I am losing a bit of coolant, not thru the rad cap, but through the plastic cap on the overflow bottle, even though I only have the bottle about 1/3 full (to the designated mark) and the bottle cap is not damaged, and seems to pop on properly. I drive carefully--ie. don't careen around corners to create possible slop, etc. There should be no pressure in the overflow bottle, yet there is coolant moisture around the cap--not alot, but over the course of a week or two, it adds up so I have to top up the overflow bottle to the required level again--any suggestions? I don't really want to go to the trouble of buying/installing a new overflow bottle just for that, but it is a nuisance.
Frank

 

How old is your radiator cap? It might letting too much coolant into the overflow.

 

Thats what Im bankin on. Theres only one way that it could be leakin out of that overflow bottle around the cap..... and thats if its full. Are you saying thats its always at 1/3 of the way full or does it add up after a week or so?

 

change the radiator cap I'll bet that is your problem my truck did the same thing dose the truck start to boil over after you have stopped?

 

Thanks guys, but still a problem. In answer to your questions, the heat guage always stays constant around the N of Normal, and never overheats. The rad does not boil over. The overflow tank does not fill with coolant--I refill it to the mark (about 1/3 full), and it gradually drops from there by about an inch every couple of weeks, and I can see green coolant, or a green stain from dried coolant around the plastic cap of the overflow bottle. I think it could only be the rad cap itself if the overflow bottle was filling from the main rad, but that is not the case. The rad is full to the top when I take the rad cap off, and I never get extra coolant in the overflow--so any other suggestions?
I can't understand how the coolant, being only 1/3 full in the overflow, could splash out under the plastic overflow top, even though it pops in place tight, and I drive fairly conservatively, never in off-road bumpy areas.
Thanks for any more ideas.
Frank.

 

I had this happen on my truck more than once...take note if you are adding coolant then you have a leak and it may be a small leak.. and this is what is happening you add new coolant and the system draws that coolant in and then it expands because you have air in your system. so then the cap does what it is designed to do. release coolant to the reservior along with air which causes the system to burp ( for lack of a better term). that is where your coolant on the outside of your reservoir is coming from. look around your fittings exspecially at the tee pipe that is right behind the tstat housing. it if the is any white residue then there is a small leak there..also under the t-stat housing the paper gasket there is not the best..also the small custom fitted house to the TB and the small bypass at the pump...and last but least Ford radiators have a knack for leaking at the lower corners of the radiator..when cold no leak only when warmed up...as for the temp gage not the most accurate aand will not denote a small leak as it does not cause that much of a change in temp..

try this dont put in any coolant and then check the system you will see a difference

 

I've got two of these trucks and neither of the overflow bottles "work". I'll fill them to the mark and within a few weeks they'll be empty. But the radiator won't ever lose coolant. I've noticed the same thing on a couple '96's I service at work.

 

I had the very same problem on my truck. It was the radiator. Very small leak that was difficult to notice and a pressure check said the radiator was ok. Seems the leak only occured when the radiator was hot. The radiator had always seemed full because It was taking fluid from the fill tank. This went on for months. I replaced the radiator and it has never happened again.

 

I understand that a small leak in the system would result in losing some coolant, but it doesn't explain why I am losing some out of the top of the plastic overflow bottle, even though it is at most 1/3 full at any time.
But thanks for the ideas--please keep them coming.
Frank.

 

Alright lemme try to explain something. You guys are throwin coolant in the overflow and in a few weeks its empty right? Mine does the same thing. The reason why this happens is because your coolant system somewhere other than between the rad and overflow bottle has a slow leak. Could be a frost plug leaking (you will never notice anything until you look at em and see old coolant gunked up). My truck for instance has a bad frost plug. Ill put coolant in the overflow and then once the coolant in the radiator leaks out to a certain point, it will take coolant from the overflow back into the rad. I know this is kind of confusing but thats why they say keep that thing 1/3 of the way full. Because if you are loosing coolant, it has to come from somewhere to keep from runnin your engine low on coolant and overheating. As for the fluid comin out of the cap, I'm at a loss. I don't have that problem but my overflow tank will go dry in a matter of 3 weeks or so and i will notice that my radiator is a little low (because there was none in my overflow to replace what was lost in the radiator)

 

Frank have you seen it actually leak from the top of the overflow tank? I'd bet your just seeing condensation or such up there or its leaking from the hose when a little fluid goes into the tank. There is no other way for the cap to leak unless that overflow tank is full. I don't think you can buy those caps but maybe replace that hose and clamps from the rad. to the tank. But I'd bet you have a small leak in your system and your seeing the moisture on that cap and putting the blame there. If you don't see any water marks (white chalky lines) on the outside of the tank then it's not leaking from there.

 

From the information I have gathered, this is caused by air pockets in the coolant system. When on the throttle, creating alot of heat quickly, the air expands quickly and coolant will overflow into the resivoir. It will actually fill the resivoir up and overflow it. When you slow down or stop, the engine cools down a bit, the air pockets shrink, and the coolant that was pushed into the resivoir is sucked back in.

If this continues to happen for a long time, your coolant lines are not bleeding the air out like they normally do. You may have to use one of those coolant purge systems to get the air out.

I had this all happen to me. I just kept the resivoir half full at all times(never letting go empty as to not let air back in) and the problem went away after about a week.

 

Hey guys the dammed thing just started happening to my reservoir. I started getting coolant at the open of the tank and my level was and the cold line when i check so.. I loaded up the engine with the e brake on and in gear with all four wheels chalked.. the get the heat nice an toasty..then i watch the resivoir and sure enough the coolant rose in the tank and spilled over the top ..so I knew I had air entering into the system from some where or bad stat...then I got into the truck an noticed a sheen on the windshield and it would turn out that I have a small leak at the heater core..hey truck is tens years young...so i will be fixxing that next couple days..just wanted to chime in again just in case soem out there may be adding coolant and it is disappearing...dont forget to check your core Frank..

 

makes perfect sense....