Coolant Leak When Cold

[gdgiordano]

So the shop pressure tested the whole system and found the thermostat housing to be seepy even though its brand new (less than 2 years old).

I found a connection with an obvious leak when the vehicle is cold and sitting. Its the top metal hose immediately below the radiator cap. Its behind the washer. Is there a rubber gasket that leaks or should I be replacing the radiator for the 3rd time in 3 years?

 

[XLTrunner]

We all know the problem these trucks have with leaky t-stat housings. Do you know which brand was installed last time? Dorman and Four Seasons have a very spotty reputation for dependability. In my own case, my Four Seasons lasted all of 2 wks. Got smart and went with the Motorcraft upgrade and no problems in over a year.

Not sure if that fitting is serviceable on your radiator. It is a common leak point, however. Seems like I've tried tightening up that thin nut in front of the rubber gasket on my previous Explorers and it didn't help. With that said, if you've replaced your radiator twice in the past three years, I'd be looking at another brand of radiator.

 

[J_C]

Wow 3 radiators in 3 years. I'd be annoyed enough to put some Stop Leak in the radiator and see if that works. I'd also wonder if the radiator cap was still releasing excess pressure or contributing to the problem, or did you replace the cap a time or two since the first radiator? I suppose if you replaced the cap with the first radiator swap, that the original radiator could have been at end of life but it was the new cap that was bad and contributing to the 2nd and 3rd leaking, or I could just be barking up the wrong tree, as I don't remember many people having this problem.

Anyway, I'd pull the line and see if there's a seal that needs replaced, clean any residue off, and then put it back on, which may fix the leak. I'd be more worried if it had never came off and was now rusting for 19 years but with it taken off twice in the last 3 years it shouldn't be too hard to get off again without damaging the radiator or line.

 

[koda2000]

I was wondering about the cap too. I've replace 3-4 radiators in my fleet with relatively inexpensive single-core aftermarket CSF brand radiators (along with installing new rad caps) and I've not had any problems. I'd also check the hose going to the coolant reservoir to make sure it's not clogged.

 

[J_C]

Come to think of it, I wonder if anyone has tried using teflon tape on a fitting like that, both to help guard against leaks and keep metal to metal corrosion from fusing some of the threads together.

 

[koda2000]

IDK what metal line you're referring to. The only metal lines on my '97's radiator are the transmission lines. The neck of the rad cap has a plastic nipple that the rubber hose that goes to the coolant reservoir pushes onto. This is the same on all my Ex's, Monty's and ST.

If you're talking about the trans lines leaking coolant, or ATF, did you make sure to hold the fitting on the rad tightly when you tightened the line fittings?

If it's only leaking a little coolant when cold, I'd toss in a bottle of K-Seal. It has worked very well for me on several Ex's with small (and not so small) coolant leaks. What I like about it is that it wont clog or hurt anything.

 

[XLTrunner]

You can get coolant leaks around the fitting where the tranny line nipple threads into the radiator. It doesn't leak around the nipple threads...but, between the radiator casing and the female fitting inside that receives the tranny line nipple. Kind of hard to explain. I've had that problem on two of my previous Explorers. It was never much...but, would leave a trail of coolant down the side. Had nothing to do with the radiator cap or the overflow tube being blocked.

I am curious about the K-Seal. I tried Bars Leak years ago on my '93 due to an intake leak and it pretty much stopped it. But, I did it with some trepidation as I had read reviews that said the ingredients could plug your heater core, smaller water jacket passages and even prematurely wear out the water pump impellers. But, at that point in the truck's life, it was about due for retirement anyway...so, I took a shot with it to get by. Haven't had the need to try any of them since.

 

[koda2000]

You can get coolant leaks around the fitting where the tranny line nipple threads into the radiator. It doesn't leak around the nipple threads...but, between the radiator casing and the female fitting inside that receives the tranny line nipple. Kind of hard to explain. I've had that problem on two of my previous Explorers. It was never much...but, would leave a trail of coolant down the side. Had nothing to do with the radiator cap or the overflow tube being blocked.

I am curious about the K-Seal. I tried Bars Leak years ago on my '93 due to an intake leak and it pretty much stopped it. But, I did it with some trepidation as I had read reviews that said the ingredients could plug your heater core, smaller water jacket passages and even prematurely wear out the water pump impellers. But, at that point in the truck's life, it was about due for retirement anyway...so, I took a shot with it to get by. Haven't had the need to try any of them since.

Re using a sealant:
I've tried Bars in the past. I think it might have worked once for the 5-6 times I've used it over the years and the fix was only temporary.

I like the K-Seal because it will not clog anything (it's quite thin. It looks like thin chocolate milk with cookie crumbs in it). It's considered a permanent repair and it stays in the cooling system to seal future leaks. I put it in my 2000 Mountaineer 5.0L, because it was leaking from the timing cover gasket on the passenger side. At first it leaked only when then outside temps got down into the 30's-40's, but then it developed a constant drip. I was going to remove the timing cover to replace the gasket (which is a big job on the 5.0L) but someone suggested I try the K-Seal. It worked w/in 15 minutes. That was 2 years and at least 15.000 miles ago and it hasn't leaked a drop since. Then my '00 5.0L XLT started leaking badly from the area of the w/p. It was a stream of coolant leaking. I had a second bottle of K-Seal, so I tossed it in (not expecting much) and took the truck for a ride around the block. By the time I got home the leak had completely stopped. That was about 20 months ago and it hasn't leaked a drop since.

If K-Seal was less expensive I'd put it in all my vehicles before they develop leaks, As it is I keep a bottle in the garage for when I'll need it. You can get it on eBay for around $11-$12 with free shipping, or buy it in most auto parts stores for around $5 more.

 

[gdgiordano]

We all know the problem these trucks have with leaky t-stat housings. Do you know which brand was installed last time? Dorman and Four Seasons have a very spotty reputation for dependability. In my own case, my Four Seasons lasted all of 2 wks. Got smart and went with the Motorcraft upgrade and no problems in over a year.

Not sure if that fitting is serviceable on your radiator. It is a common leak point, however. Seems like I've tried tightening up that thin nut in front of the rubber gasket on my previous Explorers and it didn't help. With that said, if you've replaced your radiator twice in the past three years, I'd be looking at another brand of radiator.

It was either Dorman or Motorcraft. The shop that did it has a lifetime part warrenty on the radiator so idk.

 

[gdgiordano]

Idk if it means anything but my vehicle does have a separate trans cooler. Koda, The metal line goes in the driver side of the radiator on the back just below the cap.

Little bit of an update the cap was leaking under heat with pressure but not the other way around. The new cap is also leaking under heat and pressure. Is it possible that excess pressure is causing this? It was only 95 today. I have had it in worse with no issue.

What could be causing the excess pressure? The vehicle isn't extremely hot, it might be a smidge hotter than normal but not much. No lights or errors, could it be the water pump? that is the only thing I have never replaced on the cooling system. There's no chirp or anything from under the hood.

 

[J_C]

What do you mean the cap was leaking? You mean coolant was coming out between the cap and radiator opening it seals on? If so it should not do that, check to see if the reservoir hose is clogged, or the reservoir cap is clogged.

Coolant is poisonous so I wouldn't be blowing on it with my mouth but you could take the hose off the radiator, keeping it higher than the reservoir so it doesn't leak, and shove the end of a turkey baster in to push some air through to see if it's clogged, or an air pump, compressor, etc, then to test the reservoir cap, do that with the cap on and with it off to see if the cap is adding resistance.

Water pump usually fails from a bad bearing, will start leaking coolant there or in worst case the bearing practically seizes and bogs down if not stalling the engine.

 

[koda2000]

Whether you have the trans cooler or not (most have one) the trans lines still connect to the driver's side of the radiator. It sounds like the fitting on the radiator is leaking a bit. If that's where it's leaking from you can put in some coolant sealant or take it back to whoever installed the radiator as a warranty claim. They may have damaged the seal when they tightened the trans line.

If your leak is coming from the cap, the cap isn't making a good seal on the radiator neck. Remove the cap (when cool) and inspect the sealing surface on the rad to make sure it's smooth. If not 100% smooth take a piece if fine sand paper to it. You can blow on the overflow hose to the reservoir with you mouth without poisoning yourself, just don't get an antifreeze in you mouth, if you get a taste, spit it out. I don't think a turkey baster will make enough pressure to blow air through the line, It'll take a couple of PSI.

It doesn't sound like you have any other coolant system issues, just a radiator problem or two.

 

[J_C]

I don't think a turkey baster will make enough pressure to blow air through the line, It'll take a couple of PSI.

Zip tie the bulb onto the tube, then it's capable of a surprising amount of pressure.