Overheading problems - WHY?

31 years old and I have built my first Hot Rod. 1931 Model A. I have drove it about 5 miles. All the things that I wondered how they would work. Worked great including the Hand-built clutch and brake pedals, 4 wheel disc brakes, and the steering drives like a dream.

Problem is that it runs hot. 240 idling in driveway and 230 out on the highway. Mild 350 Chevy w/2.02 hump heads, High flow waterpump, 14.5" belt driven flex fan, stock 65 mustang radiator. I am starting to think that it is the radiator. However, I have seen lots of hot rods running this set up without problem. Please advise!!!

 

Make sure your sender is working properly. Swap it out and check again. Lately I have heard of a lot of guys chasing a phantom overheating problem because of faulty senders.

 

how close to the radiator is your fan? and is it shrouded or not? was the radiator clean? or used and not cleaned out? are you getting good flow thru it once it reaches temp? if this all checks out look into your timing and carberation, check for lean condition and or too advanced timing.

 

That's a little warm.

Running a thermostat ?
Running vacuum advance ?

What brand is the gauge and sender ?

 

dreddybear makes a good point too

 

Some aftermarket flex fans are junk.
Factory fans are better.

 

Already checked the sending unit. I took out the electric sender and put a thermometer in the intake. Gauge is reading correctly.

Brand new mustang radiator.

I might add that I havent built a shroud yet.

180 degree thermostat. I am 100% sure that it isnt airlocked either.

Current temp outside in Kansas is 70 degrees. If it runs this hot now what will happen when it is 100 degrees outside.?

 

Get it hot and then hose the rad down with water from head to toe.....look for uneven (streaks) drying of the core.....where the water remains (if any) is where the core is plugged.

 

Yep , ben there and done that. Chased a heating problem for 2 weeks. Replaced everything, bad temp unit, expensive lesson learned. Bought a infa-red temp laser shooter thing a mabob at Sears, thats the first thing I grab when I start up a fresh motor or start driving a fresh unproven ride.

Works great when trying to tune a motor also, you can pulll temps of individual cylinder to see if one is running rich or fat.

 

If it's not boiling over, then I too would vote for the gauge being off-calibration.

You can try an actual thermometer stuck in the water under the radiator cap like the old shops did long ago to verify that the gauge is reading right.

You might be surprised at the difference betwwen gauge reading and the actual water temp. Sometimes the sending unit location can be picking up a reading that does not represent the rest of the engine.

 

Timing set correct. Radiator is about 2 in from fan. Wish I could run larger but that is as large as I can go before it hits the lower outlet.

 

Already determined that the gauge is correct with actual thermometer

 

1) the fan is too small
2) the fan is not close enough
3) Need a larger radiator
4) need a shroud



And there is a raised up water pump riser made for SBC's ...



I always use one on 32's ...

 

BUT is the timing correct under the front cover? One tooth off and you'll never be able to fix it outside.
Fan should be no more than one(1) inch from the radiator core especially of unshrouded. I used a funky X-style 4-blade stock steel 55-57 Chevy fan on my old Model T and had no cooling problems.

 

Degreed the cam and all is correct with the timing and carb adjustments. What brand of radiator is the best? Aluminum or brass, 1in tubes or 5 row? Where did you get the shourd?

 

This probably has nothing to do with yours, but make sure the lower hose has some built-in ribs or wires to keep the hose from flattening out when the water pump pulls.

If your lower hose can be squeezed and you don't feel any wires inside keeping the hose in a round shape, then you could be sucking the hose flat when the pump sucks coolant from the lower radiator outlet.

I saw that happen to a friend of mine with a Ford pickup. I did a quick side-of-the-road repair by putting a coiled up coat hanger wire inside the lower hose to keep it open, and we finished the trip with no more overheating.

That is a longshot, but squeeze the lower hose to see that it has something inside to keep it round and free flowing. If it squeezes out-of-round too easily, you will need to trade it for a hose with internal stiffeners so it won't go flat under suction. You don't want to use a soft upper hose where you really need a reinforced lower hose.

It doesn't matter if you have the system under pressure from the radiator cap, it can still have a strong negative pressure in the lower hose when the water pump pulls very hard, especially if you have a radiator with small tubes or small pipes, or a thermostat closed, or thermostat housing restricted. A revving water pump can create strong suction at the bottom and strong pressure at the top. That means the lower hose needs to stay open even in a vacuum situation, so make sure it has a coil inside it or built into the walls. Soft upper hoses should not be used on the bottom.

 

What are your crank pulley and water pump pulley diameters? Underdrive crank or a huge water pump puller can jack the ratios around and spin the pump too slow.

 

yep.

 

I am goignt o assume themotor is good. If the compression is off, it will heat up.

I can tell right now, the problem is in the fan setup. The flex fan is a POS. Get a stock clutch fan, and you NEED a shroud!!!!! Try these and report back.

Dima

 

You are running too hot reguardless of a fan or not. to be completley honest you should run cooler than that on the highway without a fan as long as you have good airflow across the radiator. I would give the system one last burp. also you may have much fluid flow speed. that makes a difference in a big way. everything else seems to check out. i would just try burping it one last time.

 

Buy or borrow an infrared scope and shoot the radiator , hoses and engine in differant places.

 

I agree the flex fans are POS but I cant fit a factory one 14.5" before it hits the lower hose outlet.

Factory crank and water pump pulleys.

Measured the fan to radiator distance at 1.25"

I cant see that a shroud is going to bring it down 50 degrees??

Has anyone else had problems with the mustang radiator set up?

 

I dunno about that, I have a 17in. flexfan, no shroud and the fan is about 2 in from rad. and runs 185-190 all day in town or on the road in 90 plus degree weather. I agree a shroud is very important but in this case I think there's something else goin on

 

"Stock '65 Mustang radiator" hhhhhhhhhhhhuuuuuuuuuuummmmmmmmmm....Lot of miles on that puppy. I'm guessin'........don't buy a bunch of shit to test it with....use a water hose like I suggested before.....never fails. I'll bet a fart in the breeze some of the tubes are plugged

 

I ran an aluminum radiator in my 32' 3 window. I had a themostatically controlled electric fan. Fan never came on, even in 100 degree weather. Radiator developed a leak and I switched to a brass/copper radiator. After that, the fan would come on in stop'n go traffic. Car ran at 175 degrees.

 

The shroud I use is made for Walker Radiators ... and I use a 4 core Walker. My engine is 430 HP so ... I need a good cooling system.



You can see the raised up pump (raises the fan centerleine over 5 inches ) ... and I can use a 18 inch 6 blade fan with it.

14.5 inch fan = 7.25 X 7.25 = 56.5625 X 3.1417 = 165 inches

18 inch fan = 9 x9 =81 X 3.1417 = 254 inches.

The extra 3.5 inches in diameter really increases the amount of air the fan CAN MOVE. The more the pitch on the blades and the number of blades alos affect the amount of air moved.

A good Walker Radiator and shroud ... plus the cost of the ZIPS raised pump ... is not cheap ... but replacing a overheated ruined engine is not cheap either ...
... and then you still have the overheating problem.

 

Check your pulleys if you have checked everthing else,,,you don't want the same size water pump pulley and crank pulley,,

as small a diameter as possible for the water pump,,,,as largeas the make for the crank,,,,in essence you speed up the water flow,,HRP

 

Ok, I thought about this for a bit.......The '65 radiator is new.....I missed that earlier. Still doesn't mean some of the core isn't plugged with something (Foam peanuts, for example) How would you go about testing a water temp gauge above 212 degrees, unless under pressure?......at 240 degrees it should be blowing off the pressure cap...... on the highway you wouldn't even need a fan,so it's not the fan.....a laser temp gun would be helpful.....on second thought go buy one.

 

your thermostat is not opening. take it out and see what happens.

 

Here's how I checked the guage.
key on gauge read 210. Then I removed the sending unit from the intake and inserted an actual thermometer into the water -210 degees.

I have a laser temp gun and used it. However, that is measuring surface temp only and not water temp. Different metals and different thicknesses will affect this reading. cast block, brass freeze plugs, aluminum intake, brass sending unit, etc.