Weird Coolant Leak... need some help

[1997XLTRollover]

Hey guys I've got a really odd coolant leak that I can't understand. I've got a 96 5.0 that I just completely rebuilt. It's basically a stock rebuild and I replaced everything when I did the build, pistons, valve springs, lifters, all sensors, radiator hoses etc.

Now the truck runs great, doesn't overheat, runs a solid 194 degrees, no noises, sounds like well... a new engine. I'm running the Stant Superstat (195 deg) and I can't believe I would have put it in backwards (is this even possible?). But I've got about 450 miles on the engine now and I have this phantom coolant leak form the upper radiator hose. I say phantom because it doesn't leak when the truck is driving around, nor does it leak all the time. It seems to only leak when I let the truck idle for 10+ minutes warming up.

I already tried double clamping it and replaced the radiator cap. but it still leaks from the hose on the radiator side. I'm almost wondering if there is a micro crack in the radiator I can't see or if for some reason coolant pressures are rising higher at idle than when driving.

Any ideas? I'm really at a loss and I depend on this truck daily to get me to work.

 

[koda2000]

I usually not a big fan of additives to solve problems, but someone turned me on to a product that stops coolant leaks immediately, doesn't hurt anything, is easy to use, says it's a permanent fix and it remains in the system to stop future leaks. It's called K-Seal and is available in most auto parts stores. It comes in an 8 ounce bottle. You just make roomi the rad for it, shake it well, pour it in, idle the engine for 30 mins and you're done. I've stopped 2 fairly bad leaks in 2 different vehicles in the past couple of months using this stuff. I think I'm going to put it in all my trucks to stop any future leaks.

As far as you hose leak, did you replace the radiator hose? They tend to fail from the inside and leak from between the layers.

 

[1997XLTRollover]

I usually not a big fan of additives to solve problems, but someone turned me on to a product that stops coolant leaks immediately, doesn't hurt anything, is easy to use, says it's a permanent fix and it remains in the system to stop future leaks. It's called K-Seal and is available in most auto parts stores. It comes in an 8 ounce bottle. You just make roomi the rad for it, shake it well, pour it in, idle the engine for 30 mins and you're done. I've stopped 2 fairly bad leaks in 2 different vehicles in the past couple of months using this stuff. I think I'm going to put it in all my trucks to stop any future leaks.

As far as you hose leak, did you replace the radiator hose? They tend to fail from the inside and leak from between the layers.

Yeah I've heard of K-seal. Heard good things about it too actually. But there's no way I'd dump that in a brand new engine. Maybe a vehicle on it's last legs getting ready for the scrap yard, but that gets in the heater core and all over the place.

The radiator hose is a brand new Goodyear hose. Maybe the hose is defective? But why would it only leak at idle and only on a cold start?

 

[1997XLTRollover]

What are he odds I have a cold coolant leak and there's a crack in the hose that's sealing itself up when warm? I'm wondering now if it's my radiator, but that didn't leak before I swapped the engine. Maybe I cracked it somehow during the swap? Don't think I did though but who knows.

 

[koda2000]

Yeah I've heard of K-seal. Heard good things about it too actually. But there's no way I'd dump that in a brand new engine. Maybe a vehicle on it's last legs getting ready for the scrap yard, but that gets in the heater core and all over the place.

The radiator hose is a brand new Goodyear hose. Maybe the hose is defective? But why would it only leak at idle and only on a cold start?

The thing with K-Seal is that it's a thin liquid and doesn't clog anything. I would have no issue with putting it in a brand new engine, but that's your choice. I guess the hose could be defective. I know that most hoses have a plastic thing poked in them to hang them from a peg (much like a long price tag). Maybe the hole isn't near the end where it's supposed to be??? As far as when it leaks, at cold start makes sense as things expand when they get warm. Maybe the pressure in the system is higher at idle?

 

[1997XLTRollover]

The thing with K-Seal is that it's a thin liquid and doesn't clog anything. I would have no issue with putting it in a brand new engine, but that's your choice. I guess the hose could be defective. I know that most hoses have a plastic thing poked in them to hang them from a peg (much like a long price tag). Maybe the hole isn't near the end where it's supposed to be??? As far as when it leaks, at cold start makes sense as things expand when they get warm. Maybe the pressure in the system is higher at idle?

That's what I was thinking that the idle pressure is high for some reason. But even at that, I replaced the rad cap and it should release the pressure regardless.

Also this is not something I would ever fix with a coolant additive. Every leak should be fixed properly without an additive. It shouldn't be leaking, so there is an underlying problem that should be addressed.

 

[koda2000]

That's what I was thinking that the idle pressure is high for some reason. But even at that, I replaced the rad cap and it should release the pressure regardless.

Also this is not something I would ever fix with a coolant additive. Every leak should be fixed properly without an additive. It shouldn't be leaking, so there is an underlying problem that should be addressed.

Even with the correct radiator cap, it will not release pressure until it exceeds 16 PSI.

 

[1997XLTRollover]

Even with the correct radiator cap, it will not release pressure until it exceeds 16 PSI.

Correct. But my point is it should not have any leaks below 16 PSI.

 

[1997XLTRollover]

On a side note does anyone know if the factory radiator is a 1 or 2 core radiator? I might be looking at having to get a new one and was thinking of getting a 2 core.

 

[koda2000]

On a side note does anyone know if the factory radiator is a 1 or 2 core radiator? I might be looking at having to get a new one and was thinking of getting a 2 core.

I believe the '96 would have been a 2-core. Ford changed to a single core around 2000.

 

[Justme63]

I too have a mystery leak from an unknown location. I replaced the engine a year ago and have had intermittent coolant leaks for the last 2 months. First I went back through and re-tightened all the hose clamps. It stopped, for a little while. 2 days ago we had -10 degree weather and I noticed a good puddle again, determined that the water pump bolts had come loose just a touch, which baffles me because they had Medium Lock Tite and were torqued. Now after re tightening the water pump bolts I hope I have solved my mysterious coolant leak. I suppose while I am in a warm garage and the truck is already in repair mode I better double check all my bolts or as many as I can get to. This isn't the only FORD I have had where stuff like this loosens up. Yes I own a torque wrench and I adjusted for used bolts. If I find anything else that might be causing this I will let you know

 

[MAS Tequila]

Koda is correct about the K seal.

It won't hurt anything.

I recently was coming back to south FL from NC. While still 500+ miles from home, my t-stat housing started leaking badly. I was losing 1-1/2 gallons of coolant every 100 miles.

K seal sealed the leak and allowed me to get home.

I wouldn't use Bars Leak but the K seal will not clog anything up.

Just try a new rad hose.

MT

 

[1997XLTRollover]

I too have a mystery leak from an unknown location. I replaced the engine a year ago and have had intermittent coolant leaks for the last 2 months. First I went back through and re-tightened all the hose clamps. It stopped, for a little while. 2 days ago we had -10 degree weather and I noticed a good puddle again, determined that the water pump bolts had come loose just a touch, which baffles me because they had Medium Lock Tite and were torqued. Now after re tightening the water pump bolts I hope I have solved my mysterious coolant leak. I suppose while I am in a warm garage and the truck is already in repair mode I better double check all my bolts or as many as I can get to. This isn't the only FORD I have had where stuff like this loosens up. Yes I own a torque wrench and I adjusted for used bolts. If I find anything else that might be causing this I will let you know

I would appreciate it. My engine only has 600 miles on it and it's been leaking for at least 300 of them. Sometimes it leaks and sometimes it doesn't, but whenever it does it's only at a cold idle. It's definitely coming from the upper radiator hose and or radiator area. I can see the drips running down the radiator.

Koda is correct about the K seal.

It won't hurt anything.

I recently was coming back to south FL from NC. While still 500+ miles from home, my t-stat housing started leaking badly. I was losing 1-1/2 gallons of coolant every 100 miles.

K seal sealed the leak and allowed me to get home.

I wouldn't use Bars Leak but the K seal will not clog anything up.

Just try a new rad hose.

MT

I guess I'll put my old 142k mile hose back on and see if there is in fact something wrong with this brand new goodyear hose.

 

[bill06447]

Some of these places string a plastic loop through the ends of the hoses to hang them up; I've seen the loop so far up that it doesn't get covered by the radiator inlet/outlet when the hose is installed, so then you get a leak.

Bill

 

[rb142]

Some of these places string a plastic loop through the ends of the hoses to hang them up; I've seen the loop so far up that it doesn't get covered by the radiator inlet/outlet when the hose is installed, so then you get a leak.

Bill

Good thought. I'd be pissed if I ran into that, but it is possible.


Since the location is pretty much narrowed down, dry it all off really well, let it idle, and figure out exactly where the fluid id coming out. If you still can't tell, get a pressure tester on it. 15 psi will make even the most stubborn leak show itself. It is definitely possible that you have a hairline crack in the inlet neck. It may be leaking form the rad end cap. It may just be leaking from the hose. I have found that some of the aftermarket hoses are just a little too big in diameter and are very hard to get to seal properly. The other thing is the type of clamp. Screw clamps do not seal well -- especially as the temperature changes. Leaking when cold is symptomatic of this. The constant-tension wire clamps (like OE) do a much better job of sealing these.

As a side thought, is the cooling fan working OK? Not pulling enough air at idle could cause some increase in pressure.

 

[koda2000]

Good thought. I'd be pissed if I ran into that, but it is possible.


Since the location is pretty much narrowed down, dry it all off really well, let it idle, and figure out exactly where the fluid id coming out. If you still can't tell, get a pressure tester on it. 15 psi will make even the most stubborn leak show itself. It is definitely possible that you have a hairline crack in the inlet neck. It may be leaking form the rad end cap. It may just be leaking from the hose. I have found that some of the aftermarket hoses are just a little too big in diameter and are very hard to get to seal properly. The other thing is the type of clamp. Screw clamps do not seal well -- especially as the temperature changes. Leaking when cold is symptomatic of this. The constant-tension wire clamps (like OE) do a much better job of sealing these.

As a side thought, is the cooling fan working OK? Not pulling enough air at idle could cause some increase in pressure.

Some of these places string a plastic loop through the ends of the hoses to hang them up; I've seen the loop so far up that it doesn't get covered by the radiator inlet/outlet when the hose is installed, so then you get a leak.
Bill

I mentioned this in post #5 . Guess no one bothered to read it.

 

[Justme63]

I did find my leak. I had bolts work themself loose, not much but when I would first start up in the cold it must have been enough to seep out while idling as I wait for it to warm up. I retighted and my leak has vanished. Your leak seems to be coming from a different area. Good luck and I hope you find it soon

 

[1997XLTRollover]

Good thought. I'd be pissed if I ran into that, but it is possible.


Since the location is pretty much narrowed down, dry it all off really well, let it idle, and figure out exactly where the fluid id coming out. If you still can't tell, get a pressure tester on it. 15 psi will make even the most stubborn leak show itself. It is definitely possible that you have a hairline crack in the inlet neck. It may be leaking form the rad end cap. It may just be leaking from the hose. I have found that some of the aftermarket hoses are just a little too big in diameter and are very hard to get to seal properly. The other thing is the type of clamp. Screw clamps do not seal well -- especially as the temperature changes. Leaking when cold is symptomatic of this. The constant-tension wire clamps (like OE) do a much better job of sealing these.

As a side thought, is the cooling fan working OK? Not pulling enough air at idle could cause some increase in pressure.

That's the problem. I start my truck every day and let it warm up. It's only leaked 3 times in the past 600 miles and probably 50 starts. I also have the factory style clamp on the hose AS WELL AS a screw/worm type clamp that I tightened the **** out of. I know, I know, if it's too tight it might leak, but I didn't put that on until after I had leaks and it apparently didn't stop the leak. Although the leak did get much much better.

 

[koda2000]

I think the reason your leak seems to be lessening is because it's a tiny leak and small sediments in your coolant are eventually clogging the leak (in much the same way a sealant would work). the swelling of the component once warm/hot also stops it from leaking. you may have a hairline crack in the thermostat housing. it's your time and money, but I would have thrown in the K-Seal a week ago and gone on with my life. it won't hurt anything and it will stay in there to repair future leaks.

 

[1997XLTRollover]

I don't like covering up issues; I like fixing them. Band aids will come bite you in the ass at the worse possible time. It shouldn't leak period. They didn't run K-seal from the factory and I shouldn't have to now. If I run K-Seal, the thing could crack completely when I'm 2 hours from home or further and leave me stranded when it's so big K-seal cant seal it.

If this was some pile of crap Land Rover I'd dump it in and scrap the thing when it blew apart. But it's a brand new 306 in a Ford. No stop leaks for me, I just want to find the actual issue .