Coolant leak with no puddle

[scrivyscriv]

I loose the equivalent of one full coolant reservoir every two weeks, but no external leak points or puddles on the ground.

The T-stat neck is rusty from having leaked there, but as much coolant as I'm loosing it can't just be dripping out there.

My exhaust is white, but I can't tell if it's just a normal color from it vaporizing in the cold weather or if it's really white smoke.

If it's anything significant, I'm not going to put the money into it, but if I can fix it without lengthy breakdown or high parts cost I'll give it a shot.\

In the past I've put in the Prestone radiator leak fixer stuff, and it's slowed the leak very much, but after a month the leak slowly gets worse, and now since I just flushed my system, it's like peeing through a seive.
Okay, maybe not that bad, but it feels like it.

Where to start?

 

[IZwack]

Compression check on each cylinder through the spark plug hole

 

[Anime]

Since you say the exhaust is white, I'd also suggest the compression/leakdown check, plus the condition of the plugs can let you know what it's burning.

You can get a radiator leak or have a few loose bolts on the water pump (or a leaky gasket at the pump) and just get a slow loss of fluid that's only noticable at the reservoir. If the front of the oil pan is slimy, chances are some coolant is involved. You might be losing more coolant than you think from a leaky gasket around the thermostat, too. It's some hassle to replace, but the gasket is just a few cents, and it's not a bad idea to wire brush the neck and paint it while it's off...and maybe even replace the thermostat too in case it's not opening completely and the extra pressure is a cause of the leak.

 

[bvenvert]

There is a pretty good track record of issues with the lower intake manifold gasket developing a leak at the number 5 cylinder. When this occurs the coolant will actually leak from the cooling system right into the number 5 cylinder and it gets burned with the fuel. When this happens you will not note any coolant on the pavement, since the truck is burning the coolant during the firing process.

I think I need to replace my lower manifold gasket ob my truck, since I was having the same problem, but I dumped a can of Bar's leak in the radiator and my coolanr loss from the radiator has disappeared. I think the Bar's Leak may have eliminated the manifold gasket leak at least for the time being, but eventually it will probably need to be replaced. The leaking manifold gasket is well documented on this site, so you amy want to search and read some of the information. You can do the gasket replacement yourself, but it involves removing a boatload of equipment on the top of the motor. Good Luck

 

[scrivyscriv]

I found the biggest problem - Haven't checked compression yet, but was draining the flush chemical out of my system and replacing it with antifreeze, and when I cranked the engine to get the air out, I found a fat leak.

I installed my Prestone flush kit adapter tee on the heater hose about six inches from the firewall - more on that later - and when I was backflushing the other day, I must have loosened up the hose clamps; one side was squirting antifreeze out.

Don't put the adapter tee close to your firewall. It may be coincidence, but mine is right over the blower motor and resistor pack, and I just had to replace both less than six months prior to catching this leak.

 

[Whiteman_01]

I Just picked up a 92 ex. I am also loosing about a half gallon of coolant a week with no puddle, and the oil is clean. Also, my exhaust seems white all the time. Will a compression test tell me whats going on for sure? Stupid question i know, but how are the cylinders numbered on the 4.0? Is it 135/246, or 123/456

Thanks.

 

[arco777]

I Just picked up a 92 ex. I am also losing about a half gallon of coolant a week with no puddle, and the oil is clean. Also, my exhaust seems white all the time.... ...how are the cylinders numbered on the 4.0? Is it 135/246, or 123/456

Check for an unusually clean plug when you are pulling them, indicating a coolant leak into a cylinder (white smoke). Head gasket, or, as is common with stock heads, a cracked head. Cylinder numbering is 123/456 running rearwards down the left then right rows as viewed from the front of the car, firing order is 142536. Hope this helps.

 

[Whiteman_01]

Thank you very much. I will check it out today.