Coolant leak, can't pinpoint.

My first leak at the front was a thermostat housing leak. Replaced gasket, put in new coolant, still leaked. Replaced gasket with coating of thermostat gasket sealant, new coolant again, finally stopped leak. Within a year, water pump leaked. There's lots that can leak up front.

Regarding heater hose T's, I figure the ACDelco one on my Tahoe lasted a good 15 years, replacement ACDelco T's should last until my next coolant change easily. I don't like the system, but it seems to work. Ford uses the same style connections and they run their cooling systems (at least the 4.6L V8) at 20 psi.

 

normally they leak because of dirty coolant, dirt can wear away the seals and internal parts i.e water pump blades ( dirt can get in via the coolant reservoir as they're open to the atmosphere and don't have a breather filter)

 

my water pump was leaking from the seal for the shaft that has the pulley where the mechanical fan goes attached.

 

Strange. My surge tank is open to the atmosphere only when the cap is removed. You must be referencing a different cooling system.

 

All automotive coolant contains water and ethylene glycol plus a "buffer" to control acidity. As long as the coolant does not become acidic, it won't eat away at the metals in the engine, radiator, thermostat, water pump, etc. As time goes on, a little fresh oxygen always enters the system as the coolant cools after driving. This small amount of oxygen enters the coolant and during the next heating cycle will chemically react with the ethylene glycol and other additives to make acids. The buffer then neutralizes the acids, protecting the metallic parts of the engine, water pump, radiator, etc.

If you get a leak, such as a cracked head, air can enter through these cracks as well. In fact, the cracked head will let in some acidic vapours that would normally be collected by the PCV system, making the situation even worse. If the crack allows in exhaust gases, that's worse yet still as those gases are extremely acidic.

If the coolant is not changed before the buffer wears out, the acids will then eat away at metals. Old coolant is probably one of the biggest causes of water pump failure due to its acidity. I had a Grand Marquis with 300000 km on it, with the original water pump. Unfortunately, I neglected the last coolant change and my coolant pH dropped down to about pH=4 which is quite acidic. A few months after I changed the coolant I had to replace the radiator. A few months after that, my water pump went. I don't believe that was a coincidence.

 

the reservoir is open to the atmosphere on some cars

it might have a overflow relief port that might be hidden or it grenades




even still coolant sludge can still build up from the aluminium oxidation and iron (if you have an iron block) which will at some point wear away parts inside..


also water can wear away metal