The Mysterious Case of the Disappearing Coolant

[Big Jim M]

Sorry if I have offended you guys

Problem is I have had too many vehicles brought to me with fellers telling me they can't find the leak... All of which simply raised the hood and looked at the top of the engine.
By simply climbing UNDER the vehicle with a flashlight I have found EVERY ONE of their leaks..
So My attempt to get the guy UNDER his vehicle might have been a bit pushy..
Big JIm

 

[koda6966]

What about adding the UV dye to the cooling system? Then run it a few days, one time at night take a black light and use it to inspect the engine. If it's dripping or running out a hose or on the block then it will show up. If it's a cracked head or gasket then a leak down pressure test is in order to find it.

Never thought of that... I usually just looked for the bright green water dripping under my truck.
But then again, I had a bad leak.

....next time my pool leaks I'm gonna fill it with UV dye, that idea could work in a lot of places.

 

[rboyer]

Under the vehicle is usually the first place I go when i'm looking to buy a used vehicle. Right after I make sure the body is in perfect shape of course. What I find underneath most likely doesn't effect actually buying the vehicle as much as it does my ability to talk the person down in price because whatever is leaking under there can usually be fixed without breaking open the good 'ol piggy bank and most people don't realize that. In my opinion certain leaks are only worth fixing to a certain extent. If you're driving a junk car with a beat up body and you have to top off the coolant overflow every two months then leave it alone as long as you have a good memory. But if you got a great deal on the vehicle, it looks great on the outside, and you can sink a decent amount of money into it before hitting blue book value then it's worth fixing the problem. Oil and coolant are two important things that should stay inside your engine and when you're leaking one of them it should be fixed, but there are certain exceptions to the rule. I myself only let a leak go if I don't have time to fix it and need to drive the vehicle, but I always remember to keep tabs on it until I repair the problem. Just make sure that you diagnose it thorough enough and find out what the problem definitely is so that you're not digging a hole in your wallet over a coolant leak.

 

[golosov]

A few things to look at on your truck. Check around the resevoir its self. Sometimes the cooling system can build up to much pressure from a blown head gasket. Then it will push water back out the resevoir. I would definately suggest UV dye, it will help find the tiniest of leaks. The pressure test will help you the most. if the head gasket is bad you will get a rapid spike in pressure as soon as you start the engine. if it doesn't spike then pump the presssure up to around 19psi watch the needle to see if it starts bouncing up and down, that indicates cumbustion chamber leak. I have seen many 4.0 heads cracked just bellow the exaust valve spring. When this happens the water evaporates in the exaust port. it doesn't burn in chamber so you don't see a white smoke.
I would like to point out to Big Jim that there are half a dozen ways for you to loose coolant like you describe that are all internal and there for no drips to see. please don't critisize others when they are looking for help. especially when you are mistaken yourself. No offense but you comments were out of line, rude, and offensive. Lets all try to help each other not belittle.

 

[koda6966]

Just don't spill the dye all over when you go to put it in your truck.
Then you'll never find the leak.

 

[V8 Level II]

Another thought: invisible coolant leaks are common through the intake manifold gaskets into the intake runners on the 4.0 OHV. A dead giveaway is a concurrent problem with misfire on cylinder #4 or sometimes #1.

 

[almostclueless]

Thats what I said....

 

[mike0179]

I had a coolant leak on my 99, 4.0 and had it to a mechanic several times, and they couldnt find anything. fnally we discovered the head gaskets were leaking coolant to the outside of the block and Evaporating before it hit the ground. look up through the wheel well and see if you can see any coolant leaks. hope this helps.

mike

 

[MAKG]

I just found my mystery leak. Pissed me off.

It turned out to be a little bit of seepage out the overflow line; it had just loosened from the rad a tiny bit due to heat and age. There was ONE drop of coolant on it.

That one drop was enough to eat up nearly a quart of coolant per day (75 miles).

I was really scratching my head since the system seemed to be pressurizing just fine.

 

[Big Jim M]

Good job MAKG... That's what I'm talk'n.. ONE drop and the mystery is solved.. Gotta look everywhere doncha?
Big JIm

 

[MAKG]

Absolutely. And the thing that REALLY pisses me off is that I did FOUR inspections on this thing before I found that. I even took the cover off the heater core, replaced the radiator (it WAS seeping out one of the tank seals), cranked down the hoses, and so on. I knew it had to be a tiny leak because it was pressurizing. But it was CLEAN!

The one thing I didn't try is looking at the core plugs on the backs of the heads. That would have required some real work, and I wasn't that far away from trying it.

 

[skippy]

Absolutely. And the thing that REALLY pisses me off is that I did FOUR inspections on this thing before I found that. I even took the cover off the heater core, replaced the radiator (it WAS seeping out one of the tank seals), cranked down the hoses, and so on. I knew it had to be a tiny leak because it was pressurizing. But it was CLEAN!

The one thing I didn't try is looking at the core plugs on the backs of the heads. That would have required some real work, and I wasn't that far away from trying it.

inspection mirror?

 

[bottledgt]

Problem is I have had too many vehicles brought to me with fellers telling me they can't find the leak... All of which simply raised the hood and looked at the top of the engine.
By simply climbing UNDER the vehicle with a flashlight I have found EVERY ONE of their leaks..
So My attempt to get the guy UNDER his vehicle might have been a bit pushy..
Big JIm

yeah well before you spout off some more, i had a leak on the explorer that had 0 srips under it. turned out to be a small crack in the plastic thermostat housing,and the coolant was going into the valley and burning off..no dripping whatsoever

 

[Roadkill]

That is exactly why I mentioned UV dye. If it boils off and dries the dye stays behind and is visible under blacklight. I've had to find coolant leaks that looked like they weren't really there.

 

[Simple_serf]

What has worked for me before is pressurizing the system (rent the tester at autozone or somewhere similar). With no engine running you can usually find the leak if it is serious. So long as the oil isn't getting frothy, I wouldn't worry too much.

Makg, my truck had/has a similar leak as yours. I put a hose clamp on it and that solved it... Vibration was loosening it.