RANDOM OVERHEATING??? HELP!!!

[dkbanjo]

I have a fresh 306 longrod with only 1000 miles. I have put a new ford racing H/D radiator, new cap, bypassed the heater core (because it was leaking), a new thermostat, and I put a high volume water pump also. The wierd part is that about once a day or every other day, out of no where the temp guage will pin as hot as it can go, and as a result it will lose about half a gallon of coolent out of the overflow. But just as fast as it pin's at 250 it falls back down, but because of the loss of coolent it will run a little bit warmer until i refill it, then it will at some piont it will happen again. If anyone has any idea whats going on, any feedback would be great. thank you. Plus, I really want a paint job, but I don't want to put any more money into it until this problem it solved.

heres the set up too.
v1 sc/6 psi for now 3500 stall w/ lock up
e303 3.90 gears
ported e7's srp pistons
holly intake 70mm vlavle body
dual valve springs ect...
30lb injectors

 

[2000xp8]

Sounds like there is air in the system, or air getting into the system through a slow leak.

 

[kpack5982]

Sounds like there is air in the system, or air getting into the system through s slow leak.

x2

 

[dkbanjo]

How do I track it down? thier's no drips on the concerete under the car. The half gallon of coolant i loose comes out of the top of overflow.

 

[Beasty306GT]

thermostat in the right way?

 

[2000xp8]

How do I track it down? thier's no drips on the concerete under the car. The half gallon of coolant i loose comes out of the top of overflow.

A slow leak can be hard to spot, if it drips anywhere on the engine it may evaporate before you ever see it.

You can either rent/borrow or buy a pressurizing test kit from most auto stores.

It will quickly exploit any leaks.

Basically you attach a fitting and bicycle pump to where the radiator cap is and pump it up.

 

[Kdubslugga]

Start it with the radiator cap off. Let it run until operating temp is reached. This should get most of the air out and you should see the thermostat open "by fluid drop in the radiator" top it off and it should be good! Sounds to me you didnt properly bleed the coolant system out when you did the water pump/thermo.

 

[90FoxBdy]

How are you filling the radiator? What works best for me is putting the driver side front up on a ramp, adding a little bit of coolant then starting the car and filling the radiator leaving the cap off. Like mentioned before you will notice the air escaping and then a drop in fluid. Keep adding fluid till the radiator is full and you have no more burps. Throw a pan under the car, it will burp some fluid out as you fill.

Also you mentioned your car cools back down. Is that moving or will it cool itself by just idleing. When does your problem happen? Only in traffic or normal driving as well?

 

[dkbanjo]

The thermostats in the right way, and i have tried filling it on an incline to let as much air out of the system as possible. it happend mostly on the freeway like last night, but also on the street like this morning. it can cool down while at idle, but not while in motion. otherwise, It runs really well. Temp stayes fine most of the time. It tend to think that air is getting into the system some how. I hope its not combustion gas

 

[dkbanjo]

No other suggestions? somebody did tell me that after the heads got machined that thiers vertually no deck clearance. That the the heads could be lifting up off the block and allowing combustion gas into the cooling system. Could that be true?

 

[reddevils86]

Did you check the seal of the water pump and tstat housing if they arent properly sealed air will come in also make sure the water pump doesnt have cavitation when they go bad it does all sorts of weird stuff my friends water pump would make his temp fly all over until he replaced it although his was more really hot then back down then really hot then back down.

 

[fox92]

I DONT NO WHAT A HIGH VOLUME WATERPUMP ACTUALLY DOES BUT IT SOUNDS LIKE YOU HAVE CAVITATION PROBLEMS LIKE RED DEVIL SAID. TO ME IT SEEMS YOUR PUMP IS SPINNING TO FAST SO THE COOLANT DOESNT PUMP THREW THE MOTOR IT JUST STAYS IN PLACE AND THEN IT COOLS DOWN AT IDLE B/C THE PUMP SLOWS DOWN AND STARTS WORKING. I WOULD MAYBE TRY AND DIFFERENT PUMP IF NO LEAKS ARE FOUND.

 

[elarm1]

were the head gaskets put on the right way? This can be easily fudged up

 

[reddevils86]

Did you ever figure out what it was or are you still hunting?

 

[dkbanjo]

Thanks for the replies. I'm going to checkout some the these theories when the semester is over. I hope its not the head gasket.