Where is the leak?

[rbuckin111]

I just put a "supposedly" rebuilt 230 in my GMC and have been working the bugs out. My latest is I checked the coolant level and it was way down. There is no evidence of a fluid leak on the outside or underneath. This leads me to think (shudder) that it is leaking inside somewhere. How do I figure out where it is leaking and fix it without the "replace and hope" method? I appreciate any wisdom you can share with me.

[T2vigil]

IMO first make certain it did not have any air in the system by bringing it up to temp. T-stat open heater on high and then make sure it is full of coolant. If you have already done this check the dipstick and make sure it is not milky in color. If it is milky you could have several things wrong. All bad some worse than others. Blown head gasket to a cracked head or block. Good luck.

[Wrenchbender Ret]

If it was low just one time you probably had an air pocket. Dont fill it to full so to allow for expansion. Watch for white smoke vfrom the tail pipe.

[joedoh]

I had a car once that lost coolant while driving (you could even smell it) but in the engine compartment there was not a trace of a leak and the oil and exhaust were both clean, I could not figure it out.

One day I was accelerating and in the mirror saw a stripe on the road behind me. It was a split heater hose that held at low pressure but at higher rpm was shooting coolant straight at the ground!

check you hoses for this kind of evidence, on the bottom side there will be residue.

[padresag]

you could pressure test your system for leaks. a lot simpler than running it up to temp. if you do have an internal leak and running it, water tends to create a little stress on things. better to be safe than sorry.
ron