cooling question.

[peterkin]

i had my dad take a radiator that i got to a local radiator shop where the guy worked his magic on it supposedly. my dad said something about dipping the core in acid or some mess, but anyway. the car is cooler ( 173-178 ) on a hot day than before, but sometimes the temperatures can go back to where they were before this radiator ( 190-203 ) range with the a/c on or sitting at a light to long with or without the a/c. what gives?

is it the thermostat, believe me i checked the stamp on the thermostat and it has 160 on it. could that be bad or faulty? does a thermostat work or not work or is there some middle ground there?

 

[BJM]

A 160 thermostat opens at that temperature and the engine will cool only if the radiator can pull enough heat out. The thermostat only keeps the engine from overcooling.

Your radiator is not clean enough to keep the temperature down. Even a tiny amount of buildup in the tubes will significantly impair its cooling ability. The heat has to conduct through the deposits before getting to the tube wall. Nothing can beat a brand new core for total conductivity.

At a stop light the fan cannot pull enough air through the radiator compared to the car driving at speed. Have you modified your fan to operate only at high speed, that would help. If its stock the computer can only command the low speed to come on. Only the A/C and the overheat sensor can trigger the high speed.

 

[Nick Micale]

The "magic" the guy at the radiator shop worked was to part your money from you to him!

Seems like only yesterday there was a thread about "rodding" a 15 year-old worn out radiator. Guess you have just validated my point that it should be trashed, and at least a new core installed between the end tanks. [If you do go for a new core, get a high effiency 3-row.]

 

[gofstbuick]

A 160 thermostat opens at that temperature and the engine will cool only if the radiator can pull enough heat out.

that is correct

The thermostat only keeps the engine from overcooling

But the thermostat restricts the flow of coolant / water (to the radiator) below the temp (in this case 160*), to allow (the air flowing across the radiator fins) the radiator to remove the heat form the coolant / water (or some combination there of). If the thermostat cannot restict the flow enough (for the coolant / water mixture) to allow the radiator to cool the liquid, then the temp will keep rising.

 

[peterkin]

i never thought about it like that. well, it didn't cost me anything. my dad thought that he would try that for me, and it's better than before but not as good as it could be. thanks for the insight guys.

 

[gofstbuick]

Out of curiosity, how did you purge the air out of the cooling system? Maybe you have a air pocket in your cooling system.

Just from experience, I place a funnel in the fill neck (of the radiator), and then fill the radiator full and then add enough liquid until the funnel is 1/2 full. I then move the heater rheostat to hot, start the engine and warm until the t stat opens a few times (usually around 20 or so minutes). If the liquid goes below 1/2 full on the funnel, I add more liquid. As the air is purged, the liquid will bubble (like the release of air bubbles). After I'm quite sure that the airis purged from the cooling system, I accelerate the engine to 2500 rpm, the level in the funnel will go down. While the engnie is still at 2500 rpm, I remove the funnel and install the radiator cap. Then release the throttle and fill your overflow bottle to normal. Maybe this is kind of an anal way of doing things, but the one place you don't want a air pocket is the steel heater hose (above the DS valve cover), because if this unit deteriorates (it is no longer available from GM and some reprod units are crappy IMHO) you'll have to seach for a good used piece. Before I was aware of this board, I had to have mine fabricated to resolve the problem.

 

[BJM]

On my engine I fill the rad full and start the car. I idle the engine until the liquid flows through the rad when the thermostat opens. The level will usually drop at this point because trapped air is expelled into the rad. I just top it off and watch it for a few more minutes. Fill the overflow tank quite full. On the next cool down cycle the contraction of the coolant draws more in from the overflow tank. It stops drawing fluid after a few full warm-up and cool down cycles.

Only if the radiator has enough heat lift will the engine temp drop enough for the thermostat to cycle open and closed. Under most ambient conditions of 90 deg F or more with A/C on the thermostat will not cycle even with a good rad. Mine is a brand new GM one. Actually the engine has trouble warming up when its 55 def or cooler. The engine temp won't rise above 160 unless I stop.

 

[peterkin]

i just fill and and let it run with the cap off and keep refilling it everytime it goes down until it's full. then i just put some coolant in the overflow tank. i figured it would just burp itself through the overflow tank if there was air in there.