Visit The Dirt Forum for More Information

Author Topic:   Overheating on Cautions
posted April 21, 2003 01:14 PM
This is my first year in a hobby stock. I have a 31 in. aluminum radiator, tight shroud w/the 15 inch 6 blade fan half way into the shroud, and i'm running a washer in place of the thermostate w/a 3/4 inch hole. When i'm running green flag the temp is about between 205 and 215 usually, but as soon as I slow down for a caution and shift down into 2nd gear (i run a 3 speed saginaw) the temp goes right up to 230 and farther. Any recomendations?

posted April 21, 2003 02:16 PM
What do you have for a water pump and pulleys? They can make a big difference also.

posted April 21, 2003 05:43 PM
A couple of things to look at;
How old is the alum radiator? If it is new,let's go to the next step. But if it is a couple of seasons old or used,it may be not flowing 100%.
Are your pulleys shiney? Maybe belt slippage?
Do you have direct openings to the radiator where outside air can get in? Look at where your grille opening vs the location of the radiator is.
Maybe a circle track water pump maybe the answer. Look at the Day Motorsports or JR Motorsports for a better unit.
Is the fan set well in reguards to the radiator? Maybe a spacer to push the fan out to the radiator maybe needed?
Have a good fan shroud?
Last,but always my first place to start because it tells not you don't have a engine problem,pressure checker on the radiator will cross out any motor problems.
How about a good racing radiator cap?

redneck racing
posted April 21, 2003 06:43 PM
Try running distilled water with some Hyper-Lube coolant additive in it, brought my temp down to around 200-210. Eddie

posted April 21, 2003 10:53 PM
check that radiator cap--you would be surprised what a good racing cap will do for temps.--i run a 28-32 lb cap and during green flag racing it stays around 180--no more than 205 when setting still or during caution periods--inexpensive fix to a big problem. leftturn29

posted April 22, 2003 09:42 AM
The higher pressure Rad. caps keep pressure on the water and help reduce the water boiling at the cylinder walls. forcing the water to move away for more water to replace.

Cap has my vote.
Then Pump problems probly belts.

Add some Water Wetter It really works.

[This message has been edited by DirtDobber (edited April 22, 2003).]

posted April 22, 2003 12:01 PM
one thing i forgot to mention to you the other nite 88 is how much of an opening do you have cut in that plastic nose might need to open that up a bit

posted April 22, 2003 12:22 PM
Every lb. of pressure you place on the cooling system raises the boiling point of the water 5 degrees just an example; If the boiling point of water is 212 ad a good 20# cap shouldnt let the water boil until 312 degrees.Just my 2 cents....towman

posted April 22, 2003 01:14 PM
One very smart racer once told me if you overheat when idling/stopped it's not enuf airflow,at speed/higher rpm's not enuf water flow.So i'd look at airflow to radiator and thru it and maybe even out of the engine compartment as a cause.

posted April 22, 2003 06:28 PM
i went from a 15" fan in my stockcar to a 17" and i dropped frm 220-230 to 190-200 maybe 210 on a rally hot night. and i dont have holes in my nose piece


posted April 23, 2003 10:46 AM
Thanks for all the help guys.

The radiator is brand new and the pulley's are 25% reduction and don't show any sign of belts slipping.

I'll probably open up the nose of the car to get more airflow and switch to a 17 inch fan. If that doesn't help we'll try some of the other ideas you all have given me.

posted April 23, 2003 11:15 AM
Make sure your radiator is clean and not full of dirt.

posted April 29, 2003 10:46 PM
I run a 15 inch flex fan about a half inch into the shroud approx. 4 inches from a stock chevy truck radiator with a 5/8 restrictor plate in the thermostat housing stock pulleys and 100% water runs around 190
P.S. Cant stress how important the rad. shroud really is needs to be compltely sealed on the bsckside to effectively pull air also build an airdam blow out of plastic to help scoop air up

posted April 30, 2003 08:45 AM
One suggestion that I didn't see posted yet....make sure that the top of your radiator is ABOVE the water neck on your intake manifold. If it's mounted below it..the water doesn't flow freely. We had it happen to us and I've seen it happen to a few other people. Other than that...the cap is definately a good place to start.


racin fool
posted May 08, 2003 04:17 PM
Okay if 1 lb of pressure equals 5 degrees. then what are the answer to the following temp.

= 23lb

180 = 25lb

= 30lb

posted November 01, 2003 08:43 PM
Something that creates a lot of questions...
Do you run a restrictor??? Remember the restrictor works in reverse to the way most want to slow the water down so it will stay in the radiator longer so it will cool,,,not expel from the block faster.

So make sure your not circulating the water too fast.

posted November 03, 2003 01:55 PM
I'm old, that's why it's old techonogy... It still works.

RCRacing #08
posted November 04, 2003 03:52 AM
so how does changing the lbs on the cap effect the car temp.?

posted November 04, 2003 10:08 AM
1. Gas engines need one to one pulleys.
( thats your problem)
2. Use distilled water only.

3. Use at least a 20 lb cap.

your water isnt getting out of your rad. and into your engine fast enough when your at lower rpms, your pump is going to slow.

posted November 04, 2003 11:03 AM
Just out of curiosity, why is distilled water so much better for cooling purposes than good ol' tap water?

posted November 04, 2003 04:10 PM
I hope Im not the only one that knows we are posting on a topic started in april.

distilled has no impurities, its good for 15-20 degrees according to everyone including myself that has changed just that one thing in their system.

there have been several, 3-4 guys on here also that private messaged me and said it worked for them when they switched just their water.

Im getting tired of posting it over and over, so pass it on!!!!

posted November 05, 2003 11:31 AM
Powerglide...I've argued this point (yours and mine) for years. We're splitting hairs on a fine line. Too an extent you're right and so am I.

Raising the pressure on the cooling system;
Each 1lb pressure raises the "BOILING POINT" 3 degrees. once the pressure is realeased the boling point is back to 212 degrees. It keeps the water from boiling but doesn't keep it from getting hot.

posted November 07, 2003 08:24 AM
I've also heard of cutting/breaking/removing half the blades in the water pump (do it evenly). Moves water slower thus letting radiator cool water longer and uses less energy/power to move water thus more HP. When doing this remove restrictor/thermostat. Always use 24#+ cap, distilled water and water wetter or the like. Always make sure of proper shroud/fan placement. Watch timing and jetting.

Reduction pulleys will move water slower also but the fan is moving slower therefore not as much air flow over radiator to cool it. On the flip reduction pulleys do help HP slightly.

Basically, there are many scenerios - what works for one may not be trick for the next guy.

posted November 07, 2003 08:33 AM
water wetter has been tested a dozen times with published results...

it doesnt work, unless you want a water pump lube??

posted November 07, 2003 01:39 PM
i agree with the theory the pump is turning too slow its cooling ok when your running the crap out of it which is usually when you may heat up your overheating when rpm is down thus slowing flow down make sense to anyone?

Back to the Archives