2005 express van coolant leak

[Greg Richardson]

2005 Chevy Express 2500 Cargo Van. My mechanic has done pressure test to find coolant leak. After tests, inspecting it. Still can't find it. Oil looks fine. You can fill up coolant maybe drive 3 days or so and low again. Same mechanac over 15 years he has never been stumped on a problem but this one got him. Any idea's?

[davester]

Well, there's only a limited number of places the coolant can go:

-engine oil

-transmission oil (if transmission is cooled/heated through main radiator)

-onto the ground

-through the engine and out the exhaust

 

Maybe pull the spark plugs and examine them to see if any look different?

[Jsdirt]

If the mechanic couldn't find the problem with the vehicle right in front of him, we don't have a chance in hell of coming up with a reason for the coolant loss.

 

It can only be going one of the 4 ways Dave described above. I would imagine your mechanic investigated all of those routes already.

 

Exactly how much are you adding in 3 weeks? "Low" is a relative term - it could be 1 pint, or one gallon ...

 

My guess is it's a small leak - less than a half gallon, closer to a quart in that time? If she's got high miles, it could very well be going through the head gasket into the combustion chamber. When head gasket leaks first start out, there will be no way to detect it by checking the oil for coolant, or the coolant for oil. Sometimes they fail completely without either telltale sign as well.

[txab]

Y'all are also missing the water pump or wp gaskets...... The reason why I mention this is from personal experience..... I've seen these wp gaskets leak for a bit then stop for a while. Never could get them to leak when pressure tested, but would leak after pressure dropped

 

You can add dye to the coolant to help detect, which your mech. should have already done at this point

[Jsdirt]

Ahh, you're absolutely right on that! Sad part is, I just repaired a '03 6.0 with that exact issue! Totally forgot about it. Was just 2 weeks ago, too, lol.

 

I let the thing run for a half hour in the shop - not a drop. Shut it down, swapped out all 4 shocks and both CV axles. Engine cold by then, and still nothing. Fired it up again, and INSTANT stream! Would've emptied the whole system in a day, easily. Changed the water pump since that was the only logical place it could have came from, even though I couldn't even see a weep hole on the pump while up on the lift (thought that was strange - I don't recall seeing one at all, even with the pump in my hand). New pump fixed the leak.