I have a 99 Express 3500 5.7 liter. I add more anti-freeze to this vehicle than I have had to any of my other vehicles combined (30 years worth).
It seems to just get rid of it . . . somewhere. Temp is fine, no white tailpipe smoke. I can only assume the head gasket is fine. 150k. I carry a gallon of 50/50 with me and add about a pint once a week, at least. Vehicle is awesome otherwise, except I have to put gas in it . . . ouch.

 

Sounds liek an internal haed gasket leak, but itsounds like it is to small to detect or to be a big deal. Leakdown test would be a alternative, but again, it is a VERY small leak. I wouldnt worry about it until it gets worse.

 

Wouldn't I be able to tell at the tail pipe (exhaust or residue) or in the oil if it were a small headgasket leak. I can come home from work, park it the garage, go to work the next morning and there will be a quarter cup of anti-freeze on the garage floor. If I fill up the overflow expansion tank reservoir, it will simply dump the coolant, somewhere and somehow within a 20 minute drive. As long as I check it every couple of days and make sure it doesn't get to low, it seems to operate fine. I've been doing this for 5 years. If something simple can be done it would be nice. I had a friend who saw my van once and casually asked me "does that thing mysteriously dump anti-freeze?" To which I replied "what do you mean" and he said "they all do, nothing to worry about, just keep track of it" He said he didn't know how or why but said they did. Then, I discovered this forum and I thought I would shoot it by some other folks. Thanks.

 

My 2000 does the same thing and I agree, I add more coolant to this thing than any other vehicle I own. Might want to check the intake manifold gaskets as this is a known leak area. I had mine replaced twice, the leaks were probably always there but when it gets bad, all the coolant just comes pouring out. I also notice now that there is always a few drops of coolant coming from the overflow tube at the reservoir even though the van is not overheating and running fine. Must be a design flaw because no matter how light or heavy I am on the van there will always be some coolant coming from the overflow tube at the plastic reservoir after a drive (I've changed reservoirs but still the same problem).

 

My 98 Express does the same. I had a leak from the water pump gasket which was replaced, I then noticed this new ? leak.
I've had a quick look under the van and a small amount of coolant is leaking from the passenger side of the engine somewhere and dripping onto the axle (its just a bit too high up for me to see so I'll remove the engine cover and try to identify it from there).
I only notice a small amount of coolant under the van after it has been stood for a couple of days but always seem to top up with more than looks to have leaked out !
Its always had what I would consider too much smoke/vapour coming from the exhaust when cold but I just assumed that was due to the size of the exhaust system holding alot of condensation and being burned off ?
There is no sign of water in the oil and vice versa though recently there has been a sort of thickening (very small amount) of the coolant under the cap though not the consistency you would associate with head gasket problems (the coolant in the rad and bottle is fine) ?
The van has always run fine though I would want to sort any problems before any damage occurs.

 

If it is the lower intake gasket, you will have anti-freeze in the oil, check dipstick. You might get a pressure pump tester, goes on where rad cap is, pump the system to 12-15 psi, then check for leaks. It might also be the cap.

 

If its coming from the top passenger side, I've had this issue too. There is a heater valve on the passenger side where all the heater hoses connect just before it goes into the passenger compartment heater core. It is a plastic valve so it breaking or a loose hose clamp would cause it to leak out from there and then down along the passenger side control arm. I believe you can see it from the wheel well area if you take off the tire and lift up the rubber shield on the wheel well. Just look directly up from this area. If I recall correctly all the coolant lines connect there and 1 small vacuum line.

Hope this helps,
Luke

 

Great, thanks for the tip. That will be the first thing I check. Hopefully that will be the problem as I'd hate to have some major gasket failure !! Fingers crossed.