Where'd my coolant go? *Fixed*

[BoxDriver86]

Long story short: I am driving my wife to her family's house when my coolant light comes on after some "spirited driving." I pull the car over, and notice there is no coolant in the reservoir. Strange thing is, the engine is bone dry.

I go into a supermarket, grab some distilled water and fill the tank up. Start car, get it up to temp, and bleed the system. No visable leaks, so I carry on the drive.

I drop off the wife, head over to NAPA and grab some stop leak. Letting the car run for a few minutes, and double checking there were no air pockets in the system I start the normal "is it my head gasket" checks.

Oddly enough, there was no white smoke coming out of the tailpipe. There is no moisture coming out of the tailpipe. I did notice a few very miniscule bubbles on the dipstick oil but up top everything looks clean.

I drove the car home 6+ hours last night without any issues. It did not get hot, it did not run poorly (although my valves were a tad louder, but I think I was being paranoid). It was idling a little higher than normal (1200rpm vs the normal 650).

Should I just rip it apart and replace the head gasket to be safe? This motor is pushing nearly 420K and I don't know what else could cause this. I do know I am a few months away from a motor swap and there is no fiscal way to make that happen sooner...and this car really needs to be running.

Any advice or thoughts would be fantastic. Thanks in advance.

[FLG]

Pressure test the system. You sure there are no leaks? I'd also have a smoke test done for intake leaks.

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[jlevie]

+1, a leak is a better explanation than a head gasket failure. And the leak may only be present when the cooling system is under pressure and the engine is running. A pressure test will find the leak and should be the first diagnostic.

If the pressure test doesn't reveal a leak, the possibility of a head gasket leak can be re-examined. An inexplicable loss of coolant can be caused by a small head gasket leak that over pressurizes the cooling system and causes the cap to lift and vent pressure (and coolant). That may only happen while driving and leave no evidence of what happened.

There are two DIY ways to diagnose this. The simplest is to open the cap when the engine is cold to vent any pressure, then drive the car, and let it cool down overnight. If the hoses are hard after the engine has completely cooled down, air is being pumped into the cooling system. The other check is to completely bleed the cooling system, drive the car, and re-bleed. Release of a significant amount of air on a re-bleed is evidence of a head gasket leak.

[BoxDriver86]

Thanks for the advice folks.

I should have run a pressure test prior to posting. Turns out the hose at the bottom of the reservoir that leads the the water pump was cracked right at the connection point, as well as a similar crack on the return line to the reservoir.

I always keep an extra set of hoses on hand for long road trips so I drained the system, replaced the hoses and all seems well. The coolant smell was coming from the exhaust manifold, where most of the coolant was leaking to under pressure. When the car was at idle, the coolant was leaking down the actual reservoir and dripping down the strut tower onto the frame rail hence why I wasn't seeing it.

I hope this helps anyone with a similar issue in the future.