2 4 cyl 5sp 110k fuel sipping daily driver
83' F250 4x4 300-6 4sp ???k 4" up w/ 36x12.5x16.5s ---my toy and winter beater
gone but not forgotten....
90' F150 4x2 300-6 5sp 120k rotted out and scrapped, kept the motor
93' F150 4x2 300-6 5sp 223k 5 years of service, sold for what i paid... blown up by stupidity...


Fri Sep 07, 2012 9:09 am
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Post Re: 300-6 overheating mystery ...please help
ALWAYS towards the engine. If it blew forwards, it would resist the natural airflow from the vehicle's motion and reduce the cooling.

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1993 Mustang 5.0 (hot rod and auto-x monster)
1982 Tiga Formula Ford (SCCA racecar)
2013 Hyundai Elantra Coupe (daily driver)


Fri Sep 07, 2012 9:35 am
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Post Re: 300-6 overheating mystery ...please help
I think they can be wired to pull or push?

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Fri Sep 07, 2012 10:03 am
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Post Re: 300-6 overheating mystery ...please help
While you are checking to see if the lower hose is colapsing or not, check to see how much of a temperature difference there is between the top and bottom hoses. If there isn't much difference, then the coolant is flowing through the radiator too fast. This is why some of the other guys are saying to keep a thermostat instead of running without it. The bottom hose will be warm but you should still be able to hold your hand on it without fear of getting a burn from it.

As far as the top hose being hot, I'm not comfortable touching it even when it's only at about 160-180 degrees. If you've ever tried to wash dishes or take a shower with 110-120 degree water, you'll know that that is already getting too hot to touch, so 180 degree water flowing through the top hose is going to feel really hot to the touch.

Just my two cents.

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Sat Sep 22, 2012 10:14 am
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Post Re: 300-6 overheating mystery ...please help
are you using the stock temp gauge? or is it aftermarket? is it electric or mechanical? where it the temp gauge located in the stock location the back cylinder? mine runs hot on the hwy 210-220 but mine is in a jeep with a big winch blocking some of the air flow, but that is on a run over an hour reving 2200-2500. on the trial it runs 160-180. could you have an air lock somewhere in the block? maybe near the gauge? that may cause your hi temp when idling.

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Tue Sep 25, 2012 2:45 pm
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