New radiator cap?

[ckomai]

I just upgraded to an aluminum radiator with 3 rows. It runs much cooler and I gained some horsepower. The thing is, when its cool the radiator is full and the overflow tank is full also. Then when I check it while its hot, the overflow coolant is still there. Is this normal or do I need to get a radiator cap that opens at a lower temp??

 

[Tbars4]

...It would help greatly if your location ws under your name as your definition of hot is probably a bit cooler than what we get..

..and same as stock swap? Some may want to know make and model when they read this looking for a swap of their own..


..I like to run what pressure cap that was on my vehicle, for instance..My 2.3L Ranger came with a 16# cap (higher than the 4.0's) while over the counter shows it would be 13#...In Fact, most every Ford truck I've owned over the past few decades said 13# OEM in the aftermarket books but they all came with different poundage and I sought the original poundage caps out..

..Your designed coolant system is sealed and requires a certain pressure to run at, with a pressure cap to relieve pressure build up inside it, but it will heat up and not cool properly if it doesn't have enough pressure in it..

..What most don't realize is, you may actually and easily overheat your engine if the pressure is released at a lower poundage than what it was designed for..

..In the old days you could run your cap loose and it would keep your engine cooler as it would still circulate and the pressure wouldn't build up to spray coolant if you had a leak...There were no computers that made lot's of decision's and changed how the vehicle ran etc. based on a certain temperature..

..Try running your vehicle with the cap loose on these vehicles and your temp will soar in a hurry..

..The overflow tank has a mark on it for cold level..This is designed and leaves enough room if your system does expels coolant which will fill the bottle but not overfill it...

..It is also designed (overflow tank) if your system does burp a little bit and has room to take a drink, to do so...Most with leaky head gaskets fill these quite often but it seems your system seems to be happy so far..:scratch:

 

[ckomai]

ok so i'm out here in Long Beach, so not as hot as you in Anaheim Hills. I picked up an all aluminum 3 row rad from "classic radiators" on ebay for $159, no tax out the door free delivery. Can't beat that. Fit in stock location perfectly and while the rad was out I replaced the fan clutch and fan. Went from 9 to 10 blade fan. Totally worth the money spent.
So from what your saying, looks like I should be fine if coolant isn't going in and out of resevoir all the time. I have however found the resevoir high and the radiator a little lower when cold. This might be the pressure issue you were talking about.
So as far as the cap goes. Now that I run cooler is it better to go higher or lower on the radiator cap to keep optimum pressure?

 

[Tbars4]

ok so i'm out here in Long Beach, so not as hot as you in Anaheim Hills.

..See...You easily made that assessment because the location was under my name...You could have been in Alaska..

...The radiator should have been designed for the application/vehicle it is going into so the cap should be the same as original unless the MFG company says one size fits all or will only warranty it with a certain size or brand of pressure cap. They would be the one to verify if it is required to be any different than original....

..Is this a pre-runner build or ? pics with radiator in vehicle?

 

[ckomai]

cool because I bought a new oem cap with the radiator. Yes prerunner build, thus wanting to cool for hot desert runs. Let me work on pics to pursuade the masses to do this.

 

[Tbars4]

..Awesome...

..I'm not sure if you already have one but you could start a build thread here as we have several other prerunners and racers that pop in from time to time with their build updates too..

http://www.explorerforum.com/forums/forumdisplay.php?f=39

 

[Maniak]

I just upgraded to an aluminum radiator with 3 rows. It runs much cooler and I gained some horsepower. The thing is, when its cool the radiator is full and the overflow tank is full also. Then when I check it while its hot, the overflow coolant is still there. Is this normal or do I need to get a radiator cap that opens at a lower temp??

When its cool you should have a full radiator AND a full, up to the cold line, "overflow" reservoir.

When its hot AND the pressure builds up to more than your radiator cap the cap will let some more fluid into the overflow. Normally it won't over fill the overflow. If you had the overflow AND the radiator completely full then when it does move some fluid to the overflow you put coolant on the ground.

Now, as thing cool off the pressure will drop in the radiator and it will pull the fluid from the overflow back into the radiator. This is assuming you didn't mess with the cooling system (release the pressure) before if pulled the coolant back from the overflow.

Changing the psi on the radiator cap won't change the temp the vehicle runs. All it changes is where the boiling point is. You get 3F for every psi of pressure added to the boiling point of the coolant. We run 16 psi caps on all our vehicles as we want the extra boil over protection it gives you.

~Mark