How small of a coolant leak....

[turbojimmy]

....would it take to lose pressure in the cooling system?

I know I'm being anal about this, but I want to be 100% sure there's no combustion-related coolant leak before I really start to hammer on the car.

The coolant pressure check revealed a very slow pressure leak somewhere. I noticed this morning that the bottom of the rad support is damp over by the lower rad hose. Not dripping wet but too damp to be left over from when I drained the rad to take the motor out. Could a very small leak - not big enough to even cause a drip or noticable loss in coolant - cause the pressure loss?

Thanks,
Jim

 

[gofstbuick]

How long did the pressure tester hold pressure? Personally, I would wash off the radiator support and any area where coolant accumulated during the engine install, re-check all the hose clamps, and re do the pressure test. If the pressure holds for say 15 minutes or so, you're probably okay. While the system is pumped up, check for leaks and listen for internal leaks

 

[turbojimmy]

Originally posted by gofstbuick
How long did the pressure tester hold pressure? Personally, I would wash off the radiator support and any area where coolant accumulated during the engine install, re-check all the hose clamps, and re do the pressure test. If the pressure holds for say 15 minutes or so, you're probably okay. While the system is pumped up, check for leaks and listen for internal leaks

It didn't hold the full 16 psi for more than a minute. I only watched it for about 10-15 mins where it had creeped down to about 12 psi.

While the system was pumped up, I couldn't hear anything but an occasional gurgle from within the radiator, which to me means there's a leak somewhere - but would a gurgle in the radiator mean that the leak is at the radiator or could it be somewhere else?

Thanks,
Jim

 

[gofstbuick]

Try looking at the obvious places first: through the fan shroud along the radiator tank, the heater hoses, the passenger carpet area (heater core), drain petcock, heater control valve, throttle body hoses, water pump and hose connections. I assume you put some type of thread sealant on the (thread of the) bolts that attach the water pump to the timing cover. Once, I had a lower hose to the radiator that was not seated properly and it seeped a little until the hose popped off one day. Also, the metal tubes that connect the block to the heater hoses sometimes deteriorates. Have you checked your oil level, and is it up or is there alot of water showing on the dipstick?