Have been having to add about 8oz of coolant weekly for some time now. Suspected head gasket problem but I tested with combustion leak tester and fluid, tested ok, no gases in radiator. I've seen no fluids on the ground and truck does not smoke. Where is the coolant going? Appreciate the help.

 

Head gasket a possibility but could be intake manifold gasket as well. Have to pull intake to do head gasket anyways so look close where the coolant passages are.

 

My 88 5.7 has been doing this for many years. Same as you. No exhaust in coolant. They are known for having intake manifold problems. Like yours, mine runs fine and passes smog. Since it seems to pose no operational problems, I just live with it. I dont drive it much. Less than 3k a year so I check the coolant level every few months and I top it off. I still use green coolant so I change it every 2 years anyway.

 

I've got a 1996 with the 5.0L engine, and have had to replace the intake manifold gasket TWICE over the years due to coolant loss. It would be slight at first, but eventually both times, about 10 years apart, it turned into catastrophic coolant loss.

Another easy place to check would be the water pump - there are weep holes on the bottom side that will drip coolant if the water pump seals are going, which could account for a gradual loss, and the thermostat housing gasket.

 

Thanks for the advice. I'm pretty sure I found the problem. Pressure checked the system and found slight leak at the heater hose connector fitting at the manifold. Hard to see but there was dried coolant on the manifold around the fitting, apparently from the coolant dripping onto the manifold. However I changed the fitting and it looks like there is still a leak. I'm going to tighten the fitting some more and see if that stops it for good.

 

Good luck! Hope tightening things solves it.

 

Is this the fitting in the top of the intake , towards the back of the engine?
Originally mine was a “quick release “ design made of cheap pot metal.
if that’s the one. I had a nightmare removing it. Mine snapped off at the base and I literally had to chip the rest out , without ruining the threads.
That’s why yours might be leaking. Teflon tape or some kind of thread seal might be needed to prevent leaks.,

 

Maybe leaking around radiator cap or overflow tank has a small leak. If not, add some Barr's stop leak and hope it fixes any manifold leakage.