Radiator Cap Leaking!

[jzak]

Hey guys!

So i'm having this issue with the radiator cap slowly releasing antifreeze as the engine heats up. Originally i thought I had over-filled the radiator with coolant, but it's been doing it continuously for months.

Again, it's not pouring out. The coolant level in the radiator doesn't dramatically drop. It's just a very slow release of coolant. The vehicle isn't overheating either. The temp rages from 160 to 180 degrees. I replaced the 16 PSI radiator cap with a new one, and it's still doing the same thing. Do i need to get a higher PSI radiator cap, or is this a sign of a bigger problem? I know there is some coolant overflow, but should this be happening every time I drive it?

Thanks!

 

[Torxhead]

How did you verify the operating temp? Is you coolant going into a recovery bottle? or somewhere else? Like down into the combustion chambers?

 

[jzak]

How did you verify the operating temp? Is you coolant going into a recovery bottle? or somewhere else? Like down into the combustion chambers?

Hi Torxhead!

Just using the temp gauge on my dash to verify operating temperature. The hose going to the overflow bottle is split at the point where it attaches to the radiator (Been meaning to fix it). Therefore the coolant is leaking out under the radiator cap where the overflow port is. At least that's what it looks like it's coming from.


Thanks!

 

[Torxhead]

You might be overheating, when was the last time you had the system professionally cleaned out? Those recovery bottles can be purchased thru the big box 4wd outfits. If you think there is a bad seal even with a new cap, there might be a problem with the mating surface. When the coolant gets hot and exits into the bottle, it should suck back into the radiator when it cools down, keeping the radiator always full. When wheeling thru steep ups and downs you can loose coolant thru the top of the bottle, so try and keep the bottle on the low side. Radiator shops can do a pressure test for checking leaks.

 

[jzak]

You might be overheating, when was the last time you had the system professionally cleaned out? Those recovery bottles can be purchased thru the big box 4wd outfits. If you think there is a bad seal even with a new cap, there might be a problem with the mating surface. When the coolant gets hot and exits into the bottle, it should suck back into the radiator when it cools down, keeping the radiator always full. When wheeling thru steep ups and downs you can loose coolant, so try and keep the bottle on the low side. Radiator shops can do a pressure test for checking leaks.

I think I should stop being lazy, and fix that overflow hose. Thanks for the feedback. So are you telling me that every time you drive, you should expect some coolant to come out into the overflow bottle, or only when it's running hot?

I had a mechanic pressure test and flush the radiator, hoses, heater core a few months back. No Problems!

 

[TexasBlues]

I think I should stop being lazy, and fix that overflow hose. Thanks for the feedback. So are you telling me that every time you drive, you should expect some coolant to come out into the overflow bottle, or only when it's running hot?

I had a mechanic pressure test and flush the radiator, hoses, heater core a few months back. No Problems!

yes sir, every time you drive, the coolant heats and expands and goes into the tank (called the expansion tank) and as the engine cools down after shut down, the coolant contracts and flows back into the radiator... its a closed system and should remain full at all times (unless you have a leak somewhere)...

also, some vehicles have bleeder screws on the high side of the water neck (thermostat housing) where you can bleed out the air as the engine runs and heats up... this should spit fluid only when its burped all the way...

hope this helps!

 

[jzak]

Thanks bud! I think that's my problem right there.

Should be a easy fix, but i'll keep you guys posted.

 

[Torxhead]

Jzak, in reference to post#5, loosing coolant can happen going up and down extremely steep angles like when off-road where some coolant can pour out thru the vent hole on the overflow bottle. There might be a small amount evaporating thru that vent hole but not much. The overflow bottle or expansion tank does not need a lot of coolant, just enough to keep the radiator full as the coolant flows back into the radiator.

 

[jzak]

Thanks guys for the feedback!

So I got a chance to take a look at the overflow system, and I think I may have found the problem. The overflow port is directly underneath where the radiator cap sits. I took the cap off, put in a new hose, and lopped off about 4 inches of excess hose, but when I tried to put the cap back on, it wouldn't let me. The hose was too thick, and blocked the radiator cap from locking into place. The only way I could get it back on, was to pull the hose back from the port about a quarter of a inch. I put in a hose clamp to help secure it.


I think that is what started the leak. The locking teeth of the cap was grounding up the hose every time you turned it.

I haven't had a chance to drive it yet, but I think this should do it!

Thanks!

Josh

 

[Torxhead]

Hopefully the fix will keep that expensive coolant in the radiator. You might have used fuel line instead of a thinner wall coolant line.

 

[Hedgehog]

It is amazing how much the level in your overflow tank will vary during operation. I have one of those SS tube tanks found on hot rods in my jeep. It is not very big around, but tall. The fluid level will raise 5" or 6" depending on a hot or cold engine. Hot it's high, cold it's low, but always at the same levels so I'm not losing any fluid.

Torxhead - Man you are right, radiator fluid is practically made of solid gold these days. Where I once drained and flushed old radiator fluid I now strain and reuse it, that is if the fluid is relatively new like when working on a leaking radiator hose or adjusting the radiator in some way.

 

[73CJ]

Hedge. Drain & strain

Now come on. What are you staining out?

Anti freeze has lubricants for the water pump and anti corrosion additives.

These additives lose their effectiveness over time as they break down.

More important up here in the North country is the freeze protection.

I like my vehicles and only new goes back in.

Now on to the catch tank

73 six cylinders never had one. Mine does not run hot or puke out. Thought of putting a tank on but then asked "Why?" Next upgrade.

 

[Hedgehog]

Sorry my cat brushed my touch screen and sent this post before I was ready to post.

 

[Hedgehog]

A challenge to my integrity, okay the details........

Last summer I got a new Radiator, hoses, cap, water pump and refilled with about $25.00 worth of radiator fluid. Shortly the radiator sprung a small leak from a poorly soldered joint. The fluid was saved in a relatively clean bucket which quickly got some leaves and a little grass in it. With the new radiator in place I strained the fluid using a few layers of cloth over the funnel and the radiator was topped off with more new fluid. Unfortunately the lower radiator hose was lose and needed to be reset so the fluid came out yet again. The hose was reset and the fluid was trained once again. I figure about $50.00 was saved by reusing practically new radiator fluid. Under the same situation I'd do it again. No, I'm not talking about old used up fluid.

Frankly, if you don't run your a full radiator the fluid won't over flow and you won't need a catch tank. I drove like that for years with other vehicles. No, I never over heated either. In this state an over flow tank is required if the vehicle is going to be driven in a municipal area. Unfortunately I live in Tucson and the tank is required. With the new tank in place I watched the fluid level very closely. At first I thought the engine was using or losing fluid. Then it occurred to me that the cold fluid was always low and the hot was always high, right around the over flow tube in the tank. If challenged on this I'd put serious money down and I'm not a betting man.

 

[73CJ]

OK that makes sense. New antifreeze. I'd do the same.

I read it as straining old antifreeze.

Now if you run the numbers on thermal expansion using the following:

3 gallon system -half water and half ethylene glycol
EG coefficient - .00032
Water coefficient - .ooo12
70F cold
190F hot

The liquid will expand 18.3 cubic inches

I'm ignoring the change in pressure as the gas volume is minute compared to liquid volume of the system.

Makes sense for catch tanks but vehicles ran fine for years without them. So where does it go in my old 73 AMC 258 i6 / 4.2l . Does the anti freeze leak down from the head or water pump hoses?

 

[Torxhead]

That is too much math for me. I would think a CJ style overflow tank would fit into the usual location on the left fenderwell on your CJ.